JP2000082909A - Calibration method for transmitting array antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a calibration method for a transmitting array antenna to fast obtain a coefficient with high stability to cancel unevenness between the amplitude other than that of a prescribed excitation distribution and a phase and also to perform quick calibration with high accuracy. SOLUTION: The synchronous orthogonal signals S1 to SN are inputted to a digital signal processing part 11 of a transmitting system 10, undergo the amplitude/phase fluctuation via a following circuit, radiated through the antenna elements #1 to #N and received by an antenna element 21 of a receiving system 20 which is located at a position that is satisfactorily far from the front of an array antenna of the system 10 and set in the θ direction. These received signals S are converted into the digital signals, and a digital processing part 22 performs a digital operation of a calibration coefficient. The calibration coefficient is sent to the system 10 and multiplied by a every signal system at the part 11 of the system 10. Thus, the unevenness is canceled between those antenna elements.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for calibrating a transmission array antenna for calibrating nonuniformity of amplitude and phase of each antenna element of a transmission array antenna composed of a plurality of antenna elements.

[0002]

2. Description of the Related Art As a method for calibrating the amplitude and phase of a transmission array antenna composed of a plurality of antenna elements, a phase shifter connected to each element antenna is used to shift the phase of one element antenna by 360 °. An element electric field vector rotation method (first conventional example) is known in which the change in the amplitude of an array combined electric field when rotated is measured, and the result is processed by a computer to find the amplitude and phase of the element. I have. According to the element electric field vector rotation method, there is a feature that non-uniformity of amplitude and phase can be detected in all lines including the antenna element and the reflector itself.

[0003] Further, by using a root-mean-square error of an error between a signal obtained by passing a transmission signal through an adaptive filter and a reception signal as an evaluation function and calculating a complex weight so as to minimize the error, the relative amplitude and A method of obtaining a relative phase (second conventional example) is also known. According to this technology,
Calculations for equalizing the amplitude and phase of each antenna element can be performed by batch processing, and this has the advantage that the calculation time for obtaining the relative amplitude and relative phase of each element of the transmitting antenna can be reduced.

[0004]

However, in the first conventional example, when the number of antenna elements of the array antenna is large, it is necessary to rotate the phase of each antenna element to measure the combined power. It takes time. In addition, when the transmission power per antenna element is weak, there is a problem that the calibration accuracy cannot be sufficiently secured.

Further, in the second conventional example, there is a problem that an unstable element remains in the operation since a closed loop is formed over the transmission system and the reception system.

Accordingly, the present invention has been made to solve the above problems, and to obtain a coefficient for canceling non-uniformity of amplitude and phase other than a predetermined excitation distribution with high speed and high stability. It is an object of the present invention to provide a method for calibrating a transmission array antenna which can perform high-precision calibration quickly.

[0007]

Accordingly, a method for calibrating a transmission array antenna according to the present invention is directed to a method for calibrating a transmission array antenna, wherein each signal system connected to each antenna element of a transmission system having a transmission array antenna composed of a plurality of antenna elements. Input a synchronous quadrature signal, give a predetermined excitation distribution for obtaining a predetermined transmission beam pattern, transmit with an array antenna having non-uniform amplitude characteristics and phase characteristics other than the predetermined excitation distribution, and Received by a one-element antenna of the receiving system arranged in the direction, converts the received signal into a digital signal, performs digital arithmetic processing based on a predetermined arithmetic expression, and performs an amplitude error and an amplitude error other than a predetermined excitation distribution. Detecting a phase error, finding a calibration coefficient for canceling the non-uniformity,
The non-uniformity of each antenna element is canceled by sending the calibration coefficient obtained by the receiving system to the transmitting system and multiplying each signal of the transmitting system by each system.

According to a second aspect of the present invention, there is provided a method for calibrating a transmission array antenna, comprising: a transmission system including a transmission array antenna comprising a plurality of antenna elements; After distributing the signal and giving an appropriate phase difference, the signal is output to each antenna element system, a predetermined excitation distribution for obtaining a predetermined transmission beam pattern is provided, and an amplitude characteristic and a phase other than the predetermined excitation distribution exist. The signal is transmitted by an array antenna having non-uniform characteristics, received by a one-element antenna of a receiving system arranged in a known direction, the received signal is converted into a digital signal, and a digital operation is performed based on a predetermined operation expression. Is performed to detect an amplitude error and a phase error existing other than the predetermined excitation distribution, to obtain a calibration coefficient for canceling the non-uniformity, and to calculate the calibration coefficient obtained by the receiving system. Feed the signal system is multiplied to each signal each line of the transmission system, it is characterized in that it has to cancel the non-uniformity of each antenna element.

According to a third aspect of the present invention, there is provided a method for calibrating a transmission array antenna according to the first or second aspect, wherein the digital operation performed by the receiving system is performed between each synchronous orthogonal signal prepared in advance and the received signal. After taking a complex correlation and taking a complex conjugate, the amplitude and phase are determined by the power of the signal, the number of transmitting antenna elements, a predetermined excitation distribution in the transmitting antenna, the position of the transmitting antenna element, and the like. It is.

[0010] A fourth aspect of the present invention provides a method for calibrating a transmission array antenna, wherein the digital arithmetic processing performed by the receiving system includes a spatial discrete Fourier transform.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a method for calibrating a transmission array antenna according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a first embodiment including a transmission system and a reception system capable of realizing the method for calibrating a transmission array antenna according to the present invention. In the first embodiment, a synchronous orthogonal signal is input and transmitted for each of the antenna elements # 1 to #N configuring the array antenna of the transmission system 10, and
A digital signal processing is performed on the received signal received by the single antenna element 21 of the receiving system 20 to obtain a calibration coefficient for calibrating the transmitting array antenna.

Synchronous orthogonal signals S _{1 to} S _N corresponding to antenna elements # 1 to #N are input to digital signal processing unit 11 of transmission system 10, and each of the synchronous orthogonal signals S _{1 to} S _N has an amplitude and After receiving the phase change, each of the antenna elements # 1 to #N
Radiated from The synchronous orthogonal signals S _{1 to} S _N output from the digital signal processing unit 11 are converted into digital signals in a high frequency band or an intermediate frequency band into analog signals by respective D / A converters, and transmitted signals S ′ _{1 to} S ′. ' _N is transmitted from each of the antenna elements # 1 to #N.

On the other hand, a receiving system 20 receives a signal received by a one-element antenna 21 arranged in a known direction with respect to the transmitting system 10 and converts the received signal into a digital signal by an A / D converter. The digital signal processor 22 uses the received signal and a transmission signal (synchronous quadrature signal) prepared in advance on the receiving side to cancel the nonuniformity of the amplitude and phase in each system of the transmission antenna. Is generated and sent to the transmission system 10.

In the transmission system 10 described above, N synchronous orthogonal complex baseband signals S _n (n = 1, 2,..., N
-1, N) is input to the digital signal processing unit 11 and output to each system as it is without performing complex weighting for beam forming, and a predetermined excitation amplitude coefficient a _n for giving an appropriate side lobe characteristic. (Real number) is multiplied. When a coefficient expressed by a complex number a nonuniformity of the amplitude and phase with each system from the digital signal processing unit 11 to the antenna elements #. 1 to # N and e _n, the signal S _'n emitted from the element number #n Is represented by the following equation [Equation 1].

[0016]

(Equation 1)

Further, the signal S _'n radiated from the antenna elements #. 1 to # N are spatially combining, the antenna 21 (1 element of the receive system 20 located sufficiently far in the θ direction from the transmission array antenna front The signal received by the antenna) is expressed by the following equation [Equation 2].

[0018]

(Equation 2)

Here, φ _n represents the transmission phase distribution from transmission antenna element #n to reception antenna element 21, and is determined by the position of transmission antenna element #n and θ. φ _n is given by the following equation [Equation 3] in the case of a linear array antenna having an equal interval.

[0020]

(Equation 3)

Here, χ _n is a coordinate value representing the position of the transmitting antenna element, and λ is the wavelength of the transmitting carrier.

The quasi synchronous detection a reception signal S, the digital signal processor 22, taking the transmission signal S _n and the complex correlation prepared in advance at the receiving side (time average), from the relationship of the following formula [Formula 4] , the coefficient e _n representing the heterogeneous component can be calculated by the following formula [formula 5].

[0023]

(Equation 4)

[0024]

(Equation 5)

Therefore, the calibration coefficient is given by the following equation (Equation 6).

[0026]

(Equation 6)

According to the above [Equation 6], the complex correlation between the received signal S and the transmission signal prepared in advance on the receiving side is obtained, the complex conjugate is obtained, appropriate amplitude / phase weighting is performed, and the output is performed. By sending the calibration coefficient to the transmission system and multiplying each system, the non-uniformity of the elements can be canceled.

FIG. 2 shows a second embodiment comprising a transmission system and a reception system capable of implementing the method for calibrating a transmission array antenna according to the present invention. In the second embodiment, a multi-beam corresponding to a synchronous quadrature signal is transmitted from the array antenna of the transmission system 30, and the reception signal received by the single antenna element 41 of the reception system 40 is digitally processed. A calibration coefficient for calibrating the transmission array antenna is obtained.

Synchronous quadrature signals S _{1 to} S _N are input to and distributed to the digital signal processing unit 31 of the transmission system 30 and given an appropriate phase difference, and then radiated from each of the antenna elements # 1 to #N. You. The signals output from the digital signal processing unit 31 to the respective systems are converted from digital signals in a high frequency band or an intermediate frequency band into analog signals by respective D / A converters, and transmitted from the antenna elements # 1 to #N. Because

On the other hand, a receiving system 40 receives a signal received by a one-element antenna 41 arranged in a known direction with respect to the transmitting system 30 and converts the received signal into a digital signal by an A / D converter. The digital signal processing unit 42 uses the received signal S to calculate a calibration coefficient for canceling the non-uniformity of the amplitude and phase in each system of the transmitting antenna, and sends the calculated coefficient to the transmitting system 30.

In the transmission system 30 described above, N synchronous orthogonal complex baseband signals S _l (l = 1, 2,... N−
, N) is input to the digital signal processing unit 31, and each signal is duplicated N times, and the phase difference between adjacent elements of the signal _Sl is "2 (l-1) π / N" (l = 1,2) , ... N-1, N)
A predetermined excitation amplitude coefficient a _n for giving a phase so that
(Real number). Assuming that the amplitude and phase non-uniformity of each system from the digital signal processing unit 31 to the antenna elements # 1 to #N is represented by a complex number, e _n is radiated from each of the antenna elements # 1 to #N. The signals are spatially combined to form N orthogonal multi-beams corresponding to each signal _Sl . The signal S received by the antenna element 41 of the receiving system 40 arranged in the direction of θ from the front of the transmitting antenna is given by the following equation [Equation 7].

[0032]

(Equation 7)

Here, φ _n represents the transmission phase distribution from antenna element #n of transmission system 30 to antenna element 41 of reception system 40, and is determined by the position of antenna element 41 of transmission system 40 and θ. Also, φ _n is given by the above equation [Equation 3] in the case of an evenly spaced linear array antenna.

[0034] Then, the quasi-synchronous detection a reception signal S, the digital signal processing unit 42, taking the previously prepared transmitted signal S _n and the complex correlation at the receiving side (time average), the above equation [Expression 4] from the relationship, the coefficient e _n representing the heterogeneous component is calculated by the following formula [formula 8].

[0035]

(Equation 8)

Therefore, the calibration coefficient is given by the following equation (Equation 9).

[0037]

(Equation 9)

The above equation [Expression 9], after taking the complex correlation between the transmission signal S _n which is prepared in advance the reception side and the reception signal S, performs spatial discrete Fourier transform (DFT), the complex conjugate Then, appropriate amplitude / phase weighting is performed, the output calibration coefficient is sent to the transmission system 30, and multiplication is performed on each system, thereby canceling the non-uniformity of the elements.

As a specific example of the second embodiment, a simulation result of calibrating a linear array antenna (four elements) with a half wavelength interval is shown.

FIG. 3 shows an ideal transmission orthogonal multi-beam pattern when there is no nonuniformity of each antenna element. As shown in Table 1 below, amplitude and phase deviations are given to each element. In this case, the transmission multi-beam pattern is as shown in FIG.

[0041]

[Table 1]

Then, the antenna element 41 of the receiving system 40 is arranged in a direction of 20 ° from the front of the array antenna of the transmitting system 30, and the transmission after performing the calibration based on the calibration coefficient generated by performing the above-described predetermined calculation is performed. The multi-beam pattern is as shown in FIG. 5, indicating that the beam pattern has been improved.

[0043]

As described above, according to the transmission array antenna calibration method according to the first to fourth aspects, the following specific effects can be obtained.

(1) Since the calibration coefficient is obtained by using the received signal received by the receiving system, the transmission array antenna can be calibrated by remote control.

(2) Since the receiving system performs the batch processing by digital signal processing to obtain the calibration coefficients, the calculation of the calibration coefficients is fast.

(3) In the calculation of the calibration coefficient performed in the receiving system, since a closed loop circuit is not formed, the operation is stable.

[Brief description of the drawings]

FIG. 1 is a first embodiment including a transmission system and a reception system capable of implementing a method for calibrating a transmission array antenna according to the present invention.

FIG. 2 is a second embodiment including a transmission system and a reception system capable of realizing the transmission array antenna calibration method according to the present invention.

FIG. 3 is a transmission orthogonal multi-beam pattern diagram of a four-element linear array antenna having a half-wavelength interval when the amplitude and phase characteristics are uniform.

FIG. 4 is a half wavelength interval 4 when the amplitude / phase characteristics are not uniform.
It is a transmission multi-beam pattern diagram of an element linear array antenna.

FIG. 5 is a transmission multi-beam pattern diagram of a half-wavelength-spaced four-element linear array antenna after calibration.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Transmission system 11 Digital signal processing part 20 Receiving system 21 Antenna element 22 Digital signal processing part 30 Transmission system 31 Digital signal processing part 40 Receiving system 41 Antenna element 42 Digital signal processing part

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[Procedure amendment]

[Submission date] October 18, 1999 (1999.10.
18)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5J021 AA05 AA06 CA06 DB02 DB03 EA04 EA07 FA16 FA20 FA21 FA29 FA32 GA08 HA05 JA10 5K052 AA02 BB02 BB07 CC06 DD04 GG20 GG31 GG41 GG48 5K059 CC02 DD32 DD41 5K060 CC04 CC01

Claims (4)

[Claims] 1. A synchronous orthogonal signal is input to each signal system connected to each antenna element of a transmission system having a transmission array antenna composed of a plurality of antenna elements, and a predetermined signal for obtaining a predetermined transmission beam pattern is obtained. An excitation distribution is given, transmitted by an array antenna having non-uniform amplitude and phase characteristics other than a predetermined excitation distribution, received by a one-element antenna of a receiving system arranged in a known direction, and receiving the received signal. Converted to a digital signal, performs digital arithmetic processing based on a predetermined arithmetic expression, detects an amplitude error and a phase error existing other than a predetermined excitation distribution, and obtains a calibration coefficient for canceling the non-uniformity, The calibration coefficient obtained in the receiving system is sent to the transmitting system, and each signal of the transmitting system is multiplied by each system to cancel the non-uniformity of each antenna element. Calibration method of transmission array antenna. 2. A transmission system having a transmission array antenna composed of a plurality of antenna elements, wherein a plurality of synchronous orthogonal signals are input to a digital signal processing unit, each signal is distributed, and an appropriate phase difference is given. Output to each antenna element system to give a predetermined excitation distribution for obtaining a predetermined transmission beam pattern, and transmit by an array antenna having non-uniform amplitude characteristics and phase characteristics other than the predetermined excitation distribution. Is received by a one-element antenna of the receiving system arranged in the direction of, the received signal is converted into a digital signal, and a digital operation process is performed based on a predetermined operation expression, and an amplitude error existing outside a predetermined excitation distribution is obtained. And the phase error is detected, a calibration coefficient for canceling the non-uniformity is obtained, the calibration coefficient obtained by the reception system is sent to the transmission system, and each signal of the transmission system is multiplied by each signal. Calibration method of transmission array antenna, characterized in that it has to cancel the non-uniformity of each antenna element. 3. A digital operation process performed by a receiving system is to obtain a complex correlation between each synchronous orthogonal signal prepared in advance and a received signal, take a complex conjugate, and then obtain the signal power, the number of transmitting antenna elements, and 3. The calibration method for a transmission array antenna according to claim 1, wherein the amplitude and phase are determined by a predetermined excitation distribution in the antenna, a position of the transmission antenna element, and the like. 4. The method according to claim 3, wherein the digital operation performed by the receiving system includes a spatial discrete Fourier transform.