JP2018207403A - Radio communication device and delay adjustment method - Google Patents

Abstract

To improve accuracy in calibration of an array antenna.SOLUTION: A base station includes a plurality of antennas 13, a plurality of transmission circuits, a plurality of cables 12, a signal generator 35, and an adjustment section 36. Each transmission circuit is provided corresponding to each antenna 13. Each cable 12 is provided corresponding to each antenna 13, and connects the antenna 13 and the transmission circuit corresponding to the antenna 13. The signal generator 35 generates a test signal to be input to each transmission circuit. With the end of an array antenna side in each cable 12 open, the adjustment section 36 adjusts delay time in each transmission circuit so that the difference in time from the timing in which the test signal is input in the transmission circuit from the signal generator 35 to the timing in which the test signal reflected at the open end in the cable 12 is received through the transmission circuit and the cable 12 is less than a predetermined value, among the transmission circuits.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a wireless communication apparatus and a delay adjustment method.

  A so-called “heterogeneous network” in which a small cell is arranged in a macro cell can further improve the throughput of the mobile network. However, when many small cells are arranged in a macro cell, inter-cell interference occurs. As one means for avoiding this, for example, beam forming is effective.

  Beam forming can concentrate power in a specific area by concentrating the directivity of a plurality of antennas in a certain direction. Thereby, the leakage power to an adjacent cell can be reduced and inter-cell interference is reduced. In beam forming, a beam can be formed with high accuracy by aligning phase errors between a plurality of antennas. Therefore, antenna calibration is performed to correct a phase error between a plurality of antennas.

  For example, a technique is known in which a delay correction amount of a transmission circuit circuit corresponding to each antenna included in an array antenna is obtained using a delay measurement result of a calibration signal, and the obtained delay correction amount is set in a delay element of the transmission / reception circuit circuit. It has been.

JP 2010-213217 A

  In the above technique, the calibration signal that has passed through the transmission circuit circuit is fed back in the analog circuit, and the delay correction amount of the transmission circuit circuit is calculated based on the fed back signal. An antenna is connected to the analog circuit via a cable. Since the antenna and the analog circuit are installed in different places, the cable connecting the antenna and the analog circuit is long. In addition, strictly speaking, each cable connecting each antenna and each transmission circuit circuit is often of a different length. Therefore, even if the delay amount of the transmission circuit circuit corresponding to each antenna is corrected based on the calibration signal fed back in the analog circuit, the cable delay difference in each antenna remains. For this reason, it is difficult to accurately adjust the phase and the like of the signal radiated from each antenna to the space.

  The disclosed technique has been made in view of the above point, and an object thereof is to provide a radio communication apparatus and a delay adjustment method capable of improving the accuracy of calibration of an array antenna.

  In one aspect, a wireless communication device disclosed in the present application includes an array antenna including a plurality of antennas, a plurality of transmission circuits, a plurality of lines, a generation unit, and an adjustment unit. Each transmission circuit is provided corresponding to each antenna. Each line is provided corresponding to each antenna, and connects the antenna and a transmission circuit corresponding to the antenna. The generation unit generates a test signal input to each transmission circuit. The adjustment unit is configured such that the test signal is input to the transmission circuit from the generation unit through the transmission circuit and the line between the plurality of transmission circuits in a state where the end on the antenna side is opened in each line. The delay time in each transmission circuit is adjusted so that the time difference until the timing when the test signal reflected by the open end of the line is received is less than a predetermined value.

  According to one aspect of the wireless communication apparatus and the delay adjustment method disclosed in the present application, there is an effect that the accuracy of calibration of the array antenna can be improved.

FIG. 1 is a block diagram illustrating an example of a base station. FIG. 2 is a block diagram illustrating an example of an RRH (Remote Radio Head) according to the first embodiment. FIG. 3 is a diagram for explaining an example of the flow of test signals during calibration of the transmission circuit. FIG. 4 is a diagram for explaining an example of the delay of the test signal during calibration of the transmission circuit. FIG. 5 is a diagram for explaining an example of the flow of test signals during calibration of the receiving circuit. FIG. 6 is a diagram for explaining an example of the delay of the test signal at the time of calibration of the receiving circuit. FIG. 7 is a flowchart illustrating an example of calibration of the transmission circuit according to the first embodiment. FIG. 8 is a flowchart illustrating an example of calibration of the receiving circuit according to the first embodiment. FIG. 9 is a diagram illustrating another example of the antenna. FIG. 10 is a block diagram illustrating another example of RRH. FIG. 11 is a block diagram illustrating an example of RRH in the second embodiment. FIG. 12 is a diagram for explaining an example of the delay of the test signal at the time of calibration of the transmission circuit. FIG. 13 is a flowchart illustrating an example of calibration of the transmission circuit according to the second embodiment. FIG. 14 is a diagram for explaining an example of the delay of the test signal at the time of calibration of the transmission circuit in the modification of the second embodiment. FIG. 15 is a flowchart illustrating an example of calibration of the transmission circuit according to the modification of the second embodiment. FIG. 16 is a block diagram illustrating an example of RRH in the third embodiment. FIG. 17 is a diagram illustrating an example of a combiner. FIG. 18 is a diagram illustrating an example of RRH hardware.

  Hereinafter, embodiments of a wireless communication device and a delay adjustment method disclosed in the present application will be described in detail with reference to the drawings for each example. The disclosed technology is not limited by the following embodiments. In addition, the embodiments can be appropriately combined within a range in which processing contents are not contradictory.

[Base station 10]
FIG. 1 is a block diagram illustrating an example of the base station 10. The base station 10 includes a BBU (Base Band Unit) 11, an RRH 20, and an array antenna 14. The array antenna 14 includes a plurality of antennas 13-1 to 13-n. Each of the plurality of antennas 13-1 to 13-n is connected to the RRH 20 via any one of the plurality of cables 12-1 to 12-n. The base station 10 is an example of a wireless communication device.

  The RRH 20 includes a control unit 30 and a plurality of radio units 40-1 to 40-n. Each of the plurality of radio units 40-1 to 40-n is connected to one of the plurality of antennas 13-1 to 13-n via one of the plurality of cables 12-1 to 12-n. The control unit 30 controls the phase and amplitude of signals transmitted / received by each of the plurality of radio units 40-1 to 40-n, so that the radio signal transmitted / received via the array antenna 14 has a predetermined direction. A beam having directivity is formed.

  In the following description, the plurality of cables 12-1 to 12-n are collectively referred to as the cable 12 without being distinguished, and the plurality of antennas 13-1 to 13-n are not distinguished from each other. When referring generically, they are simply referred to as antenna 13. Hereinafter, the radio units 40-1 to 40-n are simply referred to as the radio unit 40 when collectively referred to without being distinguished from each other. Each cable 12 is an example of a track.

[RRH20]
FIG. 2 is a block diagram illustrating an example of the RRH 20 according to the first embodiment. The RRH 20 includes a control unit 30, a plurality of radio units 40, an ADC (Analog to Digital Converter) 50, and a switch 51. In FIG. 2, two radio units 40-1 and 40-2 are shown in the RRH 20 corresponding to the two antennas 13-1 and 13-2 for simplicity of explanation. However, when three or more antennas 13 are connected to the RRH 20, three or more radio units 40 may be provided in the RRH 20 corresponding to the respective antennas 13.

  Each wireless unit 40 includes a DAC (Digital to Analog Converter) 41, a PA (Power Amplifier) 42, a circulator 43, a BPF (Band Pass Filter) 44, a switch 46, an LNA (Low Noise Amplifier) 47, and an ADC 48. In the present embodiment, each wireless unit 40 transmits and receives signals based on a TDD (Time Division Duplex) method. Each wireless unit 40 is connected to the cable 12 via a connector 45. Each antenna 13 is detachably connected to the cable 12 by a connector 120.

  The DAC 41 converts the signal output from the control unit 30 from a digital signal to an analog signal. The PA 42 amplifies the signal converted into the analog signal by the DAC 41. The circulator 43 passes the signal amplified by the DAC 41 to the BPF 44. Further, the circulator 43 passes the signal received by the antenna 13 and passed through the BPF 44 to the switch 46. The BPF 44 limits the frequency band of the signal amplified by the PA 42 and passed through the circulator 43 to a predetermined frequency band. The BPF 44 limits the frequency band of the signal received by the antenna 13 to a predetermined frequency band.

  The switch 46 switches the output destination of the signal output from the circulator 43 to either the LNA 47 or the switch 51. The LNA 47 amplifies the signal output from the switch 46. The ADC 48 converts the signal amplified by the LNA 47 from an analog signal to a digital signal, and outputs the signal converted to the analog signal to the control unit 30.

  The switch 51 switches the test signal input to the ADC 50 to either the test signal output from the radio unit 40-1 or the test signal output from the radio unit 40-2. The ADC 50 converts the test signal output from the switch 51 from an analog signal to a digital signal, and outputs the converted test signal to the control unit 30.

  The control unit 30 includes a plurality of switches 31-1 to 31-2, a plurality of delay units 32-1 to 32-2, a plurality of switches 33-1 to 33-2, and a plurality of delay units 34-1 to 34-2. , A signal generator 35, an adjustment unit 36, and a detection unit 37. Each of the plurality of switches 31-1 to 31-2, the plurality of delay units 32-1 to 22-2, the plurality of switches 33-1 to 33-2, and the plurality of delay units 34-1 to 34-2 are respectively It is provided corresponding to each of the plurality of antennas 13. In the example of FIG. 2, the switch 31-1, the delay unit 32-1, the switch 33-1, and the delay unit 34-1 are provided corresponding to the antenna 13-1. Further, the switch 31-2, the delay unit 32-2, the switch 33-2, and the delay unit 34-2 are provided corresponding to the antenna 13-2.

  In the following description, when a plurality of switches 31-1 to 31-2 are collectively referred to without being distinguished, they are simply referred to as a switch 31, and each of the plurality of delay units 32-1 to 32-2 is distinguished. When referring generically, they are simply referred to as a delay unit 32. In the following description, when a plurality of switches 33-1 to 33-2 are collectively referred to without being distinguished, they are simply referred to as a switch 33, and each of the plurality of delay units 34-1 to 34-2 is distinguished. When referring generically, they are simply referred to as the delay unit 34. In each antenna 13, the delay unit 32, the DAC 41, the PA 42, the circulator 43, and the BPF 44 are examples of a transmission circuit, and the LNA 47, the ADC 48, and the delay unit 34 are examples of a reception circuit.

  Each switch 31 switches the signal input to the corresponding delay unit 32 to either a transmission signal output from the BBU 11 or a test signal output from the signal generator 35.

  Each delay unit 32 delays the signal output from the switch 31 by the delay amount set by the adjustment unit 36, and outputs the delayed signal to the radio unit 40 corresponding to the delay unit 32. Each delay unit 32 is, for example, an FIR (Finite Impulse Response) filter.

  Each delay unit 34 delays the signal output from the radio unit 40 corresponding to the delay unit 34 by the delay amount set by the adjustment unit 36, and the delayed signal is a switch 33 corresponding to the delay unit 34. Output to. Each delay unit 34 is, for example, an FIR filter.

  Each switch 33 switches the output destination of the signal output from the delay unit 34 corresponding to the switch 33 to either the BBU 11 or the detection unit 37.

  For each antenna 13, the signal generator 35 generates a test signal that is used to adjust the delay amount of the transmission circuit corresponding to the antenna 13. In this embodiment, the signal generator 35 generates a pulsed test signal. Then, the signal generator 35 outputs the generated test signal to each switch 31 and the detection unit 37. The signal generator 35 is an example of a generation unit.

  Based on the transmission time that is the time difference between the test signal output from the signal generator 35 and the test signal fed back via each radio unit 40, the detection unit 37 and the delay unit 32 corresponding to each antenna 13 and The amount of delay set in the delay unit 34 is calculated. Then, the detection unit 37 outputs the delay amount calculated for each antenna 13 to the adjustment unit 36.

  The adjustment unit 36 sets the delay amount calculated for each antenna 13 by the detection unit 37 to the corresponding delay unit 32 and delay unit 34, respectively.

[Flow of test signal during calibration of transmitter circuit]
FIG. 3 is a diagram for explaining an example of the flow of test signals during calibration of the transmission circuit. In the calibration of the transmission circuit in the present embodiment, the phase of the signal radiated from each of the plurality of antennas 13-1 to 13-2 is adjusted. Note that, with one antenna 13 as a reference, the phase of the signal is adjusted between the reference antenna 13 and the other antenna 13, so that three or more antennas 13 are also radiated from each antenna 13 into the space. The phase of the signal to be adjusted can be adjusted. Therefore, below, the calibration regarding the two antennas 13 is demonstrated.

  In calibration of the transmission circuit, for example, as shown in FIG. 3, each antenna 13 is detached from the cable 12. As a result, the end portion of the cable 12 provided with the connector 120 is electrically open (high impedance). In each switch 31, the signal input to the corresponding delay unit 32 is switched to the test signal output from the signal generator 35. Each delay unit 32 is set to “0” as a delay amount. In each radio unit 40, the switch 46 is switched so that the signal output from the circulator 43 is output to the switch 51.

Then, the transmission time ΔT _t1 of the transmission circuit corresponding to the antenna 13-1 is measured. Specifically, the switch 51 is switched so that the signal output from the radio unit 40-1 is input to the ADC 50. Then, the signal generator 35 outputs the test signal to the switch 31-1 and the detection unit 37. The test signal output from the signal generator 35 to the switch 31-1 is input to the radio unit 40-1 via the delay unit 32-1. The test signal input to the radio unit 40-1 is output to the cable 12-1 via the DAC 41, PA 42, circulator 43, BPF 44, and connector 45 in the radio unit 40-1.

  Here, in the calibration in the present embodiment, since the antenna 13-1 is removed from the cable 12-1, the test signal output to the cable 12-1 passes through the cable 12-1 and is connected to the connector. Reflected at 120. The test signal reflected at the connector 120 is fed back to the detection unit 37 via the cable 12-1, the connector 45, the BPF 44, the circulator 43, the switch 46, the switch 51, and the ADC 50.

FIG. 4 is a diagram for explaining an example of the delay of the test signal during calibration of the transmission circuit. Detector 37, for example as shown in FIG. 4 (a), on the basis of the transmission timing T _cal1 of the output test signal from the signal generator 35, the timing T _Tdet1 feedback to the test signal is received, The transmission time ΔT _t1 of the transmission circuit corresponding to the antenna 13-1 is measured.

Next, the transmission time ΔT _t2 of the transmission circuit corresponding to the antenna 13-2 is measured. Specifically, the switch 51 is switched so that the signal output from the radio unit 40-2 is input to the ADC 50. Then, the signal generator 35 outputs the test signal to the switch 31-2 and the detection unit 37. The test signal output from the signal generator 35 to the switch 31-2 is input to the radio unit 40-2 via the delay unit 32-2. The test signal input to the radio unit 40-2 is output to the cable 12-2 via the DAC 41, PA 42, circulator 43, BPF 44, and connector 45 in the radio unit 40-2.

  Since the antenna 13-2 is removed from the cable 12-2, the test signal output to the cable 12-2 passes through the cable 12-2 and is reflected by the connector 120. The test signal reflected at the connector 120 is fed back to the detection unit 37 via the cable 12-2, the connector 45, the BPF 44, the circulator 43, the switch 46, the switch 51, and the ADC 50.

Detector 37, for example as shown in FIG. 4 (b), on the basis of the transmission timing T _cal2 of the output test signal from the signal generator 35, the timing T _Tdet2 feedback to the test signal is received, The transmission time ΔT _t2 of the transmission circuit corresponding to the antenna 13-2 is measured. In the example of FIG. 4, the transmission time ΔT _t2 is longer than the transmission time ΔT _t1 . Next, the detector 37 calculates a difference T _td between the measured transmission times ΔT _t1 and ΔT _t2 . Then, the detection unit 37 adjusts an instruction to set the calculated difference T _td in the delay unit 32 in the transmission circuit in which the shorter transmission time among the measured transmission times ΔT _t1 and ΔT _t2 is measured. To the unit 36.

The adjustment unit 36 sets a delay amount corresponding to the difference T _td instructed from the detection unit 37 in the delay unit 32 in the transmission circuit instructed from the detection unit 37. For example, in the example of FIG. 4, as shown in FIG. 4C, the difference T instructed from the detection unit 37 to the delay unit 32 in the transmission circuit in which the transmission time ΔT _t1 is measured, that is, the delay unit 32-1. A delay amount corresponding to _td is set. Thereby, in the transmission circuit corresponding to the antenna 13-1, the timing at which the fed back test signal is received is T _tdet1 ′, and the transmission time of the transmission circuit of the antenna 13-1 is ΔT _t1 ′. This reduces the difference between the transmission time ΔT _t1 ′ of the transmission circuit of the antenna 13-1 and the transmission time ΔT _t2 of the transmission circuit of the antenna 13-2. Therefore, the base station 10 can accurately adjust the phase of the signal radiated from each antenna 13 to the space.

  Here, the cable 12 connecting each antenna 13 and each radio unit 40 may have different lengths and delay characteristics. Therefore, if the difference in transmission time of each transmission circuit is calculated based on the test signal fed back in each radio unit 40, the difference in the calculated transmission time includes the cable 12 connected to each transmission circuit. The transmission time difference is not included. Therefore, it is difficult to accurately adjust the phase of the signal radiated from each antenna 13 to the space.

  On the other hand, in the base station 10 of the present embodiment, the end of the cable 12 connected to the antenna 13 is opened, and the difference in transmission time between the transmission circuits is calculated using the test signal reflected at the end. The Thus, the calculated transmission time difference includes the transmission time difference of the cable 12 connected to each transmission circuit. Therefore, the phase of the signal radiated from each antenna 13 to the space can be adjusted with high accuracy.

[Test signal flow during calibration of receiver circuit]
FIG. 5 is a diagram for explaining an example of the flow of test signals during calibration of the receiving circuit. In the calibration of the receiving circuit, the phase difference of the signals received by each of the plurality of antennas 13-1 to 13-2 is adjusted so as to become small when it is input to the BBU 11. The calibration of the receiving circuit in the present embodiment is performed after the calibration of the transmitting circuit is executed. In the calibration of the receiving circuit, the phase of the signal is adjusted between the reference antenna 13 and the other antennas 13 with respect to one antenna 13, so that three or more antennas 13 can also be calibrated. The phase difference can be adjusted. Therefore, below, the calibration regarding the two antennas 13 is demonstrated.

The calibration of the reception circuit is performed after the calibration of the transmission circuit. Therefore, for example, as shown in FIG. 5, each antenna 13 is disconnected from the cable 12, and in each switch 31, the signal input to the corresponding delay unit 32 is output from the signal generator 35. The signal has been switched. In each delay unit 32, a delay amount corresponding to the difference calculated in the calibration of the transmission circuit is set. When the transmission time of the transmission circuit corresponding to each antenna 13 has a relationship as shown in FIG. 4, for example, a delay amount corresponding to the difference T _td is set in the delay unit 32-1, and the delay unit 32-2 “0” is set as the delay amount.

  In each radio unit 40, the switch 46 is switched so that the signal output from the circulator 43 is output to the LNA 47. Further, “0” is set as a delay amount in each delay unit 34.

Then, the transmission time ΔT _r1 of the receiving circuit corresponding to the antenna 13-1 is measured. Specifically, the switch 33-1 is switched so that the signal output from the delay unit 34-1 is output to the detection unit 37. Then, the signal generator 35 outputs the test signal to the switch 31-1 and the detection unit 37. The test signal output from the signal generator 35 to the switch 31-1 is input to the radio unit 40-1 via the delay unit 32-1 in which the delay amount corresponding to the difference T _td is set, for example. The test signal input to the radio unit 40-1 is output to the cable 12-1 through the DAC 41, PA 42, circulator 43, BPF 44, and connector 45.

  Since the antenna 13-1 is detached from the cable 12-1, the test signal output to the cable 12-1 passes through the cable 12-1 and is reflected by the connector 120. The test signal reflected by the connector 120 is fed back to the detection unit 37 via the cable 12-1, the connector 45, the BPF 44, the circulator 43, the switch 46, the LNA 47, the ADC 48, the delay unit 34-1 and the switch 33-1. The

FIG. 6 is a diagram for explaining an example of the delay of the test signal at the time of calibration of the receiving circuit. Detector 37, for example as shown in FIG. 6 (a), on the basis of the transmission timing T _cal1 of the output test signal from the signal generator 35, the timing T _Rdet1 feedback to the test signal is received, The transmission time ΔT _r1 of the receiving circuit corresponding to the antenna 13-1 is measured. For example, as shown in FIG. _6A , the transmission time ΔT _r1 includes the transmission time ΔT _t1 ″ of the transmission circuit corresponding to the antenna 13-1, and the difference corresponding to the delay amount set in the delay unit 32-1. T _td is included.

Next, the transmission time ΔT _t2 of the transmission circuit corresponding to the antenna 13-2 is measured. Specifically, the switch 33-2 is switched so that the signal output from the delay unit 34-2 is output to the detection unit 37. Then, the signal generator 35 outputs the test signal to the switch 31-2 and the detection unit 37. The test signal output from the signal generator 35 to the switch 31-2 is input to the radio unit 40-2 via the delay unit 32-2 in which a delay amount of “0” is set, for example. The test signal input to the radio unit 40-2 is output to the cable 12-2 via the DAC 41, PA 42, circulator 43, BPF 44, and connector 45.

  Since the antenna 13-2 is removed from the cable 12-2, the test signal output to the cable 12-2 passes through the cable 12-2 and is reflected by the connector 120. The test signal reflected at the connector 120 is fed back to the detection unit 37 via the cable 12-2, the connector 45, the BPF 44, the circulator 43, the switch 46, the LNA 47, the ADC 48, the delay unit 34-2, and the switch 33-2. The

For example, as illustrated in FIG. 6B, the detection unit 37 transmits the transmission time based on the transmission timing T _cal2 of the test signal output from the signal generator 35 and the timing T _{rdet2 at} which the fed back test signal is received. ΔT _r2 is measured. The transmission time ΔT _r2 includes the transmission time ΔT _t2 ″ of the transmission circuit corresponding to the antenna 13-2 as shown in FIG. 6B, for example.

Here, since the calibration of the transmission circuit is completed, in the calibration of the reception circuit, the difference T _rd between the transmission times ΔT _r1 and ΔT _r2 of the respective reception circuits is the difference in the transmission time of the reception circuit. . Therefore, if a delay amount corresponding to the difference T _rd between the transmission times ΔT _r1 and ΔT _r2 is added to the receiving circuit in which the shorter one of the transmission times ΔT _r1 and ΔT _r2 is measured, The difference in transmission time is reduced. In the example of FIG. 6, the transmission time ΔT _r1 is shorter than the transmission time ΔT _r2 . Therefore, the detection unit 37 outputs an instruction for setting the difference T _rd between the transmission times ΔT _r1 and ΔT _r2 to the adjustment unit 36 in the delay unit 34 of the receiving circuit in which the shorter transmission time ΔT _r1 is measured.

The adjustment unit 36 sets the delay amount corresponding to the difference T _rd instructed from the detection unit 37 in the delay unit 34 corresponding to the transmission circuit instructed from the detection unit 37. In the example of FIG. 6C, the difference T _rd instructed from the detection unit 37 is set in the delay unit 34 of the reception circuit in which the transmission time ΔT _r1 is measured, that is, the delay unit 34-1. Accordingly, the timing at which the test signal fed back in the receiving circuit corresponding to the antenna 13-1 is received is T _rdet1 ′, and the transmission time of the receiving circuit of the antenna 13-1 is ΔT _r1 ′. Thereby, the difference between the transmission time ΔT _r1 ′ of the receiving circuit of the antenna 13-1 and the transmission time ΔT _r2 of the receiving circuit of the antenna 13-2 is reduced. Therefore, the phase of a signal received via each antenna 13 and output to the BBU 11 can be adjusted with high accuracy.

[Calibration of transmitter circuit]
FIG. 7 is a flowchart illustrating an example of calibration of the transmission circuit according to the first embodiment. The calibration of the transmission circuit shown in FIG. 7 is executed at a predetermined timing, for example, when the RRH 20 is installed. Each antenna 13 is removed from the cable 12 before the execution of calibration of the transmission circuit shown in FIG. In the flowchart shown in FIG. 7, the transmission circuit corresponding to the antenna 13-1 is described as branch 1, and the transmission circuit corresponding to the antenna 13-2 is described as branch 2.

  First, a transmission circuit calibration path is set for branch 1 (S100). Specifically, for example, as illustrated in FIG. 3, the switch 31-1 is switched so that the test signal output from the signal generator 35 is input to the delay unit 32-1. In addition, the switch 46 in the wireless unit 40-1 is switched so that the signal output from the circulator 43 in the wireless unit 40-1 is output to the switch 51. Further, the switch 51 is switched so that the test signal output from the switch 46 in the wireless unit 40-1 is output to the ADC 50. In the delay unit 32-1, “0” is set as the delay amount.

  Next, the signal generator 35 outputs a test signal to the branch 1 (S101). Specifically, the signal generator 35 outputs a test signal to the switch 31-1 and the detection unit 37. The test signal output to the switch 31-1 is input to the radio unit 40-1 through the delay unit 32-1 and output to the cable 12-1 through the DAC 41, PA 42, circulator 43, BPF 44, and connector 45. Is done. The test signal output to the cable 12-1 passes through the cable 12-1 and is reflected by the connector 120. The test signal reflected by the connector 120 is fed back to the detection unit 37 via the cable 12-1, the connector 45, the BPF 44, the circulator 43, the switch 46, the switch 51, and the ADC 50.

Then, detecting unit 37, for example as described in FIG. 4 (a), the transmission timing T _cal1 of the output test signal from the signal generator 35, a timing T _Tdet1 feedback to the test signal is received Based on the above, the transmission time ΔT _t1 of the branch 1 is measured (S102).

  Next, a transmission circuit calibration path is set for branch 2 (S103). Specifically, for example, as illustrated in FIG. 3, the switch 31-2 is switched so that the test signal output from the signal generator 35 is input to the delay unit 32-2. In addition, the switch 46 in the wireless unit 40-2 is switched so that the signal output from the circulator 43 in the wireless unit 40-2 is output to the switch 51. Further, the switch 51 is switched so that the test signal output from the switch 46 in the radio unit 40-2 is output to the ADC 50. In the delay unit 32-2, “0” is set as the delay amount.

  Next, the signal generator 35 outputs a test signal to the branch 2 (S104). Specifically, the signal generator 35 outputs a test signal to the switch 31-2 and the detection unit 37. The test signal output to the switch 31-2 is input to the radio unit 40-2 via the delay unit 32-2, and is output to the cable 12-2 via the DAC 41, PA 42, circulator 43, BPF 44, and connector 45. Is done. The test signal output to the cable 12-2 passes through the cable 12-2 and is reflected by the connector 120. The test signal reflected by the connector 120 is fed back to the detection unit 37 via the cable 12-2, the connector 45, the BPF 44, the circulator 43, the switch 46, the switch 51, and the ADC 50.

Then, detecting unit 37, for example as described in FIG. 4 (b), the transmission timing T _cal2 the test signal from the signal generator 35 is transmitted, the timing T _Tdet2 feedback to the test signal is received Based on the above, the transmission time ΔT _t2 of the branch 2 is measured (S105).

Next, the detector 37 calculates a difference T _td between the measured transmission times ΔT _t1 and ΔT _t2 (S106). Then, the detection unit 37 determines whether or not the calculated difference T _td is less than a predetermined value (S107). When the difference T _td is less than the predetermined value (S107: Yes), the processing shown in this flowchart ends.

On the other hand, when the difference T _td is equal to or greater than the predetermined value (S107: No), the detection unit 37 sets the calculated difference T _td in the delay unit 32 corresponding to the branch whose shorter transmission time is measured. The instruction is output to the adjustment unit 36. The adjustment unit 36 sets the delay amount corresponding to the difference T _td instructed from the detection unit 37 in the delay unit 32 corresponding to the branch instructed from the detection unit 37 (S108). Note that a delay amount of “0” is set in the delay units 32 corresponding to other branches. Then, the process shown in this flowchart ends.

In the flowchart shown in FIG. 7, the detection unit 37 calculates the difference T _td between the transmission times ΔT _t1 and ΔT _t2 , and the delay amount corresponding to the calculated difference T _td is the delay unit of the short transmission time branch. However, the disclosed technique is not limited to this. For example, the delay amount set in the delay unit 32 of the short transmission time branch may be increased by a predetermined value until the value of the difference T _td calculated by the detection unit 37 becomes less than a predetermined value.

[Receiver circuit calibration]
FIG. 8 is a flowchart illustrating an example of calibration of the receiving circuit according to the first embodiment. The calibration of the reception circuit shown in FIG. 8 is executed after the calibration of the transmission circuit shown in FIG. Each antenna 13 is disconnected from the cable 12 before the start of calibration of the receiving circuit shown in FIG. In the flowchart shown in FIG. 8, the receiving circuit corresponding to the antenna 13-1 is described as branch 1, and the receiving circuit corresponding to the antenna 13-2 is described as branch 2.

  First, a receiving circuit calibration path is set for branch 1 (S200). Specifically, for example, as illustrated in FIG. 5, the switch 33-1 is switched so that the test signal output from the delay unit 34-1 is output to the detection unit 37. Further, the switch 46 in the radio unit 40-1 is switched so that the signal output from the circulator 43 in the radio unit 40-1 is output to the LNA 47 in the radio unit 40-1. Further, “0” is set as the delay amount in the delay unit 34-1. Since the calibration of the transmission circuit has been completed, each switch 31 is switched so that the test signal output from the signal generator 35 is input to each delay unit 32. Each delay unit 32 is set with a delay amount corresponding to a value calculated by calibration of the transmission circuit.

  Next, the signal generator 35 outputs a test signal to the branch 1 (S201). Specifically, the signal generator 35 outputs a test signal to the switch 31-1 and the detection unit 37. The test signal output to the switch 31-1 is input to the radio unit 40-1 through the delay unit 32-1 and output to the cable 12-1 through the DAC 41, PA 42, circulator 43, BPF 44, and connector 45. Is done. The test signal output to the cable 12-1 passes through the cable 12-1 and is reflected by the connector 120. The test signal reflected by the connector 120 is fed back to the detection unit 37 via the cable 12-1, the connector 45, the BPF 44, the circulator 43, the switch 46, the LNA 47, the ADC 48, the delay unit 34-1 and the switch 33-1. .

Then, detecting unit 37, for example as described in FIG. 6 (a), the transmission timing T _cal1 the test signal from the signal generator 35 is transmitted, the timing T _Rdet1 feedback to the test signal is received Based on the above, the transmission time ΔT _r1 of the branch 1 is measured (S202).

  Next, a transmission circuit calibration path is set for branch 2 (S203). Specifically, for example, as illustrated in FIG. 5, the switch 33-2 is switched so that the test signal output from the delay unit 34-2 is output to the detection unit 37. Further, the switch 46 in the radio unit 40-2 is switched so that the signal output from the circulator 43 in the radio unit 40-2 is output to the LNA 47 in the radio unit 40-2. In the delay unit 34-2, “0” is set as the delay amount.

  Next, the signal generator 35 outputs a test signal to the branch 2 (S204). Specifically, the signal generator 35 outputs a test signal to the switch 31-2 and the detection unit 37. The test signal output to the switch 31-2 is input to the radio unit 40-2 via the delay unit 32-2, and is output to the cable 12-2 via the DAC 41, PA 42, circulator 43, BPF 44, and connector 45. Is done. The test signal output to the cable 12-2 passes through the cable 12-2 and is reflected by the connector 120. The test signal reflected by the connector 120 is fed back to the detection unit 37 via the cable 12-2, the connector 45, the BPF 44, the circulator 43, the switch 46, the LNA 47, the ADC 48, the delay unit 34-2, and the switch 33-2. .

Then, detecting unit 37, for example as described in FIG. 6 (b), the transmission timing T _cal2 the test signal from the signal generator 35 is transmitted, the timing T _Rdet2 feedback to the test signal is received Based on the above, the transmission time ΔT _r2 of the branch 2 is measured (S205).

Next, the detector 37 calculates a difference T _rd between the measured transmission times ΔT _r1 and ΔT _r2 (S206). Then, the detection unit 37 determines whether or not the calculated difference T _rd is less than a predetermined value (S207). When the difference T _rd is less than the predetermined value (S207: Yes), the processing shown in this flowchart ends.

On the other hand, when the difference T _rd is equal to or larger than the predetermined value (S207: No), the detection unit 37 sets the calculated difference T _rd in the delay unit 34 corresponding to the branch whose shorter transmission time is measured. The instruction is output to the adjustment unit 36. The adjustment unit 36 sets the delay amount corresponding to the difference T _rd instructed from the detection unit 37 in the delay unit 34 corresponding to the branch instructed from the detection unit 37 (S208). Note that a delay amount of “0” is set in the delay units 34 corresponding to other branches. Then, the process shown in this flowchart ends.

In the flowchart shown in FIG. 8 as well, for example, the delay set in the delay unit 34 of the branch in which the short transmission time is measured until the value of the difference T _rd calculated by the detection unit 37 becomes less than a predetermined value. The amount may be increased by a predetermined value.

[Effect of Example 1]
In the above, Example 1 was demonstrated. As is clear from the above description, the base station 10 of the present embodiment includes an array antenna 14 including a plurality of antennas 13, a plurality of transmission circuits, a plurality of cables 12, a signal generator 35, and an adjustment unit 36. Have Each transmission circuit is provided corresponding to each antenna 13. Each cable 12 is provided corresponding to each antenna 13 and connects the antenna 13 and a transmission circuit corresponding to the antenna 13. The signal generator 35 generates a test signal input to each transmission circuit. The adjustment unit 36 is configured to transmit the transmission circuit from the timing at which the test signal is input from the signal generator 35 to the transmission circuit between the plurality of transmission circuits in a state where the end of the antenna 13 side of each cable 12 is opened. And the delay time of each transmission circuit is adjusted so that the time difference until the timing when the test signal reflected at the open end of the cable 12 via the cable 12 is received is less than a predetermined value. Thereby, the base station 10 can improve the accuracy of calibration of the array antenna 14 between the transmission circuits.

  In addition, the base station 10 of this embodiment includes a plurality of receiving circuits and a circulator 43. Each receiving circuit is provided corresponding to each antenna 13. The circulator 43 is provided between the antenna 13 and the transmission circuit and the reception circuit corresponding to the antenna 13 corresponding to the antenna 13. The circulator 43 passes the signal output from the transmission circuit to the cable 12 and passes the signal output from the cable 12 to the reception circuit. In addition, the adjustment unit 36 inputs the test signal from the signal generator 35 to the transmission circuit between the plurality of reception circuits in a state where the end of the cable 12 is opened after the delay time of the transmission circuit is adjusted. The difference in time from the generated timing to the timing at which the test signal reflected at the open end of the cable 12 through the transmission circuit and the cable 12 and passed through the circulator 43 and the reception circuit is less than a predetermined value. Thus, the delay time of each receiving circuit is adjusted. Thereby, the base station 10 can improve the accuracy of calibration of the array antenna 14 between the receiving circuits.

  In the first embodiment described above, each antenna 13 is connected to the cable 12 via the connector 120 and is removed from the cable 12 at the connector 120 during calibration. However, the disclosed technology is not limited thereto. For example, as shown in FIG. 9, the electrical connection between the antenna 13 and the cable 12 may be released by a switch 132 provided in the antenna 13.

  FIG. 9 is a diagram illustrating another example of the antenna 13. The antenna 13 in another example includes an antenna element 131 and a switch 132 as shown in FIG. One end of the switch 132 is connected to the antenna element 131, and the other end of the switch 132 is connected to the connector 120 via the wiring 133 on the substrate. The switch 132 is an example of a switching unit. In the switch 132, connection and release between the wiring 133 and the antenna element 131 are controlled by a control signal input via the wiring 134. The control signal is supplied from the wireless unit 40 to the antenna 13 via the cable 121 connected to the antenna 13 by the connector 122. The cable 12 and the wiring 133 illustrated in FIG. 9 are an example of a line that connects the antenna 13 and the wireless unit 40.

  In the antenna 13 illustrated in FIG. 9, when the transmission circuit and the reception circuit are calibrated, the electrical connection between the wiring 133 and the antenna element 131 is released by the control signal supplied to the switch 132. . As a result, the test signal that has passed through the cable 12 passes through the wiring 133 in the antenna 13 and is reflected by the switch 132. Therefore, when the antenna 13 illustrated in FIG. 9 is used, in the calibration of the transmission circuit and reception / reception, the calibration can be performed in consideration of the difference in the transmission time of the wiring 133 between the plurality of antennas 13. Thereby, the delay amount of the transmission circuit and the reception circuit corresponding to each antenna 13 can be adjusted more accurately.

  Further, in the antenna 13 illustrated in FIG. 9, electrical connection and release between the wiring 133 and the antenna element 131 are controlled by a control signal supplied to the switch 132. Therefore, the transmission circuit and the reception circuit can be calibrated for each antenna 13 not only when the base station 10 is installed but in a short time when transmission / reception of radio waves is stopped. Therefore, calibration of the transmission circuit and the reception circuit can be performed at any time according to changes in the delay characteristics of the wireless unit 40 and the cable 12 due to environmental changes, secular changes, and the like. Therefore, a state in which the phase difference between the transmission circuit and the reception circuit is small among the plurality of antennas 13 can be maintained.

  In the first embodiment, the ADC 50 and the switch 51 are provided to supply the test signal fed back from each radio unit 40 to the BBU 11 in calibration of the transmission circuit. However, the disclosed technique is limited to this. Absent. For example, as shown in FIG. 10, when the RRH 20 is provided with a circuit for compensating for distortion of the PA 42, a feedback path included in the circuit may be used. FIG. 10 is a block diagram illustrating another example of the RRH 20.

  In the RRH 20 illustrated in FIG. 10, a coupler 400, an amplifier 401, and an ADC 402 are provided in each radio unit 40. Further, a switch 403 is provided in any of the wireless units 40. The switch 403 switches the signal input to the amplifier 401 to any one of a signal output from the coupler 400, a signal output from the switch 46, or a signal output from the switch 46 of another radio unit 40.

  In the wireless unit 40 provided with the switch 403, the coupler 400 outputs a part of the signal output from the PA 42 to the circulator 43 to the switch 403. The amplifier 401 amplifies the signal output from the switch 403 and outputs the amplified signal to the ADC 402. In the wireless unit 40 in which the switch 403 is not provided, the coupler 400 outputs a part of the signal output from the PA 42 to the circulator 43 to the amplifier 401. The amplifier 401 amplifies the signal output from the coupler 400 and outputs the amplified signal to the ADC 402. The ADC 402 converts the signal amplified by the amplifier 401 from an analog signal to a digital signal and outputs the signal to the control unit 30.

  In the control unit 30, a plurality of DPDs (Digital Pre-Distortion) 38-1 to DPD 38-2 and a switch 39 are provided. Each of the plurality of DPDs 38-1 to DPD38-2 is provided corresponding to each of the plurality of radio units 40-1. The switch 39 switches the output destination of the signal output from the ADC 402 of the wireless unit 40 provided with the switch 403 to either the DPD 38-1 or the detection unit 37. In the RRH 20 of another example shown in FIG. 10, the switch 39 outputs the signal output from the ADC 402 to the DPD 38-1 during operation, and the signal output from the ADC 402 during calibration of the transmission circuit and the reception circuit. Output to the detector 37. The DPD 38-1 corresponding to the radio unit 40 provided with the switch 403 performs distortion compensation of the PA 42 based on the transmission signal fed back through the switch 39. The DPD 38-2 corresponding to the radio unit 40 in which the switch 403 is not provided performs distortion compensation of the PA 42 based on the transmission signal fed back via the ADC 402 of the radio unit 40.

  Thus, in calibration of the transmission circuit, the number of components of the RRH 20 can be reduced by using the feedback path provided in the circuit that performs distortion compensation of the PA 42.

  In the RRH 20 according to the first embodiment described above, the transmission time is measured for each branch, and the delay amount of each branch is adjusted based on the difference between the measured transmission times. On the other hand, in the RRH 20 of the second embodiment, the test signal is simultaneously supplied to the two branches, and the delay amount of each branch is adjusted based on the result of combining the power of the test signal fed back from each branch. In addition, since the structure of the base station 10 in Example 2 is the same as that of the base station 10 in Example 1 demonstrated using FIG. 1, description is abbreviate | omitted.

[RRH20]
FIG. 11 is a block diagram illustrating an example of the RRH 20 according to the second embodiment. The RRH 20 includes a control unit 30, a plurality of radio units 40, an ADC 50, and a combiner 52. Except for the points described below, in FIG. 11, blocks denoted by the same reference numerals as those in FIG. 2 have the same functions as the blocks described in FIG. In the present embodiment, the calibration of the receiving circuit is the same as the calibration of the receiving circuit performed by the RRH 20 of the first embodiment. Therefore, hereinafter, calibration of the transmission circuit will be mainly described.

  The combiner 52 combines the power of the test signal output from the switch 46 of each radio unit 40. Then, the combiner 52 outputs the test signal combined with the power to the ADC 50. The ADC 50 converts the test signal output from the synthesizer 52 from an analog signal to a digital signal, and outputs the converted test signal to the control unit 30. The combiner 52 is an example of a combining unit.

  Further, the signal generator 35 of the present embodiment generates a test signal having a different power for each branch in the calibration of the transmission circuit. Then, the signal generator 35 outputs the test signal generated for each branch to each branch at the same timing. Specifically, the test signal generated for the branch corresponding to the antenna 13-1 is output to the switch 31-1, and the test signal generated for the branch corresponding to the antenna 13-2 is output to the switch 31-2. The Further, the signal generator 35 outputs at least one of information regarding the branch from which the test signal with higher power is output or information regarding the branch from which the test signal with lower power is output to the detection unit 37. .

  The detection unit 37 calculates the difference in transmission time between the branches based on the power value of the test signal output from the ADC 50.

FIG. 12 is a diagram for explaining an example of the delay of the test signal at the time of calibration of the transmission circuit. In the second embodiment, in the calibration of the transmission circuit, for example, as shown in FIG. 12A, test signals with different powers P ₁ and P ₂ are output to each branch at the same timing T _cal .

Then, the power of the test signal fed back in each branch is combined by the combiner 52 and input to the detection unit 37 via the ADC 50. Here, if the difference between the transmission times of the branches is sufficiently small, for example, as shown in FIG. 12B, the transmission time of the test signal fed back from each branch is substantially ΔT _t . Therefore, the power of the test signal fed back from each branch is synthesized at the timing T _tdet by the synthesizer 52 and becomes _equal to or higher than the predetermined threshold value P _th . For example, the predetermined threshold P _th is smaller than a first value that is a value obtained by adding the powers P ₁ ′ and P ₂ ′ of the fed back test signal, and among the powers P ₁ ′ and P ₂ ′, The value is larger than the second value, which is the larger power value. For example, the predetermined threshold P _th may be ½ of a value obtained by adding the first value and the second value.

On the other hand, if the difference in transmission time between the branches is large, for example, as shown in FIG. 12C, the power of the test signal fed back from each branch is combined at different timings by the combiner 52. In the example of FIG. 12C, the transmission time of the test signal fed back from the branch 1 is ΔT _t1 , and the transmission time of the test signal fed back from the branch 2 is ΔT _t2 . In this case, the power value of the test signal synthesized by the synthesizer 52 is less than the predetermined threshold value P _{th at} any timing. Further, the power of the test signal fed back from each branch is detected at timings T _tdet1 and T _tdet2 , for example. When the power value of the test signal synthesized by the synthesizer 52 is less than the predetermined threshold value P _th , the detection unit 37 calculates a transmission time difference T _td fed back from each branch.

Based on the test signal fed back from each branch, the detection unit 37 determines whether the power of the test signal with the longer transmission time is larger than the power of the test signal with the shorter transmission time. When the power of the test signal having the longer transmission time is larger than the power of the test signal having the shorter transmission time, the detection unit 37 calculates the delay unit 32 of the branch to which the test signal having the smaller transmission time is input. The adjustment unit 36 is instructed to set the set difference T _td . On the other hand, when the power of the test signal with the longer transmission time is smaller than the power of the other test signal, the detection unit 37 calculates the calculated difference in the delay unit 32 of the branch to which the test signal with the larger power is input. The adjustment unit 36 is instructed to set T _td .

As a result, the difference T _td is set in the branch with the shorter transmission time, and the time difference between the test signals fed back from each branch becomes small. For example, as shown in FIG. The power value of the test signal is equal to or greater than a predetermined threshold value _Pth .

[Calibration of transmitter circuit]
FIG. 13 is a flowchart illustrating an example of calibration of the transmission circuit according to the second embodiment. The calibration of the transmission circuit shown in FIG. 13 is executed at a predetermined timing, for example, when the RRH 20 is installed. Note that each antenna 13 is disconnected from the cable 12 even before the execution of calibration of the transmission circuit shown in FIG. In the flowchart shown in FIG. 13, the transmission circuit corresponding to the antenna 13-1 is described as branch 1, and the transmission circuit corresponding to the antenna 13-2 is described as branch 2. Also in the second embodiment, the antenna 13 shown in FIG. 9 may be used.

  First, a transmission circuit calibration path is set for branch 1 and branch 2 (S300). Specifically, as shown in FIG. 11, for example, the switches 31-1 and 31-2 are switched so that the test signal output from the signal generator 35 is input to the delay units 32-1 and 32-2. It is done. Further, the switch 46 in each radio unit 40 is switched so that the signal output from the circulator 43 is output to the combiner 52. In the delay units 32-1 and 32-2, “0” is set as the delay amount.

Next, the signal generator 35 generates a test signal with different power for each branch, and outputs the generated test signal to each branch at the same timing (S301). For example, the signal generator 35, for example, respectively to generate the test signal of the power P ₁ and the power P ₂ test signal, and outputs a test signal of the power P ₁ to the switch 31-1, switch a test signal of the power P ₁ Output to 31-2. Then, the signal generator 35 outputs information related to the branch to which the test signal with the higher power is output or the branch to which the test signal with the lower power is output to the detection unit 37.

  The test signal output to each switch 31 is input to each radio unit 40 via each delay unit 32, and is output to each cable 12 via the DAC 41, PA 42, circulator 43, BPF 44, and connector 45. The test signal output to each cable 12 passes through each cable 12, is reflected by the connector 120, and is input to the combiner 52 via the connector 45, BPF 44, circulator 43, and switch 46. The combiner 52 combines the power of the test signal output from the switch 46 of each wireless unit 40 (S302). Then, the combiner 52 outputs the test signal combined with the power to the ADC 50. The ADC 50 converts the test signal output from the synthesizer 52 from an analog signal to a digital signal, and outputs the converted test signal to the control unit 30.

Next, the detection unit 37 determines whether or not the value of the combined power of the test signal output from the ADC 50 is greater than or equal to the threshold P _th based on the combined power of the test signal output from the ADC 50 (S303). When the value of the combined power is greater than or equal to the threshold value P _th (S303: Yes), the processing shown in this flowchart ends.

On the other hand, when the value of the combined power is less than the threshold value P _th (S303: No), the detection unit 37 calculates a difference T _td of the transmission time of the test signal fed back from each branch (S304). Based on the test signal fed back from each branch, the detection unit 37 determines whether or not the power of the test signal with the longer transmission time is larger than the power of the test signal with the shorter transmission time ( S305).

When the power of the test signal with the longer transmission time is larger than the power of the test signal with the shorter transmission time (S305: Yes), the detection unit 37 delays the branch to which the test signal with the smaller power is input. The adjustment unit 36 is instructed to set the difference T _td in the unit 32. The adjustment unit 36 sets the difference T _td in the delay unit 32 of the branch designated by the detection unit 37 (S306). Then, the process shown in this flowchart ends.

On the other hand, when the power of the test signal with the longer transmission time is smaller than the power of the test signal with the shorter transmission time (S305: No), the detection unit 37 receives the test signal with the larger power. The adjustment unit 36 is instructed to set the difference T _td to the delay unit 32. The adjustment unit 36 sets the difference T _td in the delay unit 32 of the branch designated by the detection unit 37 (S307). Then, the process shown in this flowchart ends.

In the flowchart shown in FIG. 13, when the power of the test signal synthesized by the synthesizer 52 is less than the threshold P _th , the detection unit 37 calculates the difference T _td between the transmission times ΔT _t1 and ΔT _t2 . The delay amount corresponding to the calculated difference T _td is set in the delay unit 32 corresponding to the short transmission time branch, but the disclosed technique is not limited to this. For example, when the power of the test signal synthesized by the synthesizer 52 is less than the threshold value P _th , the detection unit 37 has a short transmission time until the power of the test signal synthesized by the synthesizer 52 becomes equal to or higher than the threshold value P _th . The delay amount set in the branch delay unit 32 may be increased by a predetermined value.

In the flowchart illustrated in FIG. 13, when the power of the test signal combined by the combiner 52 is equal to or greater than the threshold value P _th , the delay amount is not set, but the disclosed technique is not limited thereto. For example, the detection unit 37 may adjust the delay amount of each branch so that the power of the test signal combined by the combiner 52 is maximized.

[Effect of Example 2]
The example 2 has been described above. As is clear from the above description, the base station 10 of this embodiment includes a combiner 52 that combines the power of the test signal reflected at the open end of the cable 12 for each transmission circuit. The adjustment unit 36 adjusts the delay time in each transmission circuit so that the power of the signal output from the combiner 52 is equal to or higher than a predetermined power in a state where the end of the cable 12 is open. Thereby, the base station 10 can adjust the delay amount of the transmission circuit corresponding to each antenna 13 with high accuracy.

In the second embodiment, the signal generator 35 generates a test signal having different power for each transmission circuit, and outputs the generated test signal to each transmission circuit. Accordingly, the detection unit 37 can easily determine which branch the delay unit 32 should set the calculated difference T _td when the power of the test signal combined by the combiner 52 is less than the threshold value P _th. Can be specified.

  In the second embodiment described above, test signals with different powers are output to each branch. However, the disclosed technology is not limited to this, and the power of the test signal output to each branch is not different between the branches. May be. FIG. 14 is a diagram for explaining an example of the delay of the test signal at the time of calibration of the transmission circuit in the modification of the second embodiment.

In the present modification, in the calibration of the transmission circuit, for example, as shown in FIG. 14A, a test signal with power P ₃ is output to each branch at the same timing T _cal . In the example of FIG. 14, the power of the test signal output to each branch is equal between the branches, but the power of the test signal output to each branch may be different between the branches.

The power of the test signal fed back in each branch is combined by the combiner 52 and input to the detection unit 37 via the ADC 50. However, the larger the difference T _td transmission time [Delta] T _t1 and [Delta] T _t2 of each branch, for example, as shown in FIG. 12 (b), the power P ₃ of the fed back test signal from each branch 'is different timings T _Tdet1 And T _tdet2 respectively. Therefore, the power value of the test signal synthesized by the synthesizer 52 is less than the predetermined threshold value P _th .

When the power value of the test signal synthesized by the synthesizer 52 is less than the threshold value P _th , the detection unit 37 sends the transmission time of each branch to the delay unit 32 of one of the two branches. A delay amount corresponding to the difference T _td is set. Then, the signal generator 35 outputs the test signal having the power P ₃ to each branch again at the same timing T _cal , and the detection unit 37 determines that the power value of the test signal synthesized by the synthesizer 52 is the threshold value P. It is determined again whether it is greater than or _{equal to th} . When the transmission time of the branch in which the delay amount is set is shorter than the transmission time of the other branch, for example, as shown in FIG. The value of the power of the synthesized test signal is equal to or greater than the threshold value P _th .

On the other hand, when the transmission time of the branch for which the delay amount is set is longer than the transmission time of the other branch, for example, as shown in FIG. 12D, the difference between the transmission times of the two branches increases. Therefore, the power value of the test signal synthesized by the synthesizer 52 remains below the threshold value P _th . In this case, the detection unit 37 replaces the branch in which the delay amount corresponding to the difference T _td is set among the two branches. As a result, for example, as shown in FIG. 12C, the difference between the transmission times of the two branches is reduced, and the value of the power of the test signal synthesized by the synthesizer 52 becomes equal to or greater than the threshold value P _th .

[Calibration of transmitter circuit]
FIG. 15 is a flowchart illustrating an example of calibration of the transmission circuit according to the modification of the second embodiment. Each antenna 13 is disconnected from the cable 12 even before the execution of calibration of the transmission circuit shown in FIG. In the flowchart shown in FIG. 15, the transmission circuit corresponding to the antenna 13-1 is described as branch 1, and the transmission circuit corresponding to the antenna 13-2 is described as branch 2.

  First, a transmission circuit calibration path is set for branch 1 and branch 2 (S310). Specifically, as shown in FIG. 11, for example, the switches 31-1 and 31-2 are switched so that the test signal output from the signal generator 35 is input to the delay units 32-1 and 32-2. It is done. Further, the switch 46 in each radio unit 40 is switched so that the signal output from the circulator 43 is output to the combiner 52. In the delay units 32-1 and 32-2, “0” is set as the delay amount.

  Next, the signal generator 35 generates a test signal for each branch and outputs the generated test signal to each branch at the same timing (S311). The signal generator 35 may output a test signal having the same power to each branch, or may output a test signal having a different power.

  The test signal output to each branch is input to the synthesizer 52 via the switch 46 of each branch. The combiner 52 combines the power of the test signal output from each branch (S312). Then, the combiner 52 outputs the test signal combined with the power to the ADC 50. The ADC 50 converts the test signal output from the synthesizer 52 from an analog signal to a digital signal, and outputs the converted test signal to the detection unit 37.

Next, the detection unit 37 determines whether or not the value of the combined power of the test signal output from the ADC 50 is greater than or equal to the threshold value P _th (S313). When the value of the combined power is greater than or equal to the threshold value P _th (S313: Yes), the processing illustrated in this flowchart is terminated.

On the other hand, when the value of the combined power is less than the threshold value P _th (S313: No), the detection unit 37 calculates the difference T _td of the transmission time of the test signal fed back from each branch (S314). Then, the detection unit 37 instructs the adjustment unit 36 to set the difference T _td in the delay unit 32 of one of the two branches. The adjustment unit 36 sets the difference T _td in the delay unit 32 of the branch designated by the detection unit 37 (S315).

  Next, the signal generator 35 again generates a test signal for each branch, and outputs the generated test signal to each branch at the same timing (S316). The test signal output to each branch is input to the combiner 52 via the switch 46 of each branch, and is combined by the combiner 52 (S317). The test signal combined with the power by the combiner 52 is converted from an analog signal to a digital signal by the ADC 50 and output to the detection unit 37.

Next, the detection unit 37 determines again whether or not the value of the combined power of the test signal output from the ADC 50 is equal to or greater than the threshold value P _th (S318). When the value of the combined power is greater than or equal to the threshold value P _th (S318: Yes), the processing shown in this flowchart ends.

On the other hand, when the value of the combined power is less than the threshold value P _th (S318: No), the detection unit 37 switches the branch for setting the difference T _td in the delay unit 32 (S319). Specifically, the difference T _td in the delay unit 32 which is set to 0 is set in step S315, the delay amount corresponding to the difference T _td in the delay unit 32 the difference T _td has not been set is set in step S315 The Then, the process shown in this flowchart ends.

  In the above, the modification of Example 2 was demonstrated. As is clear from the above description, also in this modification, the delay amount of the transmission circuit of each antenna 13 can be adjusted with high accuracy.

  In the RRH 20 according to the first embodiment described above, the transmission time is measured for each branch, and the delay amount of each branch is adjusted based on the difference between the measured transmission times. On the other hand, in the RRH 20 of the third embodiment, the test signal is simultaneously supplied to the two branches, and the delay amount of each branch is set based on the combined result of the voltages according to the power of the test signal fed back from each branch. adjust. In addition, since the structure of the base station 10 in Example 3 is the same as that of the base station 10 in Example 1 demonstrated using FIG. 1, description is abbreviate | omitted.

[RRH20]
FIG. 16 is a block diagram illustrating an example of the RRH 20 according to the third embodiment. The RRH 20 includes a control unit 30, a plurality of radio units 40, an ADC 50, a converter 53, a converter 54, and a combiner 55. Except for the points described below, in FIG. 16, blocks denoted by the same reference numerals as those in FIG. 2 have the same functions as the blocks described in FIG. In the present embodiment, the calibration of the receiving circuit is the same as the calibration of the receiving circuit performed by the RRH 20 of the first embodiment. Therefore, hereinafter, calibration of the transmission circuit will be mainly described.

  Converters 53 and 54 convert the power of the test signal output from switch 46 of each radio unit 40 into a voltage corresponding to the power. In the example of FIG. 16, the converter 53 converts the power of the test signal output from the switch 46 of the wireless unit 40-1 into a voltage corresponding to the power. The converter 54 converts the power of the test signal output from the switch 46 of the wireless unit 40-2 into a voltage corresponding to the power. The converters 53 and 54 are log amplifiers, for example. The converters 53 and 54 are an example of a conversion unit.

The synthesizer 55 adds the voltage output from the converter 53 and the voltage output from the converter 54. Then, the synthesizer 55 outputs the added voltage to the ADC 50. The synthesizer 55 is an example of a synthesizer. FIG. 17 is a diagram illustrating an example of the synthesizer 55. The synthesizer 55 includes, for example, a resistor R1, a resistor R2, a resistor R3, and an operational amplifier 550 as shown in FIG. The synthesizer 55 is configured as an inverting addition circuit, and the voltage V _o output to the ADC 50 is obtained by using the voltage V _in1 input from the converter 53 and the voltage V _in2 input from the converter 54, for example. It is expressed as the following formula (1).
V _o = −R3 · {(V _in1 / R1) + (V _in2 / R2)} (1)

  In this embodiment, by adjusting the values of the resistors R1, R2, and R3 in the above (1), the voltage of the test signal of each branch added by the synthesizer 55 is weighted.

  The ADC 50 converts the voltage output from the synthesizer 55 from an analog signal to a digital signal, and outputs the converted test signal to the control unit 30.

  In the calibration of the transmission circuit, the signal generator 35 outputs the test signal generated for each branch to each branch at the same timing. Specifically, the signal generator 35 outputs a test signal to each switch 31 and the detection unit 37. In this embodiment, the signal generator 35 outputs a test signal having the same power level to each branch. The test signal output to each switch 31 is input to the radio unit 40 via the delay unit 32, and is output to the cable 12 via the DAC 41, PA 42, circulator 43, BPF 44, and connector 45. Also in the present embodiment, at the time of calibration, the antenna 13 is detached from the cable 12, so that the test signal output to the cable 12 passes through the cable 12 and is reflected by the connector 120. Also in the third embodiment, the antenna 13 shown in FIG. 9 may be used. The test signal reflected by the connector 120 is output to the converters 53 and 54 via the cable 12, connector 45, BPF 44, circulator 43, and switch 46. The test signals output to the converters 53 and 54 are converted into a voltage corresponding to the electric power, the voltage is added by the synthesizer 55, converted into a digital signal by the ADC 50, and fed back to the detection unit 37.

The detection unit 37 adjusts the delay time of each branch based on the voltage value of the test signal output from the ADC 50. Specifically, the detection unit 37 determines whether or not the voltage value added by the synthesizer 55 is equal to or greater than a predetermined threshold value _Vth . For example, the predetermined threshold V _th is smaller than a first value which is a value obtained by adding the voltages V ₁ ′ and V ₂ ′ of the fed back test signal, and among the voltages V ₁ ′ and V ₂ ′, The larger voltage value is larger than the second value. For example, the predetermined threshold value V _th may be ½ of a value obtained by adding the first value and the second value.

When the value of the voltage added by the synthesizer 55 is less than the threshold value V _th , the detection unit 37 calculates a difference T _td in the transmission time of the test signal fed back from each branch. Based on the test signal fed back from each branch, the detection unit 37 instructs the adjustment unit 36 to set the calculated difference T _td in the delay unit 32 of the branch with the shorter transmission time. The adjustment unit 36 sets a delay amount corresponding to the difference T _td instructed from the detection unit 37 in the delay unit 32 of the branch instructed from the detection unit 37.

Here, the voltage of the test signal of each branch added by the synthesizer 55 is weighted by the above-described equation (1), and the detection unit 37 recognizes in advance which branch of the test signal voltage is higher. doing. Therefore, when the value of the voltage added by the synthesizer 55 is less than the threshold value V _th , the detection unit 37 determines the transmission time of which branch based on the test signal of each branch output from the synthesizer 55. Whether it is long can be determined. Therefore, when the value of the voltage added by the synthesizer 55 is less than the threshold value V _th , the detection unit 37 sets the calculated difference T _td in the delay unit 32 of the branch having a shorter transmission time. The adjustment unit 36 can be instructed. In the equation (1), the resistance value of the resistor R1 and the resistance value of the resistor R2 may be set to approximately the same value, and the power of the test signal generated by the signal generator 35 may be different for each branch.

In this embodiment, when the power of the test signal synthesized by the synthesizer 55 is equal to or higher than the threshold value V _th , the delay amount is not set, but the disclosed technique is not limited to this. For example, the detection unit 37 may adjust the delay amount of each branch so that the voltage of the test signal synthesized by the synthesizer 55 becomes maximum.

[Effect of Example 3]
The example 3 has been described above. As is clear from the above description, the base station 10 of this embodiment includes a converter 53, a converter 54, and a combiner 55. The converter 53 and the converter 54 convert the power of the test signal reflected by the end opened in the cable 12 for each radio unit 40 into a voltage. The synthesizer 55 synthesizes the voltages of the radio units 40 converted by the converters 53 and 54. The adjustment unit 36 adjusts the delay time of each branch so that the voltage of the test signal output from the synthesizer 55 becomes equal to or higher than a predetermined voltage in a state where the end of the cable 12 is opened. Thus, in this embodiment, the test signal fed back in each branch is converted into a voltage corresponding to the power, and the delay time of each branch is adjusted based on the converted voltage value. This makes it possible to use low-speed components in the components such as the operational amplifier 550 used in the synthesizer 55. Thereby, the cost of the base station 10 can be reduced.

In the third embodiment, the combiner 55 combines the voltages for the transmission circuits converted by the converters 53 and 54 by applying different weights to the transmission circuits. Thereby, when the value of the voltage added by the synthesizer 55 is less than the threshold value V _th , the detection unit 37 transmits the transmission time of which branch based on the test signal of each branch output from the synthesizer 55. Can quickly identify which is long.

[hardware]
The RRH 20 in the first to third embodiments described above is realized by hardware as shown in FIG. 18, for example. FIG. 18 is a diagram illustrating an example of hardware of the RRH 20. For example, as illustrated in FIG. 18, the RRH 20 includes an interface circuit 21, a memory 22, a processor 23, a plurality of radio circuits 24-1 to 24-n, and a feedback circuit 25. Hereinafter, the plurality of radio circuits 24-1 to 24-n are simply referred to as radio circuits 24 when collectively referred to without being distinguished from each other.

  The interface circuit 21 is an interface for performing wired communication with the BBU 11. The antenna 13 is connected to each radio circuit 24 via the cable 12. Each radio circuit 24 performs processing such as amplification on the signal output from the processor 23 and radiates the processed signal to the space via the cable 12 and the antenna 13. Each radio circuit 24 receives a signal received from the space via the antenna 13 via the cable 12, performs a process such as amplification on the received signal, and outputs the processed signal to the processor 23. Each radio circuit 24 includes, for example, a DAC 41, a PA 42, a circulator 43, a BPF 44, a connector 45, a switch 46, an LNA 47, and an ADC 48.

  The feedback circuit 25 feeds back the test signal via the radio circuit 24 and the cable 12 to the processor 23 in the calibration of the branch corresponding to each antenna 13. In the first embodiment described above, the feedback circuit 25 includes the ADC 50 and the switch 51. In the second embodiment, the feedback circuit 25 includes, for example, an ADC 50 and a synthesizer 52. In the third embodiment, the feedback circuit 25 includes the ADC 50, the converter 53, the converter 54, and the synthesizer 55.

  The memory 22 stores, for example, various programs and data for realizing the functions of the switch 31, the delay unit 32, the switch 33, the delay unit 34, the signal generator 35, the adjustment unit 36, and the detection unit 37. . The processor 23 implements the functions of, for example, the switch 31, the delay unit 32, the switch 33, the delay unit 34, the signal generator 35, the adjustment unit 36, and the detection unit 37 by executing the program read from the memory 22. To do.

  Note that not all programs, data, and the like in the memory 22 need be stored in the memory 22 from the beginning. For example, a program, data, or the like may be stored in a portable recording medium such as a memory card inserted into the RRH 20, and the RRH 20 may appropriately acquire and execute the program, data, or the like from such a portable recording medium. . Further, the RRH 20 may appropriately acquire and execute the program from another computer or server device storing the program, data, etc. via a wireless communication line, public line, Internet, LAN, WAN, or the like. Good.

[Others]
The disclosed technology is not limited to the above-described embodiments, and various modifications can be made within the scope of the gist.

  For example, in each of the embodiments described above, the base station 10 has been described as an example, but the disclosed technique is not limited thereto. As long as the wireless communication device has the array antenna 14, the disclosed technology can be applied to other wireless communication devices such as a terminal device.

  In each of the above-described embodiments, the base station 10 having the BBU 11 and the plurality of RRHs 20 has been described as an example. However, the disclosed technique is not limited to this, and any other base station 10 having the array antenna 14 may be used. The disclosed technology can also be applied to the base station 10 having the configuration.

  In each of the above-described embodiments, the delay amount of each transmission circuit is reduced so that the difference in delay amount between the transmission circuits of each antenna 13 becomes small with the connection point between the cable 12 and the antenna 13 open. Although adjusted, the disclosed technique is not limited to this. For example, in a state where the connection point between the cable 12 and the antenna 13 is opened, the gain of each transmission circuit may be adjusted so that the difference in the amplitude of the test signal between the transmission circuits of each antenna 13 becomes small.

  In each of the above-described embodiments, each processing block of the base station 10 is classified according to the function according to the main processing contents in order to facilitate understanding of the base station 10 in the embodiment. For this reason, the disclosed technique is not limited by the processing block classification method and its name. In addition, each processing block of the base station 10 in the above-described embodiment can be subdivided into more processing blocks according to the processing contents, or a plurality of processing blocks can be integrated into one processing block. it can. For example, the functions of the adjustment unit 36 and the detection unit 37 may be realized by one processing block. Further, the processing executed by each processing block may be realized as processing by software, or may be realized by dedicated hardware such as ASIC (Application Specific Integrated Circuit).

10 Base station 11 BBU
12 Cable 13 Antenna 14 Array antenna 20 RRH
30 control unit 31 switch 32 delay unit 33 switch 34 delay unit 35 signal generator 36 adjustment unit 37 detection unit 40 radio unit 41 DAC
42 PA
43 Circulator 44 BPF
45 Connector 46 Switch 47 LNA
48 ADC
50 ADC
51 Switch 52 Synthesizer 53 Converter 54 Converter 55 Synthesizer

Claims (8)

An array antenna including a plurality of antennas;
A plurality of transmission circuits provided corresponding to the respective antennas;
A plurality of lines provided corresponding to each of the antennas and connecting the antenna and the transmission circuit corresponding to the antenna;
A generator for generating a test signal input to each of the transmission circuits;
With the end on the antenna side being opened in each of the lines, the transmission circuit and the transmission circuit and the transmission circuit and the transmission circuit and the transmission circuit and the transmission circuit The delay time in each of the transmission circuits is adjusted so that the difference in time to the timing at which the test signal reflected by the end opened in the line via the line is received is less than a predetermined value. A wireless communication apparatus comprising: an adjustment unit. A plurality of receiving circuits provided corresponding to the respective antennas;
Corresponding to each of the antennas, provided between the antenna and the transmitting circuit and the receiving circuit corresponding to the antenna, the signal output from the transmitting circuit is passed through the line, and output from the line A plurality of circulators that pass the received signal to the receiving circuit corresponding to the antenna,
The adjustment unit is
After the delay time in the transmission circuit is adjusted, the test signal is input from the generation unit to the transmission circuit between the plurality of reception circuits in a state where the end of the line is open. The difference in time from the timing to the timing at which the test signal reflected at the end opened in the line via the transmission circuit and the line and passed through the circulator and the reception circuit is less than a predetermined value The radio communication apparatus according to claim 1, wherein a delay time in each of the receiving circuits is adjusted so that A combining unit that combines the power of the test signal reflected by the end opened in the line for each transmission circuit,
The adjustment unit is
The delay time in each of the transmission circuits is adjusted so that the power of the signal output from the combining unit is equal to or higher than a predetermined power in a state where the end of the line is open. The wireless communication apparatus according to claim 1 or 2. The generator is
The radio communication apparatus according to claim 3, wherein the test signal having different power is generated for each of the transmission circuits, and the generated test signal is input to each of the transmission circuits. A converter for converting the power of the test signal reflected by the end opened in the line for each transmission circuit into a voltage;
A combining unit that combines the voltages of the transmission circuits converted by the conversion unit, and
The adjustment unit is
The delay time in each of the transmission circuits is adjusted so that the voltage of the signal output from the combining unit is equal to or higher than a predetermined voltage in a state where the end of the line is open. The wireless communication apparatus according to claim 1 or 2. The synthesis unit is
The wireless communication apparatus according to claim 5, wherein the voltages for the transmission circuits converted by the conversion unit are combined by applying different weights to the transmission circuits.   7. The device according to claim 1, further comprising a switching unit that is provided corresponding to each of the antennas and that switches connection and release between the antenna and the line corresponding to the antenna. 8. Wireless communication device. Wireless communication device
In the plurality of lines connecting each of the plurality of antennas included in the array antenna and each of the plurality of transmission circuits provided corresponding to each of the antennas, with the end on the antenna side being open , Input a test signal to each of the transmission circuits,
A time difference from a timing at which the test signal is input to the transmission circuit to a timing at which the test signal reflected at the end opened at the line via the transmission circuit and the line is received is predetermined. A delay adjustment method comprising: performing a process of adjusting a delay time in each of the transmission circuits so as to be less than a value.

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