JPH10200320A - Antenna system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To combine the control channel of a difference beam and the control channel of a sum beam at the time of suppressing an unnecessary signal inputted to an array antenna. SOLUTION: An unnecessary signal included in each output of the main beam forming circuits 51 and 52 can be suppressed by an adaptive beam forming circuit 70 by using sum beams Σ<1> -ΣM and difference beams Δ<1> -ΔM synthesized by analog beam forming circuits 21-2M and combining control channels b11-bL1 of the sum beams and control channels b12-bL2 of the difference beams. Moreover, the adapter beam forming circuit 70 limits the control channels b11-bL1 of the sum beams so that the main beam pattern can not be disturbed due to adaptation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna device for automatically suppressing unnecessary signals input to an array antenna.

[0002]

2. Description of the Related Art A conventional antenna which performs one-dimensional digital beam forming (hereinafter referred to as DBF) synthesizes a signal in one of an azimuth direction and an elevation direction among the outputs of respective radiating elements, and synthesizes the analog output. After performing the frequency conversion and the digital conversion, the digital beam is formed.

[0003] Fig. 10 shows the configuration, in which the elevation angle outputs of the antenna elements 11 to MN are analog-combined by analog beam-forming circuits 21 to 2M. At this time, in the analog beam forming circuits 21 to 2M, a monopulse beam is obtained by dividing the opening into two vertically and taking the sum and difference of the respective analog combined outputs using a hybrid circuit which is a part of the analog beam forming circuits 21 to 2M. Sum beam used in Σ
¹ and ～Shiguma ^M and difference beams Δ ¹ ~Δ ^M is obtained.

[0004] The sum beam Σ ¹ ~Σ ^M output and the difference beam Δ ¹ ~
Delta ^M output is frequency converted by the frequency converter 31 and 32, (hereinafter referred to as A / D) analog / digital
After being converted into digital signals by the converters 41 and 42, digital beams are formed by the main beam forming circuits 51 and 52. The main beam forming circuit 51 divides the aperture into two in the azimuth direction, calculates the sum and difference of the sum beams Σ ^{1 to} Σ ^M in the elevation direction, and obtains the sum beam Σ and the azimuth beam ΔAZ.
2, to obtain the elevation beam ΔEL by adding the difference beam Δ ¹ ~Δ ^M elevation direction in the azimuth direction.

In the antenna apparatus of the one-dimensional DBF system, in order to suppress unnecessary waves included in the main beam forming circuits 51 and 52, for example, digital sum beams and difference beams of A / D converters 41 and 42 are used. There is a method of suppressing unnecessary waves by using one of them as a control channel and using a preprocessor circuit and a cancellation circuit provided in the adaptive beam forming circuit 70 (see Japanese Patent Application No. 63-190080). Here, the preprocessor circuit has a function of decomposing a plurality of unnecessary signal components included in the control channel, and the cancellation circuit has a function of suppressing the unnecessary signal components included in the beam output using the decomposed unnecessary signal components.

Hereinafter, a method for suppressing unnecessary waves will be described with reference to FIGS. First, sum beam Σ ¹
A case where 説明^M is a control channel will be described.
FIG. 11 shows patterns of sum beams Σ ^{1 to} Σ ^M ,
Now, consider a case where an unnecessary wave arrives from the direction shown in FIG. In this case, the null of the antenna is formed in the unnecessary wave direction by performing the adaptation. However, since the adaptation is performed using the control channel arranged one-dimensionally in the azimuth direction, the cone corresponding to the one-dimensional axis is formed. A null is formed. Therefore, the unnecessary wave can be suppressed, but the main beam cannot be formed in the direction of the conical null other than the unnecessary wave direction. This imposes restrictions on the main beam forming direction, which is not preferable for a radar system, for example.

[0007] Next, the case where the control channel a difference beam Δ ¹ ~Δ ^M. FIG. 13 shows the difference beam Δ ¹
Shows the pattern of ~Δ ^M, consider the case where unnecessary wave arriving from a direction shown in FIG. 14. In this case, even if the adaptation is performed, the main beam is not affected because the control channel having no response in the main beam direction is used. However, since the difference beam is used as the control channel, it cannot be suppressed if an unnecessary wave arrives from the null direction of the difference beam.

[0008]

As described above, in the conventional one-dimensional DBF type antenna apparatus, either the sum beam or the difference beam is used as a control channel. There has been a problem of restricting the suppression direction.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a DBF antenna apparatus which does not restrict the main beam forming direction and the unnecessary wave suppressing direction.

[0010]

According to the present invention, an output signal of a plurality of antenna elements and an output signal of an antenna element arranged in a first direction among the plurality of antenna elements are analog-combined, and a first sum beam is formed. A plurality of analog beam forming means for forming a first difference beam; a plurality of converting means for converting analog signals from the plurality of analog beam forming means into digital signals directly or after frequency conversion, respectively; And a main beam forming means for receiving a digital signal from the converting means and obtaining a second sum beam and a second difference beam by digital beam forming, wherein the first sum beam and the first Combination of difference beams to suppress unnecessary signal components included in each output of the main beam forming means as a control channel There, the null direction of the first difference beam, those having an unnecessary signal suppression means for suppressing unwanted signal components by using a control signal forming the amplitude-limited sum beam.

According to the above means, first, by using the difference beam in the azimuth direction or the elevation direction as a control channel, unnecessary waves arriving from other than the null direction of the channel can be suppressed, and the main beam can be suppressed. No constraints on direction. Unwanted waves arriving from the null direction of the difference beam in the azimuth or elevation direction can be suppressed by the control channel of the sum beam in the azimuth or elevation direction. Here, a limiter is applied to the sum beam in the azimuth direction or the elevation direction in the control channel, and since the sum beam hardly contributes, the disturbance of the main beam is small.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. However, in FIG. 1, the same parts as those in the configuration diagram shown in FIG. The signals input to the antenna elements 11 to MN shown in FIG. 1 are combined in the elevation direction by the analog beam forming circuits 21 to 2M. Analog beam forming circuits 21 and 2
M sum beam outputs Σ ^{1 to} Σ ^M and difference beam outputs Δ ^{1 to} Δ
^{The M} high-frequency signal (RF signal) is directly or after being converted into an intermediate frequency signal (IF signal) by the frequency converters 31 and 32, respectively, and then converted by the A / D converters 41 and 42 into the I signal (in-phase component). It is converted into a digital signal of a Q signal (quadrature component). The digital signal of each channel is
These are input to the main beam forming circuits 51 and 52, respectively.

The main beam forming circuits 51 and 52 are generally configured as shown in FIG. 2, and the main beam forming circuit 51 will be described below as a representative. The input digital sum beams Σ ^{1 to} Σ ^M are given a desired delay by the delay circuits 511 having sequentially different delay times, and then the operation cells A
(51211-512M1) as well as to arithmetic cell A (51212-512M2). As shown in FIG. 3, the operation cell A (51211 to 512M2) includes a multiplier A1 and an adder A2, and performs the following operation. Yout = Yin + W.Xin W; amplitude, phase weight (complex weight) That is, the element input Xin is multiplied by the complex weight W, and the signal Yin from the adjacent cell is added to obtain the output Yout. The operation cells A (51211 to 512M2) are connected in a systolic array, so that a main beam output is obtained from one end. At this time, the main beam forming circuit 51 divides the aperture into two in the azimuth direction and divides the sum beam in the elevation direction by 方向.
By taking the sum and difference of ^{1 ~Σ M,} beamsum output Σ and the beam orientation output ΔAZ is obtained. Further, the main beam-forming circuit 52, the elevation angle output ΔEL is obtained by adding the difference beam Δ ¹ ~Δ ^M elevation direction in the azimuth direction.

Further, in order to suppress unnecessary waves, each channel signal of the A / D converters 41 and 42 is used as a control channel. Here, the sum beams Σ ¹ -Σ of the A / D converter 41.
^M is b11 to bL1 (1 ≦ L ≦ M), and the A / D converter 4
The second difference beam Δ ¹ ~Δ ^M and B12～bL2. Some or all signals of the control channels b11 to bL2 are input to the adaptive beam forming circuit 70.

FIG. 4 shows the internal structure of the adaptive beam forming circuit 70, in which control channels b11-bL2
Are input to the preprocessor circuit 710, and the timings are sequentially adjusted by the delay circuits 711 having different delay times, and then the following operations are performed in the operation cells B (7121 to 712L) and the operation cells C (71321 to 713L (L-1)). Is performed.

Arithmetic cell B Yout1 = Xin Yout2 = Xin ^* / | Xin | Arithmetic cell C W (n) = a.W (n-1) + g.Xout (n) .Yin2 Xout (n) = Xin (n-) 1) -Yin1 (n-1) .W (n-1) a; constant n; sampling time *; complex conjugate g; constant As shown in FIG. The element input Xin is used as an output Yout1 and the element input Xin is used as an output Youu via a normalization unit B1 and a complex conjugate unit B2 in series.
Let it be t2.

As shown in FIG. 6, the operation cell C includes a multiplier C3, an adder C4, a sample delay unit C5, a coefficient unit C6,
The coefficient C7 and the limiter C8 are used to determine the complex weight W (n) of the current sample, and the multiplier C2 outputs the output Yout1 (n-1) one sample earlier and the complex weight W (n-1) one sample earlier. , And this is subtracted by the subtractor C1 into 1
Output X subtracted from element input Xin (n-1) before sample
out (n).

That is, the operation cell B normalizes the input power, and the operation cell C removes a signal component having a correlation with Yin among components of the input Xin. When these operation cells B and C are connected in the form of a systolic array as shown in the preprocessor circuit 710 of FIG. 4, the same output as that obtained when the input signal is decomposed using Gram-Schmidt orthogonalization is provided at each stage. can get. Moreover, since the normalization is performed, the magnitudes of the decomposed signals are all the same. These decomposed signals are input to the cancellation circuit 720 shown in FIG.

The decomposed signals are sequentially input to operation cells C (72212 to 7223L) connected in a systolic array via delay circuits 721 having different delay times. The cancellation circuit 720 includes the main beam forming circuit 5.
An unnecessary signal included in each of the outputs 1 and 52 is suppressed using the decomposition signal of the preprocessor circuit 710. That is, the sum beam Σ, the azimuth beam ΔAZ, and the elevation beam ΔEL of the main beam forming circuits 51 and 52 are input to the respective columns, and components having high power among these beam outputs are sequentially removed. As a result, a beam output having undergone the adaptation is obtained in the last-stage operation cell C.

Here, when suppressing unnecessary waves, first, adaptation is performed using the difference beam as a control channel. However, in this case, the unnecessary wave arriving from the null direction of the difference beam cannot be suppressed. Therefore, in this direction, the adaptation using the sum beam as the control channel is performed.
That is, as shown in FIG. 7, the control channel b of the difference beam
At the null point of 12 to bL2, the control channel b of the sum beam
Responses of 11 to bL1 are high. By utilizing this fact, unnecessary waves arriving from the null direction of the difference beam can be suppressed.

Here, in the control channel of the sum beam,
The limiter C8 provided in the operation cell C of the adaptive beam forming circuit 70 limits the complex weight W so that the adaptation does not disturb the main beam pattern. The limit value of the limiter C8 may be selected so as to suppress the side lobe on the null plane of the control channel of the difference beam. Therefore, it is possible to satisfactorily receive a desired signal and suppress unnecessary signals.

When the side lobe of the difference beam is low, only the control channel of the difference beam has a wide beam width.
For example, if a differential beam pattern having a Taylor distribution is used, the method of the present invention can be applied without impairing the low side lobe characteristics of the entire differential beam.

As the configuration of the adaptive beam forming circuit 70, the case of the open loop system using the preprocessor circuit 710 and the cancellation circuit 720 has been described, but the present invention can also be applied to the case of the closed loop system or the like.

FIG. 8 shows the configuration, which is of a closed loop type using a cancellation circuit 720. Each of the control channels b11 to bL2 is input to multipliers C2 and C3 constituting the operation cell C of the corresponding cancellation circuit 720, and the operation is performed. After the outputs of the multipliers C2 are added by the adder C9, the outputs of the subtractors C1
Is subtracted from the sum beam で to obtain an adaptive beam Σ. Hereinafter, the adaptive beams ΔAZ and ΔEL are obtained in a similar manner.

Although the case of a single beam has been described above, the present invention can also be applied to multi-beam formation as shown in FIG. 9, the same components as those in the configuration diagram also shown in FIG. 1 are denoted by the same reference numerals, and the description thereof will be omitted. This configuration is shown in FIG.
And the other configurations are exactly the same.

Although the present invention has been described with respect to the case where analog beam formation is performed in the elevation direction and DBF is performed in the azimuth direction, analog beam formation is performed in the azimuth direction and D is performed in the elevation direction.
Of course, it can be applied to the case where BF is performed. Also, the sum beam Σ, the azimuth beam ΔAZ and the elevation beam ΔE
Although the case where the L monopulse beam is formed has been described, the same method can be applied to the case where only the sum beam Σ is formed.

[0027]

As described above, according to the present invention, it is possible to provide a one-dimensional DBF antenna apparatus which does not restrict the main beam forming direction and the unnecessary wave suppressing direction.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a one-dimensional DBF type antenna device according to the present invention.

FIG. 2 is a configuration diagram when the main beam forming circuit shown in FIG. 1 is realized by a systolic array method.

3 is an arithmetic cell A of the main beam forming circuit shown in FIG.
The block diagram which shows the specific example of.

FIG. 4 is a configuration diagram in a case where the adaptive beam forming circuit shown in FIG. 1 is realized by a systolic array method.

5 is a configuration diagram showing a specific example of an operation cell B of the adaptive beam forming circuit shown in FIG.

FIG. 6 is a configuration diagram showing a specific example of an arithmetic cell C of the adaptive beam forming circuit shown in FIG. 4;

FIG. 7 is a diagram showing an antenna pattern of a control channel.

FIG. 8 is a configuration diagram showing an embodiment when the adaptive beam forming circuit shown in FIG. 1 is realized by a systolic array method.

FIG. 9 is a configuration diagram when the present invention is applied to multi-beam formation.

FIG. 10 is a configuration diagram showing a conventional one-dimensional DBF antenna device.

FIG. 11 is a diagram illustrating an antenna pattern of a control channel of a sum beam.

FIG. 12 is a diagram for explaining a problem when a sum beam is used as a control channel.

FIG. 13 is a diagram showing an antenna pattern of a difference beam control channel.

FIG. 14 is a diagram for explaining a problem when a difference beam is used as a control channel.

[Description of Signs] 11 to MN: antenna elements, 21 to 2M: analog beam forming circuits, 31, 32: frequency converters, 41, 42 ...
A / D converters, 51, 52 ... main beam forming circuit, 70 ...
Adaptive beam forming circuit, Σ ^{1 to} Σ ^M … sum beam,
Δ ¹ ~Δ ^M ... difference beam, b11~bL2 ... control channel, sigma ... sum beam, .DELTA.AZ ... azimuth beam, .DELTA.EL ... elevation beam, 51211~512M2 ... arithmetic cells A, A1 ...
Multiplier, A2: Adder, B1: Normalizing unit, B2: Complex conjugate unit, 511, 711: Delay circuit, 710: Preprocessor circuit, 720: Cancellation circuit, 712
1 to 712L ... Calculation cell B, 71321 to 713L (L
-1) Operation cells C, C1 Subtractor, C2 Multiplier, C
3 Multiplier, C4 Adder, C5 Sample delayer, C
6: coefficient unit, C7: coefficient unit, C8: limiter, C9: adder.

Claims (2)

[Claims] An analog signal is output from a plurality of antenna elements and an output signal of an antenna element arranged in a first direction among the plurality of antenna elements to form a first sum beam and a first difference beam, respectively. A plurality of analog beam forming means, a plurality of converting means for converting the analog signals from the plurality of analog beam forming means into digital signals directly or after frequency conversion, and a digital signal from the plurality of converting means. An antenna apparatus provided with main beam forming means for obtaining a second sum beam and a second difference beam by digital beam forming, wherein the first sum beam and the first difference beam are combined as a control channel. This is for suppressing unnecessary signal components contained in each output of the main beam forming means.
An unnecessary signal suppressing unit that suppresses an unnecessary signal component by using a control signal that forms a sum beam whose amplitude is limited in a null direction of a difference beam of the antenna device. 2. The control channel of the first sum beam, wherein when the side lobe of the difference beam is low, only the control channel of the difference beam has a wide beam width when the side lobe of the difference beam is low. The antenna device according to claim 1, wherein the antenna device is combined with: