JP2010016704A - Array antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an array antenna which can suppress the disorder of excitation distribution in a predetermined spatial domain or an angle direction to the minimum, in a feed structure which omits isolation and permits the generation of multiple reflection wave. <P>SOLUTION: A plurality of radiation element pairs 2 each consist of a first radiation element 5 and a second radiation element 6. The plurality of radiation element pairs 2 are arrayed along a first direction A and a second direction B respectively. Each first radiation element 5 and second radiation element 6 of the plurality of radiation element pairs 2 is arranged so as to be adjacent mutually in the second direction B. A minus error included in the radiation property of the first radiation element 5 and the plus error included in the radiation property of the second radiation element 6 are mutually canceled when projected toward a first observation plane C, thereby an amplitude in the radiation property in the first observation plane C of the radiation element pairs 2 becomes the amplitude of desired radiation property. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an array antenna in which multiple reflected waves are generated in a feed circuit connecting a plurality of radiating elements and a feed point.

  As a general array antenna, a phase shifter or an amplifier is directly connected to each radiating element to achieve the desired radiation characteristics by supplying power with the desired excitation amplitude and phase (hereinafter referred to as excitation distribution). There is a phased array type that controls the amplitude and phase. However, in the case of this type, since the configuration is generally complicated and expensive, it is rarely used as an antenna that gives a fixed beam.

  On the other hand, a microstrip array antenna is known as an example of an antenna configuration that realizes a fixed beam. In this microstrip array antenna, the coplanar power feeding system in which the power feeding circuit is configured on the same plane as the radiating element can be processed by one etching, and can be easily manufactured and reduced in cost. In addition to this, it is easy to reduce the thickness and weight.

  In the microstrip array antenna, the radio wave input from the feeding point is fed to the radiating element with a desired excitation distribution by a T-branch line constituted by a microstrip line. Since this T-branch line can be configured with a relatively compact size, it is often used as a general power combining / distribution circuit in a feeding circuit of a coplanar feeding type microstrip array antenna (for example, a patent) References 1 and 2).

Japanese Patent No. 3279268 Japanese Patent No. 3279264

  Here, in general, a T-branch line is used as a distributor in a microstrip array antenna. However, since this T-branch line has no isolation, a radio wave passing therethrough is reflected or a radiating element is used. The radio wave reflected and returned to the T-shaped distributor is re-reflected by the T-branch line, and multiple reflected waves are generated.

  As a result, an error occurs in the radiation characteristic of the radiating element due to the multiple reflected waves, which greatly deviates from the desired radiation characteristic. In other words, even if impedance matching when viewed from the input terminal side is achieved, impedance matching when viewed from the output terminal side is not achieved. For this reason, the electromagnetic field distribution, that is, the excitation distribution of the array antenna is disturbed, and there is a problem that desired radiation characteristics of the radiation element cannot be obtained.

  For example, the use of a power combining / distribution circuit such as a Wilkinson distributor with isolation provided therein can suppress the generation of multiple reflected waves. However, when such a configuration using a power combining / distribution circuit is adopted, the size of the array antenna itself is increased, which is not suitable for a microstrip array antenna. In addition to this, there is a multilayer feeding system in which the radiating element and the feeding circuit are mounted on different substrates. However, even when such a configuration is adopted, there arises a problem that the size of the array antenna itself is increased and the manufacturing cost is increased.

  The present invention has been made to solve the above-described problems, and in a feed structure that allows the generation of multiple reflected waves by omitting isolation, disturbance of the excitation distribution in a predetermined spatial region or angular direction is prevented. An object is to obtain an array antenna that can be minimized.

  The array antenna according to the present invention includes a first radiating element that radiates at an amplitude smaller than an amplitude of a desired radiation characteristic due to an error due to multiple reflected waves in the feed circuit, and an amplitude of the desired radiation characteristic due to an error due to multiple reflected waves. And a plurality of radiation element pairs in which the first radiation element and the second radiation element are fed through the same branch point in the power feeding circuit. The radiating element pairs are arranged so that errors due to multiple reflected waves of the first radiating element and the second radiating element projected toward a predetermined observation surface are canceled out from each other.

  According to the array antenna of the present invention, the plurality of pairs of radiating elements are arranged so that the errors of the first radiating element and the second radiating element projected toward a predetermined observation surface are canceled out from each other. In a feed structure that eliminates isolation and allows errors due to multiple reflected waves, disturbance of the excitation distribution in a predetermined spatial region or angular direction can be minimized.

The best mode for carrying out the present invention will be described below with reference to the drawings.
Embodiment 1 FIG.
1 is a block diagram showing a microstrip array antenna according to Embodiment 1 of the present invention. In addition, the arrow A of FIG. 1 is a 1st direction and shows an azimuth (AZ: Azimuth). An arrow B is a second direction orthogonal to the first direction, and indicates an elevation angle (EL). A line C indicates a first observation surface (observation line) as a predetermined observation surface along the first direction A. This predetermined observation surface is an observation surface on which the influence of errors due to multiple reflected waves is to be suppressed. A line D indicates a second observation surface (observation line) along the second direction B. A line E is a reference line that passes through the center point of the feeder circuit and is parallel to the first observation plane C. These arrows A and B and lines C, D, and E are the same in other drawings.

  In FIG. 1, a coplanar antenna substrate is constituted by a ground conductor, a dielectric substrate, and a strip conductor. The ground conductor is disposed on one surface of the dielectric substrate. The strip conductor is disposed on the other surface of the dielectric substrate. The antenna substrate is provided with a feeding point 1 and a plurality of radiating element pairs (element pairs) 2.

  The strip conductor of the antenna substrate forms a microstrip line 3 and a plurality of T branch lines 4 (distributors). The T branch line 4 is indicated by a broken line in the figure. The microstrip line 3 and the plurality of T branch lines 4 constitute a power transmission path from the feeding point 1 to the plurality of radiating element pairs 2, that is, a feeding circuit. Each of the plurality of radiating element pairs 2 includes a first radiating element 5 and a second radiating element 6. In order to obtain a desired radiation characteristic (in order to realize a necessary excitation distribution), the length of the microstrip line 3 at each location, the distribution ratio or the shape / type of the T-branch line 4 are selected.

  Next, the radiation characteristics of the first radiating element 5 and the second radiating element 6 will be specifically described. FIG. 2 is an explanatory diagram for explaining an example of the multiple reflection model of the first and second radiating elements 5 and 6 in FIG. 1. In FIG. 2, the distance L1 between the T branch line 4 and the first radiating element 5 is shorter than the distance L2 between the T branch line 4 and the second radiating element 6 (L1 ≠ L2).

  In such a line configuration, a part of the incident wave F from the T branch line 4 is reflected by the first radiating element 5 and returns to the T branch line 4 as a reflected wave. The reflected wave is reflected again by the T-branch line (distributor) 4 and returns to the first element 5 to generate a re-reflected wave G. In addition to the re-reflected wave G, for example, the incident wave F is transmitted as a radio wave reflected by the first radiating element 5 to the second radiating element 6 and reflected again by the second radiating element 6. A re-reflected wave or an incident wave F traveling from the T branch line 4 to the second radiating element is reflected by the second radiating element 6 to be incident on the first radiating element 5 (not shown).

  The phase of the incident wave F to the first radiating element 5 and the phase of the re-reflected wave G are different from each other. As a result, the incident wave F is attenuated (interfered) by the multiple reflected wave such as the re-reflected wave G, and the amplitude of the radiation characteristic of the first radiating element 5 becomes smaller than the amplitude of the desired radiation characteristic (negative error is reduced). Occur). On the other hand, in the second radiating element 6, the incident wave is amplified (combined) by multiple reflected waves such as re-reflected waves, and the amplitude of the radiation characteristic of the second radiating element 6 becomes larger than the amplitude of the desired radiation characteristic ( A positive error occurs).

  Here, in FIG. 1, the plurality of radiation element pairs 2 are arranged along the first direction A and the second direction B, respectively. The first radiating element 5 and the second radiating element 6 of each of the plurality of radiating element pairs 2 are arranged adjacent to each other in the second direction B. Furthermore, the first radiating elements 5 of the plurality of radiating element pairs 2 are arranged adjacent to each other in the first direction A. Similarly, the second radiating elements 6 of the plurality of radiating element pairs 2 are arranged adjacent to each other in the first direction A.

  Further, the second radiating elements of the plurality of radiating element pairs 2 are arranged on the reference line E side. That is, the plurality of radiating element pairs 2 are arranged so as to be line-symmetric with respect to the reference line E. The distribution of errors included in the radiation characteristics of the first radiation element 5 and the second radiation element 6 projected toward the first observation plane C by the arrangement of the plurality of radiation element pairs 2 in FIG. ) As shown. Further, the distribution of errors included in the radiation characteristics of the first radiating element 5 and the second radiating element 6 toward the second observation surface D is as shown in FIG.

  Accordingly, as shown in FIG. 1A, the negative error included in the radiation characteristic of the first radiating element 5 and the positive error included in the radiation characteristic of the second radiating element 6 cancel each other, and the radiation The amplitude in the radiation characteristic on the first observation plane C of the element pair 2 is the amplitude of the desired radiation characteristic. That is, the plurality of radiating element pairs 2 are arranged such that errors due to the multiple reflected waves of the first radiating element 5 and the second radiating element 6 projected toward the first observation plane C cancel each other. .

  Here, FIG. 3 is a characteristic diagram showing a radiation pattern of the microstrip array antenna when the radiation element pairs 2 are arranged without considering the influence of errors due to multiple reflected waves (characteristic diagram of the conventional one). FIG. 4 is a characteristic diagram showing a radiation pattern of the microstrip array antenna of FIG. FIG. 5 is a characteristic diagram showing a radiation pattern of the microstrip array antenna in an ideal state when there is no influence of errors due to multiple reflected waves. Note that the central region (region around AZ = 0, EL = 0) of each characteristic diagram indicates the main beam radiated from the microstrip array antenna.

  In the radiation pattern in the case where the influence of the error due to the multiple reflected waves is not considered, as shown in FIG. 3, the excitation distribution is disturbed in the region other than the main beam, and the side lobe is generated from the microstrip array antenna. It can be seen that the radiation is almost irregular. On the other hand, the radiation pattern of the microstrip array antenna of FIG. 1 is substantially the same as that of FIG. 5 which is a radiation pattern in an ideal state with no error in the first direction A, as shown in FIG. I understand that it is. That is, in the microstrip array antenna of FIG. 1, the disturbance of the excitation distribution due to the influence of errors can be minimized on the desired observation plane, and the disturbance of the excitation distribution due to multiple reflected waves is suppressed.

  In the microstrip array antenna as described above, errors due to the multiple reflected waves of the first radiating element 5 and the second radiating element 6 projected onto the first observation plane C by the plurality of radiating element pairs 2 cancel each other. Are arranged to be. With this configuration, it is possible to minimize the disturbance of the excitation distribution in a predetermined spatial region or angular direction in a feed structure that eliminates isolation and allows the generation of multiple reflected waves.

Embodiment 2. FIG.
In the first embodiment, as shown in FIG. 1, the second radiating element 6 is arranged on the reference line E side. On the other hand, in the second embodiment, as shown in FIG. 6, the first radiating element 5 is arranged on the reference line E side. That is, in the second embodiment, the arrangement of the first radiating element 5 and the second radiating element 6 in the radiating element pair 2 is reversed. Other configurations are the same as those in the first embodiment.

  Here, the radiation pattern of the microstrip array antenna shown in FIG. 1 is compared with the radiation pattern of the microstrip array antenna shown in FIG. FIG. 7 is a characteristic diagram showing a radiation pattern of the microstrip array antenna of FIG. First, in the characteristic diagram of FIG. 4, the side beam level hardly increases although the main beam width in the second direction B is slightly increased as compared with the case where there is no error in the characteristic diagram of FIG. . On the other hand, in the characteristic diagram of FIG. 7, although the side lobe level in the second direction B increases, the expansion of the main beam width can be suppressed.

  Therefore, in the characteristics of the microstrip array antenna, when priority is given to the suppression of the side lobe level among the suppression of the side lobe level and the convergence of the main beam width, the configuration of the first embodiment (configuration of FIG. 1). May be used. On the other hand, when priority is given to the convergence of the main beam width, the configuration of the second embodiment (configuration of FIG. 6) may be used.

Embodiment 3 FIG.
In the third embodiment, a case where the first radiating element 15 and the second radiating element 16 are radiating elements for circularly polarized radiation of a one-point feeding method will be described as a specific configuration example of pair elements.

  FIG. 8 is a block diagram showing a part of a microstrip array antenna according to Embodiment 3 of the present invention. In FIG. 8, the first radiating element 15 and the second radiating element 16 of the third embodiment are fed from a feeding point via the microstrip line 13 and the T branch line 14. The first radiating element 15 and the second radiating element 16 are radiating elements for circularly polarized radiation of a one-point feeding method. Further, the first radiating element 15 and the second radiating element 16 are provided with circularly polarized wave excitation notches 15a and 16a, respectively.

  Further, the direction of the first radiating element 15 is shifted (rotated) by 90 degrees in the first direction or the second direction with respect to the direction of the second radiating element 16. The T branch line 14 has a phase difference of 90 degrees between the first radiating element 15 and the second radiating element 16. Other configurations are the same as those in the first or second embodiment.

  In the microstrip array antenna as described above, multiple reflected waves are generated because the phases of the reflected waves from the element ends of the first radiating element 15 and the second radiating element 16 are not in phase with the T branch line 14. As with the first and second embodiments, the disturbance of the excitation distribution due to the influence of the multiple reflected waves can be minimized without changing the structure.

Embodiment 4 FIG.
In the third embodiment, the first radiating element 15 and the second radiating element 16 are radiating elements for circularly polarized radiation of a one-point feeding method. On the other hand, in the fourth embodiment, the first radiating element 25 and the second radiating element 26 are radiating elements for circularly polarized radiation of a two-point feeding method.

  FIG. 9 is a block diagram showing a part of a microstrip array antenna according to Embodiment 4 of the present invention. In FIG. 9, the first radiating element 25 and the second radiating element 26 according to the fourth embodiment are fed from a feeding point via the microstrip line 23 and T branch lines 24a, 24b, and 24c. Other configurations are the same as those in the third embodiment.

  In the microstrip array antenna as described above, even when the first radiating element 25 and the second radiating element 26 are radiating elements for circularly polarized radiation of a two-point feeding method, the same as in the third embodiment An effect can be obtained.

  In the first and second embodiments, the first observation plane C is a predetermined observation plane, but the second observation plane may be a predetermined observation plane. That is, the first direction A may be an elevation angle and the second direction B may be an azimuth angle.

  In the first to fourth embodiments, the microstrip array antenna has been described. However, the present invention can also be applied to array antennas other than the microstrip array antenna.

  Further, in the first to fourth embodiments, the case where the number of radiating elements is 32 has been described. However, the number of radiating elements is not limited to this example, and an error projected onto a desired observation plane is based on an array of two element pairs in which the amount of error in the excitation distribution is a pair of + and −. Any number may be used as long as it is a power of 2 so that it can be offset.

It is a block diagram which shows the microstrip array antenna by Embodiment 1 of this invention. It is explanatory drawing for demonstrating an example of the multiple reflection model of the 1st and 2nd radiation | emission element of FIG. It is a characteristic view which shows the radiation pattern of the conventional microstrip array antenna. It is a characteristic view which shows the radiation pattern of the microstrip array antenna of FIG. It is a characteristic view which shows the radiation pattern of the microstrip array antenna in an ideal state. It is a block diagram which shows the microstrip array antenna by Embodiment 2 of this invention. It is a characteristic view which shows the radiation pattern of the microstrip array antenna of FIG. It is a block diagram which shows a part of microstrip array antenna by Embodiment 3 of this invention. It is a block diagram which shows a part of microstrip array antenna by Embodiment 4 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Feeding point, 2 Radiation element pair, 4, 14, 24a, 24b, 24c T branch line (branch point), 5, 15, 25 1st radiation element, 6, 16, 26 2nd radiation element, C 1st observation Surface (predetermined observation surface), D second observation surface, E reference line.

Claims (6)

A first radiating element that radiates with an amplitude smaller than the amplitude of the desired radiation characteristic due to an error due to multiple reflected waves in the power supply circuit, and radiates with an amplitude larger than the amplitude of the desired radiation characteristic due to the error due to the multiple reflected waves An array antenna including a plurality of radiating element pairs, each of which is configured by a second radiating element, and wherein the first radiating element and the second radiating element are fed through the same branch point in the feeding circuit,
The plurality of radiating element pairs are arranged such that errors due to the multiple reflected waves of the first radiating element and the second radiating element projected toward a predetermined observation surface cancel each other. Characteristic array antenna. The array antenna according to claim 1, wherein the plurality of radiating element pairs are arranged along a direction orthogonal to the observation surface. The second radiating element of the plurality of radiating element pairs is disposed on a reference line side passing through a central point of the feeder circuit and parallel to the observation plane;
The array antenna according to claim 2, wherein the plurality of radiating element pairs are arranged in line symmetry with respect to the reference line. The first radiating element of the plurality of radiating element pairs is disposed on a reference line side passing through a center point of the feeder circuit and parallel to the observation surface,
The array antenna according to claim 2, wherein the plurality of radiating element pairs are arranged in line symmetry with respect to the reference line. The array antenna according to any one of claims 1 to 4, wherein each of the first radiating element and the second radiating element is a radiating element for circularly polarized radiation. The direction of the first radiating element of the plurality of radiating element pairs is arranged to be shifted by 90 degrees with respect to the direction of the second radiating element,
The first radiating element and the second radiating element of the plurality of radiating element pairs are set so that a phase difference of an excitation voltage from the same branch point of the feeder circuit is 90 degrees. The array antenna according to claim 5.

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