JP6573745B2 - Adaptive array antenna device - Google Patents

Description

  The present invention relates to an adaptive array antenna apparatus that multiplies a plurality of signals respectively received by a plurality of subarray antennas by a weighting factor and synthesizes the plurality of signals after weighting factor multiplication.

The radar apparatus is mounted on a platform such as an aircraft, and may be operated in an environment where an interference wave arrives.
The antenna device included in the radar device forms an adaptive beam by an array antenna in which a plurality of subarray antennas are arranged.
At this time, the antenna device suppresses the interference wave included in the received signal of the array antenna, and improves the SJNR (Signal to Jamming and Noise Ratio) of the target signal related to the target to be observed. The adaptive weight is determined so that a null is formed in the arrival direction of. The adaptive weight is a weight coefficient for a plurality of signals respectively received by a plurality of subarray antennas.

The determination of the adaptive weight by the antenna device is performed by the following method, for example.
First, the antenna device temporarily stops a beam transmitted from the array antenna, and uses a plurality of signals respectively received by a plurality of subarray antennas as interference signal during a listening period in which the beam is not transmitted. get.
Next, the antenna device determines an adaptive weight from the acquired interference wave signal so that a null is formed in the arrival direction of the interference wave.

When a radar device including an antenna device is installed at a land base or the like and the radar device does not move, the arrival direction of the disturbing wave does not change unless the source of the disturbing wave moves.
However, when the radar device including the antenna device or the source of the interference wave is moving, the arrival direction of the interference wave changes.
For this reason, even if the antenna apparatus determines an adaptive weight in which a null is formed in the arrival direction of the jamming wave during the listening period, the jamming is performed in a short time until the beam transmission is resumed from the array antenna. The direction of arrival of waves changes.
That is, the arrival direction of the interference wave in the listening period and the arrival direction of the interference wave in the beam transmission period, which is a period in which the beam is transmitted after the listening period ends, are in different directions.

Due to the change in the direction of arrival of the jamming wave, there is a shift between the direction of the null formed by the adaptive weight determined during the listening period and the actual direction of arrival of the jamming wave during the beam transmission period (hereinafter referred to as “null shift”). ").
When the null shift occurs, the interference wave suppression performance of the antenna device deteriorates, and thus the target detection performance of the radar device deteriorates.
Non-Patent Document 1 below discloses an antenna device that performs a process of widening a null formed by an adaptive weight determined during a listening period in order to avoid the influence of a null shift.

J. R. Guerci, “Theory and application of covariance matrix tapers for robust adaptive beamforming,” IEEE Transactions on Signal Processing, vol. 47, no. 4, pp. 977-985, Apr 1999.

  The conventional antenna apparatus performs a process of expanding the width of the null formed by the adaptive weight, but does not appropriately set the extension width of the null width based on the change in the arrival direction of the disturbing wave. For this reason, a large change may occur in which the arrival direction of the interference wave exceeds the widened null width. Thus, when the change of the arrival direction of the jamming wave is large, there is a problem that the jamming wave included in the received signal of the array antenna cannot be suppressed.

  The present invention has been made to solve the above-described problems, and an antenna device capable of suppressing the interference wave included in the received signal of the array antenna even if the arrival direction of the interference wave greatly changes. The purpose is to obtain.

  The antenna device according to the present invention includes an array antenna in which a plurality of subarray antennas including one or more element antennas are arranged, and a plurality of subarray antennas during a listening period in which a beam is not transmitted from the array antenna. Interference waves in the listening period from a plurality of signals received respectively and a plurality of signals respectively received by a plurality of subarray antennas during a beam transmission period in which a beam is transmitted after the end of the listening period. A null shift estimation unit that estimates a null shift, which is a change between the arrival direction of the interference wave and the arrival direction of the jamming wave in the beam transmission period, and a plurality of the beam transmission periods during the beam transmission period based on the null shift estimated by the null shift estimation unit. Weighting factors for multiple signals received by each subarray antenna A compensation weight calculation unit for calculating a compensation weight for compensating for the null shift, and the beam forming unit calculates a plurality of signals respectively received by the plurality of subarray antennas during the beam transmission period by the compensation weight calculation unit. The compensated weights are multiplied to synthesize a plurality of signals after the compensation weight multiplication.

  According to the present invention, the interference in the listening period from the plurality of signals respectively received by the plurality of subarray antennas during the listening period and the plurality of signals respectively received by the plurality of subarray antennas during the beam transmission period. A null shift estimation unit that estimates a null shift that is a change between the arrival direction of the wave and the arrival direction of the disturbing wave in the beam transmission period, and the compensation weight calculation unit is based on the null shift estimated by the null shift estimation unit. In the beam transmission period, since the compensation weight for compensating for the null shift is calculated as the weighting factor for the plurality of signals respectively received by the plurality of subarray antennas, the arrival direction of the interference wave greatly changes. Also, there is an effect that the interference wave included in the received signal of the array antenna can be suppressed.

It is a block diagram which shows the adaptive array antenna apparatus by Embodiment 1 of this invention. It is a hardware block diagram which shows the signal processing apparatus 2 of the adaptive array antenna apparatus by Embodiment 1 of this invention. It is a hardware block diagram of a computer in case the signal processing apparatus 2 is implement | achieved by software or firmware. It is a block diagram which shows the null shift estimation part 11 of the adaptive array antenna apparatus by Embodiment 1 of this invention. It is a block diagram which shows the compensation weight calculation part 12 of the adaptive array antenna apparatus by Embodiment 1 of this invention. It is a flowchart which shows the process sequence in case the signal processing apparatus 2 is implement | achieved by software or firmware. It is a block diagram which shows the compensation weight calculation part 12 of the adaptive array antenna apparatus by Embodiment 2 of this invention.

  Hereinafter, in order to explain the present invention in more detail, modes for carrying out the present invention will be described with reference to the accompanying drawings.

Embodiment 1 FIG.
1 is a block diagram showing an adaptive array antenna apparatus according to Embodiment 1 of the present invention. In FIG.
FIG. 2 is a hardware configuration diagram showing the signal processing device 2 of the adaptive array antenna device according to Embodiment 1 of the present invention.
1 and 2, an array antenna 1 is an antenna in which M subarray antennas 1-m (m = 1, 2,..., M) are arranged.
The subarray antenna 1-m is an antenna including at least one element antenna.

The signal processing device 2 includes a null shift estimation unit 11, a compensation weight calculation unit 12, and a beam forming unit 13, and multiplies a plurality of signals respectively received by the M subarray antennas 1-m by weighting factors. , A device for synthesizing a plurality of signals after multiplication by weighting factors.
In FIG. 1, for simplification of the drawing, a receiver that detects a signal received by the subarray antenna 1-m, a converter that converts a received signal of the receiver from an analog signal to a digital signal, and the like are omitted. Actually, a receiver and a converter are provided.
For this reason, the null shift estimation unit 11 and the beam forming unit 13 are given digital received signals corresponding to the signals received by the M subarray antennas 1-m.
In FIG. 1, a received signal vector including M digital received signals is shown.

The null shift estimation unit 11 is realized by, for example, a null shift estimation circuit 21 shown in FIG.
The null shift estimation unit 11 receives M digital received signals corresponding to M signals respectively received by the M subarray antennas 1-m during a listening period in which a beam is not transmitted from the array antenna 1. get.
Also, the null shift estimation unit 11 corresponds to M signals respectively received by the M subarray antennas 1-m during the beam transmission period, which is a period during which the beam after the listening period is transmitted. M digital received signals are acquired.
The null shift estimation unit 11 uses the M digital reception signals during the listening period and the M digital reception signals during the beam transmission period, and the arrival direction of the interference wave during the listening period and the arrival of the interference wave during the beam transmission period. The process which estimates the null shift which is a change with a direction is implemented.
The beam transmission period includes a period in which the array antenna 1 receives a beam in addition to a period in which the array antenna 1 transmits a beam.

The compensation weight calculation unit 12 is realized by, for example, a compensation weight calculation circuit 22 illustrated in FIG.
Based on the null shift estimated by the null shift estimation unit 11, the compensation weight calculation unit 12 receives M signals corresponding to the M signals respectively received by the M subarray antennas 1-m during the beam transmission period. As a weighting factor for the digital received signal, a process of calculating a compensation weight for compensating for a null shift is performed.

The beam forming unit 13 is realized by, for example, a beam forming circuit 23 shown in FIG.
The beam forming unit 13 includes M multipliers 14-m and an adder 15, and M corresponding to M signals respectively received by the M subarray antennas 1-m during the beam transmission period. A process of multiplying the digital reception signals by the compensation weight calculated by the compensation weight calculation unit 12 and combining the M digital reception signals after the compensation weight multiplication is performed.
The multiplier 14-m multiplies the digital reception signal corresponding to the signal received by the sub-array antenna 1-m by the compensation weight calculated by the compensation weight calculation unit 12 during the beam transmission period, and after the compensation weight multiplication. The digital reception signal is output to the adder 15.
The adder 15 synthesizes the M reception signals after multiplication of the compensation weights output from the M multipliers 14-m, and outputs the synthesized digital reception signal as a reception beam.

In FIG. 1, it is assumed that each of the null shift estimation unit 11, the compensation weight calculation unit 12, and the beam forming unit 13, which are components of the signal processing device 2, is realized by dedicated hardware as shown in FIG. doing. That is, what is realized by the null shift estimation circuit 21, the compensation weight calculation circuit 22, and the beam forming circuit 23 is assumed.
The null shift estimation circuit 21, the compensation weight calculation circuit 22 and the beam forming circuit 23 are, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-). Programmable Gate Array) or a combination thereof.

However, the components of the signal processing device 2 are not limited to those realized by dedicated hardware, and the signal processing device 2 is realized by software, firmware, or a combination of software and firmware. May be.
Software or firmware is stored as a program in the memory of a computer. The computer means hardware that executes a program, and includes, for example, a CPU (Central Processing Unit), a central processing unit, a processing unit, an arithmetic unit, a microprocessor, a microcomputer, a processor, a DSP (Digital Signal Processor), and the like. .

FIG. 3 is a hardware configuration diagram of a computer when the signal processing device 2 is realized by software or firmware.
When the signal processing device 2 is realized by software or firmware, a program for causing the computer to execute the processing procedures of the null shift estimation unit 11, the compensation weight calculation unit 12, and the beam forming unit 13 is stored in the memory 31 of the computer. The computer processor 32 may execute a program stored in the memory 31.
FIG. 6 is a flowchart showing a processing procedure when the signal processing device 2 is realized by software or firmware.
The memory 31 of the computer may be, for example, a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, an EPROM (Erasable Programmable Read Only Memory Memory, or an EEPROM (Electrically Erasable Memory). A volatile semiconductor memory, a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, a DVD (Digital Versatile Disc), and the like are applicable.

FIG. 4 is a block diagram showing a null shift estimation unit 11 of the adaptive array antenna apparatus according to Embodiment 1 of the present invention.
In FIG. 4, the first correlation matrix calculation unit 41 generates interference wave signals from M digital received signals corresponding to M signals respectively received by the M subarray antennas 1-m during the listening period. A process of calculating a correlation matrix is performed.

The vector calculation unit 42 scans the scanning direction of the interference wave using the weight constraint vector for scanning the main beam direction of the beam and the interference matrix of the interference wave calculated by the first correlation matrix calculation unit 41. A process of calculating a weight vector for performing is performed.
That is, the vector calculation unit 42 is a diagonal matrix having a path difference phase component due to the difference between the main beam direction and the scan direction in the diagonal terms, the weight constraint vector, and the disturbance calculated by the first correlation matrix calculation unit 41. A process of calculating a weight vector is performed by multiplying the wave correlation matrix.
The second correlation matrix calculating unit 43 receives the received signal of the array antenna 1 from the M digital received signals corresponding to the M signals respectively received by the M subarray antennas 1-m during the beam transmission period. The process which calculates the correlation matrix of is implemented.

The evaluation function calculation unit 44 uses the weight vector calculated by the vector calculation unit 42 and the correlation matrix of the received signal calculated by the second correlation matrix calculation unit 43 to calculate an evaluation function used for estimation of the null shift. Perform the calculation process.
The null deviation estimation processing unit 45 uses the evaluation function calculated by the evaluation function calculation unit 44 to perform processing for estimating a null deviation.

FIG. 5 is a block diagram showing the compensation weight calculation unit 12 of the adaptive array antenna apparatus according to Embodiment 1 of the present invention.
In FIG. 5, the CMT matrix calculation unit 51 calculates a CMT (Covariance Matrix Tape) matrix that is a matrix for setting a null width from the null shift estimated by the null shift estimation processing unit 45 of the null shift estimation unit 11. To implement.
The weight calculation processing unit 52 includes a compensation type correlation matrix calculation unit 53 and a compensation type weight calculation unit 54.
The weight calculation processing unit 52 compensates for the null shift from the CMT matrix calculated by the CMT matrix calculation unit 51 and the interference matrix correlation matrix calculated by the first correlation matrix calculation unit 41 of the null shift estimation unit 11. The process which calculates the compensation weight to perform is implemented.

The compensation type correlation matrix calculation unit 53 calculates a null shift from the CMT matrix calculated by the CMT matrix calculation unit 51 and the interference matrix correlation matrix calculated by the first correlation matrix calculation unit 41 of the null shift estimation unit 11. A process of calculating a compensation type correlation matrix is performed.
The compensation weight calculation unit 54 performs a process of calculating a compensation weight for compensating for the null shift from the weight constraint vector and the null shift compensation correlation matrix calculated by the compensation correlation matrix calculation unit 53.

Next, the operation will be described.
First, the signal processing apparatus 2 temporarily stops the beam transmitted from the array antenna 1, and during the listening period, which is a period in which the beam is not transmitted, M subarray antennas 1-m (m = 1, 2, .., M) to obtain M signals respectively received as interference signal.
The signal processing device 2 detects M signals respectively received by the M subarray antennas 1-m, and converts each of the detected M signals from an analog signal to a digital signal.
The null shift estimation unit 11 and the beam forming unit 13 of the signal processing device 2 are provided with a received signal vector including digital received signals that are M digital signals that have been converted.

式（１）において、ｔは時刻、ａ_Ｊ（ｕ_０ ^（ｋ））は、第ｋ番目の妨害波の到来方向ｕ_０ ^（ｋ）＝［ｕ_０ ^（ｋ），ｖ_０ ^（ｋ）］^Ｔに対するステアリングベクトルである。Ｔは転置を示す記号である。
ｊ_ｋ（ｔ）は、第ｋ番目の妨害波の複素振幅、ｎ_０（ｔ）は、受信機雑音ベクトルである。During the listening period, a received signal vector x ₀ (t) shown in the following equation (1) is given to the null shift estimating unit 11 and the beam forming unit 13.

In Expression (1), t is time, and a _J (u ₀ ^(k) ) is the arrival direction u ₀ ^(k) = [u ₀ ^(k) , v ₀ ^(k) ] ^T Is a steering vector. T is a symbol indicating transposition.
j _k (t) is the complex amplitude of the k-th jamming wave, and n ₀ (t) is the receiver noise vector.

式（２）において、Ｅ［・］は、・に関するアンサンブル平均を示す記号である。Ｈは、エルミート転置を示す記号である。
式（２）では、リスニング期間における異なる時刻ｔの有限個数の受信信号ベクトルｘ_０（ｔ）を用いている。
第１の相関行列算出部４１は、算出した妨害波の相関行列Ｒ_０をベクトル算出部４２及び補償ウェイト算出部１２の補償型相関行列算出部５３に出力する。When the first correlation matrix calculation unit 41 of the null shift estimation unit 11 is provided with the reception signal vector x ₀ (t) during the listening period, the reception signal during the listening period is represented by the following equation (2). The interference matrix correlation matrix R ₀ is calculated from the vector x ₀ (t) (step ST1 in FIG. 6).

In Equation (2), E [•] is a symbol indicating an ensemble average with respect to •. H is a symbol indicating Hermitian transposition.
In Expression (2), a finite number of received signal vectors x ₀ (t) at different times t in the listening period are used.
The first correlation matrix calculator 41 outputs the calculated interference matrix correlation matrix R ₀ to the vector calculator 42 and the compensation-type correlation matrix calculator 53 of the compensation weight calculator 12.

Vector calculating unit 42 obtains the scan direction u of the disturbance, determining the scanning direction u and the main beam direction u _s difference diagonal matrix having a path difference phase component in the diagonal section by D of (u-u _s) .
The main beam direction u _s is in the beam transmission period after the listening period ends, the direction of the main beam in the beam transmitted from the array antenna 1.
Furthermore, the vector calculation unit 42, obtained during beam transmission period after the listening period has ended, the wait constraint vector a to scan the main beam direction u _s of the beam transmitted from the array antenna 1 (u _s) To do.

式（３）において、αは、事前に設定された規格化係数である。
ベクトル算出部４２は、算出したウェイトベクトルｗ（ｕ）を評価関数算出部４４に出力する。
なお、ベクトル算出部４２により算出されるウェイトベクトルｗ（ｕ）は、妨害波の到来方向ｕ_０ ^（ｋ）にヌルを形成するためのベクトルであり、メインビーム方向ｕ_ｓにおけるウェイトベクトルｗ（ｕ_ｓ）＝αＲ_０ ^−１ａ（ｕ_ｓ）を妨害波のスキャン方向ｕに走査するウェイトベクトルに相当する。The vector calculation unit 42 is output from the diagonal matrix D (u−u _s ), the weight constraint vector a (u _s ), and the first correlation matrix calculation unit 41 as shown in the following equation (3). The weight vector w (u) for scanning the scanning direction u of the interference wave is calculated by multiplying the interference wave correlation matrix R ₀ (step ST2 in FIG. 6).

In Expression (3), α is a normalization coefficient set in advance.
The vector calculation unit 42 outputs the calculated weight vector w (u) to the evaluation function calculation unit 44.
Incidentally, the weight vector w to be calculated by the vector calculating unit 42 (u) is a vector to form a null in the arrival direction u ₀ of the disturbance ^_(k), the weight vector w (u in the main beam direction u _{s s} ) = αR ₀ ⁻¹ a (u _s ) corresponds to a weight vector for scanning in the scanning direction u of the interference wave.

式（４）において、ｓ（ｔ）は目標信号、ａ_ｓは、目標信号ｓ（ｔ）の到来方向に対するステアリングベクトル、ｎ（ｔ）は、受信機雑音ベクトルであり、受信機雑音ベクトルｎ（ｔ）の特性は、リスニング期間における受信機雑音ベクトルｎ_０（ｔ）の特性と同じである。
ｕ_０ ^（ｋ）＋δｕ_ｋは、ビーム送信期間における第ｋ番目の妨害波の到来方向であり、リスニング期間における第ｋ番目の妨害波の到来方向とずれている。
δｕ_ｋ＝［δｕ_ｋ，δｖ_ｋ］^Ｔは、ビーム送信期間における第ｋ番目の妨害波の到来方向と、リスニング期間における第ｋ番目の妨害波の到来方向とのずれである。During the beam transmission period after the end of the listening period, a received signal vector x (t) shown in the following equation (4) is given to the null shift estimation unit 11 and the beam forming unit 13.

In the formula (4), s (t) is the target signal, _{a s} is the steering vector for the direction of arrival of the target signal s (t), n (t ) is the receiver noise vector, receiver noise vector n ( The characteristics of t) are the same as the characteristics of the receiver noise vector n ₀ (t) during the listening period.
u ₀ ^(k) + δu _k is the arrival direction of the k-th jamming wave in the beam transmission period, and is shifted from the arrival direction of the k-th jamming wave in the listening period.
δu _k = [δu _k , δv _k ] ^T is the difference between the arrival direction of the kth jamming wave in the beam transmission period and the arrival direction of the kth jamming wave in the listening period.

第２の相関行列算出部４３は、算出した受信信号の相関行列Ｒ_ｘを評価関数算出部４４に出力する。The second correlation matrix calculation unit 43 of the null shift estimation unit 11 is given the received signal vector x (t) during the beam transmission period after the end of the listening period, as shown in the following equation (5). The correlation matrix R _x of the received signal of the array antenna 1 is calculated from the received signal vector x (t) during the beam transmission period (step ST3 in FIG. 6).

The second correlation matrix calculation unit 43 outputs the calculated correlation matrix R _x of the received signal to the evaluation function calculation unit 44.

式（６）の分母であるｗ^Ｈ（ｕ）Ｒ_ｘｗ（ｕ）は、ウェイトベクトルｗ（ｕ）によるビームの走査出力電力である。
ウェイトベクトルｗ（ｕ）は、上述したように、メインビーム方向ｕ_ｓにおけるウェイトベクトルｗ（ｕ_ｓ）を妨害波のスキャン方向ｕに走査するためのウェイトベクトルであるため、ウェイトベクトルｗ（ｕ）により形成される妨害波の到来方向ｕに対するヌルもスキャンされる。The evaluation function calculation unit 44 of the null shift estimation unit 11 calculates the weight vector w (u) output from the vector calculation unit 42 and the correlation matrix R _x of the reception signal output from the second correlation matrix calculation unit 43. As shown in the following formula (6), an evaluation function P (u) used for estimation of null shift is calculated (step ST4 in FIG. 6).

W ^H (u) R _x w (u), which is the denominator of Equation (6), is the scanning output power of the beam by the weight vector w (u).
As described above, the weight vector w (u) is a weight vector for scanning the weight vector w (u _s ) in the main beam direction u _s in the interference wave scanning direction u, and thus the weight vector w (u). The null for the direction of arrival u of the jamming wave formed by is also scanned.

Therefore, the weight vector w (u), the scanning direction u is if _{u s} + .delta.u _k, to form a null in the direction of _{^{u 0 (k) + δu k}} .
This null the formation direction _u ^{0 _(k)} + _δu ^k coincides with the arrival direction _u ^{0 _(k)} + _δu ^k of the k-th interference wave contained in the correlation matrix _{R x} of the received signal, ^{w H} _{(u s + δu k) R} x w (u s + δu k) of the k-th included in the interference wave power is minimized.
Therefore, the evaluation function calculating unit 44 the evaluation function P calculated by (u), in the scanning direction u = u s ₊ .delta.u _k, a peak is a function value, .delta.u _k is null and u corresponding to the function value of the peak Candidate for deviation.
Since there are a total of K null-candidate candidates, the candidate having the maximum function value among the K candidates is the null-shift estimated value δu hat. In the text of the specification, for the convenience of electronic application, the symbol “^” cannot be added on the letter, so it is represented as “δu hat”.
The evaluation function calculation unit 44 outputs the calculated evaluation function P (u) to the null deviation estimation processing unit 45.

  The null deviation estimation processing unit 45 of the null deviation estimation unit 11 estimates the null deviation using the evaluation function P (u) output from the evaluation function calculation unit 44, and calculates the compensation value of the estimated null deviation value δu hat. It outputs to the part 12 (step ST5 of FIG. 6).

式（７）において、Ｄ_Δは、差ビーム形成用のテーパを対角項に有する対角行列である。
ｗ（ｕ）は、妨害波の到来方向ｕ及びメインビーム方向ｕ_ｓにヌルを形成するウェイトベクトルである。
メインビーム方向ｕ_ｓにヌルを形成するため、メインビーム方向ｕ_ｓの近傍から到来する目標信号は抑圧され、ｗ^Ｈ（ｕ_ｓ＋δｕ_ｋ）Ｒ_ｘｗ（ｕ_ｓ＋δｕ_ｋ）に含まれている目標信号の電力が低減される。Here, the power of the k-th interference wave is minimized, the power of the interference wave other than the power and the k-th target signal included in the correlation matrix R _x of the received signal is still remaining .
When calculating the estimated value .delta.u hat null ^shift, power _{w H (u s + δu k} ) R x w (u s + δu k) to Including target signal, because it is unnecessary power, advance the target signal Can be reduced, the estimation accuracy of the null shift using the evaluation function P (u) can be improved.
Therefore, the vector calculation unit 42 may calculate the weight vector w (u) for scanning the scanning direction u of the interference wave by the following equation (7) instead of the equation (3).

In Equation (7), _DΔ is a diagonal matrix having a difference beam forming taper in the diagonal terms.
w (u) is a weight vector forming a null in an arrival direction u and the main beam direction u _s jammer.
To form a null in the main beam direction _{u s,} target signal coming from the vicinity of the main beam direction _{u s} is ^suppressed, it is included in _{w H (u s + δu k} ) R x w (u s + δu k) The power of the target signal is reduced.

In the description so far, δu _k = [δu _k , δv _k ] ^T is defined as the difference between the arrival direction of the k-th jamming wave in the listening period and the arrival direction of the k-th jamming wave in the beam transmission period. However, if the difference in deviation due to the K interference waves is so small that it can be ignored, the deviation may be treated as δu = [δu, δv] ^T.
In this case, since the function value indicates a peak in the scan direction u = u _s + δu in the scan direction u = u _s + δu, u corresponding to the peak function value is a candidate for null shift, and the peak function value Δu corresponding to u is the null deviation estimated value δu hat.

式（８）において、ｉ，ｊは行列要素番号であり、ｉ＝１，２，・・・，Ｍ、ｊ＝１，２，・・・，Ｍである。
式（８）では、第ｍ番目のサブアレーアンテナ１−ｍの座標をＰ_ｍ＝［ｘ_ｋ，ｙ_ｋ］^Ｔとし、Δｘ_ｉｊ及びΔｙ_ｉｊは、それぞれ相対座標である。
Δｘ_ｉｊ＝ｘ_ｉ−ｘ_ｊであり、Δｙ_ｉｊ＝ｙ_ｉ−ｙ_ｊである。λは送信波長である。
式（８）では、ＣＭＴ行列Ｔ_ＣＭＴによる設定ヌル幅をΔｕ＝［Δｕ，Δｖ］^Ｔとしている。
ＣＭＴ行列Ｔ_ＣＭＴによる設定ヌル幅Δｕは、ヌルずれの推定値δｕハットに基づいて、以下の式（９）のように決定される。

式（９）において、ｋ_ｕ，ｋ_ｖは、任意の係数であり、ヌルずれの推定値δｕハットと関係なく、ビーム形成で用いるテーパに応じて事前に設定される値である。
ＣＭＴ行列算出部５１は、算出したＣＭＴ行列Ｔ_ＣＭＴを補償型相関行列算出部５３に出力する。When the CMT matrix calculation unit 51 of the compensation weight calculation unit 12 receives the null shift estimation value δu hat output from the null shift estimation processing unit 45 of the null shift estimation unit 11, as shown in the following equation (8): The CMT matrix T _CMT for setting the null width is calculated using the estimated null deviation estimated value δu hat (step ST6 in FIG. 6).

In equation (8), i and j are matrix element numbers, i = 1, 2,..., M, j = 1, 2,.
In Expression (8), the coordinates of the m-th subarray antenna 1-m are P _m = [x _k , y _k ] ^T, and Δx _ij and Δy _ij are relative coordinates, respectively.
Δx _ij = x _i -x _j and Δy _ij = y _i -y _j . λ is a transmission wavelength.
In the equation (8), the set null width by the CMT matrix T _CMT is Δu = [Δu, Δv] ^T.
The set null width Δu based on the CMT matrix T _CMT is determined as shown in the following formula (9) based on the null deviation estimated value δu hat.

In Equation (9), k _u and k _v are arbitrary coefficients, and are values set in advance according to the taper used in beam forming, regardless of the estimated null shift estimated value δu hat.
The CMT matrix calculation unit 51 outputs the calculated CMT matrix T _CMT to the compensation type correlation matrix calculation unit 53.

式（１０）において、二重丸の記号は、ＣＭＴ行列Ｔ_ＣＭＴと妨害波の相関行列Ｒ_０との行列要素同士の乗算を行うアダマール積を示す記号である。
補償型相関行列算出部５３は、算出したヌルずれ補償型相関行列Ｒを補償型ウェイト算出部５４に出力する。The compensation-type correlation matrix calculation unit 53 of the compensation weight calculation unit 12 and the CMT matrix T _CMT output from the CMT matrix calculation unit 51 and the first of the null deviation estimation unit 11 as shown in the following equation (10). A null shift compensation type correlation matrix R is calculated from the interference matrix correlation matrix _R0 output from the correlation matrix calculation unit 41 (step ST7 in FIG. 6).

In Expression (10), a double circle symbol is a symbol indicating a Hadamard product that performs multiplication of matrix elements of the CMT matrix T _CMT and the correlation matrix R ₀ of the interference wave.
The compensation type correlation matrix calculation unit 53 outputs the calculated null shift compensation type correlation matrix R to the compensation type weight calculation unit 54.

式（１１）において、βは規格化係数である。
補償型ウェイト算出部５４は、算出した補償ウェイトベクトルｗ_Ａをビーム形成部１３に出力する。Compensated weight calculator 54 of the compensation weight calculating unit 12 in the beam transmission period after the listening period ends, the weight constraint vector for scanning the main beam direction u _s of the beam transmitted from the array antenna 1 a Get (u _s ).
The compensation weight calculation unit 54 uses the weight constraint vector a (u _s ) and the null deviation compensation type correlation matrix R output from the compensation type correlation matrix calculation unit 53 as shown in the following equation (11). Then, a compensation weight vector w _A indicating a compensation weight for compensating for the null shift is calculated (step ST8 in FIG. 6).

In Expression (11), β is a normalization coefficient.
The compensation weight calculation unit 54 outputs the calculated compensation weight vector w _A to the beam forming unit 13.

When the reception signal vector x (t) during the beam transmission period after the end of the listening period is given, the beam forming unit 13 compensates the reception signal vector x (t) as shown in the following equation (12). _A reception beam y (t) is calculated by multiplying the weight vector w _A and combining the reception signal vector x (t) after the compensation weight multiplication (step ST9 in FIG. 6).

That is, the M multipliers 14-m in the beam forming unit 13 are included in the compensation weight vector w _A in the digital reception signal related to the subarray antenna 1-m included in the reception signal vector x (t). The compensation weight related to the sub-array antenna 1 -m is multiplied, and the digital received signal after the compensation weight multiplication is output to the adder 15.
The adder 15 of the beam forming unit 13 combines the M digital reception signals output from the M multipliers 14-m, and outputs the combined digital reception signal as a reception beam y (t).
Since the reception signal vector x (t) is multiplied by the compensation weight vector w _A , a null having a set null width Δu is formed in the reception beam y (t) with the arrival direction u ₀ of the disturbing wave as the center. ing.

  As apparent from the above, according to the first embodiment, a plurality of signals respectively received by the M subarray antennas 1-m during the listening period and M subarray antennas during the beam transmission period. A null shift estimation unit 11 that estimates a null shift, which is a change between the arrival direction of the interference wave in the listening period and the arrival direction of the interference wave in the beam transmission period, from the plurality of signals respectively received by 1-m; Based on the null shift estimated by the null shift estimation unit 11, the compensation weight calculation unit 12 uses a null coefficient as a weighting factor for a plurality of signals respectively received by the M subarray antennas 1-m during the beam transmission period. Since the compensation weight for compensating for the deviation is calculated, even if the arrival direction of the interference wave changes greatly, the array antenna 1 An effect that can suppress interference waves contained in the signal signal.

Embodiment 2. FIG.
In the first embodiment, the compensation weight calculation unit 12 includes the CMT matrix calculation unit 51, and uses the CMT matrix T _CMT calculated by the CMT matrix calculation unit 51 to provide a compensation weight indicating a compensation weight for compensating for a null shift. An example of calculating the vector w _A is shown.
In the second embodiment, an example will be described in which the compensation weight calculation unit 12 calculates a compensation weight vector w _A indicating a compensation weight for compensating for a null shift without using the CMT matrix _TCMT .

FIG. 7 is a block diagram showing a compensation weight calculation unit 12 of the adaptive array antenna apparatus according to Embodiment 2 of the present invention. In FIG. 7, the same reference numerals as those in FIG.
The weight calculation processing unit 55 includes a compensation type correlation matrix calculation unit 56 and a compensation type weight calculation unit 54.
The compensation-type correlation matrix calculation unit 56 calculates the null shift estimated by the null shift estimation processing unit 45 of the null shift estimation unit 11 and the interference wave calculated by the first correlation matrix calculation unit 41 of the null shift estimation unit 11. A process of calculating a null shift compensation type correlation matrix is performed from the correlation matrix.

Next, the operation will be described.
In the first embodiment, the difference between the arrival direction of the k-th jamming wave in the listening period and the arrival direction of the k-th jamming wave in the beam transmission period is set as δu _k = [δu _k , δv _k ] ^T. Yes.
In the second embodiment, an example will be described in which the difference between K interference waves is assumed to be negligibly small, and the difference is handled as δu = [δu, δv] ^T.

式（１３）において、ｕ_０ ^（ｋ）＋δｕは、ビーム送信期間における第ｋ番目の妨害波の到来方向であり、リスニング期間における第ｋ番目の妨害波の到来方向とずれている。Therefore, in the second embodiment, during the beam transmission period after the listening period ends, the received signal vector x (t) shown in the following equation (13) is converted to the null shift estimation unit 11 and the beam forming unit 13. Given to.

In Expression (13), u ₀ ^(k) + δu is the arrival direction of the kth jamming wave in the beam transmission period, and is shifted from the arrival direction of the kth jamming wave in the listening period.

The second correlation matrix calculation unit 43 of the null shift estimation unit 11 is given the beam transmission as in the first embodiment when the reception signal vector x (t) during the beam transmission period shown in the equation (13) is given. A correlation matrix R _x of the reception signal of the array antenna 1 is calculated from the reception signal vector x (t) during the period.
The second correlation matrix calculation unit 43 outputs the calculated correlation matrix R _x of the received signal to the evaluation function calculation unit 44.

The evaluation function calculation unit 44 of the null shift estimation unit 11 calculates the weight vector w (u) output from the vector calculation unit 42 and the correlation matrix R _x of the reception signal output from the second correlation matrix calculation unit 43. In the same manner as in the first embodiment, the evaluation function P (u) used for estimating the null shift is calculated.
W ^H (u) R _x w (u), which is the denominator of Equation (6), is the scanning output power of the beam by the weight vector w (u).
As described above, the weight vector w (u) is a weight vector for scanning the weight vector w (u _s ) in the main beam direction u _s in the interference wave scanning direction u, and thus the weight vector w (u). The null for the direction of arrival u of the jamming wave formed by is also scanned.

Therefore, the weight vector w (u) forms a null in the direction of u ₀ ^(k) + δu if the scan direction u is u _s + δu.
Since the direction u ₀ ^(k) + δu forming this null coincides with the arrival direction u ₀ ^(k) + δu of the k-th jamming wave included in the correlation matrix R _x of the received signal, w ^H (u _s + _.delta.u) power R x w _{(u s} + _δu k-th interference wave contained in) is minimized.
Therefore, the evaluation function P (u) calculated by the evaluation function calculation unit 44 has a peak function value in the scan direction u = u _s + δu, and δu corresponding to the peak function value is null-shifted. The estimated value is δu hat.
The evaluation function calculation unit 44 outputs the calculated evaluation function P (u) to the null deviation estimation processing unit 45.

  The null deviation estimation processing unit 45 of the null deviation estimation unit 11 estimates the null deviation by using the evaluation function P (u) output from the evaluation function calculation unit 44, as in the first embodiment, and the null deviation. Is output to the compensation weight calculation unit 12.

The compensation-type correlation matrix calculation unit 56 of the compensation weight calculation unit 12 outputs the null shift estimated value δu hat output from the null shift estimation processing unit 45 of the null shift estimation unit 11 and the first correlation matrix calculation unit 41. A null shift compensation type correlation matrix R ₀ ′ is calculated from the correlation matrix R ₀ of the disturbed wave.
The compensation type correlation matrix calculation unit 56 outputs the calculated null shift compensation type correlation matrix R ₀ ′ to the compensation type weight calculation unit 54.

式（１４）において、Ａ_０は、Ｋ個のステアリングベクトルａ_Ｊ（ｕ_０ ^（ｋ））を並べた行列、Ｊはｊ_ｋ（ｔ）の相関行列、σ^２は受信機雑音電力である。
一方、ビーム送信期間中の妨害波の相関行列Ｒ_０’は、以下の式（１５）のように表すことができる。ビーム送信期間中の妨害波の相関行列Ｒ_０’は、ヌルずれ補償型相関行列に相当する。

式（１５）において、Ａ_０’は、Ｋ個のステアリングベクトルａ_Ｊ（ｕ_０ ^（ｋ）＋δｕ）を並べた行列である。Here, the interference matrix correlation matrix R ₀ calculated by the first correlation matrix calculator 41 can be expressed as the following Expression (14).

In Expression (14), A ₀ is a matrix in which K steering vectors a _J (u ₀ ^(k) ) are arranged, J is a correlation matrix of j _k (t), and σ ² is receiver noise power.
On the other hand, the interference matrix R ₀ ′ of the interference wave during the beam transmission period can be expressed as the following equation (15). The interference matrix correlation matrix R ₀ ′ during the beam transmission period corresponds to a null shift compensation correlation matrix.

In Expression (15), A ₀ ′ is a matrix in which K steering vectors a _J (u ₀ ^(k) + δu) are arranged.

よって、式（１５）は、以下の式（１７）のように表すことができる。

式（１７）の関係より、ヌルずれの推定値δｕハットと、妨害波の相関行列Ｒ_０とから、ヌルずれ補償型相関行列として、以下の式（１８）のようにＲ_０’を算出することができる。

At this time, if a diagonal matrix having a path difference phase component due to the deviation δu in the diagonal term is D (δu), the following equation (16) is established.

Therefore, Expression (15) can be expressed as the following Expression (17).

From the relationship of the equation (17), R ₀ ′ is calculated as a null displacement compensation type correlation matrix from the null displacement estimation value δu hat and the interference matrix correlation matrix R ₀ as in the following equation (18). be able to.

補償型ウェイト算出部５４は、算出した補償ウェイトベクトルｗ_Ａをビーム形成部１３に出力する。Compensated weight calculator 54 of the compensation weight calculating unit 12 in the beam transmission period after the listening period ends, the weight constraint vector for scanning the main beam direction u _s of the beam transmitted from the array antenna 1 a Get (u _s ).
The compensation weight calculation unit 54 calculates the weight constraint vector a (u _s ) and the null deviation compensation correlation matrix R ₀ ′ output from the compensation correlation matrix calculation unit 53 as shown in the following equation (19). Using this, a compensation weight vector w _A indicating a compensation weight for compensating for the null shift is calculated.

The compensation weight calculation unit 54 outputs the calculated compensation weight vector w _A to the beam forming unit 13.

When the reception signal vector x (t) during the beam transmission period after the end of the listening period is given, the beam forming unit 13 adds the compensation weight vector to the reception signal vector x (t) as in the first embodiment. The reception beam y (t) is calculated by multiplying w _A and synthesizing the reception signal vector x (t) after the compensation weight multiplication.
Since the reception signal vector x (t) is multiplied by the compensation weight vector w _A , a null having a set null width Δu is formed in the reception beam y (t) with the arrival direction u ₀ of the disturbing wave as the center. ing.

  As is apparent from the above, according to the second embodiment, as in the first embodiment, even if the arrival direction of the disturbing wave changes greatly, the disturbing wave included in the received signal of the array antenna 1 There is an effect that can be suppressed.

  In the present invention, within the scope of the invention, any combination of the embodiments, or any modification of any component in each embodiment, or omission of any component in each embodiment is possible. .

  The present invention is suitable for an adaptive array antenna apparatus that multiplies a plurality of signals received by a plurality of subarray antennas by a weighting factor and synthesizes the plurality of signals after the weighting factor multiplication.

  1 array antenna, 1-1 to 1-M subarray antenna, 2 signal processing device, 11 null shift estimation unit, 12 compensation weight calculation unit, 13 beam forming unit, 14-1 to 14-M multiplier, 15 adder, 21 Null shift estimation circuit, 22 Compensation weight calculation circuit, 23 Beam forming circuit, 31 Memory, 32 Processor, 41 First correlation matrix calculation unit, 42 Vector calculation unit, 43 Second correlation matrix calculation unit, 44 Evaluation function calculation , 51 CMT matrix calculation unit, 52 weight calculation processing unit, 53 compensation type correlation matrix calculation unit, 54 compensation type weight calculation unit, 55 weight calculation processing unit, 56 compensation type correlation matrix calculation unit.

Claims (5)

An array antenna in which a plurality of subarray antennas including one or more element antennas are arranged;
During a listening period in which no beam is transmitted from the array antenna, a plurality of signals respectively received by the plurality of subarray antennas and a beam transmission in which the beam after the listening period is transmitted are transmitted. During the period, a null shift that is a change between the arrival direction of the interference wave in the listening period and the arrival direction of the interference wave in the beam transmission period is estimated from the plurality of signals respectively received by the plurality of subarray antennas. A null shift estimation unit;
Based on the null shift estimated by the null shift estimation unit, a compensation weight that compensates for the null shift is calculated as a weighting factor for a plurality of signals respectively received by the plurality of subarray antennas during the beam transmission period. A compensation weight calculation unit for
A beam forming unit that multiplies a plurality of signals respectively received by the plurality of sub-array antennas during the beam transmission period by a compensation weight calculated by the compensation weight calculation unit, and combines the plurality of signals after the compensation weight multiplication. And an adaptive array antenna device. The null shift estimator is
A first correlation matrix calculation unit for calculating a correlation matrix of the jamming wave from a plurality of signals respectively received by the plurality of subarray antennas during the listening period;
The weight for scanning the scanning direction of the interference wave using the weight constraint vector for scanning the main beam direction of the beam and the correlation matrix of the interference wave calculated by the first correlation matrix calculation unit. A vector calculation unit for calculating a vector;
A second correlation matrix calculation unit for calculating a correlation matrix of a received signal of the array antenna from a plurality of signals respectively received by the plurality of sub-array antennas during the beam transmission period;
An evaluation function calculation unit that calculates an evaluation function used for estimation of the null using the weight vector calculated by the vector calculation unit and the correlation matrix of the received signal calculated by the second correlation matrix calculation unit; ,
The adaptive array antenna apparatus according to claim 1, further comprising: a null shift estimation processing unit that estimates the null shift using the evaluation function calculated by the evaluation function calculation unit.   The vector calculation unit is calculated by a diagonal matrix having a path difference phase component due to a difference between the main beam direction and the scan direction in a diagonal term, the weight constraint vector, and the first correlation matrix calculation unit. The adaptive array antenna apparatus according to claim 2, wherein the weight vector is calculated by multiplying a correlation matrix of an interference wave. The compensation weight calculation unit
A CMT matrix calculating unit that calculates a CMT matrix that is a matrix for setting a null width from the null shift estimated by the null shift estimation processing unit;
A weight calculation processing unit that calculates a compensation weight for compensating for the null shift from the CMT matrix calculated by the CMT matrix calculation unit and the interference matrix of the interference wave calculated by the first correlation matrix calculation unit; The adaptive array antenna apparatus according to claim 2, wherein: The compensation weight calculation unit
A weight for calculating a compensation weight for compensating the null shift from the null shift estimated by the null shift estimation processing unit, the correlation matrix of the interference wave calculated by the first correlation matrix calculation unit, and the weight constraint vector. The adaptive array antenna apparatus according to claim 2, further comprising a calculation processing unit.

Images