JP5747173B2 - Antenna switching reception system - Google Patents

Description

  The present invention relates to an antenna switching reception 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.

  In addition, there are measures by “switching diversity”, “selective diversity” for switching a plurality of antennas, and “combined 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 one antenna has the influence of multipath fading (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.

  Further, the wireless LAN is based on a system that receives a plurality of frames (a lump of payload signals) and switches antennas when an error is detected over a plurality of frames, that is, antenna switching after an error occurs. The generated error is dealt with by sending the same frame again to the transmitter (retransmission function). However, when the communication environment is poor due to multipath fading, the number of retransmissions increases, making it unsuitable for devices that need to receive new payload signals one after another at high speed, such as voice and video.

  The present invention provides an antenna switching reception system that can reduce the influence of level fluctuation due to multipath fading by selecting an antenna having a high reception level accurately even in an environment with many multipaths with a simple configuration. Objective.

In order to achieve the above object, the antenna switching receiving system of the present invention comprises:
In an antenna switching reception system that receives a radio signal transmitted from a transmission system by switching a plurality of antennas,
From the transmission system, an antenna switching timing detection signal, a plurality of test signals received by different antennas, and a payload signal received by a selected antenna are transmitted in this order,
The antenna switching timing detection signal is transmitted at a transmission rate lower than the transmission rate of the payload signal,
An automatic gain control unit that automatically adjusts the amplification factor according to the signal received by any of the plurality of antennas and optimizes the reception level of the signal,
Before receiving the payload signal from the transmission system, the antenna switching timing detection signal is received from the transmission system by any antenna, and the antenna switching timing detection signal is compared with the reference signal stored in advance. If the degree of coincidence is equal to or greater than a predetermined threshold, it is determined that the antenna switching timing detection signal has been detected, and if it is determined that the antenna switching timing detection signal has been detected, The test signal is received, and an antenna that receives the payload signal is selected based on an amplification factor of the test signal by the automatic gain control unit.

  The antenna switching reception system includes an average value calculation unit that detects an amplification factor of the automatic gain control unit for each antenna and calculates an average value thereof, and is calculated for each antenna by the average value calculation unit. It is preferable to select an antenna that receives the payload signal based on the average value of the amplification factors.

  In this antenna switching reception system, it is preferable not to consider the amplification factor of the automatic gain control unit during a predetermined period at the time of switching when selecting and determining an antenna that receives a payload signal when switching the antenna.

  In this antenna switching reception system, it is preferable that output of the amplification factor is stopped from the automatic gain control unit for a predetermined period at the time of switching when the antenna is switched.

  In this antenna switching reception system, it is preferable that the operation of the automatic gain control unit is stopped during a predetermined period at the time of switching when the antenna is switched.

  In this antenna switching reception system, when the payload signal is received by an antenna other than the antenna whose level has been detected last, the gain of the automatic gain control unit when receiving the test signal is received. It is preferable to use it as the initial value of the amplification factor in the process.

  The antenna switching reception system further includes an amplification factor storage unit that stores the amplification factor of the automatic gain control unit when receiving the test signal at each antenna, and newly receiving the test signal at each antenna. Preferably, the amplification factor detected and stored in the previous frame in the amplification factor storage unit is used as the initial value of the amplification factor of the automatic gain control unit.

  The antenna switching reception system further includes an average value storage unit for calculating and storing an average value of amplification factors detected in a plurality of previously received frames, and when the test signal is newly received by each antenna. It is preferable to use the average value of the amplification factors stored in the average value storage unit as the initial value of the amplification factor of the automatic gain control unit.

  The antenna switching reception system further includes an amplification factor variation calculation unit that calculates a variation rate of the amplification factor of the automatic gain control unit when each antenna receives the test signal, and the amplification factor variation calculation unit When the calculated variation rate of the amplification factor is less than a predetermined threshold, the amplification factor storage unit stores the previous value as an initial value of the amplification factor of the automatic gain control unit when the antenna receives a new test signal. It is preferable to use the stored amplification factor.

  The antenna switching reception system further includes an amplification factor variation calculation unit that calculates a variation rate of the amplification factor of the automatic gain control unit when each antenna receives the test signal, and the amplification factor variation calculation unit When the calculated variation rate of the amplification factor is less than a predetermined threshold, the amplification factor average value storage unit is used as an initial value of the amplification factor of the automatic gain control unit when the antenna receives a new test signal. It is preferable to use the average value of amplification factors stored last time.

  In this antenna switching reception system, the automatic gain control unit at the time of newly receiving the test signal at each antenna when the rate of variation of the gain calculated by the gain variation calculation unit is equal to or greater than a predetermined threshold It is preferable to use a predetermined value as the initial value of the amplification factor.

  According to the present invention, since the antenna that receives the test signal and receives the payload signal is selected before receiving the payload signal, the influence of level fluctuations due to multipath fading can be reduced with a simple configuration. As a result, even in a multipath environment, it becomes easy to avoid the occurrence of an error due to reception level deterioration due to multipath fading.

1 is a block diagram showing a schematic configuration of an antenna switching reception system according to an embodiment of the present invention. The figure which shows the operation | movement of the said antenna switching reception system when the signal received using two antennas and this signal are received in the same antenna switching reception system. The flowchart which shows operation | movement of the antenna switching reception system. The block diagram which shows schematic structure of the modification of the antenna switching receiving system by the said embodiment. The figure which shows the operation | movement of the said antenna switching receiving system when the signal received using two antennas and this signal are received in the modification. The flowchart which shows operation | movement of the modification. The block diagram which shows schematic structure of another modification of the antenna switching receiving system by the said embodiment. The figure which shows the operation | movement of the said antenna switching receiving system when the signal received using two antennas and this signal are received in the modification. The flowchart which shows operation | movement of the modification. The block diagram which shows schematic structure of another modification of the antenna switching receiving system by the said embodiment. The figure which shows the operation | movement of the said antenna switching receiving system when the signal received using two antennas and this signal are received in the modification. The flowchart which shows operation | movement of the modification. The block diagram which shows schematic structure of another modification of the antenna switching receiving system by the said embodiment. The figure which shows the operation | movement of the said antenna switching receiving system when the signal received using two antennas and this signal are received in the modification. The flowchart which shows operation | movement of the modification. The block diagram which shows schematic structure of another modification of the antenna switching receiving system by the said embodiment. The figure which shows the operation | movement of the said antenna switching receiving system when the signal received using two antennas and this signal are received in the modification. The flowchart which shows operation | movement of the modification. The figure which shows the operation | movement of the said antenna switching receiving system when receiving the signal received using two antennas in another modification of the antenna switching receiving system by the said embodiment, and this signal. The flowchart which shows operation | movement of the modification. The block diagram which shows schematic structure of another modification of the antenna switching receiving system by the said embodiment. The figure which shows the operation | movement of the said antenna switching receiving system when the signal of the flame | frame received using two antennas and this signal is received in the modification. The flowchart which shows operation | movement of the modification. The block diagram which shows schematic structure of another modification of the antenna switching receiving system by the said embodiment. The figure which shows the operation | movement of the said antenna switching receiving system when the signal of the flame | frame received using two antennas and this signal is received in the modification. The flowchart which shows operation | movement of the modification. The block diagram which shows schematic structure of another modification of the antenna switching receiving system by the said embodiment. The figure which shows the operation | movement of the said antenna switching receiving system when the signal of the flame | frame received using two antennas and this signal is received in the modification. The flowchart which shows operation | movement of the modification.

(First embodiment)
An antenna switching reception system according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a schematic configuration of an antenna switching reception system. The antenna switching reception system 10 includes an antenna unit 11 having two antennas, an antenna switching unit 12, an antenna switching timing detection unit 13, an antenna switching determination unit 14, and the like. The antenna switching unit 12 switches from two antennas to one of the antennas. The antenna switching timing detection unit 13 detects the timing at which the antenna switching unit 12 switches the antenna, for example, by detecting a signal of a predetermined level or higher. The antenna switching determination unit 14 selects an antenna that receives the payload signal based on the reception level of the signal received by any one of the antennas via the antenna switching unit 12, and sends a control signal to that effect to the antenna switching unit 12. Output to. In the following, a case will be described where two antennas are connected to the antenna switching unit 12 and switched, but three or more antennas may be used.

  FIG. 2 shows a signal received using two antennas, that is, antenna A and antenna B, in the antenna switching reception system 10, and an operation of the antenna switching reception system 10 when receiving this signal. In particular, an example in which the antenna A is initially selected and the test signal 1 is received by the antenna A is shown. FIG. 3 is a flowchart showing the operation of the antenna switching reception system 10 of the first embodiment.

  The signal shown in FIG. 2 is transmitted from a transmission system corresponding to the antenna switching reception system 10 of the present embodiment. From the transmission system, a test 1 signal, a test 2 signal and a payload signal are transmitted. One frame is composed of the test 1 signal, the test 2 signal, and the payload signal. Before the payload signal, a unique word signal is transmitted as necessary.

  The test 1 signal and test 2 signal are used to select the antenna that receives the payload signal. The test 1 signal is received by the initially selected antenna, and the test 2 signal is received by the switched antenna. This test signal is added as appropriate according to the number of antennas switched by the antenna switching unit 12. The payload signal includes, for example, data such as a header, video, audio, and temperature, or various control signals.

  The operation of the antenna switching reception system 10 according to the first embodiment will be described with reference to FIGS. The antenna switching reception system 10 is initially waiting (# 1). When the antenna unit 11 of the antenna switching reception system 10 receives a signal (# 2) and the antenna switching timing detection unit 13 detects the antenna switching timing (YES in # 3), the antenna switching determination unit 14 The reception level is detected (# 4). Here, the reception level is detected from, for example, an amplification factor when the received signal is amplified by the automatic gain control circuit. Then, the antenna switching determination unit 14 switches to the antenna B (# 5) and detects the reception level of the antenna B (# 6). The antenna is switched based on the antenna switching timing detected by the antenna switching timing detector 13. Thereafter, the antenna switching determination unit 14 compares the reception level of the antenna A with the reception level of the antenna B (# 7). When the reception level of antenna A is higher (YES in # 8), antenna switching determination unit 14 selects antenna A as an antenna for receiving the payload signal. That is, the antenna switching determination unit 14 outputs a control signal for switching to the antenna A to the antenna switching unit 12 (# 9), and receives a payload signal by the antenna A (# 10). The example shown in FIG. 2 corresponds to this case. When the reception level of antenna B is higher (NO in # 8), antenna B is selected as the antenna for receiving the payload signal. That is, the antenna switching determination unit 14 receives the payload signal by the antenna B while being fixed to the antenna B (# 11). If the reception level of antenna A is the same as the reception level of antenna B, the payload signal is received by antenna B that last received the test signal (# 11).

  According to this antenna switching reception system 10, since the antenna that receives the test signal and receives the payload signal is selected by each antenna before receiving the payload signal, the influence of level fluctuations due to multipath fading is achieved with a simple configuration. Can be reduced. Thereby, even in a multipath environment, it is possible to avoid the occurrence of errors due to reception level deterioration due to multipath fading. Further, near real-time transmission can be realized by reducing the number of retransmissions. Further, when retransmission is unnecessary, it is possible to eliminate the retransmission function and contribute to cost reduction and size reduction.

(Modification)
FIG. 4 shows a schematic configuration of a modified example of the antenna switching reception system 10 of the first embodiment. In this antenna switching reception system 10, a correlation value calculation unit 15 is applied as an example of the antenna switching timing detection unit 13 of FIG. In addition, before the test signal 1, the transmission system transmits an antenna switching timing detection signal composed of a specific sequence of signal sequences. The antenna switching timing detection signal is a signal for detecting a reference timing for switching the antenna to be used to the antenna A or the antenna B when receiving the test 1 signal and the test 2 signal. The antenna switching timing detection signal is transmitted at a transmission rate lower than the transmission rate of the payload signal. The correlation value calculation unit (storage unit) 15 stores a signal sequence (reference signal) in the same sequence as the antenna switching timing detection signal transmitted from the transmission system. Examples of the signal sequence include a random signal such as 01100101011000101..., An M sequence having excellent correlation characteristics, and a similar signal sequence. The correlation value calculation unit 15 calculates a correlation value between the stored signal sequence and the signal sequence of the received antenna switching timing detection signal. In this modification, the antenna switching timing detection signal is detected based on the correlation value calculated by the correlation value calculation unit 15.

  FIG. 5 shows a signal received using the antenna A and the antenna B in the antenna switching reception system 10 of this modification, and an operation of the antenna switching reception system 10 when receiving this signal. FIG. 6 is a flowchart showing the operation of the antenna switching reception system 10 of this modification. In this modification, the process of # 12 is executed instead of the process of # 3 shown in FIG.

  From the transmission system, an antenna switching timing detection signal, a test 1 signal, a test 2 signal, and a payload signal are transmitted. Of the antenna switching timing detection signal, the test 1 signal, the test 2 signal, and the payload signal constituting one frame, the antenna switching timing detection signal is transmitted at a lower transmission rate than the other signals. The signal received via any one of the antennas is compared with the reference signal stored by the correlation value calculation unit 15 while shifting by 1 bit or symbol, and the correlation value is calculated by sequentially digitizing the degree of coincidence. . If the degree of coincidence is equal to or greater than a predetermined threshold, it is determined that an antenna switching timing detection signal has been detected (YES in # 12), and antenna switching determination unit 14 detects the reception level of antenna A (# 4). The following processing is the same as that in FIG.

  According to this antenna switching reception system 10, since the antenna switching timing is detected by detecting the correlation value, the antenna switching timing detection signal and the noise can be more clearly distinguished, and the resistance to noise is enhanced. Is possible. Moreover, the tolerance with respect to interference waves, such as the signal transmitted from the other system used adjacently, or the other apparatus in the same system, can be strengthened. In addition, since antenna switching can be determined at any time by simply inserting the signal sequence of the antenna switching timing detection signal at a location where the antenna switching is to be performed, the degree of freedom in frame configuration can be increased.

  In addition, since the antenna switching timing detection signal transmitted at a lower transmission rate than the payload signal is received, the influence of intersymbol interference due to multipath is avoided and the energy of the signal per bit increases. High sensitivity. Therefore, even when an antenna affected by reception level deterioration due to communication environment deterioration such as multipath fading is selected, the antenna switching timing detection signal can be detected without fail. Therefore, the reception level can be detected more accurately from the test signal at each antenna, and the antenna for receiving the payload signal can be properly selected. For example, even if the initially selected antenna is affected by level degradation caused by multipath fading, the payload can be received by an antenna with less influence. As a result, it is possible to avoid a reception error due to the level deterioration due to multipath fading.

(Modification)
FIG. 7 shows a schematic configuration of still another modified example of the antenna switching reception system 10 of the first embodiment. The antenna switching reception system 10 is configured by adding an automatic gain control unit 31, a signal processing unit 32, and the like to the antenna switching reception system 10 of FIG. The automatic gain control unit 31 automatically adjusts the amplification factor according to the received signal to optimize the reception level of the signal. The amplification factor when the automatic gain control unit 31 performs level adjustment is input to the signal processing unit 32, for example, and the reception level is determined based on this amplification factor.

  FIG. 8 shows a signal received using the antenna A and the antenna B in the antenna switching reception system 10 of this modification, and an operation of the antenna switching reception system 10 when receiving this signal. FIG. 9 is a flowchart showing the operation of the antenna switching receiving system 10 of this modification. In this modification, the process of # 41 is executed instead of # 4 shown in FIG. 6, and the processes of # 42 and 43 are executed instead of # 6 and # 7.

  As shown in FIG. 8, when the antenna switching timing signal is detected by the correlation value calculation unit 15, the signal processing unit 32 takes a corresponding period until the amplification rate is stabilized. And wait for the gain to stabilize. The count value for detecting the amplification factor is set corresponding to the lengths of the test signal 1 and the test signal 2. When the amplification factor detection count ends, the signal processing unit 32 detects the reception level of the test signal 1, causes the antenna switching unit 12 to switch from the antenna A to the antenna B, and starts the amplification factor detection count again. To do. When the count for amplification factor detection ends, the signal processing unit 32 detects the reception level of the test signal 2, and the antenna switching determination unit 14 compares the reception levels and selects and fixes the antenna that receives the payload signal. To do.

  In detecting and comparing the reception level, the gain of the automatic gain control unit 31 is used in this modification, as shown in FIG. In other words, when the antenna switching timing detection signal is detected by correlation value calculation unit 15 (YES in # 12), signal processing unit 32 detects the amplification factor of automatic gain control unit 31 in antenna A (# 41). At this time, the signal processing unit 32 estimates the reception level of the antenna A from the amplification factor detected at the end of the count for amplification factor detection. The gain obtained here is stored in a memory or the like. Thereafter, the antenna switching unit 12 switches to the antenna B, and the signal processing unit 32 infers the reception level of the antenna B from the amplification factor of the automatic gain control unit 31 (# 42) as in # 41. Then, the antenna switching determination unit 14 compares the reception levels obtained from the amplification factors of the automatic gain control unit 31 for the antenna A and the antenna B (# 43). Here, it is determined that the reception level of the antenna having a lower amplification factor is higher. The following processing is the same as that in FIG.

  According to the antenna switching reception system 10, the reception levels of the antennas are compared using the amplification factor of the automatic gain control unit 31. This eliminates the need for an RSSI (Received Signal Strength Indication) circuit or the like for detection of the reception level, and simplifies the system.

  The comparison of the reception level (amplification factor) is not limited to the comparison of absolute values, but may be a comparison of relative values. In the comparison of the relative values, for example, if the gain value increases when the antenna is switched to the antenna B with respect to the gain value detected by the antenna A, the reception level of the antenna B is smaller. If it decreases, the reception level of the antenna B is higher.

(Modification)
FIG. 10 shows a schematic configuration of still another modified example of the antenna switching reception system 10 of the first embodiment. This antenna switching reception system 10 is configured by adding an average value calculation unit 33 and the like to the antenna switching reception system 10 of FIG. The average value calculation unit 33 detects the amplification factor of the automatic gain control unit 31 for each antenna and calculates the average value. The signal processing unit 32 infers the reception level from the average value calculated by the average value calculation unit 33.

  FIG. 11 shows a signal received using the antenna A and the antenna B in the antenna switching reception system 10 of the present modification, and an operation of the antenna switching reception system 10 when receiving this signal. FIG. 12 is a flowchart showing the operation of the antenna switching reception system 10 of this modification. In this modification, the process of # 44 is executed instead of # 41 shown in FIG. 9, and the processes of # 45 and 46 are executed instead of # 42 and # 43.

  In this modification, as shown in FIGS. 11 and 12, the average value of the amplification factors of the automatic gain control unit 31 is used for comparison of the reception levels. That is, when the antenna switching timing detection signal is detected by the correlation value calculation unit 15 (YES in # 12), the average value calculation unit 33 calculates the average value of the amplification factors of the automatic gain control unit 31 in the antenna A ( # 44). At this time, the average value calculation unit 33 calculates the average value of amplification factors for several times before the count for amplification factor detection, and the signal processing unit 32 estimates the reception level of the antenna A from the average value. The average value of amplification factors obtained here is stored in a memory or the like. After that, the antenna switching unit 12 switches to the antenna B, and the average value calculation unit 33 calculates the average value of the amplification factor of the automatic gain control unit 31 as in # 44, and the signal processing unit 32 determines the antenna B from the average value. Is received (# 45). Then, the antenna switching determination unit 14 compares the reception levels obtained from the average gain of the automatic gain control unit 31 for the antenna A and the antenna B (# 46). The following processing is the same as that in FIG.

  According to this antenna switching reception system 10, by evaluating the reception level using the average value of the amplification factor, even if the reception level fluctuates due to the influence of multipath fading, the payload signal is changed. The receiving antenna can be selected more accurately. Also in this modification, the comparison of the average values of the amplification factors is not limited to the comparison of absolute values, but may be a comparison of relative values.

(Modification)
FIG. 13 shows a schematic configuration of still another modified example of the antenna switching reception system 10 of the first embodiment. This antenna switching reception system 10 is configured by adding an automatic gain control unit 31, a signal processing unit 32, and an amplification factor output control unit 35 to the antenna switching reception system 10 of FIG. The amplification factor output control unit 35 controls the output of the amplification factor value to the antenna switching determination unit 14.

  FIG. 14 shows a signal received using the antenna A and the antenna B in the antenna switching reception system 10 of the present modification, and the operation of the antenna switching reception system 10 when receiving this signal. FIG. 15 is a flowchart showing the operation of the antenna switching reception system 10 of the present modification. In this modification, the process of # 47 is executed between # 5 and # 42 shown in FIG.

  In an antenna switching reception system, it is necessary for several tens of nanoseconds to several hundreds of microseconds until the antenna can be stably received after the antenna is physically switched. Therefore, if the gain adjusted based on the unstable signal during this period is output to the antenna switching determination unit 14, the reception level may not be properly determined. Therefore, in the present modification, the amplification factor output control unit 35 performs control so that the amplification factor value is not output to the antenna switching determination unit 14 for a predetermined period after switching the antenna. Thereby, in selecting and determining the antenna that receives the payload signal, the amplification factor of the automatic gain control unit 31 in the predetermined period at the beginning of switching is not considered.

  In FIG. 15, the antenna switching operation is performed twice. The first operation is switching from antenna A to antenna B at # 5, and the amplification factor output control unit 35 controls the signal processing unit 32 so that the amplification factor value is not output to the antenna switching determination unit 14 for a predetermined period. . Thereby, the output of the amplification factor is stopped for a predetermined period (# 47). The second operation is an operation of switching from antenna B to antenna A in # 9. However, since the reception levels of the respective antennas are not compared here, it is not necessary to stop the output of the amplification factor. The predetermined period during which the amplification factor output control unit 35 performs control so as not to output the amplification factor value depends on the switch switching time specification of the antenna switching unit 12.

  According to this antenna switching reception system 10, since the gain value is not output to the antenna switching determination unit 14 for a predetermined period after the antenna switching, the gain adjusted based on the unstable signal is used as the antenna switching determination material. It will not be done. As a result, it is possible to perform antenna switching determination with higher accuracy.

(Modification)
FIG. 16 shows a schematic configuration of still another modified example of the antenna switching reception system 10 of the first embodiment. This antenna switching reception system 10 is configured by adding an automatic gain control unit 31, a signal processing unit 32, and an automatic gain control on / off unit 36 to the antenna switching reception system 10 of FIG. The automatic gain control on / off unit 36 controls the on / off operation of the automatic gain control unit 31.

  FIG. 17 shows a signal received using the antenna A and the antenna B in the antenna switching reception system 10 of the present modification, and an operation of the antenna switching reception system 10 when the signal is received. FIG. 18 is a flowchart showing the operation of the antenna switching receiving system 10 of this modification. In the present modification, the process of # 49 is executed between # 5 and # 42 shown in FIG. 9, and the process of # 50 is executed between # 9 and # 10.

  As already described, in an antenna switching reception system, it is necessary for several tens of nanoseconds to several hundreds of microseconds until the antenna can be stably received after the antenna is physically switched. Therefore, in this modification, the automatic gain control on / off unit 36 stops the operation of the automatic gain control unit 31 so that the automatic gain control unit 31 does not adjust the level for a predetermined period after switching the antenna. Let Thereby, in selecting and determining the antenna that receives the payload signal, the amplification factor of the automatic gain control unit 31 in the predetermined period at the beginning of switching is not considered. Further, it is possible to prevent the time required for convergence of the amplification factor from being prolonged due to the unstable signal input to the automatic gain control unit 31.

  In FIG. 18, the antenna switching operation is performed twice. The first is an operation of switching from antenna A to antenna B in # 5, and the automatic gain control on / off unit 36 stops the operation of the automatic gain control unit 31 for a predetermined period (# 49). The second operation is an operation of switching from the antenna B to the antenna A in # 9, and the automatic gain control on / off unit 36 stops the operation of the automatic gain control unit 31 for a predetermined period (# 50). Note that the predetermined period during which the automatic gain control on / off unit 36 stops the operation of the automatic gain control unit 31 depends on the specification of the switch switching time of the antenna switching unit 12.

According to the antenna switching reception system 10, since the operation of the automatic gain control unit 31 is stopped for a predetermined period after antenna switching, the gain is not adjusted based on an unstable reception signal. Thereby, in addition to the effect described in the paragraph (0049), the gain adjustment time from # 9 to # 10 in FIG. 18 can be shortened.

(Modification)
Another modification of the antenna switching reception system 10 of the first embodiment will be described below. The configuration of this modification is the same as that shown in FIG. 7, but this modification has a feature with respect to the initial value of the amplification factor of the automatic gain control unit 31 when receiving a payload signal.

  FIG. 19 shows a signal received using the antenna A and the antenna B in the antenna switching reception system 10 of the first embodiment, and an operation of the antenna switching reception system 10 when this signal is received. FIG. 20 is a flowchart showing the operation of the antenna switching reception system 10 of this modification. In the present modification, the process of # 51 is executed between # 9 and # 10 shown in FIG.

  In FIG. 19, when the antenna A has a higher reception level and the payload signal is received by the antenna A, the automatic gain control unit 31 of the automatic gain control unit 31 is normally based on the reception level of the antenna B that lastly received the test signal 2 The initial value of amplification factor is set. Therefore, after switching to the antenna A, level adjustment is necessary again. Therefore, in this modification, after the antenna A has a higher reception level and switched to the antenna A (YES in # 8, # 9), the amplification factor when the test signal 1 is received by the antenna A is expressed as the payload signal. Is used as the initial value of the amplification factor when receiving (# 51). In the configuration in which the gain of the automatic gain control unit 31 is not adjusted when receiving the payload signal, the gain when the test signal 1 is received by the antenna A is used as it is.

  According to this modification, when a payload signal is received by an antenna other than the antenna whose level has been detected last, the amplification factor of the automatic gain control unit 31 when receiving a test signal is the amplification factor when receiving the payload signal. Used as the initial value of the rate. This eliminates the time required for level adjustment when switching the antenna and receiving the payload signal, and improves the transmission efficiency of the payload signal.

(Modification)
FIG. 21 shows a schematic configuration of still another modified example of the antenna switching reception system 10 of the first embodiment. The antenna switching reception system 10 is configured by adding an automatic gain control unit 31, a signal processing unit 32, and an amplification factor storage unit 37 to the antenna switching reception system 10 of FIG. The amplification factor storage unit 37 stores the amplification factor of the automatic gain control unit 31 when a test signal is received by each antenna.

  FIG. 22 shows a frame signal received using the antenna A and the antenna B in the antenna switching reception system 10 of the first embodiment, and an operation of the antenna switching reception system 10 when receiving this signal. Yes. FIG. 23 is a flowchart showing the operation of the antenna switching receiving system 10 of this modification. In the present modification, the process of # 52 is executed between # 12 and # 41 shown in FIG. 9, and the process of # 53 is executed between # 5 and # 42.

  If there is no significant change in the communication environment, such as when the positions of the transmission system and the reception system are fixed, it is considered that there is little change in the reception level of each antenna between frames. Therefore, in the present modification, the amplification factor of the automatic gain control unit 31 when receiving the test signal of the previous frame at each antenna stored in the amplification factor storage unit 37, when receiving the test signal of the current frame. Is used as an initial value of the amplification factor.

  That is, when the antenna switching timing detection signal is detected by correlation value calculation unit 15 (YES in # 12), the initial value of the amplification factor of automatic gain control unit 31 when antenna A receives test signal 1 is set. (# 52). As the initial value of the amplification factor of antenna A, the amplification factor of automatic gain control unit 31 in the previous frame at antenna A stored in amplification factor storage unit 37 is set. Then, the signal processing unit 32 estimates the amplification factor of the automatic gain control unit 31 in the antenna A, and updates the amplification factor of the antenna A stored in the amplification factor storage unit 37 (# 41). After switching to antenna B (# 5). An initial value of the amplification factor of antenna B is set (# 53). As the initial value of the amplification factor of the antenna B, the amplification factor of the automatic gain control unit 31 in the previous frame at the antenna B stored in the amplification factor storage unit 37 is set as described above. Then, the signal processing unit 32 recognizes the amplification factor of the automatic gain control unit 31 in the antenna B, and updates the amplification factor of the antenna B stored in the amplification factor storage unit 37 (# 42). The following operations are the same as those in FIG.

  According to this antenna switching reception system 10, the amplification factor of the automatic gain control unit 31 of each antenna detected by the test signal of the previous frame is set as the initial value of the amplification factor of the current frame. Thereby, when there is no large change in the communication environment, the amplification factor of the automatic gain control unit 31 can be converged in a short time, and the reception time of the remaining test signals can be used for another process. For example, in order to suppress errors caused by instantaneous reception level fluctuations due to multipath fading, the accuracy of antenna switching determination can be improved by performing processing such as calculating the average reception level (amplification factor). it can. In this case, in order to further improve accuracy, it is possible to increase the number of reception level samples for calculating the average, and it is also possible to increase the number of times of calculating the average. It is also possible to perform processing such as calculating the optimum amplification factor for reception from the standard deviation of the amplification factor.

(Modification)
FIG. 24 shows a schematic configuration of still another modified example of the antenna switching reception system 10 of the first embodiment. This antenna switching reception system 10 is configured by replacing the amplification factor storage unit 37 of the antenna switching reception system 10 of FIG. 21 with an amplification factor average storage unit 38. The amplification factor average storage unit 38 calculates and stores the average value of the amplification factor of the automatic gain control unit 31 when the test signals have been received by the respective antennas so far.

  FIG. 25 shows a frame signal received using the antenna A and the antenna B in the antenna switching reception system 10 of the first embodiment, and an operation of the antenna switching reception system 10 when the signal is received. Yes. FIG. 26 is a flowchart showing the operation of the antenna switching receiving system 10 of this modification. In the present modification, the process of # 54 is executed instead of # 52 shown in FIG. 23, and the process of # 55 is executed instead of # 53. That is, in this modification, the average value of the amplification factor when receiving the test signal before the previous frame at each antenna stored in the amplification factor average storage unit 38 is used when the test signal of the current frame is received. Used as the initial value of the amplification factor (# 54, # 55).

  According to this antenna switching reception system 10, the average value of the amplification factor in each antenna detected by the test signal before the previous frame is set as the initial value of the amplification factor of the current frame. As a result, in addition to the same effects as those of the modification examples shown in FIGS. 21 to 23, the amplification factor can be converged in a short time even when the reception level of the previous frame suddenly drops suddenly. It becomes possible.

(Modification)
FIG. 27 shows a schematic configuration of still another modified example of the antenna switching reception system 10 of the first embodiment. This antenna switching reception system 10 is configured by adding an amplification factor fluctuation calculation unit 39 to the antenna switching reception system 10 of FIG. The amplification factor variation calculation unit 39 calculates the rate of variation of the amplification factor of the automatic gain control unit 31 when the test signal is received by each antenna.

  FIG. 28 shows a frame signal received using the antenna A and the antenna B in the antenna switching reception system 10 of the first embodiment, and an operation of the antenna switching reception system 10 when the signal is received. Yes. FIG. 29 is a flowchart showing the operation of the antenna switching reception system 10 of this modification. In this modification, the processes # 56 and # 57 are executed between # 12 and # 52 shown in FIG. 23, the process # 58 is executed between # 5 and # 42, and the like.

  When there is no large variation in the communication environment, such as the positions of the transmission system and the reception system being fixed, there is little variation in the reception level of each antenna between frames, and accordingly, the variation in the amplification factor of the automatic gain control unit 31 It is thought that there are few things. Therefore, in this modification, it is determined that there is no significant change in the communication environment when the rate of change in the amplification factor is less than a predetermined threshold. Then, the gain previously stored in the gain storage unit 37 is used as the initial value of the gain of the automatic gain control unit 31 when a test signal is newly received by each antenna. On the other hand, when the rate of fluctuation of the amplification factor is equal to or greater than the predetermined threshold, it is possible that either the transmission system or the reception system is moving, and there is no merit in using the previous amplification factor as it is. Conversely, there is a possibility that convergence will be slow. In such a case, a predetermined value set in advance is used as the initial value of the amplification factor of the automatic gain control unit 31 when a new test signal is received by each antenna. For example, in the specification of the automatic gain control unit 31, a median value in a range in which the gain can be controlled is used. Thereby, it becomes easy to converge the amplification factor in a short time. Note that the rate of change in amplification factor refers to, for example, the rate of change in amplification factor detected in the current frame with respect to the amplification factor detected in the previous frame.

  In FIG. 29, when the antenna switching timing detection signal is detected by correlation value calculation unit 15 (YES in # 12), gain variation calculation unit 39 is an automatic gain control unit when receiving a test signal at each antenna. The rate of change in the amplification factor of 31 is calculated. If the variation in the amplification factor of antenna A is less than the threshold (YES in # 56), the amplification factor is stored as the initial value of the amplification factor of automatic gain control unit 31 when antenna A receives test signal 1. The previously stored amplification factor is set in the unit 37 (# 52). On the other hand, when the variation rate of the amplification factor is equal to or greater than the threshold (NO in # 56), a predetermined value is used as the initial value of the amplification factor (# 57). Thereafter, after switching to the antenna B (# 5), the initial value of the amplification factor of the automatic gain control unit 31 when the antenna B receives the test signal 2 is set. Here, similarly to antenna A, when the rate of fluctuation of the gain of antenna B is less than the threshold value (YES in # 58), the gain storage unit 37 stores the initial value of the gain of automatic gain control unit 31. The amplification factor stored last time is set (# 59). On the other hand, when the variation rate of the amplification factor is equal to or greater than the threshold (NO in # 58), a predetermined value is used as the initial value of the amplification factor (# 60). The following operations are the same as those in FIG. In addition, in # 52 and # 59, the average value of the amplification factor stored last time in the amplification factor average storage unit 38 shown in FIG. 24 may be set.

  According to this antenna switching reception system 10, when the rate of fluctuation of the amplification factor for each frame in each antenna is less than the threshold value, the amplification factor value of each antenna detected in the previous frame is set to the initial value of the amplification factor of the current frame. Value. On the other hand, when the fluctuation ratio is equal to or greater than the threshold, a predetermined value is set as the initial value of the amplification factor. Thereby, it is possible to determine the movement of the transmission system or the reception system by monitoring the rate of fluctuation of the amplification factor. Therefore, automatic gain control can be performed with an initial value of an appropriate amplification factor according to changes in the communication environment, and the accuracy of antenna switching determination can be further increased.

  Note that the present invention is not limited to the configuration of the above embodiment, and at least before receiving a payload signal, a test signal is received by a plurality of antennas, and an antenna that receives the payload signal is selected based on the reception level. What is necessary is just to be comprised so that it may do. Moreover, the antenna switching receiving system which combined the characteristic of each embodiment mentioned above suitably may be sufficient.

DESCRIPTION OF SYMBOLS 10 Antenna switching reception system 11 Antenna part 12 Antenna switching part 13 Antenna switching timing detection part 14 Antenna switching judgment part 31 Automatic gain control part 33 Average value calculation part 37 Amplification rate memory | storage part 38 Amplification rate average memory | storage part 39 Amplification rate fluctuation | variation calculation part

Claims (11)

In an antenna switching reception system that receives a radio signal transmitted from a transmission system by switching a plurality of antennas,
From the transmission system, an antenna switching timing detection signal, a plurality of test signals received by different antennas, and a payload signal received by a selected antenna are transmitted in this order,
The antenna switching timing detection signal is transmitted at a transmission rate lower than the transmission rate of the payload signal,
An automatic gain control unit that automatically adjusts the amplification factor according to the signal received by any of the plurality of antennas and optimizes the reception level of the signal,
Before receiving the payload signal from the transmission system, the antenna switching timing detection signal is received from the transmission system by any antenna, and the antenna switching timing detection signal is compared with the reference signal stored in advance. If the degree of coincidence is equal to or greater than a predetermined threshold, it is determined that the antenna switching timing detection signal has been detected, and if it is determined that the antenna switching timing detection signal has been detected, An antenna switching reception system which receives a test signal and selects an antenna which receives the payload signal based on an amplification factor of the test signal by the automatic gain control unit. An average value calculating unit that detects the amplification factor of the automatic gain control unit for each antenna and calculates an average value thereof, and based on the average value of the amplification factors calculated for each antenna by the average value calculation unit The antenna switching receiving system according to claim 1, wherein an antenna that receives a payload signal is selected . 3. The gain according to claim 1, wherein when the antenna is switched, the amplification factor of the automatic gain control unit during a predetermined period at the time of switching is not considered in selecting and determining an antenna that receives a payload signal. Antenna switching reception system. 4. The antenna switching reception according to claim 1 , wherein when the antenna is switched, the output of the amplification factor is stopped from the automatic gain control unit for a predetermined period at the time of switching. system. 5. The antenna switching receiving system according to claim 1, wherein when the antenna is switched, the operation of the automatic gain control unit is stopped for a predetermined period at the beginning of switching. When receiving the payload signal with an antenna other than the antenna that detected the level last,
The amplification factor of the automatic gain control unit at the time of receiving the test signal is used as an initial value of the amplification factor at the time of receiving the payload signal. The antenna switching receiving system according to 1. An amplification factor storage unit for storing the amplification factor of the automatic gain control unit when receiving the test signal at each antenna;
The amplification factor detected and stored in a previous frame in the amplification factor storage unit is used as an initial value of the amplification factor of the automatic gain control unit when a new test signal is received by each antenna. The antenna switching receiving system according to any one of claims 1 to 6. Further comprising an amplification factor average value storage unit for calculating and storing an average value of amplification factors detected in a plurality of previously received frames ;
As a new initial value of the amplification factor of the automatic gain control unit at the time of receiving the test signal at each antenna, claims which comprises using the mean value of the amplification factor stored in said amplification factor average value storage unit The antenna switching receiving system according to any one of claims 1 to 6 . An amplification factor fluctuation calculating unit that calculates a rate of fluctuation of the amplification factor of the automatic gain control unit when receiving the test signal at each antenna ;
When the amplification factor fluctuation ratio calculated by the amplification factor fluctuation calculation unit is less than a predetermined threshold, as an initial value of the amplification factor of the automatic gain control unit when the test signal is newly received by each antenna, The antenna switching reception system according to claim 7 , wherein the amplification factor stored in the amplification factor storage unit last time is used . An amplification factor fluctuation calculating unit that calculates a rate of fluctuation of the amplification factor of the automatic gain control unit when receiving the test signal at each antenna;
When the amplification factor fluctuation ratio calculated by the amplification factor fluctuation calculation unit is less than a predetermined threshold, as an initial value of the amplification factor of the automatic gain control unit when the test signal is newly received by each antenna, antenna switching reception system according to claim 8, characterized by using the average value of the amplification factor previously stored in said amplification factor average value storage unit. When the amplification factor fluctuation ratio calculated by the amplification factor fluctuation calculation unit is equal to or greater than a predetermined threshold, as an initial value of the amplification factor of the automatic gain control unit when the test signal is newly received by each antenna, The antenna switching reception system according to claim 9 or 10 , wherein a predetermined value is used .

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