JPH047121B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD OF THE INVENTION The present invention relates to an adaptive antenna device capable of obtaining adaptive multi-beam antenna output. Technical Background of the Invention and Problems There are many advantages to an adaptive antenna system that receives only desired signals by directing the antenna beam in a desired signal direction. Additionally, a multi-beam antenna system that directs antenna beams in multiple directions simultaneously has great advantages. However, an adaptive multi-beam antenna that combines both of these advantages has conventionally been constructed by simply providing the required number of adaptive antennas independently, resulting in a fairly large antenna system, which poses practical problems. It was hot. Now, a typical conventional adaptive multi-beam antenna is, for example, as shown in Figure 1.
It is composed of a multi-beam adaptive antenna based on the MSN (Maximum Signal to Noise ratio) algorithm. That is, the antenna outputs of the N antenna elements 1 ₁ , 1 ₂ to 1 _N are distributed and outputted by the distributors 2 ₁ and 2 ₂ to 2 _N in correspondence to the required number M of multi-beams, and these are multi-beamed. The antenna beam characteristics are applied to adaptive circuits 3 ₁ , 3 ₂ to 3 _M corresponding to the number M of beams, respectively, to obtain antenna beam characteristics directed in a desired direction. However, in this case, each adaptive circuit 3 ₁ , 3 ₂ to 3
The number of variable load circuits constituting _M is N each, and a very large number of N×M variable load circuits are required overall. For this reason, the scale of the device becomes extremely large, which poses a practical problem. In addition, in the antenna device configured in this way, a condition for adaptive operation is that there is no unnecessary signal that has a strong correlation with the desired signal. Therefore, in a normal adaptive antenna system, it can be thought that the correlation between the desired signal and the unnecessary signal is generally small, but in a system using multi-beams, it goes without saying that the correlation between the desired signal and the unnecessary signal is small. Since other strong signals exist simultaneously in many directions, it is necessary to take this point into account. In this case, the output of each antenna element 1 ₁ , 1 ₂ to 1 _N is the sum of these highly correlated signals, that is, a coherent sum,
As a result, a problem arises in that the direction of antenna beam orientation deviates from the direction of the desired signal. In other words, in the adaptive antenna system based on the MSN algorithm, although it is necessary to accurately capture the desired signal direction, accurate adaptive operation cannot be expected due to the above-mentioned situation. As described above, the antenna device having the configuration shown in FIG. 1 has a problem in compatibility with the adaptive antenna system and the multi-beam antenna system. Conventionally, in order to solve such problems,
For example, a multi-beam antenna device using a subarray configured as shown in FIG. 2 has been considered.
This device has antenna elements 1 ₁ , 1 ₂ to 1 _N
The synthesizer 4 ₁ , 4 ₂ ~
4 _L , thereby realizing a sub-array. The combiners 4 ₁ , 4 ₂ to 4 _L are called beam formers, and combine the grouped antenna elements to form one antenna. Then, these antenna outputs (synthesizer outputs) are distributed by distributors 2 ₁ , _{2 2} to 2 _L and supplied to adaptive circuits 3 ₁ , 3 ₂ to 3 _M. With this configuration, the required number of variable load circuits to realize the adaptive circuits 3 ₁ , 3 ₂ to 3 _M is L×M when the number of groupings, that is, the number of subarrays is L. Therefore, the circuit scale can be made smaller than that of the device having the configuration shown in FIG. Furthermore, by appropriately arranging the subarrays in consideration of the pattern of the subarrays, compatibility between the adaptive antenna system and the multibeam antenna system can be solved to some extent. However, it is extremely difficult to construct a subarray pattern that takes the multi-beam system into consideration, and no reports regarding this have been disclosed so far. That is, when configuring the above subarray pattern, (a) it is possible to generate multi-beams in a desired direction by the subarray output when no unnecessary signals are present, and (b) an adaptive antenna is used. It is necessary to satisfy all of the following specifications: (c) the operating characteristics as an adaptive antenna should be sufficiently high; However, the reality is that no reports have been made on how to construct an antenna that satisfies these specifications. Purpose of the Invention The present invention has been made in consideration of the above circumstances, and its purpose is to provide a highly practical, small-scale structure capable of simultaneously satisfying an adaptive antenna system and a multi-beam antenna system. An object of the present invention is to provide an adaptive antenna device. SUMMARY OF THE INVENTION The present invention has a configuration in which the outputs of a plurality of antenna elements are mixed and distributed by a mixer/distributor configured using a hybrid coupler block and supplied to an adaptive circuit. By effectively utilizing the Butler matrix, which is the internal configuration of the plug block, an adaptive antenna system and a multi-beam antenna system can be realized at the same time by equivalently extracting the distributed output of the hybrid plug block as a subarray output. This is what I did. Effects of the Invention Therefore, according to the present invention, it is possible to effectively utilize the mixing and distribution effect of the antenna output by the hybrid coupler block, so that the configuration size can be significantly increased while maintaining performance substantially equivalent to that of a so-called full adaptive antenna. It is possible to realize an adaptive antenna device with adaptive multi-beam characteristics reduced in size. Furthermore, by selecting a hybrid coupler block and selecting an adaptive variable load, it is possible to form an adaptive multi-beam in the entire space. Furthermore, it has great effects such as being able to accurately direct each multi-beam in a desired direction. Embodiment of the Invention Hereinafter, an embodiment of an adaptive antenna device according to the present invention will be described with reference to the drawings. FIG. 3 is a schematic configuration diagram of the embodiment device, and 11 in the figure.
₁ , 11 ₂ to 11 _N are N antenna elements (N is an integer of N>3). In addition, here, the above antenna element is assumed to be a receiving antenna,
The signal receiving system will be explained. Further, the following description will be made assuming that the number N of the antenna elements is 8. 8 antenna elements 11 ₁ , 11 ₂ to 11
Each of the ₈ outputs x ₁ , x ₂ to _{x 8} has N=8 input terminals and N=8 input terminals configured using a hybrid coupler.
The signal is mixed and distributed into N=8 distribution outputs via a mixing/distributing device 12 having eight output terminals, and is supplied to first to third adaptive circuits 13, 14, and 15. The mixing/distributing device 12 mixes and distributes the outputs of the antenna elements 11 ₁ , 11 ₂ to 11 ₈ to obtain eight distributed outputs. The next stage hybrid coupler block 1 inputs the 4 outputs of one of the grouped outputs and further mixes and distributes the signals.
7, and this hybrid cutlet block 1
a phase shifter 18 for shifting the phase of the distributed output from the first-stage hybrid coupler block 16 supplied to
a, 18b to 18d. These hybrid coupler blocks 16, 17 form a Butler matrix. And the first stage hybrid cutlet block 16
x 0,j = 1/2 (x _j +x _j + _{4 ) x 1,j = 1/2 for each output x 1 , x 2 - x 8 of antenna elements 11 1 ,} 11 ₂ - 11 8 The output is (x _j −x _j+4 ) j=1, 2, 3, 4. These outputs are x _0,j (j=
1, 2, 3, 4) into the first group, that is, the first
is supplied to the first adaptive circuit 13 as a subarray output. In addition, the remaining output _1,j (j=1,
2, 3, and 4) are given a predetermined phase rotation via phase shifters 18a to 18d, and then supplied to the hybrid coupler block 17 at the next stage. In this hybrid cutlet block 17, the above
It forms a Butler matrix that mixes and distributes x _1,j (j = 1, 2, 3, 4), x _10,j = 1/2 (x _1,j + x _1,j+2 ) x _{11 ,j} = 1/2 (x _1,j −x _1,j+2 ) j=1, 2, 3, 4 is obtained. Then, the above output x _10,j (j=1,
2, 3, 4) are the second sub-array outputs.
is supplied to the adaptive circuit 14 of
x _11,j (j=1, 2, 3, 4) is supplied to the third adaptive circuit 15 as a third subarray output. That is, the subarray output is obtained as the output of the hybrid coupler blocks 16 and 17 constituting the mixer/distributor 12.
The fact that this subarray output is well suited for the purpose of making it adaptive will be described later. Thus, as described above, the subarrays and their sets, ie, the adaptive circuits 13, 14, 1
Once the set of inputs for 5 is determined, adaptation processing using these subarray outputs is easily realized in each adaptive circuit 13, 14, 15. FIG. 4 is a diagram showing an example of the configuration of the adaptive circuits 13, 14, 15, in which 21 ₁ to 21 _k are loaders consisting of multipliers, etc., and 22 is a beam combiner.
The loaders 21 ₁ to 21 _k receive subarray outputs x _0,j (j=1, 2, 3, 4) or x _10,j , x _11,j supplied from the hybrid coupler blocks 16 and 17. A predetermined load is applied to each. Then, the sub-array outputs _0,j , _10,j , subjected to load processing via these loaders 21 ₁ to 21 _k
x _11,j is supplied to the beam combiner 22 to obtain an adaptive output having desired directivity. The adaptive variable weight values (weights) given to the loaders 21 ₁ to 21 _k are obtained by applying the correlation values between the subarray output and the beam composite output obtained by the correlators 23 ₁ to 23 _k to the integrator 24 .
₁ to 24 _k , and the integrated value is added to the adder 25 ₁
~ _25k supplying the steering signal generator 26
is generated by adding it to the steering signal given by. Adaptive circuits configured in this manner are well known and are introduced in detail in, for example, SP Applebaum "Adaptive Arrays" IEEE Trans. vol. AP-24 No. 5 Sep. 1976. Thus, according to the antenna device configured as described above, the antenna output is mixed and distributed using the hybrid coupler block to obtain the distributed output, so the distributed output is obtained by the Butler matrix forming the hybrid coupler block. can be equivalently used as the subarray output.
Therefore, an adaptive variable load can be applied individually to each subarray output to obtain an adaptive output. Moreover, each adaptive circuit 13, 14,
The antenna element viewed from 15 through the hybrid coupler block forms a beam in a pointing direction corresponding to each adaptive circuit 13, 14, 15. Therefore, the function as a multi-beam antenna is also fully fulfilled. Furthermore, since each of the adaptive circuits 13, 14, and 15 operates independently, a sufficient adaptive effect can be achieved. Therefore, problems such as compatibility between the conventional adaptive antenna system and the multi-beam antenna system are not caused. Further, as shown in the embodiment, the number of adaptive variable load circuits constituting the adaptive circuits 13, 14, 15 is the number of distributed outputs,
In other words, since only 8 pieces need to be used here, it is possible to significantly reduce the size of the configuration.
The practical advantages are therefore considerable. FIG. 5 shows the performance SIR (Signal to Interference) of the adaptive antenna formed by the hybrid coupler blocks at each stage of the mixing/distributing device 12.
Ratio) is expressed relatively within a range that does not exceed the degree of freedom for suppressing interference signals, and the horizontal axis indicates the number of stages in the hybrid coupler block. The following table shows the basic performance of this antenna device as an adaptive multi-beam antenna.

[Table] However, the above number of multi-beams indicates the case when the apparatus is configured without using the distributor 2. Naturally, when the distributor 2 is used, such restrictions are no longer present. As described above, according to the adaptive antenna device according to the present invention, adaptive multi-beams can be easily and precisely formed in the entire space of the antenna surface by selecting a hybrid coupler block and selecting a steering signal. can do. Furthermore, as is clear from the embodiment shown in FIG. 3, when all the beams N that can be formed by k stages of hybrid coupler blocks are made adaptive, the number of variable load circuits is N.M/2 ^k Therefore, the circuit configuration scale is 1/2 ^k compared to the conventional device shown in FIG. In other words, the configuration scale can be significantly simplified. In this case, the degree of freedom for suppressing interference signals is 2 ^Mk -1 for each beam, but this function is sufficient if the degree of freedom is set to about 1 to 10, so this is not a problem at all in practice. No. Moreover,
SIR performance only shows gradual deterioration as the number of stages in the hybrid coupler block increases, so if k is set within the degree of freedom for suppressing interference signals, sufficient practical SIR performance can be ensured. It becomes possible to do so. Therefore, it is possible to realize a multi-beam antenna having substantially the same performance as a fully adaptive antenna while greatly simplifying the configuration scale. In addition, the subarray pattern in each stage of the hybrid coupler block in the antenna device having the above structure has 2 ^Mk grating lobes as shown in FIG. 6a. Furthermore, this antenna pattern is the same at each stage. Therefore, the final beam output obtained by combining these is:
This is the weighted sum of the steering signals of the antenna pattern, and one of the grating lobes is selected as shown in FIG. 6b. The selected grating globe has a spatial resolution (beam width) corresponding to approximately half the aperture length of the antenna element. Therefore, it is possible to sufficiently attenuate signal components in directions other than those in which steering is possible. This means that even if there is an unnecessary signal that has a strong correlation with the desired signal in a direction other than the desired direction and the steerable direction, loss of the desired signal can be avoided. Therefore, it becomes possible to employ an adaptive antenna in a multi-beam system, thereby making the multi-beam adaptive. Furthermore, the amplitude patterns of the subarrays at each stage of the hybrid coupler block are all the same. Therefore, since the interference signal can be obtained from all subarray outputs, the degree of freedom for suppressing interference signals does not decrease. Incidentally, if the amplitude patterns of each stage are different, the interference signal will enter the null point in a certain subarray. in this case,
Since this sub-array becomes adaptively irrelevant, the degrees of freedom are reduced. Therefore, it becomes possible to sufficiently adapt each of the multi-beams. Therefore, as described above, an adaptive antenna device with extremely great practical advantages can be provided here. Note that the present invention is not limited to the above-described embodiments. In the embodiment, a 4-port coupler was used as the first-stage hybrid coupler block, but generally a ^2n- port (n: natural number) coupler can be used. For example, when using a coupler with n=3, and with N= ^3M , x _1,j = 1/3 (x _j +x _j+N/3 +x _j+2N/3 ) in the first hybrid coupler block. All you have to do is get a distributed output. By doing so, it becomes possible to further simplify the scale of the variable load circuit that constitutes the adaptive circuit. Also, let the set of subarrays be x _0,j (j=
1, 2...N/2), but you can also select {x _0,1 , x _1,1 ...x _0,N/4 , x _1,N/4 }, etc. can. It is also possible to remove the limitation on the number of beams that can be formed simultaneously by adding a distributor that distributes the output of the mixing distributor. Furthermore, as for the adaptive algorithm, it is possible to use algorithms other than those in the embodiments.
Furthermore, it is also possible to use not only a 180° type hybrid coupler but also a 90° type hybrid coupler. In short, the present invention can be implemented with various modifications without departing from the gist thereof.

[Brief explanation of drawings]

1 and 2 are block diagrams showing an example of a conventional device, FIG. 3 is a schematic block diagram of an embodiment of the device of the present invention, FIG. 4 is a block diagram showing an example of the structure of an adaptive circuit, and FIG. 6 is a diagram showing the SIR characteristics of this device, and FIGS. 6a and 6b are antenna pattern diagrams showing the operation of this device. 11 ₁ , 11 ₂ ~ 11 _N ... antenna element,
12... Mixing distributor, 13, 14, 15... Adaptive circuit, 16, 17... Hybrid coupler block, 18a-18d... Phase shifter.

Claims (1)

[Claims] 1. Constructed using N antenna elements (N is an integer of N>3) and a hybrid coupler block, having N input terminals and N output terminals,
a mixer/distributor that mixes the outputs of the N antenna elements to obtain N distributed outputs; and a mixer/distributor that mixes the outputs of the N antenna elements to obtain N distributed outputs; An adaptive antenna device comprising: an adaptive circuit that divides distributed output into a plurality of groups and performs adaptive variable weight sum processing on the distributed output for each group to obtain an adaptive output. 2 The mixing/distributing device is a multi-stage hybrid coupler block that mixes and distributes each output of the antenna element, and a hybrid coupler block in the latter stage that further mixes and distributes a certain set of mixing and distribution outputs from the hybrid coupler block in the previous stage. An adaptive antenna device according to claim 1, which is constructed as follows. 3. The adaptive antenna device according to claim 1, wherein the adaptive circuit applies an adaptive variable load independently to each of the plurality of sets of distributed outputs to obtain adaptive outputs from each set.