Antenna device and radio wave reception method using the antenna device

Abstract

To provide an antenna device capable of reducing a second peak and detecting an arrival azimuth of radio waves with accuracy, and to provide a radio wave reception method by the same.SOLUTION: An antenna device 1 comprises: a first antenna element A1 configured to receive at least circularly-polarized waves; and a plurality of second antenna elements A2 configured to receive at least circularly-polarized waves, being arranged in a ring shape so as to surround the first antenna element A1.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an antenna device and a radio wave reception method using the antenna device.

Background Art

[0002] Patent Document 1 discloses a direction detection device that detects the arrival direction of radio waves.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Not limited to the case of detecting the arrival direction of radio waves using the method disclosed in the related art, it is still required to accurately detect the arrival direction of radio waves.

[0005] One object of the present disclosure is to provide an antenna device and a radio wave reception method using the antenna device that solve the above-described problems.

Means for Solving the Problems

[0006] According to one embodiment, the antenna device includes a first antenna element configured to receive at least circularly polarized waves, and a plurality of second antenna elements arranged in a ring shape so as to surround the first antenna element and configured to receive at least circularly polarized waves.

[0007] According to an embodiment, a radio wave receiving method by an antenna device receives radio waves by using a first antenna element configured to be capable of receiving at least circularly polarized waves and a plurality of second antenna elements arranged in a ring shape so as to surround the first antenna element and configured to be capable of receiving at least circularly polarized waves, and detects the arrival direction of the radio waves based on the phase differences of a plurality of received signals of each of the first antenna element and the plurality of second antenna elements.

Advantages of the Invention

[0008] According to the above embodiment, it is possible to provide an antenna device and a radio wave receiving method by the antenna device that can reduce the second peak and accurately detect the arrival direction of radio waves.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

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Figure 8

Figure 9

Mode for Carrying Out the Invention

[0010] Hereinafter, embodiments will be described with reference to the drawings. Since the drawings are simplified, the technical scope of the embodiments should not be narrowly interpreted based on the description of these drawings. Also, the same elements are denoted by the same reference numerals, and redundant descriptions are omitted.

[0011] In the following embodiments, when necessary for convenience, they will be described by being divided into a plurality of sections or embodiments. However, unless otherwise specified, they are not unrelated to each other, and one is related to a partial or entire modification example, application example, detailed explanation, supplementary explanation, etc. of the other. Also, in the following embodiments, when referring to the number of elements, etc. (including the number, numerical value, quantity, range, etc.), unless otherwise specified and unless it is clearly limited to a specific number in principle, it is not limited to that specific number, and it may be more than or less than the specific number.

[0012] Furthermore, in the following embodiments, the constituent elements (including operation steps, etc.) are not necessarily essential unless otherwise specified and unless it is clearly considered essential in principle. Similarly, in the following embodiments, when referring to the shape, positional relationship, etc. of the constituent elements, unless otherwise specified and unless it is clearly considered otherwise in principle, it includes those that are substantially approximate or similar to the shape, etc. This also applies to the above-mentioned number, etc. (including the number, numerical value, quantity, range, etc.).

[0013] <Embodiment 1> FIG. 1 is a block diagram showing a configuration example of an antenna device (aerial antenna device) 1 according to Embodiment 1. As shown in FIG. 1, the antenna device 1 includes an antenna element (first antenna element) A1, antenna elements (second antenna elements) A2_1 to A2_n, a receiver 21, receivers 22_1 to 22_n, and a signal processing unit 100. Here, n is an arbitrary integer of 2 or more. In the present embodiment, the case where n = 7 will be described as an example. Further, the signal processing unit 100 includes at least a direction detection unit 101.

[0014] The antenna elements A1, A2_1 to A2_7 each receive radio waves from the outside of the antenna device 1. The reception signal by the antenna element A1 is amplified and frequency-converted by the receiver 21 and then converted into a digital signal. A plurality of reception signals respectively by the antenna elements A2_1 to A2_7 are each amplified and frequency-converted by the receivers 22_1 to 22_7 and then converted into digital signals.

[0015] The signal processing unit 100 performs predetermined signal processing on a plurality of output signals output from each of the receivers 21, 22_1 to 22_7 (in other words, a plurality of reception signals respectively by the antenna elements A1, A2_1 to A2_7). Here, the direction detection unit 101 provided in the signal processing unit 100 detects the arrival direction of the radio wave based on the phase difference of the plurality of reception signals respectively by the antenna elements A1, A2_1 to A2_7.

[0016] FIG. 2 is a schematic diagram showing the periphery of the antenna element of the antenna device 1. As shown in FIG. 2, the antenna element A1 is disposed at the center of the antenna arrangement area of the pedestal (fixed part) 11. The antenna elements A2_1 to A2_7 are arranged in a ring shape so as to surround the antenna element A1. Further, the antenna elements A1, A2_1 to A2_7 are arranged such that their respective central axes are parallel.

[0017] The antenna elements A1, A2_1 to A2_7 are all configured to be able to receive radio waves over a wide band and have relatively stable gains. Also, the antenna elements A1, A2_1 to A2_7 are all configured to be able to receive circularly polarized waves. Thereby, it becomes possible to detect the azimuth of radio waves in the azimuth direction (horizontal direction) and elevation angle direction (height direction). For example, each of the antenna elements A1, A2_1 to A2_7 is a spiral antenna, a patch antenna, or the like.

[0018] In the present embodiment, a case where the antenna elements A1, A2_1 to A2_7 are all spiral antennas of the same size will be described as an example, but the present invention is not limited thereto, and it is sufficient that at least they are configured to be able to receive circularly polarized waves. Also, for example, the antenna element A1 and the antenna elements A2_1 to A2_7 may have different sizes from each other.

[0019] FIG. 3 is a diagram for explaining the detection of the arrival azimuth of radio waves by the antenna device 1. In the antenna device 1, the receivers 21, 22_1 to 22_7 and the azimuth detection unit 101 constitute, for example, a multi-channel digital oscilloscope or the like, and estimate the azimuth showing the highest value (peak) as the evaluation function as the arrival azimuth of the radio wave. In the example of FIG. 3, as the arrival azimuth of the radio wave, an azimuth with an azimuth angle of -15 degrees and an elevation angle of 30 degrees is detected.

[0020] Here, the evaluation function is a function used in a high-resolution arrival azimuth estimation method typified by, for example, the MUSIC (Multiple signal classification) method, and shows a sharp peak in the azimuth where the radio wave arrives.

[0021] Since the evaluation function depends on the position of the antenna element and the direction of arrival of the radio wave, depending on the position of the antenna element and the direction of arrival of the radio wave, there may be a peak (second peak) separate from the main peak in the direction where the radio wave is not arriving. When the second peak is larger than the main peak, the direction indicating the second peak is erroneously estimated as the direction of arrival of the radio wave. Therefore, it is important to improve the detection accuracy of the direction of arrival of the radio wave by reducing the second peak.

[0022] Normally, when detecting the direction of arrival of a radio wave using an antenna device having a plurality of antenna elements arranged in a ring shape, by adjusting the opening diameter of the ring formed by the plurality of antenna elements (specifically, the diameter of the circle passing through the centers of the plurality of antenna elements) to be equal to or less than half of the wavelength of the radio wave, it is possible to suppress the second peak. However, when relatively large antenna elements such as spiral antennas for receiving circularly polarized waves are used for each of the plurality of antenna elements arranged in a ring shape, it is difficult to adjust the opening diameter of the ring formed by the plurality of antenna elements to be equal to or less than half of the wavelength of the radio wave.

[0023] Therefore, in the present embodiment, by further arranging the antenna element A1 at the center of the plurality of antenna elements A2_1 to A2_7 arranged in a ring shape, even when the opening diameter of the ring formed by the antenna elements A2_1 to A2_7 is larger than half of the wavelength of the radio wave, the second peak is suppressed.

[0024] FIG. 4 is a schematic diagram showing the result of simulating the influence on the evaluation function by the presence or absence of the antenna element in the central portion. As shown in FIG. 4, when seven antenna elements A2_1 to A2_7 are arranged in a ring shape and the antenna element A1 is arranged in the central portion thereof (solid line), compared with the case where the antenna element A1 is not arranged in the central portion (dashed line), it can be seen that the second peak of the evaluation function is relatively small with respect to the main peak. Although not shown, when seven antenna elements A2_1 to A2_7 are arranged in a ring shape and the antenna element A1 is arranged in the central portion thereof, compared with the case where eight antenna elements A2_1 to A2_8 are arranged in a ring shape and the antenna element A2 is not arranged in the central portion thereof, the second peak of the evaluation function is relatively small with respect to the main peak.

[0025] As described above, the antenna device 1 according to the present embodiment includes the antenna element A1 and the antenna elements A2_1 to A2_7 arranged in a ring shape so as to surround the antenna element A1. Thereby, the antenna device 1 according to the present embodiment can accurately detect the arrival direction of radio waves over a wide band.

[0026] In general, the second peak tends to become smaller as the number of antenna elements increases, and also tends to become smaller as the opening diameter of the ring formed by the plurality of antenna elements becomes smaller.

[0027] FIG. 5 is a schematic diagram showing the result of simulating the influence on the evaluation function by the difference in the opening diameter of the ring formed by the plurality of antenna elements. In the example of FIG. 5, the evaluation functions of the arrival directions of radio waves in the case where the opening diameters of the rings formed by the plurality of antenna elements A2_1 to A2_7 are large, medium, and small (large > medium > small) are shown. Referring to FIG. 5, it can be seen that the second peak of the evaluation function becomes relatively smaller as the opening diameter of the antenna element becomes smaller with respect to the main peak.

[0028] However, when the number of antenna elements is increased, the opening diameter of the ring formed by the increased plurality of antenna elements will become larger. That is, there is a trade-off relationship between the increase in the number of antenna elements and the reduction in the opening diameter of the ring formed by the plurality of antenna elements.

[0029] Here, in the antenna device 1 according to the present embodiment, instead of one of the plurality of antenna elements A1, A2_1 to A2_7 being arranged to form a ring shape, it is arranged at the center of the ring. Thereby, compared with the case where all of the antenna elements A1, A2_1 to A2_7 are arranged to form a ring shape, without changing the number of antenna elements used, the number of antenna elements used for forming the ring shape is reduced by one, and the opening diameter of the ring can be reduced. That is, the antenna device 1 according to the present embodiment can suppress the second peak more than the antenna device in which a ring shape is formed using all of the same number of antenna elements, so that the detection accuracy of the arrival direction of radio waves can be improved.

[0030] In the present embodiment, the case where one of the plurality of antenna elements is arranged at the center of the ring has been described as an example, but it is not limited thereto, and two or more of the plurality of antenna elements may be arranged at the center of the ring. By increasing the number of antenna elements arranged at the center of the ring, the opening diameter of the ring can be reduced without reducing the number of antenna elements used, so that theoretically, the second peak can be further suppressed.

[0031] <First Modified Example of Antenna Device 1> Subsequently, a first modified example of the antenna device 1 will be described. FIG. 6 is a schematic diagram showing the periphery of the antenna elements of the antenna device 1a which is a first modified example of the antenna device 1. The periphery of the antenna elements of the antenna device 1a further includes a radio wave absorber 12 and a reflector 13 as compared with the periphery of the antenna elements of the antenna device 1.

[0032] The radio wave absorber 12 is formed on the main surface of the pedestal 11 so as to fill the space between the antenna elements A1 and A2_1 to A2_7. The reflector 13 is formed on the main surface of the pedestal 11 opposite to the main surface on which the antenna elements are arranged. By using these, it is possible to reduce the distortion of the steering vector (a vector representing the amplitude ratio and phase difference at each antenna element of the estimated arrival direction of the radio wave) due to the reflected wave.

[0033] <Second Modified Example of Antenna Device 1> Next, a second modified example of the antenna device 1 will be described. FIG. 7 is a schematic diagram showing the periphery of the antenna elements of the antenna device 1b which is a second modified example of the antenna device 1. The periphery of the antenna elements of the antenna device 1b has a different number of antenna elements arranged in a ring shape compared to the periphery of the antenna elements of the antenna device 1. Specifically, the antenna device 1b includes the antenna element A1 and three antenna elements A2_1 to A2_3 arranged so as to surround the antenna element A1. The antenna device 1b can also achieve the same effect as in the case of the antenna device 1.

[0034] As described above, the number of antenna elements A2_1 to A2_n arranged in a ring shape (that is, the value of n) can be arbitrarily set. However, the number of antenna elements A2_1 to A2_n arranged in a ring shape is preferably an odd number (n is odd).

[0035] FIG. 8 is a schematic diagram showing the result of simulating the influence of the difference in the number of antenna elements arranged in a ring shape on the evaluation function. In the example of FIG. 8, the evaluation function when the arrival direction of the radio wave is about 5 degrees is shown. Also, in the example of FIG. 8, the solid line represents the simulation result when an odd number of antenna elements A2_1 to A2_7 are arranged in a ring shape and the antenna element A1 is arranged at the center thereof, and the broken line represents the simulation result when an even number of antenna elements A2_1 to A2_8 are arranged in a ring shape and the antenna element A1 is arranged at the center thereof.

[0036] As shown in Fig. 8, it can be seen that when the number of antenna elements arranged in a ring shape is odd (solid line), the second peak of the evaluation function is relatively small compared to the main peak when the number of antenna elements arranged in a ring shape is even (dashed line). From this, it can be said that the number of antenna elements arranged in a ring shape is preferably odd. In the example of Fig. 8, 7 antenna elements were used as an example when the number of antenna elements arranged in a ring shape is odd, but it is not limited thereto, and for example, any odd number of antenna elements such as 5, 9, 11, etc. may be used.

[0037] In this embodiment, the case where the antenna elements A2_1 to A2_n are arranged in a ring shape so as to surround the antenna element A1 has been described as an example, but it is not limited thereto. For example, the antenna elements A3_1 to A3_m (m is an integer of 2 or more) may be further arranged in a ring shape so as to surround the antenna element A1. That is, the antenna elements A2_1 to A2_n and the antenna elements A3_1 to A3_m may be arranged in a double ring shape so as to surround the antenna element A1. At this time, the opening diameter (diameter) of the ring formed by the antenna elements A2_1 to A2_n is different from the opening diameter (diameter) of the ring formed by the antenna elements A3_1 to A3_m. Further, it is preferable that at least one of the number of the antenna elements A2_1 to A2_n arranged in a ring shape and the number of the antenna elements A3_1 to A3_m arranged in a ring shape is odd (at least one of m and n is odd). Hereinafter, a specific example will be described with reference to Fig. 9.

[0038] <The third modification example of the antenna device 1> Fig. 9 is a schematic diagram showing the periphery of the antenna element of the antenna device 1c which is the third modification example of the antenna device 1. The periphery of the antenna element of the antenna device 1c further includes the antenna element A1 and the antenna elements A3_1 to A3_m in addition to the antenna elements A2_1 to A2_n. In the example of Fig. 9, n = 3 and m = 3.

[0039] Antenna elements A2_1 to A2_3 are arranged in a ring shape so as to surround antenna element A1. Also, antenna elements A3_1 to A3_3 are arranged in a ring shape so as to surround antenna element A1. The aperture diameter D1 of the ring formed by antenna elements A2_1 to A2_3 and the aperture diameter D2 of the ring formed by antenna elements A3_1 to A3_3 are different.

[0040] In antenna device 1c, since at least one of the number of antenna elements A2_1 to A2_3 arranged in a ring shape and the number of antenna elements A3_1 to A3_3 arranged in a ring shape is odd (in this example, both are odd), the second peak is more effectively suppressed.

[0041] In FIG. 9, the case where a plurality of antenna elements are arranged in a double ring shape so as to surround antenna element A1 provided in the central part has been described as an example, but it is not limited to this, and they may be arranged in a triple or more ring shape. In this case, it is preferable that the number of antenna elements forming at least one of the triple or more ring shapes is odd.

[0042] As described above, the embodiments of the present disclosure have been described in detail with reference to the drawings, but the specific configuration is not limited to the above, and various design changes and the like are possible without departing from the gist of the present disclosure.

Explanation of Signs

[0043] 1 Antenna device 1a Antenna device 1b Antenna device 1c Antenna device 11 Pedestal 12 Radio wave absorber 13 Reflector 21 Receiver 22_1 to 22_n Receivers A1 Antenna element A2_1 to A2_n Antenna elements A3_1 to A3_m Antenna elements 100 Signal processing unit 101 Azimuth detection unit

Claims

1. A first antenna element configured to be capable of receiving at least circularly polarized waves, A plurality of odd-numbered second antenna elements arranged in a ring shape so as to surround the first antenna element and configured to be capable of receiving at least circularly polarized waves, An antenna device comprising:

2. A first antenna element configured to be capable of receiving at least circularly polarized waves, A plurality of second antenna elements arranged in a ring shape so as to surround the first antenna element and configured to be capable of receiving at least circularly polarized waves, A plurality of third antenna elements arranged in a ring shape so as to surround the first antenna element and configured to be capable of receiving at least circularly polarized waves, Comprising: The opening diameter of the ring formed by the plurality of second antenna elements is different from the opening diameter of the ring formed by the plurality of third antenna elements, At least one of the number of the plurality of second antenna elements and the number of the plurality of third antenna elements is odd, An antenna device.

3. Further comprising a radio wave absorber formed so as to fill the space between the first antenna element and the plurality of second antenna elements, The antenna device according to claim 1 or 2.

4. Further comprising a reflector formed on a surface opposite to the radio wave receiving surface of each of the first antenna element and the plurality of second antenna elements, The antenna device according to any one of claims 1 to 3.

5. The first antenna element and the plurality of second antenna elements are arranged such that their respective central axes are parallel, The antenna device according to any one of claims 1 to 4.

6. Both the first antenna element and the plurality of second antenna elements are spiral antennas, The antenna device according to any one of claims 1 to 5.

7. The first antenna element and the plurality of second antenna elements are of the same size, The antenna device according to any one of claims 1 to 6.

8. Further comprising at least a direction detecting unit that detects the arrival direction of the radio wave based on the phase difference of a plurality of received signals that are radio waves received by each of the first antenna element and the plurality of second antenna elements, The antenna device according to any one of claims 1 to 7.

9. A first antenna element configured to be capable of receiving at least circularly polarized waves, and a plurality of odd-numbered second antenna elements arranged in a ring shape so as to surround the first antenna element and configured to be capable of receiving at least circularly polarized waves, receive radio waves by, Detect the arrival direction of the radio wave based on the phase differences of a plurality of received signals of each of the first antenna element and the plurality of second antenna elements. A radio wave receiving method by an antenna device.

10. A first antenna element configured to be capable of receiving at least circularly polarized waves, a plurality of second antenna elements arranged in a ring shape so as to surround the first antenna element and configured to be capable of receiving at least circularly polarized waves, and a plurality of third antenna elements arranged in a ring shape so as to surround the first antenna element and configured to be capable of receiving at least circularly polarized waves, receive radio waves by, Detect the arrival direction of the radio wave based on the phase differences of a plurality of received signals of each of the first antenna element, the plurality of second antenna elements, and the plurality of third antenna elements. A radio wave receiving method by an antenna device, The aperture diameter of the ring formed by the plurality of second antenna elements is different from the aperture diameter of the ring formed by the plurality of third antenna elements, At least one of the number of the plurality of second antenna elements and the number of the plurality of third antenna elements is odd. A radio wave receiving method by an antenna device.

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