WO2023181146A1 - Array antenna system and calibration method for array antenna system - Google Patents

Abstract

An array antenna system according to the technology of the present disclosure is provided with a plurality of transmission systems, and is provided with: a calibration signal generation unit (30) that generates a calibration signal; a phase control unit (40) that controls the phases of extraction signals each comprising a transmission signal extracted from the transmission system and the calibration signal; a power synthesis unit (50) that synthesizes a plurality of signals the phases of which are controlled by the phase control unit (40); a calibration signal receiver (60) that modulates a signal synthesized by the power synthesis unit (50); a power measurement unit (70) that measures the power of the signal modulated by the calibration signal receiver (60); and a phase control indication unit (80) that, on the basis of the measured value of the power measured by the power measurement unit (70), indicates a phase amount to be controlled to the phase control unit (40).

Description

Array antenna system and calibration method for array antenna system

The disclosed technology relates to an array antenna system and a method for calibrating the array antenna system.

In the field of communication systems, array antenna system technology is used. For example, Patent Document 1 discloses an adaptive array antenna system for communication systems. Further, Patent Document 1 discloses a phase calibration method for an adaptive array antenna system.
The phase calibration method shown in Patent Document 1 inserts a calibration signal (corresponding to the "calibration signal" in the disclosed technology) into a main signal (corresponds to the "transmission signal" in the disclosed technology) and inserts it into a predetermined circuit. The phase of the main signal is calibrated based on the phase change of the calibration signal included in the output signal of the circuit.

Japanese Patent Application Publication No. 2005-286780

The method shown in Patent Document 1 calculates the difference between a composite signal of the transmission signals before passing through the analog circuits of each transmission system and a composite signal of the transmission signals after passing through the analog circuits of each transmission system. . According to Patent Document 1, a phase calibrator corrects a phase change in an analog circuit, that is, corrects a phase characteristic opposite to the phase characteristic in the analog circuit, so that the phases of the array antenna are aligned as a result. It says to control.
However, Patent Document 1 does not disclose in detail how to efficiently obtain the amplitude phase characteristics of the analog circuits of each transmission system. Furthermore, Patent Document 1 does not mention a method of simultaneously calibrating the transmission systems included in the array antenna system.

The disclosed technology improves the conventional array antenna system and the method of calibrating the array antenna system exemplified in Patent Document 1. More specifically, the present disclosure aims to provide an array antenna system and an array antenna system calibration method that can simultaneously calibrate all transmission systems included in the array antenna system.

The array antenna system according to the disclosed technology is an array antenna system that includes a plurality of transmission systems, and includes a calibration signal generation section that generates a calibration signal, and an extraction signal that is composed of a transmission signal and a calibration signal extracted from the transmission system. A phase control section that controls the phase, a power synthesis section that synthesizes a plurality of signals whose phases have been controlled by the phase control section, a calibration signal receiver that demodulates the signal synthesized by the power synthesis section, and a calibration signal receiver. a power measurement unit that measures the power of the signal demodulated by the power measurement unit; and a phase control instruction unit that instructs the phase control unit to control the phase amount based on the power measurement value measured by the power measurement unit. Be prepared.

Since the array antenna system according to the disclosed technique has the above configuration, it has the effect that all transmission systems included in the array antenna system can be calibrated simultaneously.

FIG. 1 is a block diagram showing the functional configuration of an array antenna system according to the first embodiment. FIG. 2 is a first diagram showing the hardware configuration of a part of the array antenna system according to the first embodiment. FIG. 3 is a second diagram showing a partial hardware configuration of the array antenna system according to the first embodiment. FIG. 4 is a flowchart showing processing steps of the array antenna system according to the first embodiment. FIG. 5 is a block diagram showing the functional configuration of the array antenna system according to the third embodiment. FIG. 6 is a flowchart showing the processing steps of the array antenna system according to the third embodiment. FIG. 7 is a block diagram showing the functional configuration of the array antenna system according to the fourth embodiment. FIG. 8 is a flowchart showing the processing steps of the array antenna system according to the fourth embodiment. FIG. 9 is a block diagram showing the functional configuration of the array antenna system according to the fifth embodiment. FIG. 10 is a flowchart showing the processing steps of the array antenna system according to the fifth embodiment. FIG. 11 is a block diagram showing the functional configuration of an array antenna system according to Embodiment 6. FIG. 12 is a flowchart showing the processing steps of the array antenna system according to the sixth embodiment. FIG. 13 is a graph showing a time-series change in the amount of electric power to be measured, and explains the timing to start a new calibration.

The method for calibrating the array antenna system according to the disclosed technology is based on the Rotating Element Electric Field Vector Method (REV method). The element electric field vector rotation method measures the change in the magnitude of the combined electric field when the amount of phase shift of a phase shifter of a phased array is changed. It is known that the magnitude of the combined electric field changes in a sinusoidal manner as the amount of phase shift changes.

Embodiment 1.
FIG. 1 is a block diagram showing the functional configuration of an array antenna system according to the first embodiment. As shown in FIG. 1, the array antenna system according to the first embodiment includes an antenna element 1, an extraction section 2, a transmitter 3, an injection section 4, a DBF section 10, a signal processing section 20, and a calibration signal. Generation unit 30, phase control unit 40, power combining unit 50, calibration signal receiver 60, power measurement unit 70, phase control instruction unit 80, calibration signal phase offset unit 90, calibration signal analysis unit 100 and, including.
As shown in FIG. 1, there are a plurality of antenna elements 1, and when distinguishing one from another, they are expressed as antenna element 1-1, antenna element 1-2, . . . , antenna element 1-N. N is the total number of antenna elements 1. As shown in FIG. 1, there are N extraction units 2, N transmitters 3, and N injection units 4. When distinguishing each of the extraction unit 2, transmitter 3, and injection unit 4, indicate by adding "-1", "-2", ..., "-N" after the code. shall be. If n is a natural number from 1 to N, the signal processing section 20, DBF section 10, injection section 4-n, transmitter 3-n, extraction section 2-n, and antenna element 1-n each constitute one transmission system. Configure. That is, the array antenna system according to the first embodiment has N transmission systems.
In the array antenna system according to the first embodiment, a calibration signal generation section 30, a phase control section 40, a power combining section 50, a calibration signal receiver 60, a power measurement section 70, a phase control instruction section 80, a calibration signal phase offset section 90 , and the calibration signal analysis section 100 constitute a calibration signal system.

<<Signal processing unit 20 in transmission system>>
The signal processing unit 20 is a component for generating a transmission signal of the array antenna system. The transmission signal may be a digitally modulated signal obtained by modulating a baseband signal. Note that in this specification, the term "transmission signal" is used to collectively refer to a baseband signal and a digital modulated signal obtained by modulating the baseband signal.

<<DBF unit 10 in transmission system>>
The DBF unit 10 is a component for performing digital beamforming on transmission signals.
First, the DBF section 10 distributes the baseband signal to N systems.
Second, the DBF unit 10 adjusts the amplitude and phase of each of the N distributed baseband signals in order to implement digital beamforming. The baseband signal whose amplitude and phase have been adjusted is sent to the transmitter 3-n via the injection section 4-n.

《Injection part 4 in the transmission system》
The injection unit 4-n is a component for injecting a later-described calibration signal into the transmission system. Details of the injection section 4 will become clear from the description below.

《Transmitter 3 in the transmission system》
The transmitter 3-n is a component for modulating a digital baseband signal into an analog RF band (Radio Frequency band) signal.
The analog RF band transmission signal modulated by the transmitter 3-n is sent to the antenna element 1-n via the extractor 2-n. Note that the analog RF band transmission signal is sometimes referred to as a data signal or a communication signal.

《Extraction unit 2 in transmission system》
The extraction unit 2-n is a component for extracting a part of the signal flowing through the transmission system. The signal extracted by the extraction unit 2-n is referred to as an "extracted signal."

《Antenna element 1 in transmission system》
The antenna elements 1-n are components for radiating an RF band transmission signal into space. The antenna elements 1-n are arranged in an array. Generally, antenna elements 1 in an array antenna system are often arranged at regular positions at equal intervals.

<<Calibration signal generation unit 30 in the calibration signal system>>
The calibration signal generation section 30 is a component for generating a calibration signal. The calibration signal generation section 30 can generate a calibration signal having an arbitrary symbol pattern. Here, the term "symbol pattern" is synonymous with the symbol pattern used in, for example, Japanese Patent Application Publication No. 2001-332925.
The calibration signal generated by the calibration signal generation unit 30 may be a chirp pulse signal in which up chirps and down chirps appear randomly when viewed on the time axis. A different calibration signal consisting of a combination of up chirp and down chirp is used for each transmission system, that is, a different combination of up chirp and down chirp is used.
The calibration signal generated by the calibration signal generation section 30 is injected into the transmission system via the injection section 4-n.

<<Phase control unit 40 in the calibration signal system>>
The phase control section 40 is a component for controlling the phase of each of the extraction signals extracted by the extraction section 2-n. Finally, the phase control unit 40 determines and controls a phase such that the components of the transmission signal are canceled when the extracted signals extracted by the extraction unit 2 are combined by a power combining unit 50 (described later). do.
The details of the phase amount controlled by the phase control section 40 will become clear from the explanation below.
The N signals whose phases have been controlled by the phase control section 40 are sent to the power combining section 50.

<<Power combining unit 50 in the calibration signal system>>
The power combining unit 50 is a component for combining N signals sent from the phase control unit 40.
The signals combined by the power combining section 50 are sent to the calibration signal receiver 60.

<<Calibration signal receiver 60 in the calibration signal system>>
The calibration signal receiver 60 is a component for detecting the signal sent from the power combining section 50. Here, the term "detect" means extracting a baseband signal from a modulated wave, that is, demodulating it.
The signal detected by the calibration signal receiver 60 is sent to the power measurement section 70 and the calibration signal analysis section 100.

<<Power measurement unit 70 in calibration signal system>>
The power measurement unit 70 is a component for measuring the amount of power of the signal sent from the calibration signal receiver 60.
The above-mentioned phase control section 40 cooperates with the power measurement section 70 to determine the amount of phase to be controlled. Cooperation between the phase control section 40 and the power measurement section 70 is realized by instructions from the phase control instruction section 80. Specifically, the phase control unit 40 gradually changes the amount of phase to be controlled, refers to the amount of power measured by the power measurement unit 70, and searches for the amount of phase that minimizes this amount of power. The mode of operation in which the phase control unit 40 searches for the phase amount that minimizes the amount of electric power will be referred to as a search mode.

<<Phase control instruction section 80 in the calibration signal system>>
The phase control instruction section 80 is a component for issuing instructions for realizing cooperation between the phase control section 40 and the power measurement section 70. The phase control instruction section 80 is also a component for storing the phase amount that minimizes the amount of electric power and for instructing the calibration signal phase offset section 90 to use this phase amount.
When the phase amount that minimizes the amount of power is sent, the phase control instruction section 80 instructs the phase control section 40 to cancel the search mode and perform control using this phase amount from now on. The mode of operation in which the phase control unit 40 performs control while fixing the amount of power to the phase amount that minimizes the amount of power will be referred to as a fixed mode. That is, in order to implement the search mode, the array antenna system according to the first embodiment uses a loop consisting of the phase control section 40, the power combining section 50, the calibration signal receiver 60, the power measurement section 70, and the phase control instruction section 80. The treatment is carried out at least once.

<<Calibration signal phase offset section 90 in the calibration signal system>>
The calibration signal phase offset section 90 is a component for offsetting the phase of the calibration signal generated by the calibration signal generation section 30 by the phase amount instructed by the phase control instruction section 80 (offsetting adjustment). .
The calibration signal whose phase has been offset (cancellation adjustment) by the calibration signal phase offset unit 90 is sent to the calibration signal analysis unit 100.

<<Calibration signal analysis unit 100 in the calibration signal system>>
The calibration signal analysis unit 100 is a component for extracting the calibration signal that has passed through the transmission system and calculating a relative amplitude and phase error (hereinafter referred to as "relative amplitude and phase error"). The calibration signal analysis unit 100 preferably calculates the correlation between signals in order to calculate the relative amplitude phase error.
The relative amplitude phase error calculated by the calibration signal analysis section 100 is sent to the DBF section 10. The DBF unit 10 corrects the beamforming design values so as to cancel the relative amplitude and phase errors.

《About hardware configuration》
FIG. 2 is a first diagram showing the hardware configuration of a part of the array antenna system according to the first embodiment. FIG. 3 is a second diagram showing a partial hardware configuration of the array antenna system according to the first embodiment.

Transmitter 3, injection unit 4, DBF unit 10, signal processing unit 20, calibration signal generation unit 30, calibration signal receiver 60, power measurement unit 70, phase control instruction unit 80, calibration signal phase offset unit 90 in the array antenna system , and the calibration signal analysis section 100 are realized by a processing circuit. Even if the processing circuit is dedicated hardware, it is also called a CPU (Central Processing Unit, central processing unit, processing unit, arithmetic unit, microprocessor, microcomputer, processor, DSP) that executes a program stored in memory. ), it doesn't matter.

Specifically, FIG. 2 is a diagram in the case of a processing circuit 500 in which the processing circuit is dedicated hardware. Processing circuit 500 may be, for example, a single circuit, a composite circuit, a programmed processor, a parallel program processor, an ASIC, an FPGA, or a combination thereof. Transmitter 3, injection section 4, DBF section 10, signal processing section 20, calibration signal generation section 30, calibration signal receiver 60, power measurement section 70, phase control instruction section 80, calibration signal phase offset section 90, and calibration signal Each function of the analysis section 100 may be realized individually by the processing circuit 500, or may be realized collectively by one processing circuit 500.

Specifically, FIG. 3 is a diagram when the processing circuit is the CPU 502. When the processing circuit is the CPU 502, each of the above functions is realized by software, firmware, or a combination of software and firmware. Software and firmware are written as programs and stored in memory 504. The CPU 502 realizes the functions of each section by reading and executing programs stored in the memory 504. That is, the array antenna system includes a memory 504 for storing a program that, when executed by the processing circuitry, results in the execution of each processing step of the array antenna system. It can also be said that these programs cause a computer to execute the procedures and methods of the array antenna system. Here, the memory 504 may be a non-volatile or volatile semiconductor memory such as RAM, ROM, flash memory, EPROM, EEPROM, etc., for example. Further, the memory 504 may have a structure including a disk such as a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, a DVD, or the like. Furthermore, the memory 504 may be in the form of an HDD or an SSD.

Note that some of the above functions of the array antenna system may be realized by dedicated hardware, and other parts may be realized by software or firmware. In this way, the processing circuit can realize each of the above functions using hardware, software, firmware, or a combination thereof.

<<About the calibration method of the array antenna system according to the first embodiment>>
FIG. 4 is a flowchart showing processing steps of the array antenna system according to the first embodiment.
As shown in FIG. 4, the processing steps of the array antenna system according to the first embodiment are mainly composed of three phases.
The first phase includes calibration signal generation ST11, calibration signal injection ST12, and calibration signal extraction ST13.
The second phase is a portion surrounded by a broken line frame labeled "P101" in FIG. 4, and is referred to as a "phase setting value search phase." The phase setting value search phase corresponds to the search mode of the phase control section 40 described above. The phase setting value search phase includes phase setting ST21, calibration signal synthesis ST22, calibration signal detection ST23, signal power measurement ST24, and confirmation of the number of changes of the phase setting value ST25.
The third phase is a portion surrounded by a broken line frame labeled "P102" in FIG. 4, and is referred to as a "calibration phase." In the calibration phase, the phase control section 40 is in fixed mode. The calibration phase includes phase setting value calculation ST41, phase setting ST42, calibration signal synthesis ST43, calibration signal detection ST44, relative amplitude phase error calculation ST45, calibration value calculation ST47, and transmission signal correction. ST48.

Calibration signal generation ST11 is a processing step performed by the calibration signal generation section 30. Generation of a calibration signal In ST11, the calibration signal generation section 30 generates a calibration signal according to a pre-designed specification.
The calibration signal may be, for example, a modulation signal that implements phase modulation. More preferably, the calibration signals are N modulation signals that are injected into the N transmission systems and have low correlation in the time axis direction, that is, high orthogonality.

The calibration signal injection ST12 is a processing step performed by the calibration signal generation section 30. In injection ST12 of positive signals, the calibration signal generation unit 30 injects N calibration signals into the injection units 4-1, 4-2, . . . , injection units 4-N of the corresponding transmission systems, respectively.
As described above, each function of the calibration signal generation section 30 and the injection section 4 may be realized by the CPU 502. That is, the injection of N calibration signals may be performed by digital processing within the CPU 502 without using physical means. In other words, the N calibration signals can be injected by performing addition processing of the transmission signal and the calibration signal in each transmission system. Each function of the injection section 4-1, injection section 4-2, ..., injection section 4-N can be performed by physical means without using physical means such as a switch or a directional coupler (coupler). This eliminates the negative effects of distortion, noise, etc. inherent in

Extraction of the calibration signal ST13 is a processing step performed by the extraction section 2-1, the extraction section 2-2, . . . , the extraction section 2-N. In calibration signal extraction ST13, each of the extraction sections 2-1, 2-2, . . . , 2-N extracts a part of the signal flowing through the transmission system as an extraction signal. The extracted signal includes a transmission signal and a calibration signal.
As described above, the signals extracted by the extraction section 2-1, the extraction section 2-2, . . . , the extraction section 2-N are analog signals in the RF band. Unlike baseband signals, RF band analog signals have too high a frequency band to be sampled and digitally processed, making it impractical. Therefore, each function of the extracting section 2-1, the extracting section 2-2, . . . , the extracting section 2-N may be realized by physical means such as a directional coupler and a switch.

The phase setting ST21 in the phase setting value search phase (P101) is a processing step performed by the phase control unit 40 in the search mode. In phase setting ST21, the phase control section 40 gradually changes the phase amount for each of the RF band analog signals extracted by the extraction section 2-1, extraction section 2-2, ..., extraction section 2-N. and control the phase. The phase control by the phase control section 40 may be realized by an analog or digital phase shifter. Only one phase shifter may be provided to switch the system, or N phase shifters may be provided for each system.

The calibration signal synthesis ST22 in the phase setting value search phase (P101) is a processing step performed by the power synthesis section 50. Combining calibration signals In ST22, the power combining section 50 combines the N signals sent from the phase control section 40. The power combining unit 50 is realized by, for example, hardware such as a power combiner.

Detection ST23 of the calibration signal in the phase setting value search phase (P101) is a processing step performed by the calibration signal receiver 60. In calibration signal detection ST23, the calibration signal receiver 60 demodulates the signal sent from the power combining section 50 and extracts a baseband signal. Note that the baseband signal extracted in the calibration signal detection ST23 is a digital signal.

Signal power measurement ST24 in the phase setting value search phase (P101) is a processing step performed by the power measurement unit 70. Signal Power Measurement In ST24, the power measurement unit 70 measures the amount of power of the signal sent from the calibration signal receiver 60.

The confirmation ST25 of the number of changes in the phase setting value in the phase setting value search phase (P101) is a processing step performed by the phase control instruction section 80. In confirmation ST25 of the number of changes in the phase setting value, the phase control instruction unit 80 at least temporarily updates the amount of phase changed by the phase control unit 40, the amount of power measured by the power measurement unit 70, and the correspondence between them. Remember and retain. Further, in confirmation ST25 of the number of changes in the phase setting value, the phase control instruction section 80 issues an instruction for realizing cooperation between the phase control section 40 and the power measurement section 70. Further, in confirmation ST25 of the number of changes in the phase setting value, the phase control instruction section 80 checks the number of changes in the phase setting value, and confirms whether the search mode of the phase control section 40 has ended.

The phase amount to be changed in the phase control unit 40 may be realized by, for example, an N-fold For statement (For Loop) that incorporates nesting. For example, in the N-fold For statement, the first For statement from the inside changes the phase amount in steps from 0 degrees to 360 degrees with respect to the first analog signal extracted from the extraction unit 2-1. . The second For statement from the inside changes the phase amount of the second analog signal extracted from the extraction unit 2-2 in steps from 0 degrees to 360 degrees. Similarly, the phase amount is changed in steps using the Nth For statement from the inside. The phase amount changed by the phase control section 40 may be realized in this manner, for example. When there are K step-like changes in each for statement, in confirmation ST25 of the number of changes in the phase setting value, the phase control instruction unit 80 checks whether the number of changes is less than or greater than K×N.

In confirmation ST25 of the number of changes to the phase setting value, the phase control instruction unit 80 determines whether the power measurement unit 70 has completed measuring the electric energy for one of the N combinations of phase amounts corresponding to the N analog signals. , instructs the phase control unit 40 to control to the next combination of phase amounts. In other words, the phase control instruction unit 80 plays the role of a “Next” command for the N-fold For statements executed by the phase control unit 40 described above.

Phase setting value calculation ST41 in the calibration phase (P102) is a processing step performed by the phase control instruction section 80. In phase setting value calculation ST41, the phase control instruction unit 80 calculates an estimated value of the phase amount that minimizes the amount of power from the temporarily stored correspondence relationship between the phase amount and the amount of power of the K×N combination. do. As described above, it is known that the amount of power (the magnitude of the combined electric field) changes in a sinusoidal manner with respect to the amount of phase (the amount of phase shift) changed by the phase shifter. Using this property, in phase setting value calculation ST41, the phase control instruction unit 80 calculates a plausible What is necessary is to calculate a theoretical sine wave and obtain an estimated value of the phase amount that minimizes the amount of power.

The phase setting ST42 in the calibration phase (P102) is a processing step performed by the phase control instruction section 80. In phase setting ST42, the phase control instruction section 80 instructs the phase control section 40 to control the phase shifter using the estimated value of the phase amount that minimizes the amount of power. Hereinafter, the phase amount instructed to the phase control unit 40 will be expressed by the term "phase setting value." The phase control unit 40 to which the phase setting value is instructed controls the phase shifter in a fixed mode.

The calibration signal synthesis ST43 in the calibration phase (P102) is a processing step performed by the power combining section 50. Combining calibration signals In ST43, the power combining section 50 combines the N signals sent from the phase control section 40.

Detection ST44 of the calibration signal in the calibration phase (P102) is a processing step performed by the calibration signal receiver 60. In calibration signal detection ST44, the calibration signal receiver 60 demodulates the signal sent from the power combining section 50 and extracts a baseband signal that is a digital signal.

The processes of phase setting ST42, calibration signal synthesis ST43, and calibration signal detection ST44 in the calibration phase (P102) are the same as those in the phase setting value search phase (P101), except for the phase amount controlled by the phase control section 40. The contents are the same as those of setting ST21, calibration signal synthesis ST22, and calibration signal detection ST23.

Calculating the relative amplitude phase error ST45 in the calibration phase (P102) is a processing step performed by the calibration signal analysis section 100. In relative amplitude phase error calculation ST45, the calibration signal analysis unit 100 refers to the calibration signal generated by the calibration signal generation unit 30 with respect to the baseband signal demodulated by the calibration signal receiver 60 in calibration signal detection ST44. The signal is subjected to processing for determining correlation (hereinafter simply referred to as "correlation processing"). The correlation process may be performed in the frequency domain or in the time domain.
If the calibration signal is a combination of up-chirp and down-chirp, the correlation process may be pulse compression.

As shown in FIG. 1, the calibration signal used as a reference signal by the calibration signal analysis section 100 in relative amplitude phase error calculation ST45 passes through the calibration signal phase offset section 90.
Calculation of Relative Amplitude Phase Error The calibration signal used as a reference signal by the calibration signal analysis section 100 in ST45 has its phase offset (cancellation adjustment) by the phase setting value by the calibration signal phase offset section 90.

Calculation of Relative Amplitude and Phase Error In ST45, the calibration signal analysis section 100 extracts the calibration signal that has passed through each transmission system.
Further, in relative amplitude phase error calculation ST45, the calibration signal analysis section 100 calculates a relative amplitude phase error (hereinafter simply referred to as "amplitude phase error") based on the extracted calibration signal. The amplitude phase error is an index indicating the variation in characteristics among the N transmission systems.

Calibration value calculation ST47 in the calibration phase (P102) is a processing step performed by the calibration signal analysis section 100. Calculating Calibration Values In ST47, the calibration signal analysis unit 100 calculates calibration values for amplitude and phase (hereinafter referred to as "amplitude phase calibration values") that cancel the calculated amplitude and phase errors.

Correction ST48 of the transmission signal in the calibration phase (P102) is a processing step performed by the DBF section 10. Correcting the transmitted signal In ST48, the DBF section 10 corrects the transmitted signal using the amplitude phase calibration value.
The processing in the calibration phase (P102) is completed with correction ST48 of the transmitted signal as the last processing step.

The array antenna system according to the present disclosure may perform the series of processes shown in FIG. 4 periodically or may perform the series of processes shown in FIG. 4 depending on the situation where calibration is required.
The method for calibrating an array antenna system according to the disclosed technology can be used for adjustment before shipping the array antenna system, daily maintenance during operation after the array antenna system is installed, and periodic maintenance. It can be used in various situations such as regular maintenance.

As described above, since the array antenna system according to the first embodiment has the above configuration, the transmission systems for all N antenna elements 1 can be calibrated simultaneously. Due to this effect, the array antenna system according to Embodiment 1 can automatically perform a series of calibration processes to improve the accuracy between antenna elements 1-n (n=1, 2,...,N) or between transmission systems. It is possible to suppress variations in characteristics.

Embodiment 2.
The method for calibrating an array antenna system according to the second embodiment is a modification of the method for calibrating an array antenna system according to the presently disclosed technology.
The symbols used in the second embodiment are the same as those used in the first embodiment, unless otherwise specified. In the second embodiment, explanations that overlap with those in the first embodiment will be omitted as appropriate.

In Embodiment 1, as a method for calibrating the array antenna system, in the phase setting value search phase (P101), the phase control unit 40 in the search mode changes the phase amount in steps from 0 degrees to 360 degrees. Although an aspect has been shown in which a solution of the phase amount is searched within the range, the disclosed technology is not limited thereto.
If there is a solution candidate that minimizes the amount of power, the search for the phase amount may be performed in the vicinity of the solution candidate. Further, in the search for the phase amount, if there is a solution candidate that minimizes the amount of power, the amount of power may be measured by changing the neighborhood of the solution candidate in small steps.

In the method for calibrating the array antenna system according to the second embodiment, when performing the second and subsequent calibrations, the phase setting value obtained in the most recent calibration may be used as a candidate for the solution that minimizes the amount of power. The array antenna system according to the second embodiment may store the phase setting value obtained in the calibration before shipping in the memory 504 as a candidate for the solution that minimizes the amount of power.

As described above, the array antenna system calibration method according to the second embodiment uses the phase setting value obtained in the most recent calibration as a solution candidate. The effect shown in 1 is achieved.

Embodiment 3.
The array antenna system and the method for calibrating an array antenna system according to the third embodiment are modified examples of the array antenna system and the method for calibrating the array antenna system according to the presently disclosed technology.
The symbols used in the third embodiment are the same as those used in the previously described embodiments, unless otherwise specified. In Embodiment 3, explanations that overlap with those of the previously described embodiments will be omitted as appropriate.

FIG. 5 is a block diagram showing the functional configuration of the array antenna system according to the third embodiment. As shown in FIG. 5, the disclosed technology can also be applied to an array antenna system that does not include the power measurement unit 70.
As shown in FIG. 5, in the array antenna system according to the third embodiment, information from the DBF section 10 is sent to the phase control instruction section 80.
Except for the above differences, the configuration of the array antenna system according to the third embodiment is the same as the configuration of the array antenna system shown in the previous embodiments.

The method of calibrating the array antenna system according to the third embodiment is not intended to perform large-scale calibration, but to cope with small changes in characteristics due to aging. The method for calibrating the array antenna system according to the third embodiment is based on the premise that the transmission system has been calibrated in the pre-shipment adjustment. The disclosed technology is based on the principle that the influence on input/output characteristics due to secular change (aging deterioration) of each element of a transmission system is not large enough to require extensive calibration.

Specifically, the method for calibrating the array antenna system according to the third embodiment is to stop the phase amount based on the magnitude of the measured composite electric field and use a fixed phase setting value. In this specification, switching from a phase amount based on the magnitude of the measured composite electric field to a fixed phase setting value will be referred to by the term "fixed setting value switching."
In the pre-shipment adjustment, it is assumed that the amplitude and phase for correcting the n-th transmission system are represented by a complex number W _n . In the method for calibrating the array antenna system according to the third embodiment, when changing the fixed setting value, for example, the corrected phase amount (φ _n ) expressed by the following equation is corrected.

Here, arg( ) of the first term on the right side of equation (1) represents a function that calculates the argument of a complex number that is an argument. In equation (1), the first term on the right side is a term that cancels the phase amount based on the magnitude of the composite electric field measured during pre-shipment adjustment, and the second term on the right side is a term related to the fixed phase setting value. This is an example.

Generally, beamforming is a technique for directing radio waves of an array antenna system in a certain direction. Beamforming can be applied whether the array antenna is used as a transmit antenna or the array antenna is used as a receive antenna. Beamforming is based on the fact that radio waves have wave properties. Specifically, radio waves, which are a type of wave, have the property that when waves of the same phase are multiplied together, they are strengthened, and when waves of opposite phases are multiplied together, they are canceled out. Beamforming actively utilizes the properties of these waves.
In beamforming, how to design the phase of each transmission system in an array antenna system depends on what spacing (d) and manner the antenna elements 1 are arranged, and in which direction the radio waves of the array antenna system are directed. It depends on whether you want it to be oriented towards. The disclosed technology is not limited to the value shown in the second term on the right side of equation (1), and may use a phase setting value designed by beamforming.

FIG. 6 is a flowchart showing the processing steps of the array antenna system according to the third embodiment. As shown in FIG. 6, the processing steps of the array antenna system according to the third embodiment include generation of a calibration signal ST11, injection of the calibration signal ST12, extraction of the calibration signal ST13, phase setting ST42, and synthesis of the calibration signal. ST43, detection ST44 of a calibration signal, calculation ST45 of a relative amplitude phase error, calculation ST47 of a calibration value, and correction ST48 of a transmission signal.

<<About the calibration method of the array antenna system according to the third embodiment>>
In the method for calibrating an array antenna system according to the third embodiment, in the first phase, processing steps of generation of a calibration signal ST11, injection of a calibration signal ST12, and extraction of a calibration signal ST13 are performed. The processing contents of calibration signal generation ST11, calibration signal injection ST12, and calibration signal extraction ST13 according to the third embodiment are the same as those shown in the first embodiment.

Phase setting ST42 according to the third embodiment is a processing step executed by the phase control instruction section 80. In phase setting ST42, the phase control instruction section 80 instructs the phase control section 40 to modify the phase amount (φ _n ) when switching the fixed set value. The corrected phase amount (φ _n ) is, for example, as shown in Equation (1), and may be determined depending on the purpose of digital beamforming performed by the DBF unit 10.
The phase control section 40 controls the phase shifter based on instructions from the phase control instruction section 80.

The processing contents of calibration signal synthesis ST43, calibration signal detection ST44, relative amplitude phase error calculation ST45, calibration value calculation ST47, and transmission signal correction ST48 according to the third embodiment are the same as those of the first embodiment. The contents are the same as those shown in .

As described above, the method for calibrating the array antenna system according to the third embodiment includes the processing step of switching the fixed setting value, so that the calibration value is switched from the calibration value based on the magnitude of the composite electric field measured during pre-shipment adjustment to the fixed setting value. This has the effect of being able to cope with small changes in characteristics due to aging.

Embodiment 4.
The array antenna system and the method for calibrating an array antenna system according to Embodiment 4 are modified examples of the array antenna system and the method for calibrating an array antenna system according to the presently disclosed technology.
The symbols used in the fourth embodiment are the same as those used in the previously described embodiments, unless otherwise specified. In Embodiment 4, explanations that overlap with those of the previously described embodiments will be omitted as appropriate.

FIG. 7 is a block diagram showing the functional configuration of the array antenna system according to the fourth embodiment. As shown in FIG. 7, the array antenna system according to the fourth embodiment includes a Butler matrix circuit 110, a route selection unit 120, and a route selection unit instead of the phase control unit 40, the power combining unit 50, and the phase control instruction unit 80. An instruction section 130 is provided.
Butler matrix circuit 110, route selection section 120, and route selection instruction section 130 are connected as shown in FIG.

In the previously described embodiments, it has been shown that calibration is performed using a phase shifter (not shown), but the disclosed technology is not limited thereto. The disclosed technology can also be applied to a method of calibrating an array antenna system that uses Butler matrix circuit 110 instead of a phase shifter. Generally, Butler Matrix refers to a network for beamforming of an array antenna system. Generally, a Butler matrix is composed of hybrid couplers arranged in an m×m matrix and a fixed phase shifter that shifts a fixed phase amount. Here, m is generally a number that is a power of 2.

《Butler matrix circuit 110》
Butler matrix circuit 110 is a circuit consisting of a hybrid circuit, a fixed phase shifter, and a coupler. Butler matrix circuit 110 has at least N input ports and at least N output ports.
As shown in FIG. 7, the input ports of the Butler matrix circuit 110 receive the signals extracted by the extracting section 2-1, the extracting section 2-2, ..., the extracting section 2-N, that is, the transmission signal and the calibration signal. A signal on which is superimposed is input.
Butler matrix circuit 110 combines signals input from input ports using a plurality of phase shift settings, and outputs each signal to a different output port.

《Route selection section 120》
The path selection unit 120 is a component that functions as a switch that switches the output ports of the Butler matrix circuit 110.

《Route selection instruction section 130》
The route selection instruction unit 130 is a component for giving instructions to the route selection unit 120. The route selection instruction section 130 is a component that plays the same role as the phase control instruction section 80 in the previously described embodiment.
The functions of the route selection instruction section 130 are realized by the processing circuit shown in FIG. 2 or 3.

<<About the calibration method of the array antenna system according to Embodiment 4>>
FIG. 8 is a flowchart showing the processing steps of the array antenna system according to the fourth embodiment.
As shown in FIG. 8, the processing steps of the array antenna system according to the fourth embodiment are also roughly composed of three phases.
The first phase includes calibration signal generation ST11, calibration signal injection ST12, and calibration signal extraction ST13. The first phase according to the fourth embodiment has the same content as that shown in the first embodiment.
The second phase is a portion surrounded by a broken line frame labeled "P401" in FIG. 8, and is a phase setting value search phase. The phase setting value search phase includes path setting ST31, calibration signal detection ST32, signal power measurement ST33, and confirmation of the number of path switching times ST34.
The third phase is a portion surrounded by a broken line frame labeled "P402" in FIG. 8, and is a calibration phase. The calibration phase includes determining a route that minimizes power ST51, setting a route ST52, detecting a calibration signal ST53, calculating a relative amplitude phase error ST54, calculating a calibration value ST55, and correcting a transmission signal ST56. include.

Route setting ST31 in the phase setting value search phase (P401) is a processing step performed by the route selection unit 120 under the direction of the route selection instruction unit 130. In route setting ST31, the route selection section 120 connects one of the output ports of the Butler matrix circuit 110 to the calibration signal receiver 60. The operation here corresponds to the operation of the phase control section 40 in the search mode.

Detection ST32 of the calibration signal in the phase setting value search phase (P401) is a processing step performed by the calibration signal receiver 60. The calibration signal detection ST32 in the phase setting value search phase (P401) has the same contents as the calibration signal detection ST23 in the phase setting value search phase (P101) shown in the first embodiment.

Signal power measurement ST33 in the phase setting value search phase (P401) is a processing step performed by the power measurement unit 70. Signal power measurement ST33 in the phase setting value search phase (P401) has the same content as signal power measurement ST24 in the phase setting value search phase (P101) shown in the first embodiment.

Confirmation ST34 of the number of route switching in the phase setting value search phase (P401) is a processing step performed by the route selection instruction section 130. The content of the process performed by the route selection instructing unit 130 in confirming the number of route switching times ST34 is the same as the content of the process performed by the phase control instructing unit 80 in confirming the number of changes of the phase setting value ST25 shown in Embodiment 1. .

The route determination ST51 in which the power in the calibration phase (P402) is minimized is a processing step performed by the route selection instruction unit 130. In ST51, the route selection instruction unit 130 determines the route that minimizes the power, based on the correspondence between the output port information obtained in the phase setting value search phase (P401) and the measured power. The output port of Butler matrix circuit 110 that outputs the signal is specified.

Route setting ST52 in the calibration phase (P402) is a processing step performed by the route selection instruction section 130. In route setting ST52, the route selection instruction section 130 instructs the route selection section 120 to select the output port specified in route determination ST51 that has the minimum power. The subsequent operation mode of route selection instruction section 130 corresponds to the fixed mode shown in the first embodiment.

Detection ST53 of the calibration signal in the calibration phase (P402) is a processing step performed by the calibration signal receiver 60. The calibration signal detection ST53 in the calibration phase (P402) has the same content as the calibration signal detection ST44 in the calibration phase (P102) shown in the first embodiment.

Relative amplitude phase error calculation ST54, calibration value calculation ST55, and transmission signal correction ST56 in the calibration phase (P402) are the relative amplitude phase error calculation ST45 in the calibration phase (P102) shown in Embodiment 1, The contents are the same as the calibration value calculation ST47 and the transmission signal correction ST48.

As described above, the disclosed technology can also be applied to a method of calibrating an array antenna system that uses the Butler matrix circuit 110 instead of a phase shifter.

Embodiment 5.
The array antenna system and the method for calibrating an array antenna system according to the fifth embodiment are modified examples of the array antenna system and the method for calibrating the array antenna system according to the presently disclosed technology.
The symbols used in the fifth embodiment are the same as those used in the previously described embodiments, unless otherwise specified. In the fifth embodiment, explanations that overlap with those of the previously described embodiments will be omitted as appropriate.

FIG. 9 is a block diagram showing the functional configuration of the array antenna system according to the fifth embodiment. As shown in FIG. 9, the array antenna system according to the present disclosure may include a delay correction section 140.

<<Delay correction section 140>>
The delay correction unit 140 is a component for correcting variations in characteristics between transmission systems not in units of signal phase but in units of direct time.
The function of the delay correction section 140 is realized by the processing circuit shown in FIG. 2 or 3.

<<About the calibration method of the array antenna system according to the fifth embodiment>>
FIG. 10 is a flowchart showing the processing steps of the array antenna system according to the fifth embodiment.
As shown in FIG. 10, the processing steps of the array antenna system according to the fifth embodiment include calculation ST46 of a relative delay difference in addition to the processing steps of the array antenna system according to the first embodiment shown in FIG. Relative delay difference calculation ST46 is a processing step in the calibration phase (P502), and is a processing step executed after relative amplitude phase error calculation ST45.

Calculating the relative delay difference ST46 in the calibration phase (P502) is a processing step performed by the delay correction unit 140. Calculation of Relative Delay Difference In ST46, the delay correction section 140 compares the calibration signals of each transmission system in the time domain and calculates a relative time delay amount.

Calibration value calculation ST47 in the calibration phase (P502) is a processing step performed by the calibration signal analysis section 100. In the case of the fifth embodiment, in calibration value calculation ST47, the calibration signal analysis section 100 calculates, in addition to the amplitude phase calibration value, a calibration value for time for canceling the relative time delay amount (hereinafter referred to as "time calibration value"). ) is also calculated.

Correction ST48 of the transmission signal in the calibration phase (P502) is a processing step performed by the DBF unit 10. In the case of the fifth embodiment, in correction ST48 of the transmission signal, the DBF section 10 corrects the transmission signal using the amplitude phase calibration value and the time calibration value.

As described above, the disclosed technology can correct variations in characteristics between transmission systems not in units of signal phase but in direct units of time.

Embodiment 6.
The array antenna system and the method for calibrating the array antenna system according to the sixth embodiment are modifications of the array antenna system and the method for calibrating the array antenna system according to the presently disclosed technology.
The symbols used in the sixth embodiment are the same as those used in the previously described embodiments, unless otherwise specified. In the sixth embodiment, descriptions that overlap with those of the previously described embodiments will be omitted as appropriate.

FIG. 11 is a block diagram showing the functional configuration of an array antenna system according to Embodiment 6. As shown in FIG. 11, the array antenna system according to the present disclosure may include a calibration trigger instruction section 150.
As shown in FIG. 11, the calibration trigger instruction section 150 is connected to acquire information from the power measurement section 70 and issue an instruction to the calibration signal generation section 30.

<<Calibration trigger instruction section 150>>
The calibration trigger instruction unit 150 is a component for outputting a trigger when it is determined to start a new calibration.
The functions of the calibration trigger instruction section 150 are realized by the processing circuit shown in FIG. 2 or 3.

<<About the calibration method of the array antenna system according to the sixth embodiment>>
FIG. 12 is a flowchart showing the processing steps of the array antenna system according to the sixth embodiment.
As shown in FIG. 12, the processing steps of the array antenna system according to the sixth embodiment include, in addition to the processing steps of the array antenna system according to the first embodiment shown in FIG. Confirmation ST02 is included.
In FIG. 12, a portion surrounded by a broken line frame labeled "P601" is referred to as a "calibration implementation determination phase." The processing steps of signal power measurement ST01 and power value confirmation ST02 added in the sixth embodiment are included in the calibration implementation determination phase.

Signal power measurement ST01 in the calibration implementation determination phase (P601) is a processing step performed by the power measurement unit 70. Signal Power Measurement In ST01, the power measurement unit 70 measures the amount of power of the signal sent from the calibration signal receiver 60.

The power value confirmation ST02 in the calibration execution determination phase (P601) is a processing step executed by the calibration trigger instruction section 150. In power value confirmation ST02, the calibration trigger instruction section 150 determines whether the amount of power measured by the power measurement section 70 is less than a preset threshold.
If the amount of power measured by the power measuring unit 70 is less than the preset threshold (in the case of YES), the processing step proceeds to calibration signal generation ST11. If the power amount measured by the power measurement unit 70 is not below the preset threshold (NO), the processing step returns to signal power measurement ST01.

FIG. 13 is a graph showing a time-series change in the amount of electric power to be measured, and is used to explain the timing to start a new calibration. In the graph shown in FIG. 13, the horizontal axis represents time, and the vertical axis represents the amount of power measured by the power measurement unit 70, respectively. Furthermore, in the graph shown in FIG. 13, the broken line labeled "Threshold Power" represents the threshold value of the amount of power used by the calibration trigger instruction section 150. Furthermore, in the graph shown in FIG. 13, the arrow labeled "Calibration Trigger" represents the timing at which the calibration trigger instruction section 150 outputs a trigger.

The processing steps after the calibration implementation determination phase (P601) shown in FIG. 13 are the same as the processing steps shown in the first embodiment.

As described above, since the array antenna system according to the sixth embodiment includes the calibration trigger instruction section 150, the magnitude of the combined electric field can be compared with a threshold value, and it can be determined to start a new calibration.

Note that the array antenna system and the method for calibrating the array antenna system according to the disclosed technology are not limited to the aspects exemplified in each embodiment, but may be performed by combining each embodiment or using any component of each of the embodiments. Any component may be modified or omitted in each of the embodiments.

The array antenna system and the method for calibrating the array antenna system according to the presently disclosed technology can be applied to an adaptive array antenna system using the CDMA method in, for example, a cellular system such as a mobile phone, and has industrial applicability.

1 antenna element, 2 extraction unit, 3 transmitter, 4 injection unit, 10 DBF unit, 20 signal processing unit, 30 calibration signal generation unit, 40 phase control unit, 50 power combination unit, 60 calibration signal receiver, 70 power measurement unit, 80 phase control instruction unit, 90 calibration signal phase offset unit, 100 calibration signal analysis unit, 110 Butler matrix circuit, 120 route selection unit, 130 route selection instruction unit, 140 delay correction unit, 150 calibration trigger instruction unit, 500 processing Circuit, 502 CPU, 504 Memory.

Claims (14)

1. An array antenna system comprising multiple transmission systems,
   a calibration signal generation unit that generates a calibration signal;
   a phase control unit that controls the phase of an extracted signal consisting of a transmission signal extracted from the transmission system and the calibration signal;
   a power combining unit that combines a plurality of signals whose phases have been controlled by the phase control unit;
   a calibration signal receiver that demodulates the signal combined by the power combining section;
   a power measurement unit that measures the power of the signal demodulated by the calibration signal receiver;
   a phase control instruction unit that instructs the phase control unit to control a phase amount based on the measured value of power measured by the power measurement unit;
   array antenna system.
2. The phase control instruction unit sets the phase amount at which the measured value of power is the minimum based on the property that the power measured by the power measurement unit changes so as to draw a sine wave with respect to the phase amount. determining it as a set value and instructing the phase control unit to control the phase shifter to the phase set value;
   The array antenna system according to claim 1.
3. a calibration signal phase offset unit that offsets and adjusts the phase of the calibration signal by the phase setting value;
   a calibration signal analysis unit that calculates a relative amplitude phase error based on the signal demodulated by the calibration signal receiver and the signal adjusted by the calibration signal phase offset unit;
   further comprising: a DBF unit that corrects the transmission signal so that the relative amplitude phase error is eliminated, and then performs digital beamforming;
   The array antenna system according to claim 2.
4. A method for calibrating an array antenna system having multiple transmission systems, the method comprising:
   A calibration signal generation section of the array antenna system generates a calibration signal,
   A phase control unit of the array antenna system controls the phase of an extracted signal consisting of a transmission signal extracted from the transmission system and the calibration signal,
   A power combining unit of the array antenna system combines the plurality of signals whose phases have been controlled by the phase control unit,
   A calibration signal receiver of the array antenna system demodulates the signal combined by the power combining section,
   A power measurement unit of the array antenna system measures the power of the signal demodulated by the calibration signal receiver,
   A phase control instructing unit of the array antenna system instructs the phase control unit to control a phase amount based on the power measurement value measured by the power measuring unit.
   How to calibrate an array antenna system.
5. The phase control instruction section sets the phase amount at which the measured value of power is the minimum based on the property that the power measured by the power measurement section changes so as to draw a sine wave with respect to the phase amount. determining it as a set value and instructing the phase control unit to control the phase shifter to the phase set value;
   The method for calibrating an array antenna system according to claim 4.
6. a calibration signal phase offset unit adjusts the phase of the calibration signal by offsetting the phase setting value;
   a calibration signal analysis unit calculates a relative amplitude phase error based on the signal demodulated by the calibration signal receiver and the signal adjusted by the calibration signal phase offset unit,
   a DBF unit corrects the transmission signal so that the relative amplitude phase error is eliminated, and performs digital beamforming;
   The method for calibrating an array antenna system according to claim 5.
7. The phase control by the phase control unit is performed using a phase setting value obtained in the most recent calibration as a solution candidate.
   The method for calibrating an array antenna system according to claim 4.
8. The phase control instruction section instructs the phase control section to correct the phase amount when switching the fixed set value;
   The method for calibrating an array antenna system according to claim 4.
9. An array antenna system comprising multiple transmission systems,
   a calibration signal generation unit that generates a calibration signal;
   a Butler matrix circuit that receives an extracted signal consisting of a transmission signal extracted from the transmission system and the calibration signal into an input port, synthesizes it with a plurality of phase shift setting values, and outputs each of the signals to different output ports;
   a path selection unit that functions as a switch for switching the output port of the Butler matrix circuit;
   a calibration signal receiver that demodulates the signal that has passed through the route selection section;
   a power measurement unit that measures the power of the signal demodulated by the calibration signal receiver;
   a route selection instructing unit that instructs the route selecting unit to switch the output port based on the power measurement value measured by the power measuring unit;
   array antenna system.
10. The route selection instruction unit specifies the output port of the Butler matrix circuit where the measured value of power is the minimum, determines a phase setting value, and causes the route selection unit to switch to the specified output port. give instructions,
    The array antenna system according to claim 9.
11. a calibration signal phase offset unit that offsets and adjusts the phase of the calibration signal by the phase setting value;
    a calibration signal analysis unit that calculates a relative amplitude phase error based on the signal demodulated by the calibration signal receiver and the signal adjusted by the calibration signal phase offset unit;
    further comprising: a DBF unit that corrects the transmission signal so that the relative amplitude phase error is eliminated, and then performs digital beamforming;
    The array antenna system according to claim 10.
12. A method for calibrating an array antenna system having multiple transmission systems, the method comprising:
    A calibration signal generation section of the array antenna system generates a calibration signal,
    A Butler matrix circuit of an array antenna system, in which an extracted signal consisting of a transmission signal extracted from the transmission system and the calibration signal is inputted to an input port, synthesizes the signal using a plurality of phase shift setting values, and outputs each signal to a different output port. output,
    A route selection unit of the array antenna system functions as a switch for switching the output port of the Butler matrix circuit,
    A calibration signal receiver of the array antenna system demodulates the signal that has passed through the route selection section,
    A power measurement unit of the array antenna system measures the power of the signal demodulated by the calibration signal receiver,
    A route selection instruction unit of the array antenna system instructs the route selection unit to switch the output port based on the power measurement value measured by the power measurement unit.
    How to calibrate an array antenna system.
13. The route selection instruction unit identifies the output port of the Butler matrix circuit where the measured value of power is the minimum, determines a phase setting value, and causes the route selection unit to switch to the identified output port. give instructions,
    The method for calibrating an array antenna system according to claim 12.
14. a calibration signal phase offset unit adjusts the phase of the calibration signal by offsetting the phase setting value;
    a calibration signal analysis unit calculates a relative amplitude phase error based on the signal demodulated by the calibration signal receiver and the signal adjusted by the calibration signal phase offset unit,
    a DBF unit corrects the transmission signal so that the relative amplitude phase error is eliminated, and then performs digital beamforming;
    The method for calibrating an array antenna system according to claim 13.

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