JP2012235438A - Antenna switching reception system and wireless communication device comprising the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the effect of level variation due to multipath fading in an antenna switching reception system even under an environment where a number of multipaths exist.SOLUTION: While switching is performed between a plurality of antennas with a predetermined period (#1), a wireless signal transmitted from a transmission system is received (#2). The received signal is down-converted and demodulated (#3, #4), and bit synchronization is established (#5). After that, a unique word UW1 is detected (#13, #22), and a signal quality of the unique word UW1 is detected (#14, #23). After that, switching is performed between the antennas (#15, #24), a unique word UW2 is detected (#17, #26), and a signal quality of the unique word UW2 is detected (#18, #27). After that, the detected signal qualities of the unique words UW1, UW2 are compared, and a later payload is received by an antenna with the better signal quality (#8).

Description

  The present invention relates to an antenna switching receiving system for switching and receiving antennas 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 directly input from the transmitting antenna to the receiving antenna but also signals input through 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 technology that can reduce the influence of level degradation due to multipath fading because 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 reduced in cost, and can be configured with a single receiver, so that it is easy to develop and the circuit scale is small and the cost can be reduced. Diversity "is installed in various radio 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 a situation where the communication environment is poor due to multipath fading, the number of retransmissions increases, making it unsuitable for devices that need to communicate with multiple devices and receive new payload signals one after another.

  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.

  To achieve the above object, the antenna switching reception system of the present invention compares the quality of received radio signals while switching antennas at a predetermined period in an antenna switching reception system that switches a plurality of antennas to receive radio signals. Selecting an antenna for receiving the payload.

  In the present invention, 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 a bit string of a radio signal received while switching antennas are searched, and the unique A unique word detection unit that detects the same bit string as the unique word stored by the word setting unit and a signal quality comparison unit that compares the quality of the radio signal received for each antenna, and the unique word detection unit is unique When a word is detected, it is preferable that 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.

  In the present invention, a plurality of unique words composed of different bit strings are transmitted from a corresponding transmission system in a specific order before a payload, and a plurality of unique words identical to the plurality of unique words transmitted from the transmission system. Is 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, and the multiple unique word detection unit is a predetermined When the unique word is detected, it is preferable that the antenna control unit selects an antenna determined to have the highest signal quality.

  In this invention, it is preferable that the signal quality comparison unit includes a reception level comparison unit that compares the levels of radio signals received by the antennas.

  In the present invention, the signal quality comparison unit includes a unique word error number comparison unit that 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. Is preferred.

  In the present invention, 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 is received by each antenna for the preamble and the bit string of the unique word. A preamble / unique word error number comparison unit that compares the number of errors in a bit string of a radio signal is preferable.

  The present invention further includes a first counter that counts a first predetermined time which is a reception interval of the unique word in one packet, and the unique word detection unit detects the unique word from the radio signal received by any antenna. When the first counter starts counting and the reception interval of the unique word is counted, it is preferable that the next unique word is detected from a signal received by another antenna.

  The present invention further includes a second counter that counts a second predetermined time after the antenna is switched, and after the antenna is switched, the unique word is detected until the second counter counts the second predetermined time. Preferably not.

  In this invention, it further includes a packet end detection unit for detecting the end of the packet, and when the packet end detection unit detects the end of the packet, the antenna control unit automatically returns to the control for switching the antenna at a predetermined cycle. Thus, it is preferable to receive the next packet.

  In the present invention, a third counter that counts a third predetermined time after detecting a specific unique word is further provided, and the unique word is not detected until the third counter counts the third predetermined time. Is preferred.

  In this invention, it further includes a reception level detection unit for detecting the level of the received radio signal, and after the reception level detection unit detects a signal level equal to or higher than a predetermined first threshold, the unique word detection unit It is preferable to start the search.

  In the present invention, a selected antenna storage unit that stores information on an antenna selected by the antenna control unit when receiving a payload, and any one of the antennas a predetermined number of times from the information stored in the selected antenna storage unit In the case where the antenna control unit is continuously selected, it is preferable to further include a notification unit that notifies the user to that effect.

  In the present invention, it is preferable that the number of preambles and unique words twice as many as the number of mounted antennas is transmitted, and that each antenna is switched at a cycle twice the preamble and unique word transmission cycle.

  In the present invention, it is preferable to further include a reception level notification unit that detects the level of the received radio signal and notifies the user, and a switching function setting unit for the user to set validity / invalidity of the antenna switching function.

  In this invention, a reception level detection unit that detects the level of a received radio signal, and a switching function control unit that disables the antenna switching function 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 comprise.

  In the present invention, 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 present invention, when the unique word cannot be detected continuously for the fourth predetermined time in a state where the antenna switching function is invalid, the switching function setting unit or the switching function control unit preferably enables the antenna switching function.

  In the present invention, when the payload is successfully received, it is preferable to transmit an ACK to that effect to the corresponding transmission system.

  In the present invention, it is preferable to periodically enable the antenna switching function even when the antenna switching function is disabled.

  In this invention, the antenna switching reception system and a transmission unit for transmitting a radio signal are further provided, and when the transmission unit transmits a radio signal after receiving a payload, the antenna control unit is selected when receiving the payload. A wireless communicator that uses a shaped antenna is preferred.

  According to the antenna switching reception system of the present invention, the quality of the received radio signal is compared while switching the antenna at a predetermined period, and the antenna that receives the 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 the deterioration of the reception level due to multipath fading.

The block diagram which shows the structure of the antenna switching receiving system by one 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.

  An antenna switching reception system according to an 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 integrated 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 this embodiment, the antenna switching unit 03 switches between two antennas 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 next loop through YES in # 6, the antenna is fixed to A (# 7), and the subsequent payload is received (# 8). If a unique word transmitted first is detected, the payload is received after detecting another unique word while the antenna is fixed.

  According to this antenna switching reception system, the unique word is searched by switching the antenna at a predetermined cycle, and when the unique word is detected, it is fixed to the received antenna and the subsequent payload is received. 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 the deterioration of the reception level due to multipath fading.

(Modification)
FIG. 4 shows a configuration of a modification 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, 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. Compare signal quality. On the other hand, when the unique words UW3 or UW4 are detected, the unique words UW1 and UW2 cannot be detected by the other antenna, so that it is not meaningful to switch the antenna. Therefore, the signal quality comparison unit 13 performs level comparison for each antenna. Not performed. 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 (# 23). ), 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 (# 22), 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, the antenna selection is performed not only by comparison of the reception level but also by the detection result of the number of errors in the bit string of the unique word, so the antenna selection is erroneously influenced by the interference wave from the transmission system other than the communication partner. Can be prevented.

(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. Thereafter, 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). If 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), the antenna control unit 10 outputs a control signal for antenna switching to the antenna switching unit 03, and the antenna 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 UW 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 UW 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 UW to each packet as shown in FIG. And 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 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 a configuration corresponding to a radio device 100 and a radio device 200, which will be described later, for example.

(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. A corresponding transmission system is implemented in the radio device 100 with one antenna. 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.

08 Unique word setting unit 09 Unique word detection unit 10 Antenna control unit 11 Threshold setting unit 12 Multiple unique word detection unit 13 Signal quality comparison unit 14 Reception level comparison unit 15 Unique word error number comparison unit 17 First counter 18 Second counter 19 Packet end detection unit 20 Third counter 21 Reception level detection unit 22 Selected antenna storage unit 23 Notification unit 24 Reception level notification unit 24-2 Diversity on / off switching unit (antenna switching function setting unit)
25 Diversity on / off control unit (antenna switching function control unit)
200 Radio equipment (wireless communication equipment)

Claims (20)

  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 sequences are transmitted in a specific order before the payload,
A plurality of unique words identical to 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 for comparing 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 reception system according to claim 2, further comprising: detecting a next unique word from the first to second unique words. 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 a 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 searching for a unique word after the reception level detection unit detects a signal level equal to or higher than a predetermined first threshold value. 11. 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 validity / invalidity of the antenna switching function. 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 receiving 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 in a state where the antenna switching function is disabled. 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.

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