JP7466810B2 - ARRAY ANTENNA SYSTEM AND METHOD FOR CALIBRATING ARRAY ANTENNA SYSTEM - Google Patents

Description

The disclosed technology relates to an array antenna system and a method for calibrating an 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. Patent Document 1 also discloses a phase calibration method for the adaptive array antenna system.
The phase calibration method disclosed in Patent Document 1 involves inserting a calibration signal (corresponding to a "calibration signal" in the disclosed technology) into a main signal (corresponding to a "transmission signal" in the disclosed technology), inputting the signal to a specified circuit, and calibrating the phase of the main signal based on a phase change in the calibration signal included in an output signal from the circuit.

JP 2005-286780 A

The method disclosed in Patent Document 1 is to obtain 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, the phase calibrator corrects the phase change in the analog circuits, i.e., performs phase correction of the inverse characteristics of the phase characteristics in the analog circuits, and controls so that the phases are aligned in the array antenna.
However, Patent Document 1 does not disclose in detail how to efficiently obtain the amplitude and phase characteristics of the analog circuits of each transmission system, and moreover, Patent Document 1 does not mention a method for simultaneously calibrating the transmission systems of the array antenna system.

The disclosed technology improves on the conventional array antenna system and calibration method for the array antenna system exemplified in Patent Document 1. More specifically, the disclosed technology aims to provide an array antenna system and a calibration method for the array antenna system that can simultaneously calibrate all transmission systems that the array antenna system has.

The array antenna system according to the present disclosed technology is a calibration method for an array antenna system having a plurality of transmission systems, in which a calibration signal generation unit 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 a calibration signal, a power combining unit of the array antenna system combines a 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 unit, a power measurement unit of the array antenna system measures the power of the signal demodulated by the calibration signal receiver, and a phase control instruction unit of the array antenna system instructs the phase control unit on the amount of phase to be controlled based on the measurement value of the power measured by the power measurement unit, and the phase control by the phase control unit is performed using the phase setting value obtained in the most recent calibration as a candidate solution.

Since the array antenna system of the disclosed technology has the above-mentioned configuration, it has the effect of being able to simultaneously calibrate all of the transmission systems possessed by the array antenna system.

FIG. 1 is a block diagram showing a functional configuration of the array antenna system according to the first embodiment. FIG. 2 is a diagram showing a 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 a functional configuration of the array antenna system according to the third embodiment. FIG. 6 is a flowchart showing processing steps of the array antenna system according to the third embodiment. FIG. 7 is a block diagram showing a functional configuration of the array antenna system according to the fourth embodiment. FIG. 8 is a flowchart showing processing steps of the array antenna system according to the fourth embodiment. FIG. 9 is a block diagram showing a functional configuration of the array antenna system according to the fifth embodiment. FIG. 10 is a flowchart showing processing steps of the array antenna system according to the fifth embodiment. FIG. 11 is a block diagram showing a functional configuration of the array antenna system according to the sixth embodiment. FIG. 12 is a flowchart showing processing steps of the array antenna system according to the sixth embodiment. FIG. 13 is a graph showing the time series change in the amount of measured power, and explains the timing for starting a new calibration. FIG. 14 is a diagram for explaining phase modulation and its demodulation in the array antenna system according to the seventh embodiment.

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

Embodiment 1.
Fig. 1 is a block diagram showing a functional configuration of an array antenna system according to embodiment 1. As shown in Fig. 1, the array antenna system according to embodiment 1 includes an antenna element 1, an extraction unit 2, a transmitter 3, an injection unit 4, a DBF unit 10, a signal processing unit 20, a calibration signal generation unit 30, a phase control unit 40, a power combining unit 50, a calibration signal receiver 60, a power measurement unit 70, a phase control instruction unit 80, a calibration signal phase offset unit 90, and a calibration signal analysis unit 100.
As shown in FIG. 1, there are a plurality of antenna elements 1, and when each element is to be distinguished from the others, they are represented 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 extracting units 2, transmitters 3, and injecting units 4. When each element of the extracting units 2, transmitters 3, and injecting units 4 is to be distinguished from the others, they are represented by adding "-1", "-2", ..., "-N" to the end of the reference numeral. If n is a natural number from 1 to N, the signal processing unit 20, the DBF unit 10, the injecting unit 4-n, the transmitter 3-n, the extracting unit 2-n, and the antenna element 1-n each constitute one transmission system. That is, the array antenna system according to the first embodiment has N transmission systems.
In the array antenna system of embodiment 1, the calibration signal generating unit 30, the phase control unit 40, the power combining unit 50, the calibration signal receiver 60, the power measuring unit 70, the phase control instruction unit 80, the calibration signal phase offset unit 90, and the calibration signal analyzing unit 100 constitute a calibration signal system.

Signal Processing Unit 20 in the 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. In this specification, the term "transmission signal" is used as a general term for a baseband signal and a digitally modulated signal obtained by modulating the baseband signal.

<<DBF unit 10 in the transmission system>>
The DBF unit 10 is a component for digitally beamforming a transmission signal.
First, the DBF unit 10 distributes the baseband signal into N streams.
Secondly, the DBF unit 10 adjusts the amplitude and phase of each of the N distributed baseband signals in order to realize digital beamforming. The baseband signals whose amplitude and phase have been adjusted are sent to the transmitters 3-n via the injection units 4-n.

<<Injection section 4 in the transmission system>>
The injection unit 4-n is a component for injecting a calibration signal, which will be described later, into the transmission system. Details of the injection unit 4 will become clear from the description given later.

<<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 extraction unit 2-n. The analog RF band transmission signal is sometimes called a data signal or a communication signal.

Extraction unit 2 in the transmission system
The extractor 2-n is a component for extracting a part of a signal flowing through a transmission system. The signal extracted by the extractor 2-n is called an "extracted signal."

<Antenna element 1 in the transmission system>
Antenna element 1-n is a component for radiating an RF band transmission signal into space. Antenna elements 1-n are arranged in an array. In general, antenna elements 1 in an array antenna system are often arranged at regular positions with equal intervals.

<<Calibration signal generating unit 30 in the calibration signal system>>
The calibration signal generating unit 30 is a component for generating a calibration signal. The calibration signal generating unit 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 Laid-Open No. 2001-332925.
The calibration signal generated by the calibration signal generator 30 may be a chirp pulse signal in which up-chirps and down-chirps appear randomly on the time axis. The calibration signal formed by combining up-chirps and down-chirps is different for each transmission system, that is, the combination of up-chirps and down-chirps is different.
The calibration signal generated by the calibration signal generating unit 30 is injected into the transmission system via the injection unit 4-n.

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

<<Power combiner 50 in the calibration signal system>>
The power combiner 50 is a component for combining the N signals sent from the phase controller 40 .
The signal combined in the power combiner 50 is sent to a 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 combiner 50. Here, the term "detect" means to extract a baseband signal from a modulated wave, that is, to demodulate it.
The signal detected by the calibration signal receiver 60 is sent to a power measurement section 70 and a calibration signal analysis section 100 .

<<Power measurement unit 70 in the calibration signal system>>
The power measurement section 70 is a component for measuring the amount of power of the signal sent from the calibration signal receiver 60 .
The phase control section 40 described above decides the phase amount to be controlled in cooperation with the power measurement section 70. The 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 section 40 gradually changes the phase amount to be controlled, and searches for the phase amount at which the amount of power is minimized by referring to the amount of power measured by the power measurement section 70. The operation mode of the phase control section 40 for searching for the phase amount at which the amount of power is minimized is referred to as the search mode.

<<Phase control instruction unit 80 in the calibration signal system>>
The phase control instruction section 80 is a component for issuing instructions to realize 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 power and for instructing the calibration signal phase offset section 90 about this phase amount.
When the phase amount at which the amount of power is minimized is sent, the phase control instruction unit 80 instructs the phase control unit 40 to stop the search mode and to control with this phase amount thereafter. The operation mode in which the phase control unit 40 controls by fixing the phase amount at which the amount of power is minimized is referred to as the fixed mode. That is, in order to implement the search mode, the array antenna system according to the first embodiment performs the processing of a loop consisting of the phase control unit 40, the power combining unit 50, the calibration signal receiver 60, the power measuring unit 70, and the phase control instruction unit 80 at least once.

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

<<Calibration signal analysis unit 100 in the calibration signal system>>
The calibration signal analyzer 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 a "relative amplitude and phase error"). In order to calculate the relative amplitude and phase error, the calibration signal analyzer 100 may calculate the correlation between signals.
The relative amplitude and phase errors calculated by the calibration signal analyzer 100 are sent to the DBF unit 10. The DBF unit 10 corrects the design values of beamforming so as to cancel the relative amplitude and phase errors.

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

The functions of the 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, and calibration signal analysis unit 100 in the array antenna system are realized by a processing circuit. The processing circuit may be either dedicated hardware or a CPU (also called a Central Processing Unit, central processing unit, processing unit, arithmetic unit, microprocessor, microcomputer, processor, or DSP) that executes a program stored in a memory.

2 is a diagram of a processing circuit 500 in which the processing circuit is a dedicated hardware. The processing circuit 500 may be, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC, an FPGA, or a combination of these. The functions of the transmitter 3, the injection unit 4, the DBF unit 10, the signal processing unit 20, the calibration signal generating unit 30, the calibration signal receiver 60, the power measuring unit 70, the phase control instruction unit 80, the calibration signal phase offset unit 90, and the calibration signal analyzing unit 100 may be realized by the processing circuit 500 individually, or may be realized by a single processing circuit 500 collectively.

3 is a diagram in which the processing circuit is a CPU 502. When the processing circuit is a CPU 502, the above functions are realized by software, firmware, or a combination of software and firmware. The software and firmware are written as programs and stored in the memory 504. The CPU 502 realizes the functions of each part by reading and executing the 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 circuit, results in each processing step of the array antenna system being executed. 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, for example, a non-volatile or volatile semiconductor memory such as a RAM, a ROM, a flash memory, an EPROM, an EEPROM, etc. The memory 504 may also be a structure having a disk such as a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, a DVD, etc. The memory 504 may also be in the form of an HDD or SSD.

Note that each of the above functions of the array antenna system may be realized in part by dedicated hardware and in part by software or firmware. In this way, the processing circuit can realize each of the above functions by hardware, software, firmware, or a combination of these.

<<Regarding 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 roughly composed of three phases.
The first phase includes generating a calibration signal ST11, injecting a calibration signal ST12, and extracting a calibration signal ST13.
The second phase is the portion enclosed by a dashed box labeled "P101" in Fig. 4, and is referred to as the "phase set value search phase". The phase set value search phase corresponds to the search mode of the phase control unit 40 described above. The phase set value search phase includes phase setting ST21, synthesizing a calibration signal ST22, detecting the calibration signal ST23, measuring the power of the signal ST24, and checking the number of times the phase set value has been changed ST25.
The third phase is the portion enclosed by a dashed frame labeled "P102" in Fig. 4, and is called the "calibration phase". In the calibration phase, the phase control unit 40 is in a fixed mode. The calibration phase includes a phase setting value calculation ST41, a phase setting ST42, a calibration signal synthesis ST43, a calibration signal detection ST44, a relative amplitude/phase error calculation ST45, a calibration value calculation ST47, and a transmission signal correction ST48.

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

Calibration signal injection ST12 is a processing step performed by calibration signal generation unit 30. In positive signal injection ST12, calibration signal generation unit 30 injects N calibration signals into injection unit 4-1, injection unit 4-2, ..., injection unit 4-N of the corresponding transmission systems.
As described above, the functions of calibration signal generation unit 30 and injection unit 4 may be realized by CPU 502. That is, injection of N calibration signals can be performed by digital processing in CPU 502 without using physical means. That is, injection of N calibration signals can be performed by adding a transmission signal and a calibration signal in each transmission system. Each function of injection unit 4-1, injection unit 4-2, ..., injection unit 4-N does not use physical means such as a switch and a directional coupler, and is therefore not adversely affected by distortion, noise, and the like that are inherent to physical means.

The calibration signal extraction ST13 is a processing step performed by the extraction unit 2-1, extraction unit 2-2, ..., extraction unit 2-N. In the calibration signal extraction ST13, each of the extraction units 2-1, 2-2, ..., extraction unit 2-N extracts a part of the signal flowing through the transmission system as an extracted signal. The extracted signal includes the transmission signal and the calibration signal.
As described above, the signals extracted by the extraction units 2-1, 2-2, ..., 2-N are analog signals in the RF band. Unlike baseband signals, RF analog signals have a frequency band that is too high to sample and digitally process, making it impractical. Therefore, it is preferable to realize the functions of the extraction units 2-1, 2-2, ..., 2-N by physical means such as directional couplers and switches.

Phase setting ST21 in the phase setting value search phase (P101) is a processing step performed by the phase control unit 40 in search mode. In phase setting ST21, the phase control unit 40 gradually changes the phase amount for each of the RF band analog signals extracted by extraction unit 2-1, extraction unit 2-2, ..., extraction unit 2-N, to control the phase. The phase control by the phase control unit 40 may be realized by an analog or digital phase shifter. Only one phase shifter may be prepared to switch between the systems, or N phase shifters may be prepared, one 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 unit 50. In the calibration signal synthesis ST22, the power synthesis unit 50 synthesizes the N signals sent from the phase control unit 40. The power synthesis unit 50 is realized, for example, by hardware such as a power synthesizer.

Calibration signal detection ST23 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 combiner 50 and extracts a baseband signal. Note that the baseband signal extracted in 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. In signal power measurement ST24, the power measurement unit 70 measures the amount of power of the signal sent from the calibration signal receiver 60.

In the phase setting value search phase (P101), checking the number of times the phase setting value has been changed ST25 is a processing step performed by the phase control instruction unit 80. In checking the number of times the phase setting value has been changed ST25, the phase control instruction unit 80 at least temporarily stores and holds the correspondence between the phase amount changed by the phase control unit 40 and the amount of power measured by the power measurement unit 70. In checking the number of times the phase setting value has been changed ST25, the phase control instruction unit 80 also issues instructions to achieve cooperation between the phase control unit 40 and the power measurement unit 70. In checking the number of times the phase setting value has been changed ST25, the phase control instruction unit 80 also checks the number of times the phase setting value has been changed, and checks whether the search mode of the phase control unit 40 has ended.

The phase amount changed in the phase control unit 40 may be realized, for example, by N-fold For statements (For Loops) incorporating nesting. For example, the first For statement from the inside of the N-fold For statement changes the phase amount stepwise from 0 degrees to 360 degrees for the first analog signal extracted from the extraction unit 2-1. The second For statement from the inside changes the phase amount stepwise from 0 degrees to 360 degrees for the second analog signal extracted from the extraction unit 2-2. In the same manner, the phase amount is changed stepwise using the Nth For statement from the inside. The phase amount changed in the phase control unit 40 may be realized, for example, in this way. If there are K step-like changes in each For statement, in the confirmation ST25 of the number of changes in the phase setting value, the phase control instruction unit 80 confirms whether the number of changes is less than or exceeds K×N.

In the phase setting value change count confirmation ST25, after the power measurement unit 70 has completed measuring the power amount for one of the N combinations of phase amounts corresponding to the N analog signals, the phase control instruction unit 80 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 statement executed by the phase control unit 40 described above.

The phase setting value calculation ST41 in the calibration phase (P102) is a processing step performed by the phase control instruction unit 80. In the phase setting value calculation ST41, the phase control instruction unit 80 calculates an estimate of the phase amount at which the power amount is minimum from the correspondence relationship between the phase amount and the power amount of the temporarily stored K × N combinations. As described above, it is known that the power amount (the magnitude of the composite electric field) changes to draw a sine wave with respect to the phase amount (phase shift amount) changed by the phase shifter. Using this property, in the phase setting value calculation ST41, the phase control instruction unit 80 uses the least squares method to calculate a plausible theoretical sine wave from the correspondence relationship between the phase amount and the power amount of the temporarily stored K × N combinations, and obtains an estimate of the phase amount at which the power amount is minimum.

Phase setting ST42 in the calibration phase (P102) is a processing step performed by the phase control instruction unit 80. In phase setting ST42, the phase control instruction unit 80 instructs the phase control unit 40 to control the phase shifter with an 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 referred to as the "phase setting value." The phase control unit 40, to which the phase setting value has been instructed, controls the phase shifter in fixed mode.

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

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

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

Calculation ST45 of the relative amplitude and phase error in the calibration phase (P102) is a processing step performed by calibration signal analyzer 100. In calculation ST45 of the relative amplitude and phase error, calibration signal analyzer 100 performs a process of determining correlation (hereinafter simply referred to as "correlation process") on the baseband signal demodulated by calibration signal receiver 60 in detection ST44 of the calibration signal, using the calibration signal generated by calibration signal generator 30 as a reference signal. The correlation process may be performed in either the frequency domain or 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 calibration signal analyzer 100 in calculation ST45 of the relative amplitude/phase error passes through calibration signal phase offset unit 90.
The calibration signal used as a reference signal by calibration signal analyzer 100 in calculation ST45 of the relative amplitude/phase error has its phase offset (adjusted to cancel) by calibration signal phase offset section 90 by the phase setting value.

In calculation ST45 of relative amplitude and phase errors, calibration signal analyzer 100 extracts the calibration signals that have passed through each transmission system.
Furthermore, in calculation ST45 of the relative amplitude and phase error, calibration signal analyzer 100 calculates the relative amplitude and phase error (hereinafter simply referred to as "amplitude and phase error") based on the extracted calibration signal. The amplitude and phase error is an index showing the variation in characteristics among the N transmission branches.

Calculation of the calibration value ST47 in the calibration phase (P102) is a processing step performed by the calibration signal analysis unit 100. In calculation of the calibration value ST47, the calibration signal analysis unit 100 calculates a calibration value for the amplitude and phase (hereinafter referred to as the "amplitude-phase calibration value") that cancels the calculated amplitude-phase error.

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

The array antenna system according to the disclosed technique may perform the series of processes shown in FIG. 4 periodically, or may perform the series of processes according to a situation where calibration is required.
The calibration method for the array antenna system according to the present disclosed technology can be used in various situations, including adjustments before shipment of the array antenna system, daily maintenance during operation after the array antenna system is installed, and scheduled maintenance that is performed periodically.

As described above, the array antenna system according to the first embodiment has the above configuration, and therefore can simultaneously calibrate the transmission systems for all N antenna elements 1. Due to this action, the array antenna system according to the first embodiment can suppress the variation in characteristics between antenna elements 1-n (n = 1, 2, ..., N) or between transmission systems, simply by automatically performing a series of calibration processes.

Embodiment 2.
The calibration method for the array antenna system according to the second embodiment is a modified example of the calibration method for the array antenna system according to the present disclosure.
Unless otherwise specified, the reference symbols used in the second embodiment are the same as those used in the first embodiment. In the second embodiment, descriptions that overlap with those in the first embodiment will be omitted as appropriate.

In embodiment 1, as a calibration method for an array antenna system, in the phase setting value search phase (P101), phase control unit 40 in search mode changes the phase amount in steps from 0 degrees to 360 degrees and searches for a solution for the phase amount in a wide range. However, the technology disclosed herein is not limited to this.
When there is a candidate solution with the minimum power amount, the search for the phase amount may be performed around the candidate solution. When there is a candidate solution with the minimum power amount, the search for the phase amount may be performed by changing the neighborhood of the candidate solution in small steps to measure the power amount.

In the calibration method of the array antenna system according to the second embodiment, when performing the second or subsequent calibration, the phase setting value obtained in the most recent calibration may be set as a candidate 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 shipment in memory 504 as a candidate solution that minimizes the amount of power.

As described above, the calibration method for the array antenna system according to embodiment 2 uses the phase setting value obtained in the most recent calibration as a candidate solution, thereby achieving the effects shown in embodiment 1 without performing an unnecessarily wide search range.

Embodiment 3.
The array antenna system and the calibration method for the array antenna system according to the third embodiment are modified examples of the array antenna system and the calibration method for the array antenna system according to the present disclosure.
The reference numerals used in the third embodiment are the same as those used in the previous embodiments unless otherwise specified. In the third embodiment, the description that overlaps with the previous embodiments will be omitted as appropriate.

5 is a block diagram showing a functional configuration of an array antenna system according to embodiment 3. As shown in FIG. 5, the disclosed technique can also be applied to an array antenna system that does not include a power measurement unit 70.
As shown in FIG. 5, in the array antenna system according to the third embodiment, information from DBF unit 10 is sent to phase control instruction unit 80 .
Except for the above differences, the configuration of the array antenna system according to the third embodiment is the same as the configurations of the array antenna systems shown in the above-mentioned embodiments.

The calibration method of the array antenna system according to the third embodiment is intended to accommodate small changes in characteristics due to aging, rather than to perform extensive calibration. The calibration method of the array antenna system according to the third embodiment is based on the premise that the transmission system has been calibrated during pre-shipment adjustment. The disclosed technology is based on the principle that the impact on input/output characteristics due to aging (deterioration over time) of each element of the transmission system is not so great as to require extensive calibration.

ここで式（１）右辺の第１項のａｒｇ（）は、引数である複素数の偏角を求める関数を表す。式（１）において、右辺の第１項は出荷前調整時の測定による合成電界の大きさに基づく位相量をキャンセルする項であり、右辺の第２項は固定された位相設定値に関する項の一例である。 Specifically, the calibration method for the array antenna system according to the third embodiment stops the phase amount based on the magnitude of the measured composite electric field and uses a fixed phase setting value. In this specification, the switching from the phase amount based on the magnitude of the measured composite electric field to a fixed phase setting value is referred to as "fixed setting value switching."
In the pre-shipment adjustment, the amplitude and phase for correcting the n-th transmission system are represented by a complex number W _n . In the calibration method for the array antenna system according to the third embodiment, when switching the fixed setting value, for example, a correction phase amount (φ _n ) represented by the following formula is corrected.

Here, arg() in the first term on the right side of formula (1) represents a function that finds the argument of a complex number. In formula (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 adjustment before shipping, and the second term on the right side is an example of a term related to a fixed phase setting value.

Generally speaking, beamforming is a technology for directing radio waves from an array antenna system in a certain direction. Beamforming can be applied whether the array antenna is used as a transmitting antenna or as a receiving 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 they are strengthened when waves of the same phase are multiplied together, and are cancelled out when waves of opposite phase are multiplied together. Beamforming actively utilizes this wave property.
In beamforming, how to design the phase of each transmission system in the array antenna system varies depending on the interval (d) and arrangement of the antenna elements 1, and the direction in which the radio waves of the array antenna system are desired to be directed. The disclosed technology is not limited to the value shown in the second term on the right side of equation (1), and a phase setting value designed by beamforming may be used.

Figure 6 is a flowchart showing the processing steps of the array antenna system according to embodiment 3. As shown in Figure 6, the processing steps of the array antenna system according to embodiment 3 include generating a calibration signal ST11, injecting a calibration signal ST12, extracting a calibration signal ST13, setting a phase ST42, synthesizing the calibration signal ST43, detecting the calibration signal ST44, calculating a relative amplitude and phase error ST45, calculating a calibration value ST47, and correcting a transmission signal ST48.

<<Regarding the calibration method of the array antenna system according to the third embodiment>>
In the calibration method for the array antenna system according to the third embodiment, the first phase includes the processing steps of generating a calibration signal ST11, injecting the calibration signal ST12, and extracting the calibration signal ST13. The processing contents of the calibration signal generation ST11, the calibration signal injection ST12, and the 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 performed by the phase control instruction unit 80. In phase setting ST42, the phase control instruction unit 80 instructs the phase control unit 40 of a correction phase amount (φ _n ) when switching the fixed set value. The correction phase amount (φ _n ) is, for example, as shown in equation (1), and may be determined according to the purpose of the digital beamforming performed by the DBF unit 10.
The phase control section 40 controls the phase shifter based on an instruction from the phase control instruction section 80 .

The processing contents of each of the steps of synthesis of the calibration signal ST43, detection of the calibration signal ST44, calculation of the relative amplitude and phase error ST45, calculation of the calibration value ST47, and correction of the transmission signal ST48 in embodiment 3 are the same as those shown in embodiment 1.

As described above, the calibration method for the array antenna system according to embodiment 3 includes a processing step for switching fixed setting values, making it possible to switch from a calibration value based on the magnitude of the composite electric field measured during pre-shipment adjustment to a fixed setting value, thereby achieving the effect of being able to respond to small changes in characteristics due to aging.

Embodiment 4.
The array antenna system and the calibration method for the array antenna system according to the fourth embodiment are modified examples of the array antenna system and the calibration method for the array antenna system according to the present disclosure.
The reference numerals used in the fourth embodiment are the same as those used in the previous embodiments unless otherwise specified. In the fourth embodiment, the description that overlaps with the previous embodiments will be omitted as appropriate.

Fig. 7 is a block diagram showing a functional configuration of an array antenna system according to embodiment 4. As shown in Fig. 7, the array antenna system according to embodiment 4 includes a Butler matrix circuit 110, a path selection unit 120, and a path selection instruction unit 130, instead of the phase control unit 40, the power combining unit 50, and the phase control instruction unit 80.
The Butler matrix circuit 110, the path selection section 120, and the path selection instruction section 130 are connected as shown in FIG.

In the above-mentioned embodiment, the calibration is performed by using a phase shifter (not shown), but the disclosed technology is not limited to this. The disclosed technology can also be applied to a calibration method of an array antenna system that uses a Butler matrix circuit 110 instead of a phase shifter. In general, a Butler matrix means a network for beamforming of an array antenna system. In general, a Butler matrix is composed of hybrid couplers arranged in an m×m matrix and fixed phase shifters that shift a fixed phase amount. Here, m is generally a power of 2.

Butler Matrix Circuit 110
The Butler matrix circuit 110 is a circuit that includes a hybrid circuit, a fixed phase shifter, and a combiner, and has at least N input ports and at least N output ports.
As shown in FIG. 7, the signals extracted by extraction units 2-1, 2-2, ..., 2-N, i.e., signals on which the transmission signal and the calibration signal are superimposed, are input to the input ports of the Butler matrix circuit 110.
The Butler matrix circuit 110 combines signals input from the input ports with a plurality of phase shift setting values, and outputs each of the combined signals to different output ports.

<<Route Selection Unit 120>>
The path selection unit 120 is a component that functions as a switch that switches the output port of the Butler matrix circuit 110 .

<<Route Selection Instructing Unit 130>>
The path selection instruction unit 130 is a component for giving instructions to the path selection unit 120. The path selection instruction unit 130 is a component that fulfills the same role as the phase control instruction unit 80 in the above-mentioned embodiment.
The function of the route selection instruction unit 130 is realized by the processing circuit shown in FIG.

<<Regarding the calibration method of the array antenna system according to the fourth embodiment>>
FIG. 8 is a flowchart showing 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 generating a calibration signal ST11, injecting the calibration signal ST12, and extracting the calibration signal ST13. The first phase according to the fourth embodiment is the same as that shown in the first embodiment.
The second phase is the portion enclosed by a dashed box labeled "P401" in Fig. 8, and is a phase setpoint search phase. The phase setpoint search phase includes a path setting ST31, a calibration signal detection ST32, a signal power measurement ST33, and a path switching count confirmation ST34.
The third phase is the portion enclosed by a dashed frame labeled "P402" in Fig. 8, and is a calibration phase. The calibration phase includes steps ST51 for determining a route that minimizes power, ST52 for setting a route, ST53 for detecting a calibration signal, ST54 for calculating a relative amplitude and phase error, ST55 for calculating a calibration value, and ST56 for correcting a transmission signal.

Path setting ST31 in the phase setting value search phase (P401) is a processing step performed by the path selection unit 120 under the instruction of the path selection instruction unit 130. In path setting ST31, the path selection unit 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 unit 40 in the search mode.

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

The signal power measurement ST33 in the phase setting value search phase (P401) is a processing step performed by the power measurement unit 70. The signal power measurement ST33 in the phase setting value search phase (P401) is the same as the signal power measurement ST24 in the phase setting value search phase (P101) shown in embodiment 1.

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

The route determination ST51 for determining the route with the minimum power in the calibration phase (P402) is a processing step performed by the route selection instruction unit 130. In the route determination ST51 for determining the minimum power, the route selection instruction unit 130 identifies the output port of the Butler matrix circuit 110 that outputs the signal with the minimum measured power value from the correspondence between the output port information obtained in the phase setting value search phase (P401) and the measured power value.

In the calibration phase (P402), route setting ST52 is a processing step performed by the route selection instruction unit 130. In route setting ST52, the route selection instruction unit 130 instructs the route selection unit 120 to select the output port identified in route determination ST51 that minimizes power. The subsequent operating mode of the route selection instruction unit 130 corresponds to the fixed mode described in embodiment 1.

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

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

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

Embodiment 5.
The array antenna system and the calibration method for the array antenna system according to the fifth embodiment are modified examples of the array antenna system and the calibration method for the array antenna system according to the present disclosure.
The reference numerals used in the fifth embodiment are the same as those used in the preceding embodiments unless otherwise specified. In the fifth embodiment, the description that overlaps with the preceding embodiments will be omitted as appropriate.

Figure 9 is a block diagram showing the functional configuration of an array antenna system relating to embodiment 5. As shown in Figure 9, the array antenna system relating to the disclosed technology may include a delay correction unit 140.

<<Delay correction unit 140>>
The delay correction unit 140 is a component for correcting the variation in characteristics between the transmission branches in direct time units, rather than in units of signal phase.
The function of the delay correction unit 140 is realized by the processing circuit shown in FIG.

<<Regarding the calibration method of the array antenna system according to the fifth embodiment>>
FIG. 10 is a flowchart showing 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 a 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. 4. The calculation ST46 of the relative delay difference is a processing step in the calibration phase (P502), and is a processing step performed after the calculation ST45 of the relative amplitude-phase error.

Calculation of the relative delay difference in the calibration phase (P502) ST46 is a processing step performed by the delay correction unit 140. In calculation of the relative delay difference ST46, the delay correction unit 140 compares the calibration signals of each transmission system in the time domain to determine the relative time delay amount.

Calculation of the calibration value ST47 in the calibration phase (P502) is a processing step performed by the calibration signal analysis unit 100. In the case of embodiment 5, in calculation of the calibration value ST47, the calibration signal analysis unit 100 calculates, in addition to the amplitude-phase calibration value, a calibration value for the time that cancels the relative time delay amount (hereinafter referred to as the "time calibration value").

The 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 embodiment 5, in the correction ST48 of the transmission signal, the DBF unit 10 corrects the transmission signal using the amplitude phase calibration value and the time calibration value.

As described above, the disclosed technology can correct the variation in characteristics between transmission systems in direct units of time rather than in units of signal phase.

Embodiment 6.
The array antenna system and the calibration method for the array antenna system according to the sixth embodiment are modified examples of the array antenna system and the calibration method for the array antenna system according to the present disclosure.
The reference numerals used in the sixth embodiment are the same as those used in the preceding embodiments unless otherwise specified. In the sixth embodiment, the description that overlaps with the preceding embodiments will be omitted as appropriate.

11 is a block diagram showing a 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 instructing unit 150.
As shown in FIG. 11, the calibration trigger instruction section 150 is connected to obtain information from the power measurement section 70 and issue instructions to the calibration signal generation section 30 .

<<Calibration trigger instruction unit 150>>
The calibration trigger instruction unit 150 is a component for outputting a trigger when it is determined that a new calibration should be started.
The function of the calibration trigger instruction unit 150 is realized by the processing circuit shown in FIG.

<<Regarding the calibration method of the array antenna system according to the sixth embodiment>>
FIG. 12 is a flowchart showing processing steps of the array antenna system according to the sixth embodiment.
As shown in Figure 12, the processing steps of the array antenna system of embodiment 6 include, in addition to the processing steps of the array antenna system of embodiment 1 shown in Figure 4, signal power measurement ST01 and power value confirmation ST02.
12, the portion enclosed by a dashed frame labeled “P601” is referred to as the “calibration execution determination phase.” The processing steps of measuring the power of a signal (ST01) and confirming the power value (ST02), which are added in the sixth embodiment, are included in the calibration execution determination phase.

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

Power value confirmation ST02 in the calibration execution determination phase (P601) is a processing step performed by the calibration trigger instruction unit 150. In power value confirmation ST02, the calibration trigger instruction unit 150 determines whether the amount of power measured by the power measurement unit 70 has fallen below a preset threshold value.
If the amount of power measured by the power measurement unit 70 falls below the preset threshold (YES), the process proceeds to step ST11 for generating a calibration signal. If the amount of power measured by the power measurement unit 70 does not fall below the preset threshold (NO), the process returns to step ST01 for measuring the power of a signal.

Figure 13 is a graph showing the time series change in the amount of power measured, and explains the timing for starting a new calibration. In the graph shown in Figure 13, the horizontal axis represents time, and the vertical axis represents the amount of power measured by the power measurement unit 70. In addition, in the graph shown in Figure 13, the dashed line labeled "Threshold Power" represents the power threshold used by the calibration trigger instruction unit 150. Furthermore, in the graph shown in Figure 13, the arrow labeled "Calibration Trigger" represents the timing at which the calibration trigger instruction unit 150 outputs a trigger.

The processing steps beyond the calibration implementation judgment phase (P601) shown in Figure 13 are the same as the processing steps shown in embodiment 1.

As described above, since the array antenna system of embodiment 6 includes a calibration trigger instruction unit 150, the magnitude of the composite electric field can be compared with a threshold value and a decision can be made to start a new calibration.

Embodiment 7.
The array antenna system and the calibration method for the array antenna system according to the seventh embodiment are modified examples of the array antenna system and the calibration method for the array antenna system according to the present disclosure.
The reference numerals used in the seventh embodiment are the same as those used in the previous embodiments unless otherwise specified. In the seventh embodiment, the description that overlaps with the previous embodiments will be omitted as appropriate.

(Introduction to the Seventh Embodiment)
(About block codes)
Codes are used for a variety of purposes in communicating and storing information, in particular for error correction.
A block code is a set of codewords. Block codes are often written as "(n, k, d) _q ", where n is the size of the block, k is the length of the message (the number of blocks to be sent), and d is the minimum distance of the code. The minimum distance is the minimum value of the Hamming distance between two different codewords. The Hamming distance is defined for two vectors (x and y), and is the number of different components, and is represented as d _H (x, y). The subscript q indicates that each component of the codeword is an element of an alphabet (including numbers) consisting of q symbols. When q=2, the code is a binary code.
The block code used for error correction is also called a "block error correcting code."
The Hadamard code, which will be described later in the seventh embodiment, is a (2 ^r , r, 2 ^r−1 ) ₂ code.
The contents described in the "Introduction to the Seventh Embodiment" are mainly quoted from the following reference documents.
Reference: "Introduction to Error Correcting Codes [Second Edition]", by Jern Kostesen and Tom Hoholt, Morikita Publishing Co., Ltd., ISBN 978-4-627-81712-8.

(Contents of the Seventh Embodiment)
As described in the first to fourth embodiments, the calibration signal may be, for example, a modulated signal that realizes phase modulation. In this case, it is important that the N modulated signals injected into the N transmission systems have low correlation in the time axis direction, that is, high orthogonality. However, even if the modulated signals themselves are designed to have high orthogonality, if there are individual differences in the N transmission systems that cause, for example, delay differences, the mutual orthogonality of the N modulated signals is lost and they interfere with each other, and ultimately, sufficient calibration accuracy cannot be obtained.

The array antenna system and the calibration method for the array antenna system according to the seventh embodiment are devised to solve the above problems. Specifically, the array antenna system and the calibration method for the array antenna system according to the seventh embodiment apply phase modulation and phase demodulation using an additional orthogonal code sequence for each modulation period of the calibration signal. Due to this technical feature, the array antenna system and the calibration method for the array antenna system according to the seventh embodiment can eliminate the influence of calibration signals from other systems.

Fig. 14 is a diagram for explaining phase modulation and its demodulation in the array antenna system according to the seventh embodiment. In Fig. 14, Fig. 14A is a diagram for explaining phase modulation. Fig. 14B is a diagram for explaining the demodulation. Fig. 14A and Fig. 14B each show four graphs. These four graphs show spectral components having a finite width in the frequency domain, i.e., occupied bands.
In Fig. 14A, {Tx1, Tx2} represents a transmission sequence. In Fig. 14B, {Rx1, Rx2} represents a reception sequence. For simplicity, the example shown in Fig. 14 has two transmission systems and two reception systems.
14A and 14B, the term "Modulation Period" means a modulation cycle. In FIG. 14, a transmission sequence or a reception sequence for two periods (#1, #2) is shown.

In the reception sequence, only the signal that should be associated with Tx1 is input to Rx1, and only the signal that should be associated with Tx2 is input to Rx2. However, in FIG. 14B, Rx1 shows two signals corresponding to Tx1 and Tx2. Similarly, Rx2 shows two signals corresponding to Tx1 and Tx2. This is an intentional reproduction of the interference situation that is the subject of the disclosed technology.

ここで、数式（２）に登場するＩ_ｎは、サイズがｎ×ｎの単位行列である。また、上添え字のＴは、転置を表す。 An orthogonal code sequence is used for the phase modulation process performed for each modulation period of the calibration signal. The orthogonal code sequence may be, for example, a Hadamard code. As described above, the Hadamard code is a (2 ^r , r, 2 ^r-1 ) ₂ code. The Hadamard code is a block code generated based on a Hadamard matrix (H).
A Hadamard matrix is a square matrix whose elements are either +1 or -1 and whose rows are orthogonal to each other. That is, any two rows of a Hadamard matrix are row vectors that are perpendicular to each other. Similarly, any two columns of a Hadamard matrix are column vectors that are perpendicular to each other. A Hadamard matrix (H) has the property shown in the following equation.

Here, I _n appearing in the formula (2) is a unit matrix of size n×n, and the superscript T represents transposition.

ここで、数式（３）左辺に登場する右下添え数字の“２”は、アダマール行列が２次であることを強調した表記である。 An example of a second order Hadamard matrix is:

Here, the subscript "2" on the left side of the formula (3) is a notation emphasizing that the Hadamard matrix is quadratic.

The array antenna system according to the disclosed technology may determine the amount of phase modulation for each modulation period of the calibration signal based on the elements of the row vector or column vector of the Hadamard matrix (H). The amount of phase modulation is determined based on the elements of the row vector or column vector of the Hadamard matrix (H), for example, to be 0 degrees for +1 and 180 degrees (π [rad]) for -1. If determined in this way, in the two systems illustrated in FIG. 14A, the first system is modulated with a phase (0, 0) corresponding to (+1, +1) in the first row of the Hadamard matrix (H) shown in formula (3), and the second system is modulated with a phase (0, π) corresponding to (+1, -1) in the second row.

As shown in Fig. 14B, the demodulation process targets a signal on which two systems of calibration signals are superimposed. This is realized by the calibration signal analyzer 100 performing phase demodulation based on the orthogonal code sequence for each period of the calibration signal and performing an integration process. In the example shown in Fig. 14B, the process of extracting the first system of calibration signals performs demodulation with a phase (0, 0), and the process of extracting the second system of calibration signals performs demodulation with a phase (0, -π).
A technical feature of the calibration method according to the disclosed technology is that, in the example of Fig. 14, two periods of demodulated signals are accumulated. This technical feature provides the effect of canceling out calibration signals of other systems. By having this technical feature, the calibration method according to the disclosed technology provides the effect of reducing the influence of calibration signals of other systems.

In general, the accumulation process is recognized to have an effect of improving the SNR for a periodic signal in which the same waveform (information) is repeated, and is performed for the purpose of improving the SNR. In other words, the accumulation process has the same effect as the averaging process, and can be considered as a type of LPF (Low Pass Filter).
In the field of radar technology, it has been reported that coherent integration is more effective at improving SNR than incoherent integration (for example, see the following non-patent literature).
Non-patent literature: Satoshi Kageme et al., "Verification of the principle of an SNR improvement algorithm using coherent integration of a target range profile," 2009, Institute of Electronics, Information and Communication Engineers General Conference, B-2-22, Proceedings of the Communication Conference 1, p. 279.

In the technical field of an array antenna calibration device or calibration method, it may not be a novel idea to provide an orthogonal code generator and assign a phase value of 0 degrees when the code is +1 and a phase value of 180 degrees (π [rad]) when the code is -1. It is also known to provide a Hadamard matrix generator and impart a phase rotation to the received signal of each antenna element according to a phase pattern in which, for example, 0 degrees for +1 and 180 degrees (π [rad]) for -1 are provided based on the elements of row vectors of a Hadamard matrix (H) (for example, International Publication No. WO 2006/051614).
However, the above-mentioned calibration device or calibration method is intended to be capable of simultaneously calibrating multiple elements and to perform efficient calibration even in array antennas with a large number of elements, and does not have as its main theme the loss of orthogonality caused by delay differences in the transmission system, which is an issue faced by the present disclosed technology.

As described above, in the seventh embodiment, the Hadamard code is shown as a specific example of the orthogonal code sequence, but the disclosed technology is not limited to this. The code sequence used in the disclosed technology may be any code sequence that has high orthogonality.
In addition, in the seventh embodiment, the phase modulation is performed for each modulation period of the calibration signal, but this is merely an example, and the disclosed technology is not limited to this. The effect shown in the seventh embodiment remains the same even if the period for which the phase modulation is performed is any period (1 period, 2 periods, 3 periods, ..., N periods) in units of the period of the calibration signal.

Note that the array antenna system and the calibration method of the array antenna system according to the disclosed technology are not limited to the aspects exemplified in each embodiment, and each embodiment may be combined, any component of each embodiment may be modified, or any component of each embodiment may be omitted.

The array antenna system and the calibration method for the array antenna system according to the present disclosure can be applied, for example, to an adaptive array antenna system using the CDMA method in cellular systems such as mobile phones, 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 combining 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 Path selection unit, 130 Path selection instruction unit, 140 Delay correction unit, 150 Calibration trigger instruction unit, 500 Processing circuit, 502 CPU, 504 Memory.

Claims (10)

A method for calibrating an array antenna system having a plurality of transmission systems, comprising the steps of:
A calibration signal generating unit of the array antenna system generates a calibration signal;
a phase control unit of the array antenna system controls a phase of an extracted signal including a transmission signal extracted from the transmission system and the calibration signal;
a power combining unit of the array antenna system combining the multiple 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 unit;
a power measurement unit of the array antenna system measures the power of the signal demodulated by the calibration signal receiver;
a phase control instruction unit of the array antenna system instructs the phase control unit on an amount of phase control based on a measurement value of power measured by the power measurement unit ;
The phase control by the phase control unit is performed using a phase setting value obtained in the most recent calibration as a candidate for a solution.
A method for calibrating an array antenna system. A method for calibrating an array antenna system having a plurality of transmission systems, comprising the steps of:
A calibration signal generating unit of the array antenna system generates a calibration signal;
a phase control unit of the array antenna system controls a phase of an extracted signal including a transmission signal extracted from the transmission system and the calibration signal;
a power combining unit of the array antenna system combining the multiple 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 unit;
a power measurement unit of the array antenna system measures the power of the signal demodulated by the calibration signal receiver;
a phase control instruction unit of the array antenna system instructs the phase control unit on an amount of phase control based on a measurement value of power measured by the power measurement unit ;
the phase control instructing unit instructs the phase control unit of a correction amount of phase when switching the fixed set value;
A method for calibrating an array antenna system. An array antenna system having a plurality of transmission systems,
a calibration signal generating unit that generates a calibration signal;
a Butler matrix circuit which receives an extracted signal composed of a transmission signal extracted from the transmission system and the calibration signal at an input port, synthesizes the extracted signal at a plurality of phase shift setting values, and outputs each of the synthesized 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 path selection unit;
a power measurement unit that measures the power of a signal demodulated by the calibration signal receiver;
a path selection instruction unit that instructs the path selection unit to switch the output port based on a measurement value of the power measured by the power measurement unit.
Array antenna system. the path selection instruction unit identifies the output port of the Butler matrix circuit that minimizes the measured value of power, determines a phase setting value, and instructs the path selection unit to switch to the identified output port.
4. The array antenna system according to claim 3 . a calibration signal phase offset unit that adjusts the phase of the calibration signal by offsetting the phase setting value;
a calibration signal analysis unit that calculates a relative amplitude and phase error based on the signal demodulated by the calibration signal receiver and the signal adjusted by the calibration signal phase offset unit;
and a DBF unit that corrects the transmission signal so as to eliminate the relative amplitude and phase error, and then performs digital beamforming.
5. The array antenna system according to claim 4 . a calibration signal analysis unit that extracts the calibration signal that has passed through the transmission system and calculates a relative amplitude and phase error;
the calibration signal generation unit performs phase modulation based on an orthogonal code sequence, with the period of the calibration signal being a unit;
the calibration signal analysis unit performs phase demodulation based on the orthogonal code sequence and performs an integration process, with the period of the calibration signal being a unit.
4. The array antenna system according to claim 3 . A method for calibrating an array antenna system having a plurality of transmission systems, comprising the steps of:
A calibration signal generating unit of the array antenna system generates a calibration signal;
a Butler matrix circuit of the array antenna system, to which an extracted signal composed of a transmission signal extracted from the transmission system and the calibration signal is input to an input port, combines the extracted signals at a plurality of phase shift setting values, and outputs each of the combined signals to a different output port;
a path 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 path selection unit,
a power measurement unit of the array antenna system measures the power of the signal demodulated by the calibration signal receiver;
a path selection instruction unit of the array antenna system instructs the path selection unit to switch the output port based on the power measurement value measured by the power measurement unit;
A method for calibrating an array antenna system. the path selection instruction unit identifies the output port of the Butler matrix circuit that minimizes the measured value of power, determines a phase setting value, and instructs the path selection unit to switch to the identified output port.
A method for calibrating an array antenna system according to claim 7 . a calibration signal phase offset unit offsets the phase of the calibration signal by the phase setting value;
A calibration signal analysis unit calculates a relative amplitude and phase error based on the signal demodulated by the calibration signal receiver and the signal adjusted by the calibration signal phase offset unit;
The DBF unit corrects the transmission signal so that the relative amplitude and phase error is eliminated, and then performs digital beamforming.
The method for calibrating an array antenna system according to claim 8 . the calibration signal generation unit performs phase modulation based on an orthogonal code sequence, with the period of the calibration signal being a unit;
a calibration signal analysis unit that extracts the calibration signal that has passed through the transmission system and calculates a relative amplitude and phase error, performs phase demodulation based on the orthogonal code sequence with the period of the calibration signal as a unit, and performs an integration process;
A method for calibrating an array antenna system according to claim 7 .

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