JP3953733B2 - Array antenna - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a multi-frequency shared array antenna apparatus.
[0002]
[Prior art]
Figure 5 shows, for example, "Element arrangement method and gain of dual-frequency shared array antenna" (Naohisa Goto and Kazuhiko Kamiyama, IEICE Technical Report AP81-40, published by IEICE, June 26, 1981). It is a block diagram of the conventional dual frequency shared array antenna with reference to the figure. In the figure, 1 is a high-frequency element antenna used in the high frequency band, 2 is a low-frequency element antenna used in the low frequency band, and 3 shows a radiation pattern of the high-frequency element antenna.
[0003]
In this array antenna, in the arrangement of the low-frequency element antenna 2 and the high-frequency element antenna 1, the low-frequency element antenna 2 and the high-frequency band are arranged so that no grating lobe is generated in a wide angle in the low-frequency band and high-frequency band, respectively. The two-frequency shared characteristics are obtained by regularly and periodically arranging the element antennas 1 on the same opening surface.
[0004]
[Problems to be solved by the invention]
In the conventional multi-frequency shared array antenna as described above, in order to regularly and periodically arrange the element antennas used in different frequency bands, it is affected by the element antenna used in a certain frequency band, and other frequency bands. In this case, the radiation pattern of the element antenna used in Fig. 1 is disturbed, and this disordered radiation pattern is periodically generated, thereby adversely affecting the radiation directivity of the array antenna.
[0005]
The present invention has been made to solve the above-described problems, and cancels the disturbance of the radiation pattern periodically generated in the element antenna due to the influence of other frequency bands, thereby obtaining a desired radiation directivity. An object of the present invention is to realize an array antenna.
[0006]
[Means for Solving the Problems]
In the array antenna according to the present invention, element antennas used in each of a plurality of frequency bands are arranged on the same aperture plane, and element antennas used in two frequency bands composed of a predetermined combination in the plurality of frequency bands are In an array antenna in which a part of the first element antenna is affected by the second element antenna and an inherent radiation pattern is changed, the first element antenna and the second element antenna are changed. A plurality of radiation patterns of the first element antenna are prepared in accordance with an arrangement pattern that defines the arrangement of the second element antenna with respect to the arrangement, and the arrangement pattern is used as a constituent element for gene expression. A genetic algorithm is used to calculate the sidelobe level of the radiation pattern as an evaluation function. It is intended to optimize the unequally spaced arrangement of the second antenna element to said first antenna element by specifying a combination of the arrangement pattern becomes.
[0007]
The genetic algorithm includes the beam width of the radiation pattern in the first element antenna as an evaluation function, and optimizes the amplitude and phase of the first element antenna.
[0008]
The genetic algorithm includes the amplitude and phase of the radiation beam generated from the first element antenna in the gene, and optimizes the amplitude and phase of the radiation beam generated from the first element antenna.
[0009]
The genetic algorithm includes a side lobe level of a radiation pattern in the second element antenna as an evaluation function.
[0010]
Furthermore, the gene algorithm includes the arrangement of the first element antenna in the gene, and optimizes the arrangement of the first element antenna.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 FIG.
1 is a block diagram of an array antenna according to Embodiment 1 of the present invention. Here, the present invention will be described based on a two-frequency shared array antenna.
In the figure, 1 is a high-frequency element antenna used in a high frequency band, and 2 is a low-frequency element antenna used in a low frequency band, both arranged on the same aperture plane. Reference numeral 3 denotes a radiation pattern of the high-frequency element antenna 1.
[0012]
Next, the operation will be described. In general, when there is a scatterer that is located near the antenna and whose size is not negligible compared to the wavelength of the antenna, the radiation pattern of the antenna is Disturbed. In the array antenna of FIG. 1, when used in a high frequency band, when the high-frequency element antenna 1 is excited, a current is induced in the low-frequency element antenna 2, thereby re-radiating. Further, when a dipole antenna, a notch antenna, or the like is used as the element antenna, there is a blocking effect by the low band element antenna 2. The high-frequency element antenna 1 whose radiation pattern is disturbed due to these causes is generated in the vicinity of the low-frequency element antenna 2. However, the arrangement of the low-frequency element antenna 2 is not obtained by calculation using a genetic algorithm described later. By arranging them at equal intervals, it is possible to prevent the effects of re-radiation and blocking from the high-frequency element antenna 1 from having periodicity, and to reduce the side lobe level of the radiation pattern.
[0013]
FIG. 2 shows an optimization process based on a general genetic algorithm. A genetic algorithm is a technique that mimics the evolutionary process of an organism and incorporates its adaptation process into a problem.
Hereinafter, a specific method for obtaining the optimum solution of the first embodiment will be described with reference to FIG.
[0014]
First, it is necessary to determine the gene expression for the solution of the problem to be solved [Step 1]. In the first embodiment, the arrangement of the low-frequency element antenna 2 is expressed as a gene. For example, it is assumed that the element pattern of the high-frequency element antenna 1 is an equidistant arrangement, and the element pattern of the low-frequency element antenna 2 can be moved from the equidistant arrangement to the left and right by 1 cm. The element patterns in that case are shown in FIGS. In FIG. 3, (a) shows that the low- frequency element antenna 2 is not moved as in the case of the equidistant arrangement, and (b) shows that the element pattern of the low- frequency element antenna 2 is moved 1 cm to the left. (C) shows the element pattern of the low- frequency element antenna 2 moved 1 cm to the right. If each arrangement pattern shown in FIGS. 3A to 3C is represented by symbols A, B, and C in order as components for gene expression, any three of A, B, and C can be selected. the arrangement pattern of the antenna formed by combining species can AAA, BBB, CCC, AAB, be envisaged 27 kinds of AAC or the like. Thus, the symbols A, B, and C correspond to the structure of the gene, and correspond to the element antenna in which the combination of the three-digit character string (AAB or the like) is expressed as a gene.
[0015]
Next, an initial generation group (number of individuals m) is randomly generated [Step 2]. With the above three antenna arrangement patterns, up to 27 element arrangements (27 individuals) can be generated. Therefore, the number m of individuals can be set with a numerical value corresponding to the number of gene combinations as an upper limit.
[0016]
Subsequently, the fitness for each individual in the current population is calculated [step 3]. This goodness of fit is a return value when the value indicated by a gene is assigned to a pre-defined evaluation function. The larger the return value, the closer to the target solution (higher the goodness of fit) the better the gene. Indicates. In the first embodiment, a function for deriving the side lobe level of the radiation pattern of the element antenna 1 is defined as the evaluation function. For example, when the fitness Gs can be expressed by an evaluation function Gs = X (a) (a is a gene), the fitness of the gene AAA is obtained as Gs = X (AAA).
[0017]
Next, the fitness is scaled [step 4]. Scaling is done to give a distribution so that the fitness of the gene population is not set to the same degree.
Subsequently, two genes are selected from the gene population [Step 5]. There are several selection methods, but the higher the matching degree, the more the selection is made.
Two new genes are generated by performing genetic operations such as crossover and mutation on the selected two genes [Step 6]. Crossing here refers to generating two new next-generation genes by dividing each of the two selected genes into two, and replacing the divided ones with each other's genes. Therefore, in the first embodiment, when the two genes are composed of three components represented by (ABC) and (BBA), respectively, the two genes separated by two at the crossing point are ( When (AB) | (C), (BB) | (A), the constituent elements (C) and (A) corresponding to the rear part of each are replaced to include the next-generation genetic constituents (ABA), ( BBC). The mutation means that the components (C) and (A) located behind the crossing point are completely different (B), and the next generation gene components (ABB) and (BBB) are created. Say.
This operation of generating a new gene is repeated until the number of genes reaches a predetermined number [Step 7]. When the number of generations reaches a predetermined number, the gene having the highest fitness at that time, that is, the arrangement of the low-frequency element antenna 2 is the optimal solution obtained by the calculation by this series of genetic algorithms. [Step 8].
[0018]
Also, the side lobe level of the radiation pattern can be evaluated for a plurality of beam directing directions. When there are a plurality of evaluation items, it is necessary to determine the priority order for each evaluation item and reflect the priority order in the evaluation function.
[0019]
Genes are obtained by the above-described method, the arrangement of the low-frequency element antennas 2 is determined, and the low-frequency element antennas 2 are arranged at unequal intervals, thereby canceling the disturbed radiation pattern and having a desired sidelobe level. An array antenna can be realized.
[0020]
Embodiment 2. FIG.
In the second embodiment, in addition to the first embodiment, as an evaluation function having two evaluation items such that the degree of fitness increases as the beam width of the radiation pattern of the high-frequency element antenna 1 approaches a desired value. The amplitude and phase of the high-frequency element antenna 1 are optimized. By doing so, in addition to the characteristics of the first embodiment, an array antenna having a desired beam width can be realized.
[0021]
Embodiment 3 FIG.
In the third embodiment, in addition to the first and second embodiments, the amplitude and phase of the radiation beam generated from the high frequency element antenna 1 are included in the gene, so that the radiation beam generated from the high frequency element antenna 1 is included in the gene. The amplitude and phase are optimized. By doing so, it is possible to realize an array antenna having a higher adaptability than the first or second embodiment.
[0022]
Embodiment 4 FIG.
In the fourth embodiment, in addition to any of the first to third embodiments, an element pattern of the low-frequency element antenna 2 is prepared, and the side lobe level of the radiation pattern of the low-frequency element antenna 2 is reduced. The evaluation function is changed so as to increase the degree, or the evaluation function is changed so that the degree of adaptation increases as the beam width of the radiation pattern of the low-frequency element antenna 2 approaches a desired value. In this way, in addition to the characteristics of the first to third embodiments, an array antenna having desired characteristics with respect to the side lobe level or beam width of the radiation pattern of the low-frequency element antenna 2 can be realized. Can do.
[0023]
Embodiment 5 FIG.
FIG. 4 shows a configuration diagram of the array antenna according to the fifth embodiment and a radiation pattern of the high-frequency element antenna 1.
In the array antenna of FIG. 4, when used in a high frequency band, as in the first embodiment, when the high frequency element antenna 1 is excited, a current is induced in the low frequency element antenna 2, thereby re-radiating. . In the fifth embodiment, in addition to any of the first to fourth embodiments, the arrangement of the high-frequency element antenna 1 is included in the gene and applied to the evaluation function. In this way, in addition to the characteristics of the first to fourth embodiments, an array antenna having desired characteristics with respect to the side lobe level or beam width of the radiation pattern of the high-frequency element antenna 1 can be realized. it can.
[0024]
In the above embodiment, the two-frequency shared array antenna has been described as an example. However, the present invention is not limited to the two-frequency shared array antenna, and functions similarly in an array antenna that shares multiple frequencies. A desired radiation directivity characteristic can be realized by suppressing the side lobe level. In that case, the present invention may be applied to a desired set of frequency bands.
[0025]
【The invention's effect】
As described above, according to the present invention, the position of an element antenna that adversely affects the radiation pattern of an element antenna used in another frequency band is calculated by a genetic algorithm including the side lobe level of the radiation pattern as an evaluation function. Since the element antennas that affect the radiation pattern are arranged at unequal intervals, the side lobe level of the multi-frequency shared array antenna can be reduced.
[0026]
Further, by including the beam width of the radiation pattern of the element antenna affected by the radiation pattern in the evaluation function, it is possible to realize a multi-frequency array antenna having a desired beam width.
[0027]
Further, by including the amplitude and phase of the element antenna affected by the above in the gene, it is possible to realize a multi-frequency shared array antenna having more excellent characteristics.
[0028]
In addition, by including the side lobe level and beam width of the radiation pattern of the element antenna having the above adverse effects in the evaluation function, a multi-frequency array antenna having the desired characteristics of the radiation pattern of the element antenna to be realized is realized. can do.
[0029]
In addition, by including the position of the element antenna affected by the above in the evaluation function, it is possible to realize a multi-frequency shared array antenna having more excellent characteristics.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an array antenna according to a first embodiment of the present invention.
FIG. 2 is a flowchart of optimization processing by a general genetic algorithm.
FIG. 3 is a diagram showing an arrangement pattern of one element antenna according to the first embodiment of the present invention.
FIG. 4 is a configuration diagram of an array antenna according to a fifth embodiment of the present invention.
FIG. 5 is a configuration diagram of a conventional dual-frequency shared array antenna.
[Explanation of symbols]
1 High frequency element antenna, 2 Low frequency element antenna, 3 High frequency element antenna 1 radiation pattern.

Claims (5)

Element antennas used in each of a plurality of frequency bands are arranged on the same aperture plane, and element antennas used in two frequency bands composed of a predetermined combination of the plurality of frequency bands are defined as a first element antenna and a second element antenna. In an array antenna in which a part of the first element antenna is affected by the second element antenna and an inherent radiation pattern changes,
A plurality of radiation patterns of the first element antenna are prepared according to an arrangement pattern that defines the arrangement of the second element antenna with respect to the arrangement of the first element antenna, and the arrangement pattern is used as a component for gene expression, A calculation by a genetic algorithm is performed using the side lobe level of the radiation pattern in the first element antenna as an evaluation function, and the combination of the arrangement patterns that maximizes the evaluation function is specified, whereby the first element antenna with respect to the first element antenna is specified. An array antenna characterized by optimizing the unequal spacing arrangement of the two element antennas. The array antenna according to claim 1, wherein
An array antenna characterized in that the genetic algorithm includes a beam width of a radiation pattern in the first element antenna in an evaluation function, and optimizes the amplitude and phase of the first element antenna. The array antenna according to claim 1 or 2,
The genetic algorithm includes an amplitude and phase of a radiation beam generated from the first element antenna in a gene, and optimizes the amplitude and phase of the radiation beam generated from the first element antenna. . The array antenna according to any one of claims 1 to 3,
The array antenna, wherein the genetic algorithm includes a side lobe level of a radiation pattern in the second element antenna in an evaluation function. The array antenna according to any one of claims 1 to 4,
An array antenna characterized in that the gene algorithm includes the arrangement of the first element antenna in a gene and optimizes the arrangement of the first element antenna.

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