WO2012028917A1

WO2012028917A1 - Antenna-switchable reception system and wireless communications device including same

Info

Publication number: WO2012028917A1
Application number: PCT/IB2011/001937
Authority: WO
Inventors: 厳茂住; 秀樹笠井; 隆藤井
Original assignee: パナソニック株式会社
Priority date: 2010-08-26
Filing date: 2011-08-25
Publication date: 2012-03-08
Also published as: TW201215014A; TWI527397B

Abstract

Provided is an antenna-switchable reception system that switches a plurality of antennae and receives a wireless signal. In the antenna-switchable reception system, the quality of a wireless signal received while switching the antenna at a predetermined cycle is compared, and the antenna that receives the payload is selected.

Description

Antenna switching reception system and wireless communication device including the same

The present invention relates to an antenna switching reception system for switching and receiving an antenna in a wireless communication system.

In wireless communication systems, level degradation due to multipath fading is one of the problems. Signals received by the receiving antenna include not only signals input directly from the transmitting antenna to the receiving antenna, but also signals input via a plurality of different paths. For this reason, signals (multipaths) having different delay times are also input to the receiving antenna, so that the reception level deteriorates by overlapping and canceling signals at the receiving antenna end. This is a phenomenon called level degradation due to multipath fading.
As a representative measure for avoiding the influence of level deterioration due to multipath fading, there is a multicarrier transmission technique such as OFDM. This is a technique that can reduce the influence of level degradation due to multipath fading because the information to be transmitted is divided into a plurality of carriers (subcarriers) and transmitted in a wide frequency band. However, in OFDM transmission, it is difficult to reduce the cost because it requires a complicated configuration for processing by transforming the frequency axis and time axis by inverse Fourier transform and Fourier transform, which increases the circuit scale. was there.
Further, there are measures by “switching diversity”, “selective diversity” for switching a plurality of antennas, and “combining diversity” for combining received signals at each antenna. These measures are based on the fact that the effects of multipath fading differ depending on the location of the receiver and the plane of polarization of the radio wave. “Selective diversity” is a technology that monitors reception levels at multiple antennas and receives signals with optimal antennas, but requires as many receivers as the number of antennas, which increases the circuit scale. There were drawbacks. “Combining diversity” is a technology that combines the phases of signals received by multiple antennas, but this also requires as many receivers as the number of antennas and a phase shifter that matches the phases of each signal. There was a drawback that the circuit scale was increased.
“Switching diversity” is a technique for reducing the influence of multipath fading by switching to the other antenna when there is an influence of multipath fading on one antenna (see, for example, Patent Document 1). In recent years, with the widespread use of portable wireless devices, the antenna switching unit is also required to be downsized and cost-reduced, and can be configured with a single receiver. Diversity "is installed in various wireless devices.
Japanese Patent Laid-Open No. 06-303218

However, in “switching diversity”, the reception level at the switching destination antenna is not known until the antenna is switched. For this reason, if the reception level at the antenna to be switched to is lower, there is a disadvantage that the signal must be received under worse conditions.
Furthermore, in wireless LAN, a system that receives multiple packets (frames: a preamble, unique word, a set of signals that make up a payload) and switches antennas when an error is detected across multiple packets, that is, an error occurs. This is based on antenna switching after The generated error is dealt with by sending the same packet again to the transmitter (retransmission function). However, in situations where the communication environment is poor due to multipath fading, the number of retransmissions increases, devices that need to communicate with multiple devices and receive new payload signals one after another, and new payload signals such as voice and video one after another at high speed It is not suitable for equipment that needs to receive
The present invention has been made to solve the above problems. That is, an object of the present invention is to provide an antenna switching receiving system that can reduce the influence of level fluctuation due to multipath fading by selecting an antenna with high signal quality accurately even in an environment with many multipaths with a simple configuration. To do.

According to the first aspect of the present invention, in an antenna switching receiving system that switches a plurality of antennas and receives a radio signal, the antenna that receives the payload by comparing the quality of the received radio signal while switching the antenna at a predetermined period In the antenna switching reception system according to the first aspect, an antenna control unit that controls switching of an antenna, a unique word setting unit that presets and stores a bit string of a known unique word, and an antenna The unique word detection unit that searches the bit string of the received radio signal while switching the signal and detects the same bit string as the unique word stored by the unique word setting unit, and the quality of the received radio signal for each antenna A signal quality comparison unit is provided for comparison. When the unique word detection unit detects a unique word, the antenna control unit selects the antenna determined to have the highest signal quality as a result of comparison by the signal quality comparison unit, and receives the subsequent payload. It is preferable to do.
In the antenna switching reception system according to the first aspect, a plurality of unique words consisting of different bit strings are transmitted from a corresponding transmission system in a specific order before a payload, and a plurality of unique words transmitted from the transmission system A plurality of the same unique words are preset and stored by the unique word setting unit, and the unique word detection unit is a plurality of unique word detection units that individually detect the plurality of unique words, and the plurality of unique words When the word detection unit detects a predetermined unique word, the antenna control unit preferably selects an antenna that is determined to have the highest signal quality.
In the antenna switching reception system according to the first aspect, it is preferable that the signal quality comparison unit includes a reception level comparison unit that compares levels of radio signals received by the antennas.
In the antenna switching reception system according to the first aspect, the signal quality comparison unit compares the number of errors in the bit string of the radio signal received by each antenna with respect to the bit string of the unique word stored in the unique word setting unit. It is preferable to have a number comparison part.
In the antenna switching reception system according to the first aspect, a preamble for establishing bit synchronization is transmitted from each corresponding transmission system before each unique word, and the unique word error number comparison unit includes a bit string of the preamble and the unique word. It is preferable that the preamble unique word error number comparison unit compares the number of errors in the bit string of the radio signal received by each antenna.
The antenna switching reception system according to the first aspect, further comprising: a first counter that counts a first predetermined time that is a reception interval of unique words in one packet, wherein the unique word detection unit receives a radio signal received by any antenna When the unique word is detected, the first counter starts counting, and when the unique word reception interval is counted, it is preferable to detect the next unique word from the signal received by another antenna.
The antenna switching receiving system according to the first aspect further includes a second counter that counts a second predetermined time after switching the antenna until the second counter counts the second predetermined time after switching the antenna. It is preferable not to detect a unique word.
The antenna switching reception system according to the first aspect further includes a packet end detection unit that detects the end of the packet, and when the packet end detection unit detects the end of the packet, the antenna control unit performs control to switch the antenna at a predetermined period. It is preferable to return automatically to receive the next packet.
The antenna switching receiving system according to the first aspect further includes a third counter that counts a third predetermined time after detecting a specific unique word, and the unique word until the third counter counts the third predetermined time. It is preferable not to detect this.
The antenna switching reception system according to the first aspect further includes a reception level detection unit for detecting a level of a received radio signal, and the unique word after the reception level detection unit detects a signal level equal to or higher than a predetermined first threshold. It is preferable that the detection unit starts searching for a unique word.
In the antenna switching reception system according to the first aspect, any one of a selection antenna storage unit that stores information on an antenna selected by the antenna control unit when receiving a payload, and information stored in the selection antenna storage unit When such an antenna is continuously selected by the antenna control unit a predetermined number of times, it is preferable to further include a notification unit that notifies the user to that effect.
In the antenna switching reception system according to the first aspect, it is preferable that preambles and unique words that are twice the number of mounted antennas are transmitted, and that each antenna is switched at a cycle that is twice the preamble and unique word transmission cycle. .
In the antenna switching reception system according to the first aspect, a reception level notification unit that detects a level of a received radio signal and notifies the user, and a switching function setting unit for the user to set the validity / invalidity of the antenna switching function. It is preferable to further provide.
In the antenna switching reception system according to the first aspect, a reception level detection unit that detects a level of a received radio signal, and an antenna switching function is disabled when the reception level detection unit detects a signal level that is equal to or higher than a predetermined second threshold. It is preferable to further include a switching function control unit.
In the antenna switching reception system according to the first aspect, when the switching function setting unit or the switching function control unit invalidates the antenna switching function, it is preferable to notify the corresponding transmission system to that effect.
In the antenna switching receiving system according to the first aspect, when the unique word cannot be detected continuously for the fourth predetermined time in a state where the antenna switching function is disabled, the switching function setting unit or the switching function control unit enables the antenna switching function. It is preferable to make it.
In the antenna switching reception system according to the first aspect, when the payload is successfully received, it is preferable to transmit an ACK to that effect to the corresponding transmission system.
In the antenna switching reception system according to the first aspect, it is preferable to periodically enable the antenna switching function even when the antenna switching function is disabled.
The antenna switching reception system according to the first aspect further includes an antenna switching reception system and a transmission unit that transmits a radio signal. When the transmission unit transmits a radio signal after receiving a payload, the antenna control unit A wireless communicator that uses an antenna selected during reception is preferred.
According to the second aspect of the present invention, in the antenna switching reception system that switches a plurality of antennas and receives a radio signal, before receiving the payload signal, the test signal is received and the payload signal is received by each antenna. An antenna switching receiving system is provided in which an antenna that selects an antenna and receives the test signal is switched based on an antenna switching timing detection signal detected before the test signal.
In the antenna switching reception system according to the second aspect, the antenna switching timing detection signals are configured by a specific sequence of signal sequences and transmitted, and are arranged in the same sequence as the transmitted antenna switching timing detection signals. And a correlation value calculation unit that calculates a correlation value of the signal sequence stored in the storage unit and the signal sequence of the received antenna switching timing detection signal, and the antenna It is preferable to detect the switching timing detection signal based on the correlation value calculated by the correlation value calculation unit.
In the antenna switching reception system according to the second aspect, it is preferable to detect the antenna switching timing detection signal transmitted at a lower transmission rate than the payload signal.
In the antenna switching reception system according to the second aspect, it is preferable that the antenna switching timing detection signal can be demodulated even in a saturated state without depending on the reception level.
The antenna switching reception system according to the second aspect includes a counter unit that counts time from a specific antenna switching reference timing to the next antenna switching reference timing, and detects the antenna switching reference timing based on the count value of the counter unit It is preferable.
In the antenna switching reception system according to the second aspect, the antenna switching timing detection signal is transmitted a plurality of times within one frame, and every predetermined period with a period not less than twice the length of the antenna switching timing detection signal. In addition, it is preferable to include an antenna periodic switching control unit for switching antennas.
In the antenna switching reception system according to the second aspect, it is preferable that the antenna switching timing detection signal is not detected for a predetermined period after the detection of the antenna switching timing detection signal.
In the antenna switching reception system according to the second aspect, it is preferable that the antenna switching timing detection signal is not detected for a predetermined period after the unique word signal is further detected after the antenna switching timing detection signal is detected.
The antenna switching reception system according to the second aspect includes a non-detection time counter unit that counts a time during which the antenna switching timing detection signal is not detected, and the non-detection time counter unit receives a predetermined value during reception by any antenna. When the time is counted, it is preferable to switch to another antenna.
In the antenna switching reception system according to the second aspect, the test signal is configured to be transmitted in a specific sequence of signal sequences, and the storage unit is a signal sequence in the same sequence as the test signals to be transmitted. Is further stored, and further includes a second correlation value calculation unit that calculates a correlation value between the signal sequence of the test signal stored in the storage unit and the signal sequence of the received test signal, and the second correlation value The calculation unit preferably receives the payload signal without performing antenna switching when detecting the test signal based on the calculated correlation value.
In the antenna switching reception system according to the second aspect, it is preferable that a plurality of the second correlation value calculation units are provided corresponding to the number of the test signals.
Advantageous Effects of Invention According to the first aspect of the present invention, the quality of received radio signals is compared while switching antennas at a predetermined period, and an antenna that receives a payload is selected. For this reason, even in an environment where multiple paths occur frequently, selection of an antenna that can obtain a high-quality received signal can be completed before receiving the payload of each packet for a signal that receives new packets one after another asynchronously. As a result, it is possible to avoid the occurrence of a reception error due to degradation of the reception level due to multipath fading.
Also, according to the second aspect of the present invention, before receiving a payload signal, the antenna that receives the test signal and receives the payload signal is selected by each antenna, so that the level fluctuation due to multipath fading can be achieved with a simple configuration. Can reduce the effects of As a result, even in a multipath environment, it is easy to avoid the occurrence of errors due to reception level degradation due to multipath fading.

The objects and features of the present invention will become apparent from the following drawings and description of preferred embodiments.
The block diagram which shows the structure of the antenna switching receiving system by 1st Embodiment of this invention. The flowchart which shows operation | movement of the antenna switching receiving system by the embodiment. The figure which shows the relationship between the signal transmitted from the corresponding transmission system, and the antenna switched by the antenna switching receiving system in the same embodiment. The block diagram which shows the structure of the modification of the antenna switching reception system by the said embodiment. The flowchart which shows operation | movement of the said modification. The block diagram which shows the structure of another modification of the antenna switching system by the said embodiment. The flowchart which shows operation | movement of the modification. The figure which shows an example of the relationship between the signal transmitted from the corresponding transmission system, and the antenna switched by an antenna switching receiving system in the modification. The figure which shows another example of the relationship between the signal transmitted from the corresponding transmission system, the antenna switched by an antenna switching receiving system, and the signal received by each antenna in the modification. The block diagram which shows the structure of another modification of the antenna switching system by the said embodiment. The flowchart which shows operation | movement of the modification. The block diagram which shows the structure of another modification of the antenna switching system by the said embodiment. The flowchart which shows operation | movement of the modification. The block diagram which shows the structure of another modification of the antenna switching reception system by the said embodiment. The flowchart which shows operation | movement of the modification. The figure which shows the relationship between the signal transmitted from the corresponding transmission system, the antenna switched by an antenna switching receiving system, and the signal received by each antenna in the modification. The block diagram which shows the structure of another modification of the antenna switching reception system by the said embodiment. The flowchart which shows operation | movement of the modification. The figure which shows an example of the relationship between the signal transmitted from the corresponding transmission system, the antenna switched by an antenna switching receiving system, and the signal received by each antenna in the modification. The block diagram which shows the structure of another modification of the antenna switching reception system by the said embodiment. The flowchart which shows operation | movement of the modification. The block diagram which shows the structure of another modification of the antenna switching reception system by the said embodiment. The flowchart which shows operation | movement of the modification. The figure which shows the relationship between the signal transmitted from a corresponding transmission system, the antenna switched by an antenna switching receiving system, and the signal received by each antenna in the structure which does not have the 2nd counter of the modification. The figure which shows the relationship between the signal transmitted from a corresponding transmission system, the antenna switched by an antenna switching receiving system, and the signal received by each antenna in the structure which has the 2nd counter of the modification. The block diagram which shows the structure of another modification of the antenna switching reception system by the said embodiment. The flowchart which shows operation | movement of the modification. The block diagram which shows the structure of another modification of the antenna switching reception system by the said embodiment. The flowchart which shows operation | movement of the modification. The figure which shows the relationship between the packet received by this modification, and 3rd predetermined time in regular communication. The figure which shows the relationship between the packet received by this modification, and 3rd predetermined time in non-periodic communication. The block diagram which shows the structure of another modification of the antenna switching reception system by the said embodiment. The flowchart which shows operation | movement of the modification. The figure which shows the relationship between the operation mode etc. of the packet received by this modification, and a receiving system. The block diagram which shows the structure of another modification of the antenna switching reception system by the said embodiment. The figure which shows the relationship between the packet received by this modification, and the antenna selected when receiving the packet. The block diagram which shows the structure of another modification of the antenna switching reception system by the said embodiment. The flowchart which shows operation | movement of the modification. The figure which shows the structure of the packet transmitted from the corresponding transmission system when the antenna switching function is validated and invalidated according to the same modification. The block diagram which shows the structure of another modification of the antenna switching reception system by the said embodiment. The flowchart which shows operation | movement of the modification. The example of the packet transmitted from the corresponding transmission system, and received by the receiving system in another modification of the antenna switching receiving system by the said embodiment. The example of the packet transmitted from the corresponding transmission system, and received by the receiving system in another modification of the antenna switching receiving system by the said embodiment. The figure which shows the outline of the radio | wireless communications system constructed | assembled applying the antenna switching receiving system of this invention. The figure which shows the relationship between the signal received and transmitted by the antenna switched by the radio | wireless machine in which an antenna switching receiving system is mounted in a radio | wireless communications system. The block diagram which shows schematic structure of the antenna switching receiving system by 2nd Embodiment of this invention. The figure which shows the operation | movement of the said antenna switching reception system when the signal received using two antennas and this signal are received in the same antenna switching reception system. The flowchart which shows operation | movement of the antenna switching reception system. The block diagram which shows schematic structure of the modification of the antenna switching reception system by the said embodiment. The figure which shows the operation | movement of the said antenna switching reception system when the signal received using two antennas and this signal are received in the modification. The flowchart which shows operation | movement of the modification. The figure which shows the operation | movement of the said antenna switching receiving system when receiving the signal received using two antennas in another modification of the same antenna switching receiving system, and this signal. The block diagram which shows schematic structure of another modification of the same antenna switching reception system. The figure which shows the relationship between the flame | frame received using two antennas, and a counter value in the modification. The figure which shows another relationship between the flame | frame received using two antennas, and a counter value in the modification. The flowchart which shows operation | movement of the modification. The block diagram which shows schematic structure of another modification of the same antenna switching reception system. The figure which shows the operation | movement of the said antenna switching reception system when the signal received using two antennas and this signal are received in the modification. The flowchart which shows operation | movement of the modification. The block diagram which shows schematic structure of another modification of the same antenna switching reception system. The figure which shows the operation | movement of the said antenna switching reception system when the signal received using two antennas and this signal are received in the modification. The flowchart which shows operation | movement of the modification. The block diagram which shows schematic structure of another modification of the same antenna switching reception system. The figure which shows the operation | movement of the said antenna switching reception system when the signal received using two antennas and this signal are received in the modification. The flowchart which shows operation | movement of the modification. The block diagram which shows schematic structure of another modification of the same antenna switching reception system. The figure which shows the operation | movement of the said antenna switching reception system when the signal received using two antennas and this signal are received in the modification. The flowchart which shows operation | movement of the modification.

Embodiments of the present invention will now be described in more detail with reference to the accompanying drawings, which form a part of this specification. The same or similar parts throughout the drawings are denoted by the same reference numerals, and the description thereof is omitted.
(First embodiment)
An antenna switching reception system according to a first embodiment of the present invention will be described with reference to the drawings. The antenna switching reception system is built in, for example, a switchboard having a wireless communication function. This type of switchboard receives instructions wirelessly transmitted from a monitor device operated by an administrator, and wirelessly transmits information such as power consumption. The monitor device that has received the information such as the power consumption transmitted from the switchboard displays the current or accumulated power consumption of the area where the power is distributed by the switchboard. The switchboard and the monitor device are provided with a wireless communication function so that the monitor device can be appropriately installed and moved according to the environment and the like.
In the present embodiment, the monitor device is provided with a single antenna, and the switchboard is provided with a plurality of antennas. The switchboard performs stable wireless communication with the monitor device while selecting and switching the antenna suitable for the surrounding environment by the antenna switching reception system.
FIG. 1 shows a configuration of an antenna switching reception system. The antenna switching reception system includes a receiver 01, a plurality of antennas 02, and the like. The receiver 01 includes an antenna switching unit 03, an RF unit 04, a baseband unit 05, and the like.
The antenna switching unit 03 switches the antenna that receives the radio signal among the two antennas A and B configuring the antenna 02. The RF unit 04 down-converts a radio signal received using the antenna A or B and extracts a baseband signal. The baseband unit 05 processes the baseband signal extracted by the RF unit 04.
The baseband unit 05 includes a demodulation unit 06, a synchronization establishment unit 07, a unique word setting unit 08, a unique word detection unit 09, an antenna control unit 10, and the like. The demodulator 06 demodulates the baseband signal extracted by the RF unit 04. The synchronization establishment unit 07 establishes bit synchronization of the demodulated baseband signal.
The unique word setting unit 08 presets and stores a bit string of a known unique word. A known unique word is shared with a corresponding transmission system, and a packet with this unique word is transmitted from the transmission system. The unique word detection unit 09 searches the demodulated baseband signal and detects a bit string of the unique word. The antenna control unit 10 controls antenna switching. That is, the antenna control unit 10 determines whether or not to switch the antenna based on the detection result of the bit string of the unique word by the unique word detection unit 09, and sends a control signal for switching the antenna to the antenna switching unit 03. Output. In the present embodiment, two antennas are switched by the antenna switching unit 03 to receive a radio signal, but the number of antennas may be three or more.
FIG. 2 shows the operation of the antenna switching reception system. FIG. 3 shows a relationship between a signal transmitted from the corresponding transmission system and an antenna switched by the antenna switching reception system. One packet is composed of a plurality of pairs of preambles and unique words followed by a payload that is transmitted subsequently.
The antenna switching reception system receives a radio signal transmitted from the transmission system (# 2) while switching the antennas A and B at a predetermined cycle (# 1). The received signal is down-converted by the RF unit 04 (# 3), demodulated by the demodulation unit 06 of the baseband unit 05 (# 4), bit synchronization is established by the synchronization establishment unit 07 (# 5), and unique word detection is performed. The unique word is detected by the unit 09 (# 6).
At this time, the preamble and the unique word are transmitted twice to each antenna so that the preamble and the unique word can be received even if the antennas A and B are switched at any timing. In this embodiment, since two antennas are used, the preamble and the unique word are transmitted four times each as shown in FIG. In this way, a preamble and unique word twice as many as the number of antennas mounted in the antenna switching reception system are transmitted, and each antenna is switched at a cycle twice the preamble and unique word transmission cycle.
In FIG. 3, the preamble transmitted for the first time cannot be received because the antenna was switched during reception, and the preamble or unique word transmitted for the second time was affected by multipath fading for antenna B. The case where it cannot receive by this is shown. In this case, since bit synchronization cannot be established, a unique word cannot be detected (NO loop is repeated in # 6). The preamble transmitted for the third time cannot be received because the antenna is switched during reception, and the preamble transmitted for the fourth time is received by the antenna A, bit synchronization is established, and a unique word is detected. . In this case, after passing through the NO loop in # 6, in the subsequent loop, through YES in # 6, the antenna is fixed to A (# 7), and the subsequent payload is received (# 8).
According to this antenna switching reception system, the quality of the received radio signal is compared while switching the antenna at a predetermined cycle, and the antenna that receives the payload is selected. For this reason, even in an environment where multipath occurs frequently, antenna selection can be completed before receiving the payload of each packet for a signal for receiving new packets one after another asynchronously. As a result, it is possible to avoid the occurrence of a reception error due to degradation of the reception level due to multipath fading.
(Modification)
FIG. 4 shows a configuration of a modified example of the antenna switching reception system according to the above embodiment. The system of this modified example further includes a threshold setting unit 11 with respect to the system shown in FIG. The threshold setting unit 11 sets a threshold relating to the degree of coincidence between the bit string of the unique word and the bit string of the received radio signal while switching the antennas A and B.
For example, when the unique word is composed of a 32-bit bit string, the bit string of the unique word and the bit string of the received wireless signal do not match by several bits due to an instantaneous change in the communication environment during reception of the unique word. There is. Even in such a case, if the communication environment is recovered before receiving the payload, the payload can be received without any problem. Therefore, in this modification, for example, when an error in the bit string of the received radio signal with respect to the bit string of the unique word is allowed up to 2 bits, the threshold is set to 30 bits. As a result, if the bit string of the unique word matches the bit string of the received radio signal by 30 bits or more, the unique word detection unit 09 determines that the unique word has been detected. As described above, the threshold value is set according to the allowable limit value of the number of errors in the bit string of the received radio signal with respect to the bit string of the unique word. More specifically, a value obtained by subtracting the number of bits of the allowable limit value from the number of bits of the unique word is set as the threshold value.
FIG. 5 shows the operation of the antenna switching reception system according to this modification. After bit synchronization is established by the synchronization establishment unit 07 (# 5), the unique word detection unit 09 compares the bit string of the unique word stored by the unique word setting unit 08 with the bit string of the received radio signal. At this time, when the number of bits equal to or greater than the threshold set by the threshold setting unit 11 matches (YES in # 9), the unique word detection unit 09 determines that a unique word has been detected, and proceeds to # 7. On the other hand, when the number of bits equal to or greater than the threshold set by the threshold setting unit 11 does not match (NO in # 9), the process returns to # 2.
According to this modified example, if the bit string of the unique word and the bit string of the received radio signal match by a threshold value or more, the unique word detection unit 09 determines that the unique word has been detected. This prevents momentary fluctuations in the communication environment during reception of the unique word, etc., and then avoids overlooking the received payload packet without problems when the communication environment recovers before receiving the payload. it can. The unique word detection operation in this modification can be applied to, for example, unique word detection in claim 2.
(Modification)
FIG. 6 shows a configuration of another modified example of the antenna switching reception system according to the above embodiment. In the system of this modification, a plurality of unique word detection units 12 is applied as one form of the unique word detection unit 09 in the system shown in FIG. Moreover, in this modification, the signal quality comparison part 13 which detects and compares the quality of the radio signal received for every antenna is further provided.
FIG. 7 shows the operation of the antenna switching reception system according to this modification. FIG. 8 shows an example of a relationship between a signal transmitted from a corresponding transmission system and an antenna switched by the antenna switching reception system. FIG. 9 shows another example of the relationship between the signal transmitted from the corresponding transmission system, the antenna switched by the antenna switching reception system, and the signal received by each antenna.
In this modification, a plurality of unique words consisting of different bit strings are transmitted from the corresponding transmission system in a specific order before the payload. A plurality of unique words that are the same as the plurality of unique words transmitted from the corresponding transmission system are preset and stored by the unique word setting unit 08. That is, in FIG. 9, each unique word (UW1 to UW4) is composed of different bit strings. In the case shown in FIG. 8, the unique words UW1 to UW3 may be the same and only the unique word UW4 may be different. The multiple unique word detection unit 12 individually detects the multiple unique words UW1 to UW4. Then, a different antenna selection operation is assigned to each unique word detected by the multiple unique word detection unit 12.
In FIG. 7, after bit synchronization is established by the synchronization establishment unit 07 (# 5), when any one of the unique words UW1 to UW3 is detected by the plural unique word detection unit 12, a preset operation is performed. (# 13 to # 32). This operation will be described later.
On the other hand, when the plural unique word detection unit 12 detects the unique word UW4 which is the last unique word (NO in # 13, # 22, and # 31, YES in # 12), the subsequent payload is received with the antenna fixed. (# 8). FIG. 8 shows a case where the unique word UW4 is received by the antenna A and the payload is received by the antenna A. On the other hand, when the plural unique word detection unit 12 does not detect the unique word UW4 which is the last unique word (NO in # 12), the process returns to # 2. In this way, in FIG. 8, it is only necessary to recognize that the last unique word UW4 has been detected in order to find the payload. Therefore, the unique words UW1 to UW3 may be the same and only the unique word UW4 may be different. .
Hereinafter, the operations of # 13 to # 32 will be described. When the unique word UW1 is searched and detected by the multiple unique word detection unit 12 (YES in # 13), the quality of the radio signal received by the signal quality comparison unit 13 is detected (# 14). That is, the signal quality of the unique word UW1 is detected. After switching the antenna (# 15), the multiple unique word detection unit 12 searches for the unique word UW2 (# 16), and when the unique word UW2 is detected (YES in # 17), the signal quality comparison unit 13 Detects the quality of the unique word UW2 (# 18). Furthermore, the signal quality comparison unit 13 compares the signal quality of the unique word UW1 and the unique word UW2 and selects the antenna that receives the payload. As an example of this case, FIG. 9 shows an operation in which the unique word UW1 received by the antenna A has better signal quality than the unique word UW2 received by the antenna B, and the antenna is switched again to receive the payload by the antenna A. It is shown.
After antenna switching, that is, if the signal quality of the unique word UW2 is good (NO in # 19), the unique word UW2 is fixed to the received antenna (# 20), and the process proceeds to # 12. On the other hand, before the antenna switching, that is, if the signal quality of the unique word UW1 is good (YES in # 19), the antenna is switched to the antenna that received the unique word UW1 (# 21), and the process proceeds to # 12. The reason why the unique word UW4 is received in # 12 is to find the payload.
When the unique word UW1 is not detected by the multiple unique word detection unit 12 (NO in # 13), the following operation is performed. When the next unique word UW2 is searched and detected by the multiple unique word detection unit 12 (YES in # 22), the quality of the radio signal received by the signal quality comparison unit 13 is detected (# 23). That is, the signal quality of the unique word UW2 is detected. After switching the antenna (# 24), the multiple unique word detection unit 12 searches for the unique word UW3 (# 25), and when the unique word UW3 is detected (YES in # 26), the signal quality comparison unit 13 Detects the quality of the unique word UW3 (# 27). Furthermore, the signal quality comparison unit 13 compares the signal qualities of the unique word UW2 and the unique word UW3 and selects the antenna that receives the payload.
After antenna switching, that is, if the signal quality of the unique word UW3 is good (NO in # 28), the unique word UW3 is fixed to the received antenna (# 29), and the process proceeds to # 12. On the other hand, before the antenna switching, that is, if the signal quality of the unique word UW2 is good (YES in # 28), the antenna is switched to the antenna that received the unique word UW2 (# 30), and the process proceeds to # 12.
When the unique word UW2 is not detected by the multiple unique word detection unit 12 (NO in # 22), the following operation is performed. When the unique word UW3 is searched and detected by the multiple unique word detection unit 12 (YES in # 31), the unique word UW3 is fixed to the antenna that received it (# 32), and the process proceeds to # 12. On the other hand, when the unique word UW3 is not detected by the multiple unique word detection unit 12 (NO in # 31), the process proceeds to # 12 without fixing the antenna (that is, with periodic antenna switching). Thus, when the unique word UW1 is detected, the signal quality comparison unit 13 compares the signal quality of the unique word UW1 and the unique word UW2, and when the unique word UW2 is detected, the unique word UW2 and the unique word UW3 are detected. Compare signal quality. However, when the unique words UW1 and UW2 cannot be detected by one antenna and the unique word UW3 or UW4 is detected by the other antenna, it is not meaningful to switch the antenna. Do not compare levels. Note that, in # 13 and # 22, the unique words UW1 and UW2 may not be detected due to the influence of instantaneous noise or the like. Therefore, when the unique word UW3 is detected by the multiple unique word detection unit 12 in # 31, the antenna is switched to detect the unique word UW4, and the signal quality of the unique word UW3 and the unique word UW4 is compared. Also good. In # 17, when the unique word UW2 cannot be detected, the unique word UW3 or UW4 may be detected, and the signal quality of the unique word UW1 and the unique word UW3 or UW4 may be compared. Similarly, when the unique word UW3 cannot be detected in # 26, the unique word UW4 may be detected and the signal quality of the unique word UW2 and the unique word UW4 may be compared.
In this modification, a plurality of unique words that are the same as the plurality of unique words stored in the unique word setting unit are transmitted in the same order before the payload, and the plurality of unique word detection units 12 UW1 to UW4 are detected individually. This makes it possible to assign different antenna selection operations for each detected unique word.
For example, when the last unique word UW4 immediately before the payload is detected, the subsequent payload can be received without switching the antenna. In addition, the signal quality comparison unit 13 compares the quality of signals received by the respective antennas, and the antenna control unit 10 selects an antenna that is determined to have higher signal quality and receives the payload. As a result, it is possible to receive a payload with an antenna that always obtains a higher quality received signal. When three or more antennas to be switched are provided, the signal quality comparison unit 13 compares the quality of the signal received by each antenna, selects the antenna that is determined to have the highest signal quality, and loads the payload. Receive.
(Modification)
FIG. 10 shows a configuration of still another modified example of the antenna switching reception system according to the above embodiment. The system of this modification applies a reception level comparison unit 14 as one form of the signal quality comparison unit 13 in the system shown in FIG. The reception level comparison unit 14 detects and compares the reception level of each antenna. The reception level of the antenna can be acquired by detecting, for example, RSSI (Received Signal Strength Indication).
FIG. 11 shows the operation of the antenna switching reception system according to this modification. After bit synchronization is established by the synchronization establishment unit 07 (# 5), when the unique word UW1 or UW2 is detected by the multiple unique word detection unit 12 (YES in # 33), the reception level comparison unit 14 determines the unique word. The reception level of the detected antenna is detected (# 34), and the antenna is switched (# 35). If the multiple unique word detection unit 12 cannot detect the unique word UW1 or UW2 (NO in # 33), the process returns to # 2. When the antenna is switched, the reception level comparison unit 14 detects the reception level of the switched antenna (# 36), and compares the reception level (# 37). As a result, if the reception level before the antenna switching is good (YES in # 37), the antenna is switched to the antenna that received the unique word UW1 or UW2 in # 33 (# 21), and the process proceeds to # 8. On the other hand, if the reception level after antenna switching is good (NO in # 37), the antenna is fixed without switching (# 20), and the process proceeds to # 8.
In this modification, since the reception level is compared after detecting the unique word UW1 or UW2, it is possible to eliminate the influence of interference waves transmitted from devices other than the corresponding transmission system. In addition, a wireless IC provided with an RSSI detection circuit can easily detect and compare the reception level, so there is no need for complicated control, development is facilitated, and the cost of the system can be reduced.
(Modification)
FIG. 12 shows a configuration of still another modified example of the antenna switching reception system according to the above embodiment. The system of this modification uses a unique word error number comparison unit 15 as one form of the signal quality comparison unit 13 in the system shown in FIG. The unique word error number comparison unit 15 compares the number of errors in the bit string of the radio signal received by each antenna with respect to the bit string of the unique word stored in the unique word setting unit. The number of errors is counted when the multiple unique word detection unit 12 detects a unique word.
FIG. 13 shows the operation of the antenna switching reception system according to this modification. After the bit synchronization is established by the synchronization establishment unit 07 (# 5), when the unique word UW1 or UW2 is detected by the multiple unique word detection unit 12 (YES in # 33), the unique word error number comparison unit 15 The number of unique word errors is detected and the antenna is switched (# 38). If the multiple unique word detection unit 12 cannot detect the unique word UW1 or UW2 (NO in # 33), the process returns to # 2.
When the unique word UW1 or UW2 is detected, the unique word error number comparison unit 15 detects the number of errors of the unique word in the switched antenna (# 39). Then, the unique word error number comparison unit 15 compares the number of unique word errors detected before and after the antenna switching (# 40). As a result, if the number of errors before antenna switching is smaller (YES in # 40), switching to the antenna that received unique word UW1 or UW2 in # 33 (# 21), and the process proceeds to # 8. On the other hand, if the number of errors after antenna switching is smaller (NO in # 40), the antenna is fixed without switching (# 20), and the process proceeds to # 8.
In this modification, since the antenna selection is performed based on the detection result of the number of errors in the bit string of the unique word, even if the reception level becomes high due to the influence of the interference wave from the transmission system other than the communication partner It is possible to prevent erroneous antenna selection.
(Modification)
FIG. 14 shows a configuration of still another modified example of the antenna switching reception system according to the above embodiment. The system of this modification uses a reception level comparison unit 14 and a unique word error number comparison unit 15 as one form of the signal quality comparison unit 13 in the system shown in FIG. The reception level comparison unit 14 detects and compares the reception level of each antenna. The reception level of the antenna can be acquired by detecting, for example, RSSI (Received Signal Strength Indication). The unique word error number comparison unit 15 compares the number of errors in the bit string of the radio signal received by each antenna with respect to the bit string of the unique word stored in the unique word setting unit. The number of errors is counted when the multiple unique word detection unit 12 detects a unique word.
FIG. 15 shows the operation of the antenna switching reception system according to this modification. FIG. 16 shows the relationship between the signal transmitted from the corresponding transmission system, the antenna switched by the antenna switching reception system, and the signal received by each antenna.
In FIG. 15, after the bit synchronization is established by the synchronization establishment unit 07 (# 5), when the unique word UW1 or UW2 is detected by the multiple unique word detection unit 12 (YES in # 33), the reception level comparison unit 14 Detects the reception level of the antenna that detected the unique word. Further, the unique word error number comparison unit 15 detects the number of unique word errors and switches the antenna (# 41). The number of errors detected here is equal to or less than the allowable limit value described in paragraph “0043” because the unique word UW1 or UW2 is detected in # 33. In FIG. 16, the unique word UW1 is received by the antenna A, the number of errors of the unique word UW1 and the reception level of the antenna A are detected, and the antenna B is switched to. If the multiple unique word detection unit 12 cannot detect the unique word UW1 or UW2 (NO in # 33), the process returns to # 2.
When the unique word UW1 or UW2 is detected, the unique word error number comparison unit 15 detects the number of unique word errors in the switched antenna, and the reception level comparison unit 14 detects the reception level of the switched antenna ( # 42). In FIG. 16, the unique word UW2 is received by the antenna B, and the number of errors of the unique word UW2 and the reception level of the antenna B are detected. Then, the number of errors detected in # 42 is compared with a predetermined allowable limit value by the unique word error number comparison unit 15, and if it is less than the allowable limit value (YES in # 43), the reception level comparison unit 14 determines the reception level. Are compared (# 37). In this case, the number of errors detected at # 41 and # 42 is both equal to or less than the allowable limit value.
As a result of the comparison of the reception levels, as shown in FIG. 16, before the antenna switching, that is, if the reception level of the unique word UW1 is good (YES in # 37), the antenna is switched to the antenna that received the unique word UW1 (# 21). ), Move to # 8. On the other hand, after antenna switching, that is, if the reception level of the unique word UW2 is good (NO in # 37), the unique word UW2 is fixed to the received antenna B (# 20), and the process proceeds to # 8.
When the unique word UW2 is first detected in # 33, the number of errors and the reception level of the unique word UW3 are detected after antenna switching (# 41) (# 42). Further, when the unique word UW3 or UW4 is detected first, antenna switching is not performed (not shown in FIG. 15).
By comparing the number of errors detected in # 41 and # 42, the probability that an antenna with high signal quality can be determined is not 100%, but it can be expected at a certain level of practically no problem. For example, even if the reception level of antenna A is sufficiently high and the reception level of antenna B is in the vicinity of the allowable limit, the same bit string received by antenna B with respect to the number of errors in the bit string of the unique word received by antenna A There is a probability that the number of errors is small. However, if the probability is low enough not to be a problem, if the number of errors is different, select an antenna with a small number of errors and select an antenna by comparing the reception level only when the number of errors is the same. You can also.
In this modification, the level of the radio signal received by a plurality of antennas and the number of errors in the bit string of the radio signal received by each antenna are compared, and the payload is received while being fixed to the optimum antenna. Thus, for example, when the reception level of one antenna is sufficiently high and the reception level of the other antenna is close to the allowable limit, no error occurs in the bit string of the unique word at the other antenna. Even in such a case, the correct antenna can be selected by comparing the reception levels. Even when the number of errors in the bit string of the radio signal received by each antenna is equal, the correct antenna can be selected by comparing the reception levels. In addition to the comparison of the reception level, the number of errors in the bit string of the unique word
Since the antenna selection is also performed in combination with the detection result, it is possible to prevent erroneous antenna selection due to the influence of the interference wave from the transmission system other than the communication partner.
(Modification)
FIG. 17 shows a configuration of still another modified example of the antenna switching reception system according to the above embodiment. In the system of this modification, a preamble / unique word error number comparison unit 16 is applied as one form of the signal quality comparison unit 13 in the system shown in FIG. The preamble / unique word error number comparison unit 16 compares the number of errors in the bit string of the radio signal received by each antenna with respect to the bit string of the preamble and the unique word. The number of errors is detected after the multiple unique word detection unit 12 detects a unique word and switches antennas.
FIG. 18 shows the operation of the antenna switching reception system according to this modification. After bit synchronization is established by the synchronization establishment unit 07 (# 5), when the unique word UW1 or UW2 is detected by the multiple unique word detection unit 12 (YES in # 33), the antenna is switched (# 35). Then, the preamble / unique word error number comparison unit 16 detects the number of errors including not only the next unique word but also the preamble immediately before the unique word (# 44). In FIG. 19, after the unique word UW1 is detected by the antenna A, the antenna is switched, and the number of errors in the preamble and the unique word UW2 is detected by the antenna B. Then, the antenna is further switched (# 45), and the preamble / unique word error number comparison unit 16 detects the number of errors of the next preamble and unique word (# 46) as in # 44. In FIG. 19, after switching to antenna A again, the number of errors in the preamble and unique word UW3 is detected. Furthermore, the preamble / unique word error number comparison unit 16 compares the number of preamble and unique word errors detected before and after antenna switching (# 47), and selects the antenna that receives the payload (# 20, # 21). . In FIG. 19, the number of preamble and unique word errors received by the antenna A is small, and the payload is received by being fixed to the antenna A.
In the example shown in FIG. 19, the unique word UW2 and the unique word UW3 are compared with each other including a pair of preambles for the following reason. That is, since the preamble that is paired with the unique word UW1 is not established in bit synchronization, it cannot be distinguished from “0” or “1” and cannot be used for comparison of the number of errors. When the unique word UW1 cannot be detected and the unique word UW2 is detected, the error numbers of the unique word UW3 and the unique word UW4 are compared with each other including the pair of preambles. When the unique word UW3 or UW4 is detected, antenna switching is not performed. In FIG. 19, after the unique word UW1 is detected by the antenna A, the number of errors in the preamble and the unique word UW2 is subsequently detected, and after switching to the antenna B, the number of errors in the preamble and the unique word UW3 is detected. May be.
In this modification, the number of errors in the bit sequence of the radio signal received by each antenna with respect to the known bit sequence of the preamble and unique word is compared, and the payload with the smallest number of errors is selected and fixed. For this reason, the number of bits used for antenna selection increases, and the accuracy of antenna selection determination can be further improved. For example, when the preamble bit string is 128 bits and the unique word bit string is 32 bits, it is possible to detect the number of errors with respect to the total 160 bits and perform antenna selection, thereby enabling more accurate determination. Become.
(Modification)
FIG. 20 shows a configuration of still another modified example of the antenna switching reception system according to the above embodiment. The system of this modification uses a unique word error number comparison unit 15 as one form of the signal quality comparison unit 13 in the system shown in FIG. Further, in this modification, a first counter 17 is further provided. The first counter 17 has a first predetermined time corresponding to the reception interval of the unique words at both ends of the preamble (after detecting a unique word in one packet, until the beginning of the next unique word is received). Time).
In FIG. 3, FIG. 8, FIG. 9, FIG. 16 and FIG. 19, etc., since the bit strings constituting each preamble are the same, the number of bits is the same, so that each unique word is at the same time interval. Sent from the corresponding transmission system. Therefore, after detecting a unique word, the first counter 17 counts the preamble transmission time, that is, the first predetermined time corresponding to the reception interval of the unique word, so that the next unique word can be found. it can.
FIG. 21 shows the operation of the antenna switching reception system according to this modification. When the unique word UW1 or UW2 is detected by the multiple unique word detection unit 12 (YES in # 33), the unique word error number comparison unit 15 detects the number of unique word errors and switches the antenna (# 38). The first counter 17 starts and continues counting (NO in # 48, # 49, and # 50), and counts the first predetermined time corresponding to the preamble transmission time (YES in # 50). Is considered to have started receiving unique words. Accordingly, the plural unique word detection unit 12 detects a unique word, and the unique word error number comparison unit 15 detects the number of errors of the unique word (# 51).
If the number of errors after antenna switching is small (NO in # 40), the antenna is switched to the antenna after switching (# 20), and the process proceeds to # 8. If the number of errors before antenna switching is small (YES in # 40), the antenna is switched again (# 21), and the process proceeds to # 8.
In this modification, the first counter 17 counts from the timing when the unique word is detected by one antenna to the timing when the unique word for comparison is detected by the other antenna. Then, the unique word error number comparison unit 15 regards the bit string starting from that timing as the bit string of the next unique word and detects the error number of the unique word. As a result, because the reception level of the other antenna is low, or due to the influence of sudden noise, etc., bit synchronization cannot be established in the next preamble, or the unique word is at the same level as the noise. Even in this case, the unique word is detected from the signal received by the other antenna, and the number of errors can be detected.
(Modification)
FIG. 22 shows a configuration of still another modified example of the antenna switching reception system according to the above embodiment. The system of this modification uses a unique word error number comparison unit 15 as one form of the signal quality comparison unit 13 in the system shown in FIG. Further, in this modification, a second counter 18 is further provided. The second counter 18 counts the second predetermined time after switching the antenna. Here, the second predetermined time counted by the second counter 18 is a time required for at least the transmission system corresponding to the transmission of the bit string constituting the unique word.
FIG. 23 shows the operation of the antenna switching reception system according to this modification. FIG. 24 shows the relationship between the signal transmitted from the corresponding transmission system, the antenna switched by the antenna switching reception system, and the signal received by each antenna in the configuration without the second counter 18 of the present modification. Indicates. FIG. 25 shows the relationship between the signal transmitted from the corresponding transmission system, the antenna switched by the antenna switching reception system, and the signal received by each antenna in the configuration having the second counter 18 of the present modification. Show.
As shown in FIG. 24, when the receiving antenna is switched from the antenna A having good reception state to the antenna B being affected by fading at the timing T1 of the remaining several bits (for example, 1 bit) of the unique word UW1. Is assumed. Here, it is assumed that the reception state of the antenna A is good before the timing T1, and the number of errors of the unique word UW1 is less than the allowable limit value described above. Originally, since antenna B is affected by fading, the remaining number of bits of unique word UW1 should not be detected, but if it is the remaining number of bits, the unique word stored in unique word setting unit 08 There is a possibility of coincidence. At this time, the unique word detection unit 09 determines that the unique word UW1 has been detected from the signal received by the antenna B that has received the “tail” of the unique word UW1. After that, the unique word UW2 is detected after switching to the antenna A at T2, but if an error of several bits or more occurs in this process, the antenna control unit 10 uses the antenna as an antenna for receiving the payload. B will be selected by mistake. However, since the antenna B is affected by fading as described above, an error occurs in receiving the payload.
The occurrence of the above problem is also caused by the unique word detection unit 09 determining that the unique word has been received by the antenna that has received the “tail” of a unique word. However, even if the unique word detection unit 09 determines that the unique word has been received by the antenna that has received the "head" of a unique word, the same problem occurs depending on the antenna switching timing.
Therefore, in this modification, after switching the antenna, until the second counter 18 counts a predetermined time, the unique word is not detected (the unique word detection result is invalidated), thereby Prevent the occurrence of defects.
That is, in FIG. 23, when the antenna is switched in # 1, after resetting the second counter (# 52), the process proceeds to # 2 while starting / continuing counting (# 53) and receives a radio signal. Then, after down-conversion, demodulation, and synchronization establishment operations (# 3 to # 5), if the count value of the second counter matches the number of unique word bits (YES in # 53-2), the process proceeds to # 13 To do. Thereafter, the operations of # 13 to # 32 are the same as those in FIG. 7. However, in this modification, when comparing the signal quality in # 19 and # 28, # 14, # 18, # The number of errors of the unique word detected in 23 and # 27 is applied. When the unique word UW4 is detected in # 12 (YES in # 12), the payload is received by the antenna (# 8). When the unique word UW4 is not detected, the loop of # 2 to # 53 is repeated until the predetermined period comes (NO in # 53). When the predetermined period arrives (NO in # 12, YES in # 53-3), the process returns to # 1, switches the antenna, and repeats the loops # 1 to # 53. Thus, the unique word UW4 is detected and the payload is received (# 8). Note that the predetermined cycle in # 53-3 is the same as the predetermined cycle in # 1, and is a cycle twice the preamble and unique word transmission cycle.
In this modification, as shown in FIG. 25, even when the antenna A that is in a good reception state is switched to the antenna B that is affected by fading at the timing T1, the second counter 18 is set to the second predetermined time. Until the word is counted, the unique word is not detected. Thereby, since the unique word UW1 is not detected by the antenna B, the problem shown in FIG. 24 does not occur. Thereafter, the unique words UW2 and UW3 are not detected by the antenna B affected by fading. Then, during the reception of the unique word UW3, when a predetermined period of switching antenna # 53 # 3 arrives and the antenna is switched, the unique word UW4 is detected by the antenna A, and the payload can be received.
In this modification, after the antenna is switched, the unique word is not detected until the second predetermined time corresponding to the time required for transmitting the bit string constituting the unique word is counted by the second counter 18. It is configured. As a result, even if it encounters when switching to the other antenna at the timing immediately before the remaining several bits are detected by one antenna, the other antenna is erroneously judged to be in a better reception state, and the antenna selection is incorrect. Can be avoided.
(Modification)
FIG. 26 shows a configuration of a modified example of the antenna switching reception system according to the embodiment. The system of this modification further includes a packet end detection unit 19 with respect to the system shown in FIG. The packet end detection unit 19 detects the end of the packet. The end of the packet can be known, for example, by detecting a packet end signal attached to the end of the payload. Further, when the packet length (or the data length of the payload) is known to the receiving system, the end of the packet may be detected by counting the time corresponding to the packet length with a counter.
FIG. 27 shows the operation of the antenna switching reception system according to this modification. When the reception of the payload is started in # 8, the reception of the payload is continued until the packet end is detected (NO in # 54). When the packet end is detected (YES in # 54), the process returns to # 1, and the antenna control unit 10 automatically returns to the control for switching the antenna at a predetermined period, and receives the next packet.
In this modification, after completion of payload reception is detected by detecting a packet end, the process automatically switches to periodic antenna switching and returns to the search for a unique word. For this reason, even when the transmission system and the reception system are asynchronous and new packets transmitted one after another from the transmission system are received, it is possible to return to the antenna switching operation and appropriately cope with it.
(Modification)
FIG. 28 shows a configuration of a modified example of the antenna switching reception system according to the above embodiment. The system of this modification further includes a unique word error number comparison unit 15 and a third counter 20 with respect to the system shown in FIG. The third counter 20 counts the third predetermined time after detecting the last unique word (immediately before the payload) in the packet being received by the multiple unique word detector 12.
Since the data included in the payload is arbitrary, it is rare that the bit string of the payload matches the bit string of the unique word. Therefore, in this modified example, the detection of the unique word is not performed for the third predetermined time during the reception of the payload, or it is invalidated even if it is detected, thereby preventing erroneous detection.
FIG. 29 shows the operation of the antenna switching reception system according to this modification. When the multiple unique word detector 12 detects the last unique word (YES in # 55), the third counter 20 starts counting (# 55-2). Then, after passing through # 7 and # 8, no unique word is detected during the counting of the third counter 20 (NO loop in # 55, # 7, # 8, and # 56). When the third counter 20 counts the third predetermined time (YES in # 56), the third counter 20 stops counting, resets the count value, and returns to # 1.
30 and 31 show the relationship between the packet received according to this modification and the third predetermined time. 30 shows regular communication, and FIG. 31 shows non-periodic communication. For example, when the packet reception interval is known in the regular communication, the third predetermined time is a time from when a unique word of a packet is received to immediately before the next packet is received. In addition, when the packet reception interval is unknown in the non-periodic communication shown in FIG. 31, after receiving a unique word of a packet, the time during which the payload in the packet is received can be set as the third predetermined time. . In this case, when the data length of the payload is known, the time corresponding to the data length is set as the third predetermined time. In addition, when the data length of the payload is unknown, the above-described packet end detection unit 19 may detect the packet end signal instead of the third counter 20 counting the third predetermined time. The multiple unique word detection unit 12 detects any specific unique word instead of detecting the last unique word, and counts a third predetermined time including the time from there to the beginning of the payload in the packet. It may be a configuration.
In the present modification, since the unique word is not detected for the third predetermined time after the unique word is detected, it is possible to avoid erroneously detecting the bit string in the payload as the unique word. Is possible. In addition, when the communication interval is known in periodic communication, the unique word is not detected even when there is no received signal, so when there is no transmission from the corresponding transmission system, the noise is Can be prevented from being erroneously detected.
(Modification)
FIG. 32 shows a configuration of a modified example of the antenna switching reception system according to the embodiment. The system of this modification further includes a reception level detection unit 21 with respect to the system shown in FIG. The reception level detection unit 21 detects the level of the radio signal received via any one of the antennas.
In the present modification, the reception system has two operation modes: a “low consumption mode” and a normal “diversity reception mode”. In the “low consumption mode”, the antenna switching unit 03, the RF unit 04, the antenna control unit 10, and the reception level detection unit 21 operate in the same manner as in the normal “diversity reception mode”, and other blocks sleep with low power consumption. Wait in state. In the “low consumption mode”, when the reception level detection unit 21 detects a signal level equal to or higher than a predetermined first threshold, the reception system shifts to a normal “diversity reception mode”. On the other hand, in the normal “diversity reception mode”, when the reception level detection unit 21 does not detect a signal level equal to or higher than a predetermined threshold for a predetermined period, the mode shifts to the “low consumption mode”. In addition, for example, in a communication system in which regular communication is performed once per hour, the configuration may be such that after the regular communication ends, the mode automatically shifts to the “low consumption mode”.
FIG. 33 shows the operation of the antenna switching reception system according to this modification. FIG. 34 shows the relationship between received packets and operation mode switching. In FIG. 33, even when the reception system is operating in the “low-consumption mode” (# 58), a control signal for antenna switching is output from the antenna control unit 10 to the antenna switching unit 03, and the antenna is set to a predetermined level. The cycle is switched (# 1). If the antenna is fixed during standby in “low-consumption mode”, if it is affected by fading, the reception level at that antenna may be kept low, and it may not be possible to switch to “diversity reception mode”. There is. Therefore, in the present modification, the antenna is switched at a predetermined cycle even when operating in the low consumption mode so that it is not affected even if fading occurs during standby in the “low consumption mode” (see FIG. 34). ).
If the reception level detection unit 21 detects a signal level equal to or higher than the predetermined first threshold shown in FIG. 34 during operation in the “low consumption mode” (YES in # 59), the reception system is in the normal “diversity reception mode”. , And the operations after # 3 are executed.
In the present modification, the reception system stands by in the “low consumption mode” until the reception level becomes equal to or higher than the first threshold value, so that the current consumption of the system can be reduced. Even in the “low consumption mode”, since the antenna is switched at a predetermined cycle, a radio signal having a reception level equal to or higher than the first threshold can be detected without being affected by fading, and “diversity reception” It can shift to "mode".
(Modification)
FIG. 35 shows a configuration of a modified example of the antenna switching reception system according to the above embodiment. The system of this modified example further includes a selected antenna storage unit 22 and a notification unit 23 with respect to the system shown in FIG. The selected antenna storage unit 22 stores the antenna selected by the antenna control unit 10 when receiving the payload. The notification unit 23 notifies the user (including the administrator of the reception system) of information related to the antenna using voice or light.
FIG. 36 shows the relationship between a packet received according to this modification and the antenna selected when the packet is received. As shown in FIG. 36, information related to the antenna (antenna A in FIG. 36) selected by the antenna control unit 10 when receiving the payload of the packet is stored in the selected antenna storage unit 22. The notification unit 23 refers to the selected antenna storage unit 22 and notifies the user to that effect when any one of the antennas is selected continuously for a predetermined number of times or more. In the case shown in FIG. 36, notification that the antenna A is continuously selected is made. Further, the notification may be made that only one antenna is continuously selected without specifying the selected antenna.
In this modification, when a payload is received continuously using any one of the antennas a predetermined number of times or more, the user is notified of that fact. For this reason, the user can know that there is no diversity effect or one of the antennas is broken, and the device can be moved to a place where the diversity effect is high, or the antenna etc. can be repaired. It becomes possible.
(Modification)
FIG. 37 shows a configuration of a modified example of the antenna switching reception system according to the embodiment. The system of this modification further includes a reception level notification unit 24 and a diversity on / off switching unit (switching function setting unit) 24, compared to the system shown in FIG. The reception level notification unit 24 detects the level of the received radio signal and notifies the user using voice or light. This notification may be performed as necessary, or may be performed in response to a request from the user. Diversity on / off switching unit 24 2 is provided for the user to manually set the antenna switching function on (valid) / off (invalid). The user can manually set the diversity, that is, the validity / invalidity of the antenna switching function by checking the notification output from the reception level notification unit 24 and operating the diversity on / off switching unit 2 2 as necessary. .
FIG. 38 shows the operation of the antenna switching reception system according to this modification. First, the reception level notifying unit 24 detects the level of the received radio signal and notifies the user using voice or light (# 60). When the diversity on / off switching unit 24 2 is operated by the user who knows the reception level by this notification and the diversity function is turned off (NO in # 60-2), a radio signal is received with the antenna fixed. (# 61). On the other hand, when the diversity function is turned on by the user (YES in # 60-2), a radio signal is received while switching the antenna at a constant cycle (after # 1).
FIG. 39 shows a configuration of a packet transmitted from a corresponding transmission system when the antenna switching function is enabled and disabled. When the antenna switching function is enabled, a unique word twice as many as the number of antennas and a pair of preambles are attached and transmitted. On the other hand, when the antenna switching function is disabled, it is sufficient if a single preamble and a unique word are attached. As a result, the packet length is shortened and transmission efficiency is improved. In this modification, the transmission function is added to the reception system, and the reception function is added to the corresponding transmission system, so that the transmission system can be notified and recognized of the validity / invalidity of the antenna switching function.
In this modification, since the reception level notification unit 24 is provided, the user can monitor the reception level from the outside of the reception system and can manually set the validity / invalidity of the antenna switching function. For this reason, for example, in a communication environment where the reception level is sufficiently high, the antenna switching function can be disabled and power consumption can be reduced. At this time, by notifying the corresponding transmission system that the antenna switching function is disabled and recognizing it, the transmission system attaches a single preamble and unique word to each packet as shown in FIG. Just send it. Therefore, the number of buckets that can be transmitted per unit time is increased, and the transmission efficiency can be improved. This also shortens the reception time by the reception system, which can contribute to further lower power consumption of the reception system. The notification that the antenna switching function is invalidated is realized by a configuration corresponding to, for example, a radio device 100 and a radio device 200 described later. In addition, if there is a concern that the communication environment may be affected by a large change in the surrounding environment, such as the placement of obstacles, even in a communication environment where the reception level is sufficiently high, the antenna switching function emphasizes communication reliability. It is possible to select according to the purpose, such as setting the item to be valid.
(Modification)
FIG. 40 shows a configuration of a modified example of the antenna switching reception system according to the embodiment. The system according to this modification further includes a reception level detection unit 21 and a diversity on / off control unit (switching function control unit) 25 with respect to the system shown in FIG. The reception level detection unit 21 detects the level of the radio signal received via any one of the antennas, similar to that shown in FIG. The diversity on / off control unit 25 automatically disables the antenna switching function based on the reception level detected by the reception level detection unit 21. That is, when the reception level detection unit 21 detects a signal level that is sufficient to receive a radio signal without switching the antenna and is equal to or higher than a predetermined second threshold, the diversity on / off control unit 25 has an antenna switching function. Is automatically disabled.
FIG. 41 shows the operation of the antenna switching reception system according to this modification. While switching the antennas A and B at a predetermined period (# 1), a radio signal transmitted from the transmission system is received (# 2), and the reception level detection unit 21 detects the level of the received radio signal. When a signal level equal to or higher than the second threshold is detected (YES in # 62), the transmission system is notified that the antenna switching function is invalidated until the next packet is received (# 63). It is automatically disabled (# 64), and the next packet is received with the antenna fixed (# 65). As shown in FIG. 39, the transmission system that has received the notification transmits a single preamble and a unique word UW attached to each packet to increase transmission efficiency. On the other hand, when a signal level equal to or higher than the second threshold is not detected, the process proceeds to # 3 and after while the antenna switching function is maintained effectively. In the above description, only level detection is performed. However, for example, level detection may be performed after UW is detected or after it is determined that a signal is to be received, thereby improving the reliability during level detection.
In this modification, when the reception level detection unit 21 detects a signal level that is sufficient to receive a radio signal without switching the antenna, the diversity level on / off control unit 25 Disable the switching function automatically. As a result, when a good communication environment is obtained, it is possible to automatically reduce power consumption without the user being aware of it. Further, the corresponding transmission system may transmit a single preamble and a unique word UW attached to each packet. Therefore, transmission efficiency can be improved.
(Modification)
In the modified example of the antenna switching reception system shown in FIG. 37 or 40, when the unique word cannot be detected continuously for the fourth predetermined time in the state where the antenna switching function is disabled, the switching function control unit enables the antenna switching function. You may comprise so that it may become. In this case, even when a change occurs in the communication environment due to an obstacle or a change in the layout of the transmission system or the reception system, the antenna switching function automatically returns to an effective state, so that it can be handled.
Furthermore, when the payload is successfully received, it can be modified to transmit an ACK to that effect to the corresponding transmission system. In this case, if the transmission system cannot receive the ACK continuously for a predetermined time, it can know that the reception system has failed to receive the payload.
At this time, as shown in FIG. 42, when the transmission system shortens the data length by using a single preamble and unique word UW, it transmits a preamble and unique word UW twice the number of antennas. Switch. As a result, the reception system can automatically and effectively function the antenna switching function, and the occurrence of a reception error due to deterioration of the reception level due to multipath fading can be restored again to an avoidable state. It becomes like this. Note that the transmission of ACK is realized by, for example, a configuration corresponding to a radio device 100 and a radio device 200 described later.
(Modification)
Further, in the modification example of the antenna switching reception system shown in FIG. 37 or FIG. 40, even when the antenna switching function is disabled, the antenna switching function is periodically switched to be enabled effectively. Also good.
In this case, as shown in FIG. 43, the reception system performs reception by periodically enabling the antenna switching function every predetermined period, and otherwise, the receiving system is fixed to the antenna selected by the most recent antenna switching operation. Receive. In the figure, after fixing to one of the antennas in the packet 1, the antenna switching function is disabled and the antenna is fixed until the reception of the packet P is completed, and the antenna is received before receiving the preamble of the next packet P + 1. Enable the switching function. By repeating this operation, it is possible to reduce power consumption compared to the case where the antenna switching function is always used, and the antenna is periodically selected by periodic diversity communication. It becomes possible to follow.
(Example of communication system construction)
FIG. 44 shows an outline of a wireless communication system constructed by applying the antenna switching reception system of the present invention. FIG. 45 shows a relationship between an antenna switched by a radio device in which an antenna switching reception system is mounted and a signal received and transmitted by each antenna in a wireless communication system.
The wireless communication system includes a wireless device 100, a wireless device (wireless communication device) 200, and the like. The radio device 100 is built in, for example, a monitor device. The radio device 200 is built in, for example, a switchboard. In the radio device 200, the antenna switching reception system of the present invention is mounted together with two antennas A and B. The corresponding transmission system is wireless with one antenna
It is mounted on the container 100. Since the wireless device 100 and the wireless device 200 perform bidirectional communication, a transmission system and a reception system are mounted, respectively.
Communication between the two is started by transmitting a wireless signal from the wireless device 100 to the wireless device 200, and the wireless signal is returned from the wireless device 200 to the wireless device 100. At this time, the radio device 200 selects an antenna suitable for the communication environment by the switching diversity function using the two antennas A and B, and receives the payload of the radio signal. Further, when a radio signal is transmitted from the radio device 200 to the radio device 100, the antenna selected at the time of reception of the immediately preceding (last) payload is used. For example, in FIG. 45, a radio signal is transmitted from the radio device 200 to the radio device 100 using the antenna A that was selected when the payload was received. The radio device 100 that receives this radio signal is not provided with a diversity function. However, by effectively utilizing the diversity function provided in the radio device 200, a communication environment between the radio device 100 and the radio device 200 is obtained. It is possible to receive a high-quality wireless signal that matches the above.
In selecting an antenna to be used when transmitting from the radio device 200, an antenna that has received a larger number of packet payloads may be selected statistically during a past specific or unspecified period.
According to the construction example of this communication system, the antenna selected at the time of reception is used for the reply after receiving by making use of the diversity function provided in the radio device 200. Thus, when communication is started by transmission from the wireless device 100, only the other wireless device 200 is provided with a plurality of antennas and has a diversity function, and both transmission and reception are performed during bidirectional communication between the two devices. Diversity effects can be obtained.
Further, when transmitting using the diversity function provided in the wireless device 200, it is necessary to transmit the number of times corresponding to the number of antennas. However, according to the construction example of this communication system, since the antenna to be used for transmission has already been determined, it is only necessary to transmit once using that antenna. Therefore, the transmission time can be shortened and the power consumption of the wireless device 200 can be reduced.
The present invention is not limited to the configuration of the above embodiment. It is only necessary to compare the quality of the received radio signal while switching the antenna at least at a predetermined cycle and select an antenna that receives the payload. The present invention can be variously modified. For example, the antenna switching reception system is not limited to the switchboard, and can be widely applied to various electrical appliances such as a lighting control switch having a wireless communication function. Further, the antenna switching reception system may be constructed by appropriately combining the configurations of the respective modifications. For example, in the modification example shown in FIG. 20, the reception level comparison unit 14 shown in FIG. 14 is further provided to compare the radio signal level and the number of errors in the bit string, and fix the payload to the optimum antenna. You may comprise so that it may receive. In addition, the reception level comparison unit 14 may be provided instead of the unique word error number comparison unit 15 to compare the radio signal levels, and fix the antenna to an optimum antenna to receive the payload.
(Second Embodiment)
An antenna switching reception system according to a second embodiment of the present invention will be described with reference to the drawings. FIG. 46 shows a schematic configuration of the antenna switching reception system. The antenna switching reception system 110 includes an antenna unit 111 having two antennas, an antenna switching unit 112, an antenna switching timing detection unit 113, an antenna switching determination unit 114, and the like. The antenna switching unit 112 switches from two antennas to one of the antennas. The antenna switching timing detection unit 113 detects the timing at which the antenna switching unit 112 switches antennas, for example, by detecting a signal of a predetermined level or higher. The antenna switching determination unit 114 selects the antenna that receives the payload signal based on the RSSI (Received Signal Strength) of the signal received by any one of the antennas via the antenna switching unit 112, and sends a control signal to that effect. Output to the antenna switching unit 112. In the following, a case where there are two antennas connected to the antenna switching unit 112 will be described. However, three or more antennas may be used.
FIG. 47 shows signals received using two antennas, that is, antenna A and antenna B, in antenna switching reception system 110, and the operation of antenna switching reception system 110 when these signals are received. In particular, an example in which the antenna A is initially selected and the test 1 signal is received by the antenna A is shown. FIG. 48 is a flowchart showing the operation of the antenna switching reception system 110 of FIG.
The signal shown in FIG. 47 is transmitted from a transmission system corresponding to the antenna switching reception system 110 of the present embodiment. At least a test 1 signal, a test 2 signal, and a payload signal are transmitted from the transmission system. One frame is composed of the test 1 signal, the test 2 signal, and the payload signal. A unique word signal (not shown) for frame synchronization is transmitted before the payload signal.
The test 1 signal and test 2 signal are used to select the antenna that receives the payload signal. The test 1 signal is received by the initially selected antenna, and the test 2 signal is received by the switched antenna. This test signal is added as appropriate according to the number of antennas switched by the antenna switching unit 112. The payload signal includes, for example, various data such as a header, video, audio, air temperature, a known signal sequence for the equalizer to estimate the multipath environment, or various control signals.
The operation of the antenna switching reception system 110 according to the second embodiment will be described with reference to FIGS. The antenna switching receiving system 110 is initially waiting (# 101). When the antenna unit 111 of the antenna switching reception system 110 receives the signal (# 102) and the antenna switching timing detection unit 113 detects the antenna switching timing (YES in # 103), the antenna switching determination unit 114 detects the antenna A. The reception level is detected (# 104). Here, the detection of the reception level is not limited to that based on RSSI, but may be based on the amplification factor when the received signal is amplified by the automatic gain control circuit. Then, the antenna switching determination unit 114 switches to the antenna B (# 105) and detects the reception level of the antenna B (# 106). The antenna switching is performed based on the antenna switching timing detected by the antenna switching timing detection unit 113. Thereafter, the antenna switching determination unit 114 compares the reception level of the antenna A with the reception level of the antenna B (# 107). When the reception level of antenna A is higher (YES in # 108), antenna switching determination unit 114 selects antenna A as an antenna for receiving the payload signal. That is, the antenna switching determination unit 114 outputs a control signal for switching to the antenna A to the antenna switching unit 112 (# 109), and receives a payload signal by the antenna A (# 110). The example shown in FIG. 47 corresponds to this case. When the reception level of antenna B is higher (NO in # 108), antenna B is selected as the antenna for receiving the payload signal. That is, the antenna switching determination unit 114 receives the payload signal by the antenna B while being fixed to the antenna B (# 111). When the reception level of antenna A is the same as the reception level of antenna B, the payload signal is received by antenna B that last received the test signal (# 111).
It should be noted that the antenna selection may be made not by comparing the reception level but by indicating signal quality such as the number of bit errors.
According to this antenna switching reception system 110, before receiving the payload signal, the antenna that receives the test signal and receives the payload signal is selected by each antenna, and therefore the influence of level fluctuations due to multipath fading with a simple configuration Can be reduced. Thereby, even in a multipath environment, it is possible to avoid the occurrence of errors due to reception level deterioration due to multipath fading. Further, near real-time transmission can be realized by reducing the number of retransmissions. Further, when retransmission is unnecessary, it is possible to eliminate the retransmission function and contribute to cost reduction and size reduction.
(Modification)
FIG. 49 shows a schematic configuration of a modified example of the antenna switching reception system 110 of the second embodiment. In this antenna switching reception system 110, a correlation value calculation unit 115 is applied as an example of the antenna switching timing detection unit 113 in FIG. The transmission system transmits an antenna switching timing detection signal composed of a specific sequence of signal strings before the test 1 signal. The antenna switching timing detection signal is a signal for detecting a reference timing for switching the antenna to be used to the antenna A or the antenna B when receiving the test 1 signal and the test 2 signal. The antenna switching timing detection signal may be transmitted at a transmission rate lower than the transmission rate of the payload signal, and may include a bit synchronization preamble before that. The correlation value calculation unit (storage unit) 115 stores a signal sequence (reference signal) in the same sequence as the antenna switching timing detection signal transmitted from the transmission system. Examples of the signal sequence include a random signal such as 01100101011000101..., A bit sequence far from the sequence of fixed bit sequences in the payload, an M sequence having excellent correlation characteristics, and a similar signal sequence. The correlation value calculation unit 115 calculates a correlation value between the stored signal sequence and the signal sequence of the received antenna switching timing detection signal. In this modification, the antenna switching timing detection signal is detected based on the correlation value calculated by the correlation value calculation unit 115.
FIG. 50 shows a signal received using the antenna A and the antenna B in the antenna switching reception system 110 of the present modification, and an operation of the antenna switching reception system 110 when receiving this signal. FIG. 51 is a flowchart showing the operation of the antenna switching reception system 110 of this modification. In this modification, # 112 is executed instead of the process of # 103 shown in FIG.
An antenna switching timing detection signal, a test 1 signal, a test 2 signal, and a payload signal are transmitted from the transmission system. Of the antenna switching timing detection signal, the test 1 signal, the test 2 signal, and the payload signal constituting one frame, the antenna switching timing detection signal is transmitted at a lower transmission rate than other signals. A signal received via any one of the antennas is compared with a reference signal stored by the correlation value calculation unit 115 while shifting by one sample (1 bit in this modification), and the degree of coincidence is sequentially digitized. A correlation value is calculated. If the degree of coincidence is equal to or greater than a predetermined threshold, it is determined that an antenna switching timing detection signal has been detected (YES in # 112), and antenna switching determination unit 114 detects the reception level of antenna A (# 104). The subsequent processing is the same as that shown in FIG.
According to this antenna switching reception system 110, the antenna switching timing is detected by correlation value detection, so that the antenna switching timing detection signal and the noise can be more clearly distinguished, and the resistance to noise is enhanced. Is possible. In addition, since antenna switching can be determined at any location simply by inserting the signal sequence of the antenna switching timing detection signal at the location where antenna switching is desired, the degree of freedom in frame configuration can be increased.
In addition, since the antenna switching timing detection signal transmitted at a lower transmission rate than the payload signal is received, the influence of intersymbol interference due to multipath is avoided and the signal energy per bit increases. High sensitivity. Therefore, even when an antenna affected by reception level deterioration caused by communication environment deterioration such as multipath fading is selected, the antenna switching timing detection signal can be detected without fail. Therefore, even when an antenna affected by reception level deterioration due to deterioration of the communication environment such as multipath fading is selected, an antenna for receiving a payload signal can be selected accurately. . For example, even if the initially selected antenna is affected by level degradation caused by multipath fading, the payload can be received by an antenna with less influence. As a result, it is possible to avoid a reception error due to the level deterioration due to multipath fading.
(Modification)
FIG. 52A shows an example of a signal (modulated signal) transmitted as an antenna switching timing detection signal of still another modified example of the antenna switching reception system 110. FIG. 52B shows an example of a demodulated signal whose level is adjusted, and FIG. 52C shows an example of a demodulated signal in a saturated state where level adjustment is not performed. Signals received and demodulated via the antenna unit 111 and the antenna switching unit 112 are level-adjusted by an automatic gain control unit (not shown) and then input to the correlation value calculation unit 115. Here, when the influence of multipath fading is large, the demodulated signal level after gain control by the automatic gain control unit may be small as shown in FIG. In view of this, the present modification is configured such that, for example, the transmission signal is a binary signal such as BPSK, thereby eliminating the need for gain control and allowing demodulation and detection even in a saturated state.
In this antenna switching reception system 110, when the transmission signal is a binary signal, the reception signal is also input to the correlation value calculation unit 115 without performing gain control by the automatic gain control unit as shown in FIG. 52 (c). As shown, since it does not depend on the reception level, it can be demodulated even in a saturated state. Therefore, it is possible to reduce the influence of multipath fading and suppress the deterioration of the reception level. As a result, it is possible to improve the detection probability of the antenna switching timing detection signal and reduce the probability that the antenna cannot be switched. Also, by fixing the gain by the automatic gain control unit to the maximum, it is possible to demodulate even in a saturated state without depending on the reception level.
(Modification)
FIG. 53 shows a schematic configuration of still another modified example of the antenna switching reception system 110 of the second embodiment. This antenna switching reception system 110 is configured by adding a counter unit 116 to the antenna switching reception system 110 of FIG. The counter unit 116 counts the time from a specific antenna switching reference timing to the next antenna switching reference timing. In the antenna switching reception system 110, the next antenna switching timing reference is detected based on the count value of the counter unit 116.
54 and 55 illustrate signals (frames) received using the antenna A and the antenna B and the operation of the counter unit 116 in the antenna switching reception system 110 according to the present modification. In particular, FIG. 54 shows a case where a frame is received at a constant cycle without an error, and FIG. 55 shows a case where a frame is not received at a constant cycle with an error. FIG. 56 is a flowchart showing an operation (particularly, an operation corresponding to FIG. 55) of the antenna switching reception system 110 of the present modification. In this modification, # 113, # 113-1, # 114, and # 114-1 are executed in place of the process of # 103 shown in FIG.
The counter unit 116 starts counting from when the antenna switching timing detection unit 113 first detects an antenna switching timing detection signal. And it counts to the count value N corresponding to the timing used as the reference | standard of antenna switching in the following flame | frame, and resets a counter. The start of counting by the counter unit 116 may be a timing determined within each frame, or may be a timing at which synchronization is established by detection of a unique word signal for frame synchronization after the test 2 signal. .
In FIG. 54, when the frames are received at a constant period, the timing at which the antenna switching timing detection unit 113 detects the antenna switching timing detection signal in the next frame matches the timing at which the counter unit 116 counts the count value N. Can be made. Therefore, when the counter unit 116 counts the count value N, it can be considered that the antenna switching timing detection signal has been detected. This eliminates the need for the antenna switching timing detection signal from the next frame onward, thereby improving the transmission efficiency of the payload signal. The operation in FIG. 54 corresponds to the operation in which the process of # 114 in FIG. 56 is omitted and the process proceeds to # 104.
On the other hand, in FIG. 55, when a frame cannot be received at a fixed period, the antenna switching timing detection unit 113 detects an antenna switching timing detection signal in the next frame while the counter unit 116 uses the count value as an auxiliary. . That is, a timing that is an approximate reference for antenna switching is detected based on the count value of the counter unit 116, and the antenna switching timing detection unit 113 is operated for a predetermined time before and after that. 55 and 56, for example, after the counter unit 116 has counted up to N-4 (YES in # 113), the antenna switching timing detection unit 113 is operated for a predetermined time, and the antenna switching timing detection signal is detected. Is detected (# 114). Thereby, even when an error is included in the frame period, the detection accuracy of the antenna switching timing detection signal can be improved by supplementarily using the count value of the counter unit 116. For example, when the correlation value calculation unit 115 is applied as the antenna switching timing detection unit 113, the antenna switching timing detection signal associated with the calculation of the correlation value is compared with the case where the antenna switching timing detection signal is always detected. The probability of erroneous detection due to noise or the like can be reduced. If the antenna switching timing detection signal can be detected in # 114 (YES in # 114), the count value of the counter unit 116 is reset (# 114-1) and the process proceeds to # 104. If NO (NO in # 114), the process returns to # 101.
(Modification)
FIG. 57 shows a schematic configuration of still another modified example of the antenna switching reception system 110 of the second embodiment. This antenna switching reception system 110 is configured by adding an antenna periodic switching control unit 117 to the antenna switching reception system 110 of FIG. The antenna periodic switching control unit 117 switches the antennas every predetermined period having a period equal to or longer than the length of the antenna switching timing detection signal. Accordingly, the antenna switching timing detection signal is transmitted over a plurality of times at least twice the number of antennas in one frame.
FIG. 58 shows a signal received using the antenna A and the antenna B in the antenna switching reception system 110 of this modification, and an operation of the antenna switching reception system 110 when receiving this signal. In particular, a case is shown in which the antenna is switched every cycle that is twice the length of the antenna switching timing detection signal. FIG. 59 is a flowchart showing the operation of the antenna switching reception system 110 of this modification. In this modified example, steps # 115 to # 118 are executed instead of the processing of # 102 and # 103 shown in FIG.
In this modification, the frame transmitted from the transmission system includes antenna switching timing detection signals 1 to 4. The antenna switching timing detection signals 1 to 4 are configured by different specific signal sequences. Since the antenna switching reception system 110 switches antennas regardless of the timing at which frames are transmitted from the transmission system, various patterns can be considered as to which signal is received by which antenna. For example, the antenna switching timing detection signal is received at the reception timing of the three patterns shown in FIG.
In the reception timing example 1, when the antenna switching timing detection signal 1 cannot be detected due to degradation of the reception level or noise, the antenna switching timing detection signal 2 is continuously received. However, since the antenna A is switched to the antenna B during the reception, the antenna switching timing detection signal 2 is not detected. However, in the present modification, the antenna is switched at a cycle that is twice the length of the antenna switching timing detection signal, so that the antenna is not switched during reception of the next antenna switching timing detection signal 3. Therefore, the antenna switching timing detection signal 3 can be detected by the antenna B.
In the reception timing example 2, first, the antenna switching timing detection signal 1 is not detected because the antenna A is switched to the antenna B during reception of the antenna switching timing detection signal 1. Subsequently, if the antenna switching timing detection signal 2 cannot be detected during reception of the antenna switching timing detection signal 2 due to reception level deterioration or noise, the antenna switching timing detection signal 3 is continuously received. However, since the antenna B is switched to the antenna A during the reception, the antenna switching timing detection signal 3 is not detected. However, in the present modification, the antenna is switched at a cycle that is twice the length of the antenna switching timing detection signal, so that the antenna is not switched during reception of the next antenna switching timing detection signal 4. Therefore, the antenna switching timing detection signal 4 can be detected by the antenna A.
Reception timing example 3 shows a case where the timing for starting reception of the antenna switching timing detection signal matches the timing for switching the antenna. In this case, when the antenna switching

timing detection signals

1 and 2 cannot be detected by the antenna B due to reception level degradation, noise, or the like, the antenna switching timing detection signal 3 is detected by switching to the antenna A.
Thus, in this modification, the antenna periodic switching control unit 117 periodically switches the antenna (# 115), and the antenna switching timing detection unit 113 detects the antenna switching timing detection signal (in # 116). YES). Since the antenna switching timing detection signals are composed of different specific signal sequences, the antenna switching timing detection unit 113 specifies which antenna switching timing detection signal the detected antenna switching timing detection signal is. it can. Then, the periodic antenna switching control unit 117 counts the time until the test 1 signal is received according to the antenna switching timing detection signal detected by the antenna switching timing detection unit 113 (# 117). For example, in the case of the reception timing examples 1 and 3 in FIG. 58, the antenna regular switching control unit 117 counts the time corresponding to the antenna switching timing detection signal 4. If the antenna switching timing detection signal 1 is detected, the time corresponding to the antenna switching timing detection signals 2 to 4 is counted. Since it is sufficient that one of the antenna switching timing detection signals is detected, the antenna switching timing detection function by the antenna switching timing detection unit 113 is stopped during the counting by the antenna periodic switching control unit 117. (# 118). Thereafter, when the count by the antenna periodic switching control unit 117 is completed, the process proceeds to # 104. Since it is the same as that of FIG. 48 after this, description is abbreviate | omitted.
According to this antenna switching reception system 110, a signal for antenna switching timing detection is received a plurality of times, and the antenna switching timing can be detected by any of the antennas by switching the antennas at predetermined intervals. For this reason, even if an antenna switching timing detection signal is being received by one of the antennas, the antenna switching timing detection signal can be detected by another antenna even if detection becomes impossible due to an instantaneous drop in reception level. it can.
(Modification)
FIG. 60 shows a schematic configuration of still another modified example of the antenna switching reception system 110 of the second embodiment. This antenna switching reception system 110 is configured by adding an antenna switching timing detection on / off control unit (antenna switching timing detection on / off control unit) 118 to the antenna switching reception system 110 of FIG. The antenna switching timing detection on / off control unit 118 controls the antenna switching timing detection unit 113 not to detect the antenna switching timing detection signal for a predetermined period after detecting the antenna switching timing detection signal.
FIG. 61 shows a signal received using the antenna A and the antenna B in the antenna switching reception system 110 of the present modification, and an operation of the antenna switching reception system 110 when receiving this signal. FIG. 62 is a flowchart showing the operation of the antenna switching reception system 110 of this modification. In this modified example, # 119 between the processes of # 102 and # 103 shown in FIG. 48, # 120 between the processes of # 103 and # 104, and # 121 after the processes of # 110 and # 111, The process of # 122 is executed.
In FIG. 62, when the antenna unit 111 receives a signal (# 102), if the signal output from the antenna switching timing detection on / off control unit 118 is on (YES in # 119), the process proceeds to # 103. When antenna switching timing detector 113 detects the antenna switching timing (YES in # 103), the signal output from antenna switching timing detection on / off controller 118 is turned off (# 120). Thereby, as shown in FIG. 61, the antenna switching timing detection function is turned off. Thereafter, the processes of # 104 to # 110 or # 111 are executed in the same manner as in FIG. 48, and the payload signal is received by one of the antennas (YES in # 121), and then output from the antenna switching timing detection on / off control unit 118. After the signal to be turned on is turned on (# 122), the process returns to # 101. If the signal output from the antenna switching timing detection on / off control unit 118 is not on (NO in # 119), the process returns to # 101.
According to this antenna switching reception system 110, after the antenna switching timing is detected, the antenna switching timing is not detected during a predetermined period including the reception time of the payload signal. As a result, it is possible to suppress erroneous detection of the antenna switching timing with respect to a payload signal or noise that becomes a random signal. Therefore, it is possible to prevent an error associated with switching the antenna during reception of the payload signal (because a physical switching time is required for switching the antenna and the payload cannot be received during that time). In addition, when only one of the antennas can be received, it is possible to prevent occurrence of a reception error due to unnecessary antenna switching. Equipped with an equalizer to suppress errors associated with antenna switching during transmission / reception of payload signals, even in systems that require fixed antennas during transmission / reception of payload signals and a fixed multipath environment for transmission / reception it can. That is, it is possible to prevent the multipath environment from being suddenly changed during transmission / reception of the payload signal and the multipath cancellation function by the equalizer from operating normally. As a predetermined period during which the antenna switching timing is not detected, a period from when the reception of the payload signal of the current frame is completed to immediately before the reception of the antenna switching timing detection signal of the next frame may be set. In this case, erroneous detection of the antenna switching timing with respect to noise after the completion of reception of the payload signal of the current frame can also be suppressed.
In this modification, even when noise is erroneously detected as an antenna switching timing detection signal, the detection function of the antenna switching timing detection signal is stopped for a predetermined period. Thus, after detecting the antenna switching timing detection signal, the antenna switching timing detection signal may not be detected for a predetermined period when a unique word signal transmitted thereafter is detected. In this case, the unique word signal is transmitted following the antenna switching timing detection signal, the test 1 signal, and the test 2 signal, for example (see FIG. 46). If a unique word can be detected after detecting the antenna switching timing detection signal, it can be determined that the previously detected antenna switching timing detection signal is correct. On the other hand, if the unique word signal cannot be detected, it can be determined that the previously detected antenna switching timing detection signal is incorrect, and the detection of the antenna switching timing detection signal is continued. According to this configuration, since the detection of the unique word signal is used in combination with the detection of the antenna switching timing detection signal, the possibility of misidentifying noise as the antenna switching timing detection signal can be reduced.
(Modification)
FIG. 63 shows a schematic configuration of still another modified example of the antenna switching reception system 110 of the second embodiment. This antenna switching reception system 110 is configured by adding a non-detection time counter unit 120 to the antenna switching reception system 110 of FIG. The non-detection time counter unit 120 counts the time during which no antenna switching timing detection signal is detected. In this antenna switching reception system 110, when the non-detection time counter unit 120 counts a predetermined time during reception by any one of the antennas, switching to another antenna is performed.
FIG. 64 shows a signal received using the antenna A and the antenna B in the antenna switching reception system 110 of this modification, and an operation of the antenna switching reception system 110 when receiving this signal. FIG. 65 is a flowchart showing the operation of the antenna switching reception system 110 of this modification. In this modified example, when NO in # 112 shown in FIG. 51, the processes of # 125 to # 128 are executed.
In this modification, as shown in FIG. 65, when the antenna switching timing detection signal that should be received by the antenna A cannot be received over the frames 1 and 2 (NO in # 112), the following operation is performed. Do. That is, if the non-detection time counter unit 120 is not counting time (NO in # 125), the non-detection time counter unit 120 starts counting (# 126) and returns to # 101. If the non-detection time counter unit 120 is counting (YES in # 125) and the count value of the non-detection time counter unit 120 is not the specified value or more (NO in # 127), the process returns to # 101. If the count value of the non-detection time counter unit 120 is equal to or greater than the specified value (YES in # 127), the count is stopped and switched to another antenna B assuming that a predetermined time has elapsed (# 128). Here, the predetermined time means a time sufficient to detect the antenna switching timing signal at least once if the antenna and the communication environment are normal. For example, in FIG. 64, the specified value is set so as to be longer than the time required for communication of frame 1 and frame 2.
According to this antenna switching reception system 110, when a signal train of antenna switching timing detection signals cannot be obtained even if a signal is received for a predetermined period, switching to another antenna is performed. Therefore, one antenna does not continue to wait for the antenna switching timing detection signal. Therefore, even when one of the antennas is broken or temporarily malfunctioned, the antenna switching timing detection signal can be received by another antenna.
(Modification)
FIG. 66 shows a schematic configuration of still another modified example of the antenna switching reception system 110 of the second embodiment. This antenna switching reception system 110 is configured by adding a second correlation value calculation unit 122 and a second correlation value calculation unit 123 to the antenna switching reception system 110 of FIG. In addition, a test signal composed of a signal sequence in a specific sequence different from the antenna switching timing detection signal is transmitted from the transmission system. The second correlation value calculation unit (storage unit) 122 stores a signal sequence (reference signal) in the same sequence as the transmitted test 1 signal. The second correlation value calculation unit 122 detects the test 1 signal based on the correlation value by calculating the correlation value between the stored signal sequence and the signal sequence of the received test 1 signal. Similarly, the second correlation value calculation unit (storage unit) 123 stores a signal sequence (reference signal) in the same sequence as the transmitted test 2 signal. The second correlation value calculation unit 123 detects the test 2 signal based on the correlation value by calculating the correlation value between the stored signal sequence and the signal sequence of the received test 2 signal. As a result, even if the antenna switching timing detection signal cannot be detected due to instantaneous reception level deterioration or instantaneous noise mixing, the frame can be detected by detecting the test 1 signal or the test 2 signal. The payload signal can be received.
FIG. 67 shows a signal received using the antenna A and the antenna B in the antenna switching reception system 110 of this modification, and the operation of the antenna switching reception system 110 when receiving this signal. FIG. 68 is a flowchart showing the operation of the antenna switching reception system 110 of this modification. In the present modification, when NO at # 112 shown in FIG. 51, processes at # 131 to # 132 are executed. If YES at # 112, the process at # 133 is executed.
The calculation of the correlation value by the second correlation value calculation unit 122 and the second correlation value calculation unit 123 is performed in parallel with the calculation of the correlation value by the correlation value calculation unit 115. As shown in FIG. 67, the test 1 signal and the test 2 signal are transmitted following the antenna switching timing detection signal. When the correlation value calculation unit 115 detects the antenna switching timing (YES in # 112), the function is stopped so that the second correlation value calculation units 122 and 123 do not detect the test 1 signal or the test 2 signal. (# 133). Thereafter, similarly to FIG. 51, the processing after # 104, that is, the antenna that receives the payload signal is determined by comparing the reception level detected by each antenna while switching the antenna. In this way, when the correlation value calculation unit 115 detects the antenna switching timing detection signal, the correlation detection by the second correlation value calculation unit 122 using the test 1 signal is not performed or is invalid even if performed. To do. In this case, after receiving the payload signal at # 110 or # 111, the second correlation value calculation units 122 and 123 are operated again in preparation for reception of the next frame.
When correlation value calculation unit 115 cannot detect the antenna switching timing (NO in # 112), if test 1 signal is detected by second correlation value calculation unit 122 (YES in # 131), current antenna A A payload signal is received (# 110). Even when the test 1 signal is not detected by the second correlation value calculator 122 (NO in # 131), if the test 2 signal is detected by the second correlation value calculator 123 (YES in # 132), the current The payload signal is received by the antenna A (# 110). If the second correlation value calculation unit 123 does not detect the test 2 signal within the predetermined time (NO in # 132), the process returns to # 101. Thus, when the second correlation value calculation unit 122 detects the test 1 signal, the antenna switching operation is not performed, and another process can be performed during the time during which the test 2 signal is transmitted. For example, when the payload signal is not binary and the reception level needs to be adjusted, it can be assigned to the gain adjustment time of automatic gain control. When the second correlation value calculation unit 123 detects the test 2 signal, the antenna switching operation is not executed and the payload signal is received with the current automatic gain control value.
According to the antenna switching reception system 110, when the antenna switching timing detection signal cannot be detected, the second correlation value calculation unit 122 or the second correlation value calculation unit 123 detects the test 1 signal or the test 2 signal. Therefore, it is possible to detect the head of the payload signal in two or three stages. As a result, even when noise or an instantaneous level drop occurs during reception of the antenna switching timing detection signal, the head of the payload signal can be detected by the test 1 signal or the test 2 signal. The probability of losing the payload signal can be reduced. Note that the second correlation value calculation unit for detecting the test signal can be further added according to the number of test signals to be transmitted (that is, the number of antennas).
Note that the present invention is not limited to the configuration of the above-described embodiment, and at least before receiving a payload signal, the antenna may be configured to receive a test signal with a plurality of antennas and select an antenna that receives the payload signal. That's fine. Moreover, the antenna switching reception system which combined the characteristic of each embodiment mentioned above suitably may be sufficient.
Although preferred embodiments of the present invention have been described above, the present invention is not limited to these specific embodiments, and various changes and modifications can be made within the scope of the following claims. It can be said that it belongs to the category of the present invention.

Claims

In an antenna switching receiving system for switching a plurality of antennas to receive a radio signal, the antenna switching is characterized in that the quality of the received radio signal is compared while the antenna is switched at a predetermined cycle, and the antenna that receives the payload is selected. Receiving system.
An antenna control unit for controlling antenna switching;
A unique word setting unit for presetting and storing a bit string of a known unique word;
A unique word detection unit that searches a bit string of a received radio signal while switching antennas and detects a bit string that is the same as the unique word stored by the unique word setting unit;
A signal quality comparison unit that compares the quality of radio signals received for each antenna is provided.
When the unique word detector detects a unique word,
The antenna according to claim 1, wherein the antenna control unit selects an antenna determined to have the highest signal quality as a result of comparison by the signal quality comparison unit, and receives a subsequent payload. Switching reception system.
From the corresponding transmission system, multiple unique words consisting of different bit strings are transmitted in a specific order before the payload,
A plurality of unique words that are the same as a plurality of unique words transmitted from the transmission system are preset and stored by the unique word setting unit,
The unique word detection unit is a multiple unique word detection unit that individually detects the plurality of unique words,
When the multiple unique word detection unit detects a predetermined unique word,
The antenna switching reception system according to claim 2, wherein the antenna control unit selects an antenna that is determined to have the highest signal quality.
The signal quality comparison unit
4. The antenna switching reception system according to claim 2, further comprising a reception level comparison unit that compares levels of radio signals received by the respective antennas.
The signal quality comparison unit
5. A unique word error number comparison unit that compares the number of errors in a bit string of a radio signal received by each antenna with respect to a bit string of a unique word stored in the unique word setting unit. The antenna switching receiving system according to any one of the above.
From the corresponding transmission system, a preamble to establish bit synchronization is transmitted before each unique word,
6. The unique word error number comparison unit according to claim 5, wherein the unique word error number comparison unit compares the number of errors in a bit string of a radio signal received by each antenna with respect to a preamble and a unique word bit string. The antenna switching receiving system described.
A first counter that counts a first predetermined time corresponding to a unique word reception interval in one packet;
When the unique word detection unit detects a unique word from a radio signal received by any antenna, the first counter starts counting, and when the first predetermined time is counted, the signal received by another antenna The antenna switching receiving system according to any one of claims 2 to 6, wherein the next unique word is detected.
A second counter for counting a second predetermined time after switching the antenna;
The antenna switching reception according to any one of claims 2 to 7, wherein after the antenna is switched, the unique word is not detected until the second counter counts the second predetermined time. system.
A packet end detector for detecting the end of the packet;
3. When the packet end detection unit detects the end of a packet, the antenna control unit automatically returns to the control for switching the antenna at a predetermined cycle and receives the next packet. Item 9. The antenna switching reception system according to any one of Items 8 to 9.
A third counter for counting a third predetermined time after detecting the specific unique word;
The antenna switching reception system according to any one of claims 2 to 9, wherein the unique word is not detected until the third counter counts a third predetermined time.
A reception level detector for detecting the level of the received radio signal;
11. The unique word detection unit starts a search for a unique word after the reception level detection unit detects a signal level equal to or higher than a predetermined first threshold value. The antenna switching receiving system according to item.
A selected antenna storage unit that stores information on the antenna selected by the antenna control unit when receiving a payload, and information stored in the selected antenna storage unit, any one of the antennas is continuously received a predetermined number of times. The antenna switching reception system according to any one of claims 2 to 11, further comprising a notification unit that notifies the user of the fact that the antenna control unit has selected the antenna control unit.
13. The preamble and unique word twice as many as the number of mounted antennas are transmitted, and each antenna is switched at a period twice as long as the transmission period of the preamble and unique word. The antenna switching reception system according to any one of the above.
The reception level notifying unit for detecting the level of the received radio signal and notifying the user, and the switching function setting unit for enabling the user to set the antenna switching function to be valid / invalid The antenna switching reception system according to any one of claims 1 to 13.
A reception level detector that detects the level of the received radio signal;
15. The switching function control unit for disabling an antenna switching function when the reception level detection unit detects a signal level equal to or higher than a predetermined second threshold value. The antenna switching reception system according to claim 1.
The antenna switching reception according to claim 14 or 15, wherein when the switching function setting unit or the switching function control unit invalidates the antenna switching function, the corresponding transmission system is notified to that effect. system.
15. The switching function setting unit or the switching function control unit enables the antenna switching function when a unique word cannot be detected continuously for a fourth predetermined time in a state where the antenna switching function is disabled. The antenna switching reception system according to any one of claims 1 to 16.
18. The antenna switching reception system according to claim 17, wherein when the payload is successfully received, an ACK to that effect is transmitted to the corresponding transmission system.
The antenna switching reception system according to any one of claims 14 to 18, wherein the antenna switching function is periodically enabled even when the antenna switching function is invalid.
An antenna switching reception system according to any one of claims 2 to 19,
A transmission unit for transmitting a radio signal;
The wireless communication device according to claim 1, wherein when the transmitting unit transmits a radio signal after receiving a payload, the antenna control unit uses an antenna selected at the time of receiving the payload.
In an antenna switching reception system that receives a radio signal by switching a plurality of antennas, before receiving a payload signal, the test signal is received by each antenna and the antenna that receives the payload signal is selected and the test signal is received. The antenna switching receiving system, wherein the antenna to be switched is switched based on an antenna switching timing detection signal detected before the test signal.
The antenna switching timing detection signal is composed of a specific sequence of signal strings and transmitted.
A storage unit for storing a signal sequence in the same sequence as the antenna switching timing detection signal to be transmitted;
A correlation value calculation unit that calculates a correlation value between the signal sequence stored in the storage unit and the signal sequence of the received antenna switching timing detection signal;
The antenna switching reception system according to claim 21, wherein the antenna switching timing detection signal is detected based on the correlation value calculated by the correlation value calculation unit.
23. The antenna switching reception system according to claim 21, wherein the antenna switching timing detection signal transmitted at a lower transmission rate than the payload signal is detected.
The antenna switching reception system according to any one of claims 21 to 23, wherein the antenna switching timing detection signal can be demodulated even in a saturated state without depending on a reception level.
22. A counter unit that counts a time from a specific antenna switching reference timing to a next antenna switching reference timing, wherein the antenna switching reference timing is detected based on a count value of the counter unit. Item 25. The antenna switching receiving system according to any one of Items 24.
The antenna switching timing detection signal is transmitted a plurality of times within one frame,
26. The antenna periodic switching control unit for switching an antenna every predetermined period having a period equal to or longer than a length of the antenna switching timing detection signal. The antenna switching receiving system described.
After the detection of the antenna switching timing detection signal or after further detection of the unique word signal after the detection of the antenna switching timing detection signal, the antenna switching timing detection signal is not detected for a predetermined period. The antenna switching reception system according to any one of claims 21 to 26.
A non-detection time counter unit that counts a time during which the antenna switching timing detection signal is not detected, and when the non-detection time counter unit counts a predetermined time during reception by any antenna, another antenna The antenna switching reception system according to any one of claims 21 to 27, wherein the antenna switching reception system is switched to.
The test signal is configured and transmitted by a signal sequence of a specific sequence,
The storage unit further stores a signal sequence in the same sequence as the test signal to be transmitted,
A second correlation value calculating unit that calculates a correlation value between the signal sequence of the test signal stored in the storage unit and the signal sequence of the received test signal;
The second correlation value calculation unit receives the payload signal without performing antenna switching when detecting the test signal based on the calculated correlation value;
The antenna switching reception system according to any one of claims 21 to 28, wherein the number of the second correlation value calculation units corresponds to the number of the test signals.