JP6278303B2 - Antenna switching system - Google Patents

Description

  The present invention relates to an antenna switching system.

  Conventionally, there has been provided a diversity apparatus that suppresses deterioration of the communication environment by appropriately selecting an antenna having the highest received electric field strength from a plurality of antennas (see, for example, Patent Document 1). The diversity apparatus described in Patent Literature 1 switches three antennas, two receiving units that receive radio signals captured by the antennas, and a connection state between the three antennas and the two receiving units. An antenna switch.

  In this diversity apparatus, a diversity control period for selecting an antenna to be used at the time of data acquisition is provided. Until this diversity control period is reached, data is transmitted by the antenna selected in the previous diversity control period. To be acquired.

  On the other hand, when the period for diversity control is reached, the antenna switch is switched, so that two antennas are selected from the three antennas, and the connection between the two selected antennas and the two receiving units is established. Is done. Radio signals captured by the two selected antennas are respectively input to the corresponding receiving units, and the received electric field strength of each antenna is calculated based on the radio signals input to the respective receiving units.

  After performing the above processing for all combinations of selecting two antennas from the three antennas, an antenna for data acquisition is selected based on the calculated received field strength of each antenna. When the diversity control period ends, data is acquired by the selected antenna. Note that the diversity control period occurs at regular intervals, and the above process is repeated each time.

Japanese Patent No. 4624186

  In the diversity apparatus described in Patent Document 1 described above, the antenna having the highest received electric field strength calculated during the diversity control period is selected as the antenna for data acquisition, and this prevents the communication environment from deteriorating. it can. However, in this diversity apparatus, since data cannot be acquired until the diversity control period ends, communication may be delayed.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an antenna switching system in which communication delay is reduced while deterioration of communication environment is suppressed.

  The antenna switching system according to the present invention includes n (n is a positive integer of 3 or more) antennas, a signal receiving unit that receives a radio signal captured by the antennas, and the antenna used in the signal receiving unit. An antenna switching unit that selectively switches, a control unit that controls the antenna switching unit and can operate in two operation modes of a normal mode and a measurement mode, and the signal receiving unit while the control unit is operating in the normal mode A signal processing unit that obtains data from the radio signal received at the control unit and measures the received signal strength of the radio signal received by the signal receiving unit while the control unit is operating in the measurement mode; When the measurement mode is entered, the antenna is sequentially switched by m (m is a positive integer less than or equal to 2 and greater than m) via the antenna switching unit, and the signal processing unit is While measuring the received signal strength of the radio signal captured by each of the m antennas replaced, the data is acquired from the radio signal, the control unit, when the measurement mode ends, The antenna to be used in the normal mode is determined based on a measurement result of a signal processing unit.

  In this antenna switching system, it is preferable that the control unit determines m antennas to be used in the normal mode from the antennas having the highest received signal strength among the n antennas.

  In the antenna switching system, the control unit may select the antenna having the highest received signal strength among the m antennas selected this time in the measurement mode, and the m antennas selected next time. It is also preferable to include it in one of them.

  According to the configuration of the present invention, the control unit determines that the antenna used in the normal mode is an antenna having a high received signal strength based on the measurement result of the signal processing unit, thereby suppressing deterioration of the communication environment. There is an effect that can be. In the state where the operation mode of the control unit is set to the measurement mode, the signal processing unit acquires data from the radio signal while measuring the received signal strength of the radio signal captured by each antenna. There is also an effect that the delay can be reduced.

It is a schematic block diagram of the antenna switching system of this embodiment. It is a schematic block diagram of the radio | wireless communications system to which the same as the above is applied. It is a signal format of a radio signal used in the same as above. It is a flowchart explaining operation | movement same as the above. It is a flowchart explaining another operation | movement same as the above.

  Hereinafter, an embodiment of an antenna switching system will be described with reference to FIGS. In the following description, when it is not necessary to distinguish the antennas 11a to 11j, they are referred to as the antenna 11.

  FIG. 2 is a schematic configuration diagram of a wireless communication system to which the antenna switching system of the present embodiment is applied. The antenna switching system of the present embodiment is mounted on the wireless communication device 1, and the wireless communication device 1 and the transmitter 2 perform wireless communication. The transmitter 2 has an antenna 21 and transmits a radio signal Sig 1 to the radio communication device 1. The transmitter 2 is built in a monitor device (not shown) operated by an administrator, for example. In addition, the antenna 21 of the transmitter 2 may be plural.

  The antenna switching system is built in, for example, a distribution board (not shown) having a wireless communication function, receives a command transmitted wirelessly from the monitor device, and wirelessly transmits information such as power consumption to the monitor device. To do. When the monitor device receives the information such as the power consumption transmitted from the distribution board, the monitor device displays the current or integrated power consumption in the area where the power is distributed by the distribution board.

  In the present embodiment, the monitor device has a single antenna 21 (see FIG. 2), and the distribution board has a plurality (ten in the present embodiment) of antennas 11a to 11j. Then, the distribution board appropriately selects the antenna 11 suitable for the surrounding environment by the antenna switching system, and performs stable wireless communication with the monitor device.

  Here, the distribution board includes a board body formed in a rectangular box shape with an opening on the front surface side, and a lid body that is attached to the board body so that the rear surface side opens and closes the opening of the board body. The ten antennas 11a to 11j arranged radially are attached to the back surface of the antenna. In addition, about the attachment structure of antenna 11a-11j, it may be formed integrally with a cover body by insert molding, and the structure affixed with respect to a cover body may be sufficient.

  As described above, by arranging the antennas 11a to 11j in a radial manner, it is possible to increase reception sensitivity even when a highly directional antenna is used. In addition, by attaching the antennas 11a to 11j to the back surface of the lid, the antennas 11a to 11j are not seen from the outside, and an attractive distribution board can be provided.

  FIG. 1 is a schematic block diagram of an antenna switching system according to this embodiment. The antenna switching system includes a wireless communication device 1 and a plurality (ten in this embodiment) of antennas 11a to 11j. The wireless communication device 1 includes an antenna switching unit 12, an RF unit 13, an antenna control unit 14 (control unit), and a signal processing unit 15.

  The antenna switching unit 12 switches to any of the antennas 11a to 11j according to the switching signal Sig2 output from the antenna control unit 14. In the present embodiment, the antenna switching unit 12 can select two antennas 11 from the ten antennas 11.

  The RF unit 13 down-converts the radio signal Sig1 captured by the antenna 11 and extracts a baseband signal. Here, in the present embodiment, the RF receiver 13 constitutes a signal receiver.

  The signal processing unit 15 includes an acquisition unit 151 and a measurement unit 152, and processes the baseband signal extracted by the RF unit 13. The acquisition unit 151 acquires data from the radio signal Sig1 captured by the selected antenna 11. The measuring unit 152 measures the received signal strength (RSSI: Received Signal Strength Indication) (hereinafter referred to as “RSSI”) of the radio signal Sig 1 captured by the selected antenna 11.

  The antenna control unit 14 has a function of controlling the antenna switching unit 12 and can operate in two operation modes, a normal mode and a measurement mode. The measurement mode is a mode in which the RSSI of the radio signal Sig1 captured by each antenna 11 is measured and the magnitude of the measured RSSI is compared in order to determine (select) the antenna 11 used in the normal mode.

  The normal mode is a mode in which data included in the radio signal Sig1 from the transmitter 2 is acquired by the antenna 11 having a high reception level among the two antennas 11 determined in the measurement mode. Accordingly, even in the normal mode, the RSSI of the radio signal Sig1 captured by each antenna 11 is measured, and the magnitudes of the measured RSSI are compared.

  That is, regardless of the operation mode of the antenna control unit 14, the measurement unit 152 of the signal processing unit 15 measures the RSSI of the radio signal Sig 1 captured by the antenna 11, and the acquisition unit 151 captures the radio signal captured by the antenna 11. Data is acquired from the signal Sig1.

  In the antenna switching system of the present embodiment, the acquisition unit 151 of the signal processing unit 15 is configured to acquire data from the radio signal Sig1 in both the normal mode and the measurement mode. Therefore, communication delay can be reduced compared to the case where data is acquired after the diversity control period ends as in the conventional example.

  FIG. 3 is an example of a signal format of the radio signal Sig1 transmitted from the transmitter 2 when the operation mode of the antenna control unit 14 is the measurement mode, and is configured by an antenna comparison unit and a data unit.

  The antenna comparison unit is made up of, for example, a general preamble signal. When a preamble is detected, the sizes of RSSIs of the two selected antennas 11 are compared, and the antenna 11 having a large RSSI is selected. The data portion includes data (for example, a request command for information such as power consumption) acquired by the antenna 11 selected according to the comparison result.

  Here, if an attempt is made to compare RSSI after detecting a unique word, the subsequent payload may not be received. In this case, a plurality of combinations of preambles and unique words may be sent continuously in the antenna comparison unit, so that the subsequent payload can be received even if the RSSI is compared after the unique word is detected. Can do.

  Next, an example of the measurement mode in the antenna switching system will be described with reference to the flowchart shown in FIG. Note that i in FIG. 4 indicates the i-th antenna 11.

  First, the antenna control unit 14 outputs a switching signal Sig2 for switching to the first and second antennas 11a and 11b to the antenna switching unit 12, and switches to the antennas 11a and 11b via the antenna switching unit 12 (step S1). . When a unique word in the radio signal Sig1 captured by the antennas 11a and 11b is detected, the antenna control unit 14 compares the performance of the antennas 11a and 11b.

  Specifically, the measurement unit 152 of the signal processing unit 15 measures the RSSI of the radio signal Sig1 captured by the antennas 11a and 11b (measures the RSSI of the antenna i and the antenna (i + 1)) (step S2). And the antenna control part 14 compares the magnitude of measured RSSI (step S3).

  When the RSSI of the antenna 11a is equal to or greater than the RSSI of the antenna 11b (Yes in step S3), the acquisition unit 151 of the signal processing unit 15 acquires data from the radio signal Sig1 captured by the antenna 11a (step S4). . When the RSSI of the antenna 11b is larger than the RSSI of the antenna 11a (No in step S3), the acquisition unit 151 of the signal processing unit 15 acquires data from the radio signal Sig1 captured by the antenna 11b (step S5). ).

  Thereafter, the antenna control unit 14 stores the acquired RSSI of the antennas 11a and 11b in a storage unit (not shown) in association with the antennas 11a and 11b (step S6).

  Next, since the antenna control unit 14 currently selects the first and second antennas 11a and 11b (No in step S7), the third and fourth antennas 11c and 11d are connected via the antenna switching unit 12. (Step S8). Then, the processes of steps S2 to S6 are similarly performed on the selected third and fourth antennas 11c and 11d.

  Similarly, the processes of steps S2 to S6 are repeated for the fifth and sixth antennas 11e and 11f, the seventh and eighth antennas 11g and 11h, and the ninth and tenth antennas 11i and 11j. When the processes of steps S2 to S6 are performed on the ninth and tenth antennas 11i and 11j (Yes in step S7), the antenna control unit 14 compares the RSSIs of the antennas 11a to 11j, and the RSSI is large. Two antennas 11 are determined (step S9).

  As described above, the antenna control unit 14 determines that the antenna 11 used in the normal mode is the antenna 11 having a large RSSI based on the measurement result of the signal processing unit 15, thereby suppressing deterioration of the communication environment. Can do. When the operation mode of the antenna control unit 14 is set to the measurement mode, the signal processing unit 15 acquires data from the radio signal Sig1 while measuring the RSSI of the radio signal Sig1 captured by each antenna 11. . Therefore, communication delay can be reduced compared to the case where data is acquired after the diversity control period ends as in the conventional example.

  Further, in the present embodiment, the number of antennas 11 selected in the measurement mode and the number of antennas 11 used in the normal mode are the same number (two). Thereby, the signal format of the radio signal Sig1 transmitted from the transmitter 2 can be shared between the normal mode and the measurement mode.

  Further, as in this embodiment, by performing diversity with the two antennas 11, it is possible to cope with multipath fading (reception level fluctuation) due to a sudden environmental change such as a person moving. Furthermore, the cost increase can be suppressed as compared with the case where two receiving units are provided as in the conventional example.

  Next, another example of the measurement mode in the antenna switching system will be described with reference to the flowchart shown in FIG. Note that i and j in FIG. 5 indicate the i-th and j-th antennas 11, respectively.

  First, the antenna control unit 14 outputs a switching signal Sig2 for switching to the first and second antennas 11a and 11b to the antenna switching unit 12, and switches to the antennas 11a and 11b via the antenna switching unit 12 (step S11). . When a unique word in the radio signal Sig1 captured by the antennas 11a and 11b is detected, the antenna control unit 14 compares the performance of the antennas 11a and 11b.

  Specifically, the measurement unit 152 of the signal processing unit 15 measures the RSSI of the radio signal Sig1 captured by the antennas 11a and 11b (measures the RSSI of the antenna i and the antenna j) (step S12). And the antenna control part 14 compares the magnitude of measured RSSI (step S13).

  When the RSSI of the antenna 11a is greater than or equal to the RSSI of the antenna 11b (Yes in step S13), the acquisition unit 151 of the signal processing unit 15 acquires data from the radio signal Sig1 captured by the antenna 11a (step S14). . When the RSSI of the antenna 11b is larger than the RSSI of the antenna 11a (No in step S13), the acquisition unit 151 of the signal processing unit 15 acquires data from the radio signal Sig1 captured by the antenna 11b (step S15). ).

  Here, the antenna control unit 14 selects one of the first and second antennas 11a and 11b having the larger RSSI as one of the two antennas 11 to be selected next, and further selects the third antenna 11c. (Steps S16 to S18). And the process of step S12-S16 is performed similarly with respect to one of the selected antennas 11a and 11b and the 3rd antenna 11c.

  Similarly, the processes of steps S12 to S16 are performed on the tenth antenna 11j and any one of the remaining antennas 11a to 11i. And if the process of step S12-S16 is performed with respect to all the antennas 11a-11j (step S17), the antenna control part 14 will compare the RSSI of the antennas 11a-11j, and two antennas 11 with large RSSI will be demonstrated. Is determined (step S19).

  As described above, the antenna 11 having a large RSSI among the two antennas 11 selected this time is set as one of the two antennas 11 selected next time, so that the antenna 11 tried so far The antenna 11 having the largest RSSI is always selected. Thereby, even in the measurement mode, the antenna 11 having a large RSSI can always be used, and data can be reliably acquired.

  In the present embodiment, the case where the number of antennas 11 selected in the measurement mode is two has been described as an example. However, the number may be three or more as long as the number is smaller than the number of antennas 11 provided in the antenna switching system. . In the present embodiment, the case where the number of antennas 11 selected in the measurement mode is the same as the number of antennas 11 used in the normal mode has been described as an example. Also good.

  Furthermore, in this embodiment, although the case where the number of the antennas 11 with which an antenna switching system is provided was 10 was demonstrated to the example, it should just be provided with the at least 3 antenna 11, and is not limited to this embodiment. Further, the method of measuring the RSSI of the antenna 11 is not limited to the present embodiment. For example, the RSSI may be measured for all combinations of selecting the two antennas 11 from the ten antennas 11a to 11j.

  Furthermore, in this embodiment, the magnitude of RSSI of the two antennas 11 is compared in the measurement mode, and subsequent data is acquired by the antenna 11 having a large RSSI. On the other hand, the subsequent payload may be received by the antenna that has detected the unique word included in the packet.

  In this case, one packet is composed of a plurality of pairs of preambles and unique words, and subsequently transmitted payload, and the packet is received while switching between two antennas at a predetermined period. At this time, when a unique word in the packet is detected by one antenna, the antenna that detected the unique word is selected, and the subsequent payload is received by the selected antenna.

  Moreover, in this embodiment, the magnitude of RSSI of each antenna 11 is compared in the measurement mode, and the antenna 11 having a large RSSI is used as the antenna 11 used in the normal mode. On the other hand, when data is acquired using two or more antennas 11 at the same time, it is preferable to select the antenna 11 in consideration of not only the RSSI of each antenna 11 but also the directivity of each antenna 11.

  For example, when two antennas 11 are selected from the ten antennas 11, if the combinations of antennas 11 having different directivities are various, the radio wave propagation areas are greatly different. Therefore, in this case, it is preferable to select a combination of antennas 11 to be used from all combinations of selecting the two antennas 11 from the ten antennas 11.

  Further, as a method of selecting the two antennas 11, the antenna 11 having the largest RSSI and the antenna 11 having the most different antenna directivity with respect to the antenna 11 may be selected. For example, when ten antennas 11 are arranged radially as in the present embodiment, the antenna 11 having the largest RSSI and the directivity in the opposite direction (180 degree opposite direction) to the directionality of the antenna 11 are set. What is necessary is just to select the antenna 11 which has.

  Further, it is preferable to periodically perform the above-described measurement mode. If the result of periodically performing the measurement mode is the same, the interval for performing the measurement mode may be increased. In addition, the measurement mode may be performed when an error is detected by cyclic redundancy check (CRC). Furthermore, it is preferable not to use the antenna combination that has been in a state where reception is impossible for a certain period of time until a change in the surrounding environment is detected.

  In addition, the measurement mode may be performed when movement of a wireless communication device equipped with the antenna switching system is detected, and the measurement mode is frequently performed when the wireless communication device continues to move. It is preferable to do this. Even if the movement of the wireless communication device is not detected, it is preferable to determine that the change in the surrounding environment is large if the measurement results in the measurement mode are different each time, and to execute the measurement mode at a high frequency.

  Further, for example, when two antennas are compared, it is preferable to select one having a correlation value between the two antennas equal to or less than a predetermined value. In addition, when receiving a continuous signal such as a streaming video, it is preferable to use a thumbnail or the like as a test signal in advance and execute the measurement mode when the test signal is received. Furthermore, in the first measurement mode, it is also preferable to measure RSSI for all antennas, and in the second and subsequent measurement modes, measure RSSI for fewer antennas than in the first measurement mode.

  The antenna switching system of this embodiment selectively selects n antennas 11, an RF unit 13 (signal receiving unit) that receives a radio signal Sig 1 captured by the antennas 11, and an antenna 11 that is used in the RF unit 13. And an antenna switching unit 12 for switching. The antenna switching system includes an antenna control unit 14 (control unit) and a signal processing unit 15. The antenna control unit 14 controls the antenna switching unit 12 and can operate in two operation modes, a normal mode and a measurement mode. The signal processing unit 15 acquires data from the radio signal Sig1 received by the RF unit 13 while the antenna control unit 14 is operating in the normal mode, and is received by the RF unit 13 while the antenna control unit 14 is operating in the measurement mode. The RSSI (received signal strength) of the received radio signal Sig1 is measured. When the antenna control unit 14 enters the measurement mode, the antenna control unit 14 sequentially switches the antennas 11 by m via the antenna switching unit 12. The signal processing unit 15 acquires data from the radio signal Sig1 while measuring the RSSI of the radio signal Sig1 captured by each of the switched m antennas 11. Further, when the measurement mode ends, the antenna control unit 14 determines the antenna 11 to be used in the normal mode based on the measurement result of the signal processing unit 15.

  Further, like the antenna switching system of the present embodiment, the antenna control unit 14 determines m antennas 11 to be used in the normal mode from the one having the larger RSSI among the n antennas 11. Is preferred.

  Further, as in the antenna switching system of the present embodiment, the antenna control unit 14 selects the antenna 11 having the highest received signal strength next time from the m antennas 11 selected this time in the measurement mode. Preferably, one of the antennas 11 is included.

11 Antenna 12 Antenna switching unit 14 Antenna control unit (control unit)
15 Signal processor Sig1 Wireless signal

Claims (3)

n antennas (n is a positive integer of 3 or more), a signal receiving unit that receives a radio signal captured by the antenna, and an antenna switching unit that selectively switches the antenna used in the signal receiving unit A control unit that controls the antenna switching unit and is operable in two operation modes of a normal mode and a measurement mode; and data from a radio signal received by the signal receiving unit while the control unit is operating in the normal mode. And a signal processing unit that measures the received signal strength of the radio signal received by the signal receiving unit while the control unit is operating in the measurement mode,
In the measurement mode, the control unit sequentially switches the m antennas (m is a positive integer smaller than or equal to 2 and smaller than n) via the antenna switching unit, and the signal processing unit is switched. Acquiring data from the radio signal while measuring the received signal strength of the radio signal captured by each of the m antennas;
When the measurement mode ends, the control unit determines the antenna to be used in the normal mode based on a measurement result of the signal processing unit.   The antenna switching according to claim 1, wherein the control unit determines m antennas to be used in the normal mode from the antennas having the highest received signal strength among the n antennas. system.   In the measurement mode, the control unit includes the antenna having the highest received signal strength among the m antennas selected this time in one of the m antennas selected next time. The antenna switching system according to claim 1 or 2.

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