Antenna device and sandwich array device

Abstract

This antenna device comprises: a circular phased array antenna (1) comprising an N number (N being a natural number of at least 3) of first antenna elements arranged at even intervals on a circle and one second antenna element arranged approximately at the center of the circle; and a circular bottom plate (2) having a radius that can be varied by switching control. The first antenna elements and the second antenna element comprise a mono-pole antenna mounted to the bottom plate (2).

Description

[Technical field]

[0001] The present invention relates to an antenna device and a sandwich array device. [Background technology]

[0002] In recent years, there are high expectations for the practical application of flying cars as vehicles that can be used for commuting to work or school while avoiding traffic jams in cities, as a new means of transportation on remote islands or in mountainous areas, or for emergency transport or rapid transportation of goods in the event of a disaster. When flying cars are put to practical use, there is much interest in the realization of communication between flying cars (between flying vehicles).

[0003] For example, Patent Document 1 discloses a receiving antenna device capable of detecting the direction of arrival of a received radio wave in a horizontal plane. According to this, by using a circularly arranged phased array antenna consisting of antenna elements arranged at equal intervals on a circle and an antenna element arranged at the center, it is possible to realize an antenna device that can be configured small and lightweight and can detect the direction of arrival of a received radio wave with high accuracy. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 59-114907 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the technology disclosed in Patent Document 1 has a problem that although it can estimate the direction of arrival waves in the horizontal direction, it cannot estimate the direction of arrival waves in the elevation angle direction. In other words, since a flying car can freely change its flight direction in the horizontal and vertical directions, unlike conventional automobiles, the target with which it communicates is not limited to the horizontal plane, and therefore an antenna with radiation characteristics over the entire solid angle is required.

[0006] The present invention has been made in consideration of the above-mentioned circumstances, and has an object to provide an antenna device and a sandwich array device capable of estimating the direction of arrival of an incoming wave not only in the horizontal direction but also in the elevation angle direction, and capable of high-speed communication. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, an antenna device according to one embodiment of the present invention comprises a circularly arranged phased array antenna consisting of N first antenna elements (N is a natural number greater than or equal to 3) arranged at equal intervals on a circle and one second antenna element arranged approximately at the center of the circle, and a circular base plate whose radius is variable by switching control, and the first antenna elements and the second antenna element are formed as monopole antennas mounted on the base plate.

[0008] This configuration makes it possible to realize an antenna device capable of estimating the direction of arrival of waves not only in the horizontal direction but also in the elevation angle direction, thereby enabling high-speed communication.

[0009] Here, for example, the first antenna element and the second antenna element are configured as 1 / 4 wavelength monopole antennas.

[0010] Also, for example, the antenna may include a subarray control unit that divides the N first antenna elements into the N / 2 subarrays orthogonal to the direction of the incoming wave, which is a direction parallel to the ground plane of the incoming wave arriving at the circularly arranged phased array antenna, and controls the directivities of the subarrays to independently form the N / 2 beams facing the direction of the incoming wave.

[0011] This configuration makes it possible to control the directivity according to the estimated direction of the incoming wave, thereby enabling an optimal received signal to be obtained at all times and realizing high-speed communication.

[0012] Here, each of the N / 2 subarrays may be configured by a combination of two antenna elements whose arrangement directions are parallel, and the combination may be changed according to the direction of arrival of the wave.

[0013] The present invention may further include a directivity control unit that controls the directivity of the circularly arranged phased array antenna within a predetermined angle range including the elevation angle direction by imparting phases to two of the first antenna elements that are closest to a desired communication direction in order to form delta directivity and sigma directivity, the phases being calculated using a path difference in an elevation angle direction, which is a direction in which an incoming wave arriving at the circularly arranged phased array antenna makes with the ground plane, and the delta directivity is a directivity that reduces radiation gain by realizing anti-phase excitation in the elevation angle direction, and the sigma directivity is a directivity that increases radiation gain by realizing in-phase excitation in the elevation angle direction.

[0014] With this configuration, directivity can be formed within an angular range in a predetermined direction, so that communication can be achieved only with the target.

[0015] The antenna may further include a calculation unit that performs statistical analysis on a first signal and a second signal obtained by multiplying the received signal of each of the first antenna elements by two weights according to the arrangement of the first antenna elements and adding them up, and a third signal that is the received signal of the second antenna element, and calculates a phase difference between the first signal and the third signal, thereby estimating a direction of arrival of an incoming wave that arrives at the circularly arranged phased array antenna, which is a direction of an incoming wave that arrives at the circularly arranged phased array antenna relative to the ground plane, wherein the calculation unit calculates a phase angle of the voltage of the third signal by averaging the phase angle of the voltage of the first signal and the phase angle of the voltage of the second signal, thereby calculating the phase difference between the first signal and the third signal, and the phase difference may be approximately proportional to the direction of arrival of the wave.

[0016] In addition, in order to achieve the above-mentioned object, a sandwich array device according to one embodiment of the present invention comprises a first antenna device and a second antenna device which are two antenna devices of any of the above-mentioned aspects, wherein the first antenna device is arranged at the zenith part of the flying vehicle and the second antenna device is arranged at the nadir part of the flying vehicle, and the erection directions of the circularly arranged phased array antennas of the first antenna device and the second antenna device as viewed from the ground plate are opposite to each other.

[0017] These general or specific aspects may be realized by a system, a method, an integrated circuit, a computer program, or a recording medium such as a computer-readable CD-ROM, or may be realized by any combination of the system, the method, the integrated circuit, the computer program, and the recording medium. Effect of the Invention

[0018] According to the antenna device etc. of the present invention, the direction of arrival of a wave can be estimated not only in the horizontal direction but also in the elevation angle direction, enabling high-speed communication. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is a diagram illustrating an example of a schematic configuration of an antenna device according to an embodiment. [Diagram 2] FIG. 2 is a diagram showing a specific configuration example of the circularly arranged phased array antenna shown in FIG. [Figure 3A] FIG. 3A is a diagram showing an example of the configuration of a base plate whose size is variable according to the embodiment. [Figure 3B] FIG. 3B is a diagram showing a specific configuration used to switch the size of the ground plate shown in FIG. 3A. [Figure 4] FIG. 4 is a diagram showing a specific example of the configuration of a sub-array when radio waves arrive from the +X-axis direction of a circularly arranged phased array antenna according to an embodiment. [Figure 5A] FIG. 5A is a diagram showing an example of a schematic configuration of a sandwich array device according to an embodiment. [Figure 5B] FIG. 5B is a diagram showing a use case of the sandwich array device shown in FIG. 5A. [Figure 6] FIG. 6 is a diagram showing a concept of communication between flying vehicles using a sandwich array device according to an embodiment. [Figure 7A] FIG. 7A is a diagram showing the positional relationship in the XY plane of the first antenna element excited to form a monopulse directivity. [Figure 7B] FIG. 7B shows the elevation path difference used to design the delta and sigma beam patterns. [Figure 7C] FIG. 7C illustrates the angles used to determine the electrical length of the excited first antenna element shown in FIG. 7A. [Figure 8] FIG. 8 is a diagram showing the relationship between the phase and elevation angle of the first antenna elements #1 and #8 required to form sigma directivity and delta directivity. [Figure 9A] FIG. 9A is a diagram showing an example of sigma and delta directivities forming a monopulse directivity that realizes the space division monopulse method. [Figure 9B] FIG. 9B illustrates the concept of two pulses transmitted to form a monopulse directivity. [Figure 10A] FIG. 10A is a diagram showing an example of an analysis result of sigma directivity and delta directivity of a circularly arranged phased array antenna formed in directional scanning in the elevation angle direction according to the embodiment. [Figure 10B] FIG. 10B is a diagram showing an example of an analysis result of sigma directivity and delta directivity of a circularly arranged phased array antenna formed in directional scanning in the elevation angle direction according to the embodiment. [Figure 10C] FIG. 10C is a diagram showing an example of an analysis result of sigma directivity and delta directivity of a circularly arranged phased array antenna formed in directional scanning in the elevation angle direction according to the embodiment. [Figure 10D]FIG. 10D is a diagram showing an example of an analysis result of sigma directivity and delta directivity of a circularly arranged phased array antenna formed in directional scanning in the elevation angle direction according to the embodiment. [Figure 10E] FIG. 10E is a diagram showing an example of an analysis result of sigma directivity and delta directivity of a circularly arranged phased array antenna formed in directional scanning in the elevation angle direction according to the embodiment. [Figure 10F] FIG. 10F is a diagram showing an example of an analysis result of sigma directivity and delta directivity of a circularly arranged phased array antenna formed in directional scanning in the elevation angle direction according to the embodiment. [Figure 11A] FIG. 11A is a diagram showing an example of an analysis result of sigma directivity and delta directivity of a circularly arranged phased array antenna formed in horizontal directional scanning according to an embodiment. [Figure 11B] FIG. 11B is a diagram showing an example of an analysis result of sigma directivity and delta directivity of a circularly arranged phased array antenna formed in horizontal directional scanning in the embodiment. [Figure 11C] FIG. 11C is a diagram showing an example of an analysis result of sigma directivity and delta directivity of a circularly arranged phased array antenna formed in horizontal directional scanning in the embodiment. [Figure 11D] FIG. 11D is a diagram showing an example of an analysis result of sigma directivity and delta directivity of a circularly arranged phased array antenna formed in horizontal directional scanning in the embodiment. [Figure 11E] FIG. 11E is a diagram showing an example of an analysis result of sigma directivity and delta directivity of a circularly arranged phased array antenna formed in horizontal directional scanning in the embodiment. [Figure 11F] FIG. 11F is a diagram showing an example of an analysis result of sigma directivity and delta directivity of a circularly arranged phased array antenna formed in horizontal directional scanning in the embodiment. [Figure 11G]FIG. 11G is a diagram showing an example of an analysis result of sigma directivity and delta directivity of a circularly arranged phased array antenna formed in horizontal directional scanning in the embodiment. [Figure 11H] FIG. 11H is a diagram showing an example of an analysis result of sigma directivity and delta directivity of a circularly arranged phased array antenna formed in horizontal directional scanning in the embodiment. [Figure 12] FIG. 12 is a diagram showing the voltage of a signal induced in a circularly arranged phased array antenna in the comparative example. [Figure 13A] FIG. 13A is a diagram showing the directional characteristics of a first signal and a third signal in the XY plane in the comparative example. [Figure 13B] FIG. 13B is a diagram showing phase characteristics in the XY plane of the first signal and the third signal in the comparative example. [Figure 14] FIG. 14 is a diagram illustrating two weighting functions of the first antenna element of the circularly arranged phased array antenna according to the embodiment. [Figure 15A] FIG. 15A shows the elevation angle directivity of the first signal obtained by performing electromagnetic field analysis using the method of moments. [Figure 15B] FIG. 15B shows the elevation angle directivity of the third signal obtained by performing electromagnetic field analysis using the method of moments. [Figure 16] FIG. 16 is a schematic diagram for explaining the principle of the phase inversion weighting method. [Figure 17] FIG. 17 is a diagram showing three-dimensional directivities of a first signal and a third signal in the embodiment. [Figure 18A] FIG. 18A shows the angular characteristics of the directivity and the estimated direction of arrival wave when the elevation angle is 30 degrees. [Figure 18B] FIG. 18B shows the angular characteristics of the directivity and the estimated direction of arrival wave when the elevation angle is 80 degrees. [Figure 19] FIG. 19 is a diagram showing a change in transmission capacity with respect to the elevation angle direction of an arriving wave when the radius of the base plate is changed in the embodiment. [Figure 20A] FIG. 20A is a diagram showing three-dimensional radiation directivity of a dipole array antenna in a comparative example. [Figure 20B] FIG. 20B is a diagram showing three-dimensional radiation directivity of the monopole array antenna in the embodiment. [Figure 21A] FIG. 21A is a diagram showing three-dimensional directivity when directional scanning is performed by the sandwich array device according to the embodiment. [Figure 21B] FIG. 21B is a diagram showing three-dimensional directivity when directional scanning is performed by the sandwich array device according to the embodiment. [Figure 21C] FIG. 21C is a diagram showing three-dimensional directivity when directional scanning is performed by the sandwich array device according to the embodiment. [Figure 21D] FIG. 21D is a diagram showing three-dimensional directivity when directional scanning is performed by the sandwich array device according to the embodiment. [Figure 22A] FIG. 22A is a diagram showing three-dimensional directivity when directional scanning is performed by the sandwich array device according to the embodiment. [Figure 22B] FIG. 22B is a diagram showing three-dimensional directivity when directional scanning is performed by the sandwich array device according to the embodiment. [Figure 22C] FIG. 22C is a diagram showing three-dimensional directivity when directional scanning is performed by the sandwich array device according to the embodiment. [Figure 22D] FIG. 22D is a diagram showing three-dimensional directivity when directional scanning is performed by the sandwich array device according to the embodiment. [Figure 23] FIG. 23 is a diagram showing the elevation angle characteristics of the transmission capacity of a MIMO array antenna using a half-wavelength dipole array antenna in a comparative example. [Figure 24A] FIG. 24A is a diagram illustrating the azimuth characteristics of the transmission capacity of a MIMO array antenna using a sandwich array device according to the embodiment. [Figure 24B]FIG. 24B is a diagram illustrating the elevation angle characteristics of the transmission capacity of the MIMO array antenna using the sandwich array device according to the embodiment. [Diagram 25] FIG. 25 is a diagram showing the three-dimensional transmission capacity over the entire solid angle of a MIMO array antenna using half-wavelength dipole array antennas in a comparative example. [Figure 26] FIG. 26 is a diagram illustrating three-dimensional transmission capacity over the entire solid angle of a MIMO array antenna using a sandwich array device according to an embodiment. [Figure 27] FIG. 27 is a diagram showing communication outage probability over the entire solid angle of a MIMO array antenna using a sandwich array device according to an embodiment. [Figure 28] FIG. 28 is a diagram showing an example of a multi-element MIMO array antenna in a modified example. [Figure 29A] FIG. 29A is a diagram showing an example of a 4×4 MIMO array antenna in a modified example. [Figure 29B] FIG. 29B is a diagram showing an example of an 8×8 MIMO array antenna in a modified example. [Figure 29C] FIG. 29C is a diagram illustrating an example of a 16×16 MIMO array antenna in a modified example. [Figure 29D] FIG. 29D is a diagram showing an example of a 32×32 MIMO array antenna in a modified example. [Figure 29E] FIG. 29E is a diagram showing an example of a 64×64 MIMO array antenna in a modified example. [Figure 29F] FIG. 29F is a diagram showing an example of a 128×128 MIMO array antenna in a modified example. [Figure 29G] FIG. 29G is a diagram showing an example of a 256×256 MIMO array antenna in a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Note that the embodiments described below each show a specific example of the present invention. The numerical values, shapes, materials, components, the arrangement and connection of the components, steps, and the order of steps shown in the following embodiments are merely examples and are not intended to limit the present invention. Furthermore, among the components in the following embodiments, components that are not described in the independent claims showing the highest concept are described as optional components.

[0021] (Embodiment) [Antenna device configuration] FIG. 1 is a diagram showing an example of a schematic configuration of an antenna device 10 according to the present embodiment.

[0022] As shown in Fig. 1, an antenna device 10 in this embodiment includes a circularly arranged phased array antenna 1, a base plate 2, a control unit 3, and a calculation unit 4. The antenna device 10 in this embodiment is mounted on, for example, a flying vehicle (also called a flying car). In the example shown in Fig. 1, the circularly arranged phased array antenna 1 has nine antenna elements. θ shown in Fig. 1 represents an elevation angle.

[0023] [Circularly arranged phased array antenna 1] Fig. 2 is a diagram showing a specific configuration example of the circularly arranged phased array antenna 1 shown in Fig. 1. φ shown in Fig. 2 is a direction that intersects with the X-axis in a horizontal plane (XY plane), and represents the direction of an arriving wave (arrival wave direction) in the XY plane.

[0024] 1 and 2, the circularly arranged phased array antenna 1 is composed of N first antenna elements (N is a natural number equal to or greater than 3) arranged at equal intervals on a circle, and one second antenna element arranged approximately at the center of the circle. The first antenna element and the second antenna element are monopole antennas mounted on a ground plate 2 and configured on the ground plate 2. In this embodiment, the first antenna element and the second antenna element are 1 / 4 wavelength monopole antennas and have a radius r g It is constructed on a base plate 2.

[0025] As a result, the circularly arranged phased array antenna 1 not only has a substantially omnidirectional directivity in the plane (horizontal plane) including the circular area, but also has a directivity in the zenith direction (the +Z-axis direction in FIG. 1).

[0026] Hereinafter, a case where N=8, that is, where the circularly arranged phased array antenna 1 includes eight first antenna elements, will be described as an example.

[0027] For example, as shown in Fig. 2, the circularly arranged phased array antenna 1 is composed of eight antenna elements (first antenna elements: #1 to #8) arranged at 45 degree intervals on a circumference of a radius a, and one parasitic antenna element (second antenna element: #9) arranged at the center of the circle. Here, the radius a is, for example, 4.9 cm. Furthermore, these nine antenna elements are quarter-wavelength monopole antennas, and are arranged on a circumference of a radius r g It is constructed on a base plate 2.

[0028] Then, by calculating the difference between the phase of the sum of the received signals of the eight first antenna elements and the phase of the received signal of the single second antenna element located in the center, the arrival direction of the received signal, which also has an angle in the elevation direction, can be estimated. The details of the estimation method will be described later, but the phase angle of the voltage of the signal induced in the second antenna element (#9) by the incoming received radio waves is synthesized using a phase inversion weighting method, which will be described later.

[0029] Furthermore, in the circularly arranged phased array antenna 1, the eight antenna elements (first antenna elements: #1 to #8) are divided and controlled (phase-difference fed) into sub-arrays consisting of four pairs of elements so as to be orthogonal to the direction of the incoming wave according to the direction of the incoming wave by the control unit 3. This allows the circularly arranged phased array antenna 1 to operate as a directional scanning array antenna such as a MIMO (Multiple Input Multiple Output) array antenna.

[0030] Moreover, the radiation directivity in the elevation angle direction of the circularly arranged phased array antenna 1 is optimized by switching control of the radius of the ground plate 2. In other words, when the circularly arranged phased array antenna 1 is operated as a MIMO array antenna, the radius of the ground plate 2 is switched and controlled to be different from that when estimating the direction of arrival waves.

[0031] Furthermore, in the circularly arranged phased array antenna 1, the directivity in the elevation angle direction is controlled within a predetermined angle range including the elevation angle direction by the control unit 3 using a space division monopulse method described later.

[0032] [Main plate 2] The base plate 2 is rotated by switching control to a radius r g In this embodiment, the ground plane 2 is a planar (plate-shaped) conductor, as shown in FIG. 1. The radius r g The size is made variable because the optimal size of the base plate 2 differs when the circularly arranged phased array antenna 1 is used to estimate the direction of arrival waves and when it is operated as a MIMO array antenna.

[0033] Fig. 3A is a diagram showing an example of the configuration of the base plate 2 having a variable size in this embodiment. Fig. 3B is a diagram showing a specific configuration used to switch the size of the base plate 2 shown in Fig. 3A.

[0034] Radius r of base plate 2 g The switching of the diode 301 is controlled by the control unit 3. In this embodiment, as shown in FIG. 3A, the diode 301 is controlled to be turned on and off, and the radius r g 3B, a diode 301 and a choke coil 302 are connected to the ground plane 2, and a bias voltage V d In this case, the size of the ground plane 2 may be controlled by applying a bias voltage V of, for example, 5V. dis given, the diode 301 turns on and current flows through the outer ground plane 2a, so that the radius r g is changed to 10 cm. Also, for example, the bias voltage V d is given, the diode 301 is turned off, no current flows through the outer ground plane 2a, and only the inner ground plane 2b is active, so that the radius r g will be changed to 7cm.

[0035] In addition, the radius r of the base plate 2 g The size is not limited to being switched to either 7 cm or 10 cm, but may be switched to an appropriate size depending on the system to be realized.

[0036] [Control Unit 3] The control unit 3 has a subarray control function for dividing and controlling the circularly arranged phased array antenna 1 into subarrays. More specifically, the control unit 3 divides the N first antenna elements into N / 2 subarrays orthogonal to the direction of the incoming wave, which is a direction parallel to the ground plane 2 of the incoming wave arriving at the circularly arranged phased array antenna 1. The control unit 3 then controls the directivity of the subarrays in this manner to independently form N / 2 beams facing the direction of the incoming wave.

[0037] Here, each of the N / 2 subarrays is composed of a combination of two antenna elements whose arrangement direction is parallel, and the combination is changed according to the direction of the incoming wave. There are N / 2 combination patterns. The control unit 3 changes the combination according to the direction of the incoming wave by selecting, from the N / 2 combination patterns, a combination pattern of two antenna elements that are parallel to the direction of the incoming wave within a predetermined angle range.

[0038] FIG. 4 is a diagram showing a specific example of the configuration of sub-arrays when radio waves arrive from the +X-axis direction of the circularly arranged phased array antenna 1 in this embodiment.

[0039] For example, since the circularly arranged phased array antenna 1 includes eight first antenna elements, the control unit 3 selects one of four combination patterns according to the direction of the incoming wave. In the example shown in Fig. 4, combinations are shown in which the first antenna elements #2 and #3, the first antenna elements #1 and #4, the first antenna elements #5 and #8, and the first antenna elements #6 and #7 are each configured as a sub-array (sub-arrays 1 to 4).

[0040] Generally, in a cluster propagation environment, when the arrangement of the subarrays is parallel to the direction of the incoming wave, the correlation of the received signals is high, whereas when it is perpendicular, the correlation of the received signals is low. The control unit 3 divides the eight first antenna elements of the circularly arranged phased array antenna 1 into four so that the combination of the subarrays is arranged perpendicular to the direction of the incoming wave, so that the four received signals have low correlation. Furthermore, since the eight first antenna elements are arranged in a circle at 45 degree intervals in the circularly arranged phased array antenna 1, the control unit 3 can rotate the combination of the subarrays every 45 degrees by switching the power supply of the subarrays according to the direction of the incoming wave.

[0041] The control unit 3 also has a full solid angle directivity control function that controls the directivity of the circularly arranged phased array antenna 1 within a predetermined angle range including the elevation angle direction by using the space division monopulse method. More specifically, the control unit 3 controls the directivity of the circularly arranged phased array antenna 1 within a predetermined angle range including the elevation angle direction by providing the phases given to form delta directivity and sigma directivity to the two first antenna elements that are closest to the desired communication direction. Here, the delta directivity is a directivity that reduces the radiation gain by realizing anti-phase excitation in the elevation angle direction, and the sigma directivity is a directivity that increases the radiation gain by realizing in-phase excitation in the elevation angle direction. The delta directivity and sigma directivity are calculated using the path difference in the elevation angle direction, which is the direction of the incoming wave arriving at the circularly arranged phased array antenna 1 and the ground plane 2. The space division monopulse method is a method of realizing an SLS function (Side Lobe Suppression) using sigma directivity and delta directivity. Details will be described later.

[0042] In addition, the control unit 3 has a switching control function for controlling the radius size of the ground plate 2. For example, as shown in FIG. 3B, the control unit 3 controls the bias voltage V d By controlling the voltage to 0V or 5V, the radius of the ground plate 2 can be controlled.

[0043] [Calculation section 4] The calculation unit 4 has an arrival wave direction estimation function for estimating the arrival wave direction, which is the direction of the arrival wave arriving at the circularly arranged phased array antenna 1. More specifically, the calculation unit 4 statistically analyzes the first signal and the second signal, which are obtained by multiplying the received signals of the first antenna elements by two weights according to the arrangement of the first antenna elements and summing them, and the third signal, which is the received signal of the second antenna element, and calculates the phase difference between the first signal and the third signal. Here, the phase difference is approximately proportional to the arrival wave direction. In this manner, the calculation unit 4 estimates the arrival wave direction, which also has an angle in the elevation angle direction of the arrival wave arriving at the circularly arranged phased array antenna 1, by calculating the phase difference between the first signal and the third signal. In this embodiment, the calculation unit 4 calculates the phase angle of the voltage of the third signal by averaging the phase angle of the voltage of the first signal and the phase angle of the voltage of the second signal, thereby calculating the phase difference between the first signal and the third signal. Furthermore, in this embodiment, a calculation for finding an average value is performed as the statistical analysis, but it is not limited to the calculation for finding an average value, and it may be combined with a calculation performed to adapt to a multipath environment.

[0044] In this embodiment, each of the eight first antenna elements has two weights according to the arrangement of the first antenna elements, as shown in Fig. 2. Therefore, the calculation unit 4 obtains a first signal by multiplying each of the received signals of the eight first antenna elements by one of the weights (counterclockwise weights) of each of the eight first antenna elements and adding up the results. The calculation unit 4 also obtains a second signal by multiplying each of the received signals of the eight first antenna elements by the other weights (clockwise weights) of each of the eight first antenna elements and adding up the results. The calculation unit 4 also obtains a third signal from the second antenna element.

[0045] The calculation unit 4 can estimate the direction of arrival of the received signal, which also has an angle in the elevation direction, by calculating the difference between the phase of the voltage of the first signal and the phase of the voltage of the third signal. The phase of the voltage of the third signal is calculated by applying a phase inversion weighting method to combine, i.e., average, the phase of the voltage of the first signal and the phase of the voltage of the second signal.

[0046] [Effects, etc.] As described above, the antenna device 10 of the present embodiment is configured with a circularly arranged phased array antenna 1 on the ground plate 2, which is composed of a plurality of first antenna elements arranged at equal intervals on a circle and one second antenna element arranged approximately at the center of the circle. The first antenna element and the second antenna element are monopole antennas mounted on the ground plate 2. As a result, the antenna device 10 of the present embodiment can estimate the direction of arrival of a wave not only in the horizontal direction but also in the elevation angle direction. In addition, the antenna device 10 of the present embodiment can control the directivity with respect to the estimated direction of arrival of a wave. As a result, an optimal reception signal can be obtained at all times, and high-speed communication can be realized. Furthermore, the antenna device 10 of the present embodiment can control the directivity to an angle range of a predetermined direction including the elevation angle direction, so that communication can be performed only with a target communication partner.

[0047] In addition, in the antenna device 10 of this embodiment, the second antenna element, which is a parasitic element arranged at the center of the circularly arranged phased array antenna 1, contributes to improving the gain by utilizing electromagnetic coupling. Moreover, the radiation directivity in the elevation angle direction of the antenna device 10 of this embodiment is optimized by switching control of the size of the base plate 2.

[0048] The antenna device 10 of this embodiment has directional characteristics not only in the horizontal direction but also in the zenith direction (+Z-axis direction in FIG. 1), but does not have directional characteristics in the downward direction of the base plate 2 (-Z direction in FIG. 1). Therefore, by arranging the antenna devices 10 in a sandwich shape above and below, it is possible to provide directivity over the entire solid angle. Below, a sandwich array device 100 in which the antenna devices 10 are arranged in a sandwich shape above and below will be described.

[0049] [Sandwich array device 100] FIG. 5A is a diagram showing an example of a schematic configuration of a sandwich array device 100 according to this embodiment.

[0050] As shown in Fig. 5A, the sandwich array device 100 includes two of the above-mentioned antenna devices 10, which are sandwiched vertically (in the Z-axis direction in Fig. 5A). More specifically, the sandwich array device 100 includes two antenna devices 10, a first antenna device 10A and a second antenna device 10B. The standing direction of the circularly arranged phased array antenna 1A as viewed from the ground plate 2A of the first antenna device 10A is opposite to the standing direction of the circularly arranged phased array antenna 1B as viewed from the ground plate 2B of the second antenna device 10B. This configuration allows the sandwich array device 100 to have radiation characteristics over the entire solid angle.

[0051] FIG. 5B is a diagram showing a use case of the sandwich array device 100 shown in FIG. 5A.

[0052] 5B, the sandwich array device 100 is mounted on an air vehicle 300 as a use case. More specifically, the first antenna device 10A is disposed at the zenith of the air vehicle 300, and the second antenna device 10B is disposed at the nadir of the air vehicle 300. The standing direction of the circularly arranged phased array antenna 1A as viewed from the ground plate 2A of the first antenna device 10A is opposite to the standing direction of the circularly arranged phased array antenna 1B as viewed from the ground plate 2B of the second antenna device 10B.

[0053] The flying vehicle 300 is also called a flying car, and can freely change its flying direction in the horizontal and vertical directions (up and down). In order to perform highly reliable communication between the flying vehicles 300, it is necessary to achieve MIMO communication between the flying vehicles 300 in any direction. In other words, the flying vehicle 300 needs an antenna having radiation characteristics over the entire solid angle. Therefore, the flying vehicle 300 is equipped with the sandwich array device 100, so that communication between the flying vehicles can be performed.

[0054] In the flying vehicle 300, the antenna devices 10A and 10B of the sandwich array device 100 can be switched according to the direction of arrival of the received signal to realize communication between the upper and lower sides. The radiation directivity of the antenna devices 10A and 10B in the elevation direction can be controlled by changing the size of the base plate 2 and the base plate 2B. Of course, if the communication partner is fixed on the zenith side of the flying vehicle 300, the flying vehicle 300 may use only the upper antenna device 10A. If the communication partner is fixed on the nadir side, the flying vehicle 300 may use only the lower antenna device 10B.

[0055] As described above, the flying vehicle 300 can estimate the direction of arrival of the received signal over the entire solid angle by mounting the sandwich array device 100, and can direct the directivity to the estimated direction of arrival, thereby realizing highly reliable communication between the flying vehicles. The antenna device 10 constituting the sandwich array device 100 can estimate the direction of arrival of the wave in a simple manner by processing in the RF section. More specifically, as shown in FIG. 5A, eight first antenna elements constituting the circularly arranged phased array antennas 1A and 1B are arranged in a circle at intervals of 45 degrees. Therefore, the flying vehicle 300 can rotate the combination of the subarrays every 45 degrees by switching the power supply for dividing and controlling the eight first antenna elements into subarrays according to the direction of arrival of the wave. As a result, even if the flying vehicle 300 freely changes the flight direction up, down, left, and right in space, it is possible to appropriately select the combination of the subarrays arranged perpendicular to the direction of arrival of the wave, thereby improving the transmission capacity.

[0056] Furthermore, the flying vehicle 300 can use the sandwich array device 100 to direct a beam in the estimated direction of the incoming wave of the received signal, making it possible to network with other flying vehicles and not only prevent collisions with other flying vehicles but also exchange high-quality video content.

[0057] Furthermore, the flying vehicle 300 can form directivity with spatial division over the entire solid angle by forming directivity while sequentially shifting (spatially dividing) the angular range in a predetermined direction using the sandwich array device 100. This allows the flying vehicle 300 to eliminate synchronous interference and communicate only with the target flying vehicle, even if there are multiple other flying vehicles with which it can communicate in the space.

[0058] The following describes the space division monopulse method used to control directivity within an angular range in a predetermined direction.

[0059] <Space division monopulse method> Fig. 6 is a diagram showing the concept of communication between flying vehicles using the sandwich array device 100 according to the present embodiment. Fig. 6 shows four flying vehicles 300 that can freely change their flight direction, and are referred to as flying vehicles 300a, 300b, 300c, and 300d, respectively. Each of the flying vehicles 300a to 300d is equipped with a sandwich array device 100 that is configured with antenna devices 10A and 10B.

[0060] As shown in FIG. 6, in order to communicate between a plurality of flying vehicles 300 (between flying vehicles), each sandwich array device 100 needs to have radiation characteristics over the entire solid angle. However, if there is synchronous interference, communication cannot be performed correctly, and there is a risk of collision between the plurality of flying vehicles 300. In other words, for example, in order for the flying vehicle 300a to communicate with the flying vehicles 300b, 300c, and 300d, it is necessary to realize communication with the flying vehicles 300b to 300d in any direction. On the other hand, if the flying vehicle 300a communicates with the flying vehicles 300b, 300c, and 300d simultaneously (synchronously), it will not be able to distinguish between the flying vehicles 300b, 300c, and 300d, and in the worst case, there is a risk of collision. For this reason, a collision prevention function is required.

[0061] This collision prevention function is realized in the sandwich array device 100, i.e., the antenna device 10, by using the space division monopulse method to control the directivity to a specified angular range while sequentially shifting (spatially dividing) the angular range in the specified direction.

[0062] Hereinafter, a method for calculating phases for forming delta directivity and sigma directivity will be described as a method for forming directivity in an angular range in a predetermined direction (hereinafter, also referred to as a method for forming monopulse directivity).

[0063] Fig. 7A is a diagram showing the positional relationship in the XY plane of the first antenna element excited to form a monopulse directivity. Fig. 7B is a diagram showing the path difference in the elevation angle direction used to design the delta directivity and the sigma directivity. Fig. 7C is a diagram showing the angle used to calculate the electrical length of the excited first antenna element shown in Fig. 7A.

[0064] To form a monopulse directivity, for example, of the eight first antenna elements shown in Fig. 7A, four first antenna elements (#1, #2, #7, #8) are excited and the remaining first antenna elements (#3, #4, #5, #6) are terminated at 50 Ω. In this case, due to the path difference in the elevation angle direction shown in Fig. 7B, the electrical length between the first antenna element #1 and the first antenna element #2 or the electrical length between the first antenna element #7 and the first antenna element #8 can be found by (Equation 1).

[0065]

number

[0066] Here, the distance S shown in Fig. 7A, in other words, the distance S between the first antenna element #7 and the first antenna element #8 in the X direction, can be expressed using the radius a of the circularly arranged phased array antenna 1 shown in Fig. 7A and the angle δ shown in Fig. 7C, i.e., S = a cos δ - a sin δ = a (cos δ - sin δ).

[0067] Additionally, from the addition theorem of trigonometric functions, sin(α-β)=sinα·cosβ-cosα·sinβ holds. If α=π / 4 and β=δ, then this can be transformed to sin(π / 4-δ)=sin(π / 4)·cosδ-cos(π / 4)·sinδ=1 / √2(cosδ-sinδ).

[0068] Therefore, we can derive that cosδ-sinδ=√2sin(π / 4-δ).

[0069] 7C is 22.5 degrees, the distance S can be transformed as follows: S=a(cos δ-sin δ)=√2a·sin(π / 4-δ)=√2a·sin(π / 8).

[0070] On the other hand, as shown in Figure 7B, Δl = S cosθ, which can be transformed to Δl = S cosθ = √2a sin(π / 8) cosθ. In this way, the above (Equation 1) can be obtained.

[0071] Here, since k=2π / λ, the sigma directivity can be expressed by the following (Equation 2), and the delta directivity can be expressed by the following (Equation 3). As described above, the sigma directivity is a directivity that increases the radiation gain by realizing in-phase excitation in the elevation angle direction, and the delta directivity is a directivity that decreases the radiation gain by realizing anti-phase excitation in the elevation angle direction.

[0072]

number

[0073]

number

[0074] Fig. 8 is a diagram showing the relationship between the phase and elevation angle of the first antenna elements #1 and #8 required to form sigma directivity and delta directivity. In Fig. 8, the phase of the first antenna elements #2 and #7 is set to 0. In Fig. 8, the frequency used in the analysis is 2 GHz, the radius a of the circularly arranged phased array antenna 1 in this embodiment is 4.9 cm, and the radius r of the base plate 2 is 1.0 cm. g is set at 7cm.

[0075] The elevation angle is an angle defined as 0 degrees in the horizontal plane (XY plane in Figure 2), +90 degrees in the zenith direction (+Z-axis direction in Figure 1), and -90 degrees in the nadir direction (-Z-axis direction in Figure 1).

[0076] From FIG. 8, when the elevation angle is 45 degrees, φ1=φ8=-45 degrees for sigma directivity, and φ1=φ8=135 degrees for delta directivity. As shown in FIG. 1, FIG. 7A, and FIG. 7C, the eight first antenna elements constituting the circularly arranged phased array antenna 1 have a rotationally symmetric structure. For this reason, four first antenna elements (#1, #2, #3, #8) rotated by 45 degrees are excited, and the other first antenna elements (#4, #5, #6, #7) are terminated with 50 Ω, and the phases that realize in-phase excitation and anti-phase excitation in this case are calculated. In other words, the combination of the four first antenna elements to be excited is rotated by 45 degrees in the azimuth direction, and the phases that realize in-phase excitation and anti-phase excitation are calculated each time, so that sigma directivity and delta directivity can be formed in all azimuth directions. The azimuth direction is an angle defined in FIG. 2 or FIG. 7B with the +X-axis direction being 0 degrees and the +Y-axis direction being 90 degrees, and is represented by φ in FIG.

[0077] Fig. 9A is a diagram showing an example of sigma directivity and delta directivity forming a monopulse directivity that realizes the space division monopulse method. Fig. 9B is a diagram showing the concept of two pulses P1 and P2 transmitted to form the monopulse directivity. As described above, the space division monopulse method is a method for realizing a side lobe suppression function by sigma directivity and delta directivity.

[0078] As shown in Fig. 9A, in the forward direction (upward in Fig. 9A), there exists an area where the sigma directivity is 9 dB higher than the delta directivity within a certain angle range. Furthermore, the side lobe of the sigma directivity is completely encompassed by the delta directivity.

[0079] In TCAS II (Traffic alert and Collision Avoidance System II), the interrogator transmits two pulses P1 and P2 to the surrounding target aircraft as shown in FIG. 9B. The pulses P1 and P2 are transmitted with the same power, with the pulse P1 being transmitted with sigma directivity and the pulse P2 being transmitted with delta directivity. The target aircraft responds by providing an ID code or the like only when the pulse P2 is 9 dB smaller than the pulse P1. In other words, in TCAS II, only the transponders of the target aircraft present in this predetermined angle range respond. This allows the interrogator to communicate only with the target aircraft present in the predetermined angle range shown in FIG. 9A, thereby eliminating synchronous interference. Furthermore, in TCAS II, the interrogator can selectively perform space division for communication, thereby implementing an interrogation-response sequence across the entire space.

[0080] In this way, by using the space division monopulse method, it is possible to achieve the same side lobe suppression function as a large SSR antenna, even with a small antenna.

[0081] 10A to 10F are diagrams showing an example of analysis results of the sigma directivity and delta directivity of the circularly arranged phased array antenna 1 formed in directional scanning in the elevation angle direction in this embodiment. More specifically, FIG. 10A to FIG. 10F are calculation results of the sigma directivity and delta directivity formed at an elevation angle represented by θ when the phase calculated using FIG. 8 is given to the first antenna elements #1 and #8. FIG. 10A is a calculation result of the sigma directivity and delta directivity formed at θ=0 degrees, FIG. 10B is a calculation result of the sigma directivity and delta directivity formed at θ=15 degrees, FIG. 10C is a calculation result of the sigma directivity and delta directivity formed at θ=30 degrees, FIG. 10D is a calculation result of the sigma directivity and delta directivity formed at θ=45 degrees, FIG. 10E is a calculation result of the sigma directivity and delta directivity formed at θ=60 degrees, and FIG. 10F is a calculation result of the sigma directivity and delta directivity formed at θ=75 degrees. Also, FIG. 10A to FIG. 10F show a predetermined angle range δ in which the delta directivity is 9 dB smaller than the sigma directivity in the directivity of each elevation angle based on the relationship between the two pulses forming the monopulse directivity described in FIG. 9B.

[0082] As can be seen from Figures 10A to 10F, the predetermined angle range δ is around 70 degrees for all elevation angles. This means that targets in a certain angle range in the azimuth direction can be captured regardless of the elevation angle. Furthermore, this value of around 70 degrees is preferable because it allows for a moderate overlap of adjacent directivities when performing directional scanning in the azimuth direction.

[0083] 11A to 11H are diagrams showing an example of analysis results of the sigma directivity and delta directivity of the circularly arranged phased array antenna 1 formed in horizontal directional scanning in this embodiment. Each of Figs. 11A to 11H shows the sigma directivity and delta directivity formed at θ=30 degrees representing the elevation angle when φ, which is the desired communication direction, is changed. Fig. 11A shows the calculation results at φ=0 degrees, Fig. 11B shows φ=45 degrees, Fig. 11C shows φ=90 degrees, Fig. 11D shows φ=135 degrees, Fig. 11E shows φ=180 degrees, Fig. 11F shows φ=225 degrees, Fig. 11G shows φ=270 degrees, and Fig. 11H shows φ=315 degrees.

[0084] As shown in Figures 11A to 11H, by performing directional scanning at 45 degree intervals from φ=0 degrees to φ=315 degrees, it can be seen that the sandwich array device 100 composed of antenna devices 10A and 10B can implement the space division monopulse method for the entire solid angle.

[0085] Therefore, the sandwich array device 100 can form monopulse directivity, which is directivity in a specific direction and angle range, by using the sigma directivity and delta directivity, and can perform three-dimensional scanning. This allows the flying vehicle 300 equipped with the sandwich array device 100 to selectively communicate with other flying vehicles by removing synchronous interference, thereby preventing collisions with other flying vehicles.

[0086] <Phase inversion weighting method> Next, a phase inversion weighting method is described, which obtains by synthesis the phase of the voltage of the signal induced in the second antenna element (#9) by the received radio wave having an angle in the elevation angle direction. In the following description, the circularly arranged phased array antenna 1 is also described as having eight first antenna elements.

[0087] First, as a comparative example, a method for estimating the direction of an incoming wave that has no angle in the elevation angle direction will be described.

[0088] Fig. 12 is a diagram showing the voltage of a signal induced in the comparative circularly arranged phased array antenna 1. Fig. 12 shows the voltage of a signal induced in the comparative circularly arranged phased array antenna 1 by a received radio wave having an arrival wave direction that has no angle in the elevation angle direction.

[0089] In the comparative example, the direction of arrival of the wave can be estimated by using the phase difference between the voltages of the antenna elements arranged at the center and on the circle. More specifically, the direction of arrival of the received signal can be estimated by calculating the difference between the phase of the sum of the received signals of the eight first antenna elements and the phase of the received signal of the one second antenna element arranged at the center.

[0090] Assume that the received radio waves arrive only from the direction that forms an angle φ with the X-axis of the XY plane, which is the plane of the circularly arranged phased array antenna 1. In this case, the signal, i.e., voltage Ei(φ), induced in the i-th first antenna element by the received radio waves can be calculated from the following (Equation 4).

[0091]

number

[0092] Since the timing of reception of each first antenna element (#1 to #8) is slightly different, the voltage Ei calculated from (Equation 4) is weighted by a weighting function that reflects this, and the signals of all the first antenna elements on the circle are added together. This results in the voltage E of the first signal, which is the sum of the received signals of each of the eight first antenna elements. Δ (φ) can be obtained. The voltage E Δ (φ) can be calculated from (Equation 5).

[0093]

number

[0094] Here, the number of elements shown in (Equation 5) is 8, but the voltage E of the first signal Δ In order to understand the nature of (φ), if the number of first antenna elements becomes infinite, the voltage E Δ (φ) can be expressed as the following (Equation 6) using the Bessel function.

[0095]

number

[0096] The voltage of the signal (third signal) induced in the second antenna element (#9) by the received radio wave coming from the direction that forms φ with the X axis is E Ω (φ). Furthermore, the voltage of the third signal E Ω (φ) phase angle ∠E Ω , the voltage of the first signal E Δ(φ) phase angle ∠E Δ Then, the phase difference φ m can be calculated using the following (Equation 7).

[0097]

number

[0098] Therefore, the phase difference φ between the first and third signals m It can be seen that is a value that is nearly proportional to the arrival wave angle φ of the received radio wave that has no angle in the elevation angle direction. In this way, by using the phase difference between the voltages of the antenna elements arranged at the center and on the circumference of the circularly arranged phased array antenna 1, it is possible to estimate the arrival wave direction that has no angle in the elevation angle direction.

[0099] Fig. 13A is a diagram showing the directional characteristics of the first signal and the third signal in the XY plane in the comparative example. Fig. 13B is a diagram showing the phase characteristics of the first signal and the third signal in the XY plane in the comparative example. Figs. 13A and 13B show the analysis results of an electromagnetic field analysis performed using the moment method assuming that the received radio waves arrive only from the comparative example, that is, from the direction that forms an angle φ with the X axis. The frequency used in the analysis is 2 GHz, and the radius a of the circularly arranged phased array antenna 1 is 4.9 cm.

[0100] As shown in Fig. 13A, the directional characteristics of the first signal and the directional characteristics of the third signal, i.e., the directional characteristics when the received signals of the first antenna element are added together and the directional characteristics of the received signal of the second antenna element, are omnidirectional in the XY plane. From Fig. 13B, it can be seen that the phase characteristics of the directivity of the first signal change according to the azimuth angle. This shows that the difference between the phase characteristics of the directivity of the first signal and the phase characteristics of the directivity of the third signal is proportional to the direction of arrival of the wave.

[0101] Next, a method for estimating the direction of an incoming wave having an angle in the elevation angle direction in this embodiment will be described.

[0102] Fig. 14 is a diagram showing two weighting functions of the first antenna elements of the circularly arranged phased array antenna 1 in this embodiment. In Fig. 14, two weighting functions, a counterclockwise weighting function (weight) and a clockwise weighting function (weight), are shown for each of the first antenna elements (#1 to #8).

[0103] In the circularly arranged phased array antenna 1 shown in Fig. 14, assume that a received radio wave having an angle in the elevation direction arrives from a direction that forms an angle φ with the X-axis. In this case, the signal, i.e., the voltage Vi(φ), induced in the i-th first antenna element located on the circumference by the received radio wave can be calculated from the following (Equation 8).

[0104]

number

[0105] Since the reception timing of each first antenna element (#1 to #8) is different, in order to reflect this, the two weighting functions W defined by (Equation 9) and (Equation 10) are used. i a , W i b is weighted by the voltage Vi calculated from (Equation 8).

[0106]

number

[0107]

number

[0108] Then, by adding up all the signals from the first antenna elements on the circle, the voltage of the first signal, which is the sum of the received signals from each of the eight first antenna elements, is obtained. Δ a , the voltage of the second signal E Δ b More specifically, the voltage E of the first signal can be obtained. Δ aFrom (Equation 11), the voltage E of the second signal is Δ b can be calculated from (Equation 12).

[0109]

number

[0110]

number

[0111] Fig. 15A shows the elevation angle directivity of the first signal obtained by performing electromagnetic field analysis using the moment method. Fig. 15B shows the elevation angle directivity of the third signal obtained by performing electromagnetic field analysis using the moment method. In Fig. 15A and Fig. 15B, the frequency used in the analysis is 2 GHz, the radius a of the circularly arranged phased array antenna 1 is 4.9 cm, and the radius r of the ground plane is 1. g is set at 7cm.

[0112] As shown in FIG. 15A, the directional characteristic of the first signal, i.e., the weighting function W i a It can be seen that the directional characteristic when the received signals of the first antenna element weighted by are added together has good radiation characteristics at high elevation angles, including the zenith direction (+Z-axis direction). In contrast, as shown in Fig. 15B, the directional characteristic of the third signal, i.e., the directional characteristic of the received signal of the second antenna element, has a deep null in the zenith direction. This shows that even if the difference between the phase characteristic of the directivity of the first signal and the phase characteristic of the directivity of the third signal is calculated using the same method as in the comparative example, it is not possible to estimate the direction of arrival of the wave including the zenith direction.

[0113] Therefore, in this embodiment, the voltage E of the first signal is calculated by using the phase inversion weighting method described below. Δ a and the voltage of the second signal E Δ b to the voltage of the third signal E Ω That is, in this embodiment, a first signal EΔ a and the voltage of the second signal E Δ b From the phase angle of Ω We came up with a method of combining the phase angles of

[0114] FIG. 16 is a schematic diagram for explaining the principle of the phase inversion weighting method. In FIG. 16, the voltage E Δ a Phase angle ∠E Δ a and the voltage of the second signal E Δ b Phase angle ∠E Δ b As shown in FIG. 16, the phase angle ∠E Δ a and phase angle ∠E Δ b has a phase angle ∠E Δ a and phase angle ∠E Δ b Therefore, the voltage E of the third signal used to estimate the direction of arrival is Ω Phase angle ∠E Ω (also referred to as the reference phase) is defined as shown in the following (Equation 13). Thus, the angle φ representing the direction of the arriving wave having an angle in the elevation angle direction is m can be expressed by (Equation 14).

[0115]

number

[0116]

number

[0117] Here, the voltage of the first signal E Δ a and the voltage of the second signal E Δ bBoth have the elevation angle directivity shown in FIG. 15A. On the other hand, according to (Equation 13), the voltage E Ω The directivity of the first signal voltage E Δ a and the voltage of the second signal E Δ b Therefore, the voltage E of the third signal is Ω 15A, and has good elevation angle directivity, making it possible to estimate the direction of arrival waves at high elevation angles.

[0118] Fig. 17 is a diagram showing three-dimensional directivities of the first signal and the third signal in this embodiment. Fig. 17 shows the three-dimensional directivities of the first signal and the third signal obtained by performing an electromagnetic field analysis using the moment method.

[0119] Voltage of the third signal E Ω The directivity of the first signal voltage E Δ a and the voltage of the second signal E Δ b Since this is the average of the directivity of the first signal, the voltage E Δ a From Fig. 17, the voltage E of the first signal Δ a and the voltage of the third signal E Ω It can be seen that the gain is high in the zenith direction, which is above the ground plane (+Z direction).

[0120] 18A shows the directivity and the estimated angle characteristic of the direction of arrival of the wave when the elevation angle is 30 degrees. In FIG. 18A (a), the voltage E Δ a and the voltage of the third signal E Ω FIG. 18A(b) shows the directivity of the angle φ defined by the above (Equation 14). m That is, the angle φ representing the direction of the incoming wave having an elevation angle of 30 degrees m is shown.

[0121] FIG. 18B shows the directivity and the estimated angle characteristic of the direction of arrival wave when the elevation angle is 80 degrees. In FIG. 18B (a), the voltage E Δ a and the voltage of the third signal E Ω FIG. 18B(b) shows the directivity of the angle φ defined by the above (Equation 14). m That is, the angle φ representing the direction of the incoming wave having an elevation angle of 80 degrees m is shown.

[0122] From (a) of FIG. 18A and (a) of FIG. 18B, the voltage E Δ a and the voltage of the third signal E Ω It can be seen that both of them maintain a constant high gain in the azimuth direction at a high elevation angle of 80 degrees. Also, from (b) of FIG. 18A and (b) of FIG. 18B, it can be seen that the estimated angle φ m is proportional to the direction of the incoming wave.

[0123] <Confirmation of the relationship between transmission capacity and ground plate size> In antenna device 10 of this embodiment, a MIMO array antenna function is realized by dividing and controlling the eight first antenna elements of circularly arranged phased array antenna 1 into four so as to form a combination of sub-arrays arranged perpendicular to the direction of incoming waves. By realizing the MIMO array antenna function, antenna device 10 of this embodiment can improve the transmission capacity.

[0124] It is known that the radiation directivity in the elevation direction of a monopole antenna attached to the center of a circular ground plane can be controlled by changing the size of the ground plane. However, the effect of the ground plane size on the transmission capacity of a MIMO array antenna has not been fully studied. Therefore, the results of confirming the relationship between transmission capacity and ground plane size are explained below.

[0125] FIG. 19 shows the radius rg FIG. 19 shows the change in transmission capacity with respect to the elevation angle of the arriving wave when the angle is changed. FIG. 19 shows the results of a Monte Carlo simulation using a channel model of a cluster propagation environment in which both the azimuth angle and the elevation angle in a three-dimensional coordinate system have Gaussian distribution of arriving waves. The radiation characteristics of the entire MIMO array antenna were calculated using the moment method. The analysis frequency was 2 GHz. All antenna elements constituting the circularly arranged phased array antenna 1 were quarter-wavelength monopole antennas with a length of 37.5 mm and a radius of 0.5 mm. The radius a of the circularly arranged phased array antenna 1 functioning as a 4×4 MIMO array antenna was set to 4.9 cm, and the spacing between the first antenna elements #2 and #3 was set to 1 / 4 wavelength at 2 GHz to form a cardioid directivity.

[0126] From Figure 19, the transmission capacity at the elevation angle is calculated by the radius r g More specifically, from FIG. 19, the elevation angle ranges from 0 to 15 degrees and the radius of the base plate r g is 13cm, and the range from 15 to 60 degrees is the radius r g is 10cm, and the range from 60 to 90 degrees is the radius r g The transmission capacity is maximum when the radius of the ground plane is 13 cm. Therefore, the optimum radius of the ground plane r g It is clear that it is necessary to control

[0127] In particular, the radius r of base plate 2 g = 10 cm, the transmission capacity is significantly increased at high elevation angles of 30 degrees to 60 degrees. From this result, taking into consideration the elevation angle characteristics and a practical antenna shape, the radius r g One side was set to 10 cm.

[0128] <Confirmation of 3D radiation directivity in subarray> Next, the three-dimensional radiation directivity in the sub-array will be described. The following describes the three-dimensional radiation directivity when the first antenna elements #1 and #4 are the sub-array 2 (hereinafter also referred to as the monopole array antenna) in the circularly arranged phased array antenna 1. As a comparative example, the three-dimensional radiation directivity when the first antenna elements #1 and #4 are the sub-array 2 (hereinafter also referred to as the dipole array antenna) in the circularly arranged phased array antenna 1 composed of nine dipole antennas without the ground plane 2 will also be described.

[0129] Fig. 20A is a diagram showing three-dimensional radiation directivity of a dipole array antenna in a comparative example, and Fig. 20B is a diagram showing three-dimensional radiation directivity of a monopole array antenna in the present embodiment.

[0130] As can be seen by comparing Fig. 20A and Fig. 20B, the three-dimensional radiation directivity of the dipole array antenna shown in Fig. 20A has a deep null in the zenith direction (+Z direction), and radiation at high elevation angles is significantly reduced. On the other hand, the monopole array antenna shown in Fig. 20B does not have a deep null in the zenith direction (+Z direction), and shows a significant improvement in radiation gain at high elevation angles compared to the dipole array antenna shown in Fig. 20A.

[0131] <Confirmation of Three-Dimensional Radiation Directivity in the Sandwich Array Device 100> Next, a three-dimensional radiation directivity when the sandwich array device 100 in this embodiment performs directional scanning will be described. The sandwich array device 100 has a function of performing directional scanning at 45-degree intervals, but the following description will be given by taking only the three-dimensional radiation directivity at 90-degree intervals as an example.

[0132] 21A to 22D are diagrams showing three-dimensional directivity when directional scanning is performed by sandwich array device 100 according to the present embodiment. In FIGS. 21A to 21D, in antenna device 10A at the top of sandwich array device 100, radius r gWhen the radius r of the ground plane 2 is 10 cm and the first antenna elements #1 and #4 are used as sub-array 2, the three-dimensional radiation directivity when changing the azimuth angle to be communicated is shown. In FIGS. 22A to 22D, in the antenna device 10B at the lower part of the sandwich array device 100, the radius r of the ground plane 2 g When the radius r of the ground plane 2 is 10 cm and the first antenna elements #1 and #4 are used as sub-array 2, the three-dimensional radiation directivity when changing the azimuth angle to be communicated is shown. Also, FIGS. 21A to 21D and FIGS. 22A to 22D show the three-dimensional radiation directivity at 90-degree intervals.

[0133] From FIGS. 21A to 22D, it can be seen that the gain in the azimuth direction to be communicated is increased. Also, as shown in FIGS. 21A to 22D, by performing directivity scanning, the directivity rotates while irradiating the high elevation angle direction. The same can be said for the directivities of the other three sub-arrays (sub-arrays 1, 3, and 4).

[0134] And by making the upper antenna device 10A and the lower antenna device 10B cooperate complementarily, it can be seen that the directivity gain in the depression angle direction can be improved and the entire solid angle can be covered.

[0135] <Confirmation of Transmission Capacity of MIMO Array Antenna> Next, the transmission capacity when the sandwich array device 100 in the present embodiment is operated as a MIMO array antenna will be described. As a comparative example, the transmission capacity when a circular array phased array antenna 1 (referred to as a half-wavelength dipole array antenna) composed of nine half-wavelength dipole antennas without a ground plane 2 is operated as a MIMO array antenna will also be described.

[0136] Fig. 23 is a diagram showing the elevation angle characteristic of the transmission capacity of a MIMO array antenna using a half-wavelength dipole array antenna in a comparative example. Fig. 23 shows an analysis result of the transmission capacity of the MIMO array antenna when the azimuth direction of the incoming wave is set to 0 degrees (φ=0 degrees) and the incoming wave elevation angle is changed. Here, the analysis frequency is 2 GHz, the SNR is 30 dB, and the XPR (cross polarization power ratio) is 10 dB. σ shown in Fig. 23 represents the spread angle (standard deviation) of the Gaussian incoming wave in the azimuth direction (horizontal direction) and the elevation direction (elevation angle direction). θ represents the angle of the elevation direction, i.e., the incoming wave elevation angle.

[0137] From Figure 23, we can see that the MIMO array antenna using half-wavelength dipole array antennas has a characteristic in which the transmission capacity is symmetrical with respect to an elevation angle of 0 degrees. We can also see that there is a significant decrease in transmission capacity in the zenith direction (θ=+90 degrees) and nadir direction (θ=-90 degrees). We can also see that when the spread angle is 10 degrees, the transmission capacity at an elevation angle of 0 degrees is degraded by 22 bits / s / Hz when comparing the transmission capacity at an elevation angle of ±90 degrees.

[0138] These results are believed to be due to the fact that, as shown in FIG. 20A, in the dipole array antenna, nulls are formed in the zenith and nadir directions.

[0139] Fig. 24A is a diagram showing the azimuth characteristic of the transmission capacity of a MIMO array antenna using the sandwich array device according to the embodiment. Fig. 24B is a diagram showing the elevation angle characteristic of the transmission capacity of a MIMO array antenna using the sandwich array device 100 according to the embodiment. Fig. 24A shows the elevation angle characteristic of the transmission capacity with respect to the azimuth angle, and Fig. 24B shows the elevation angle characteristic of the transmission capacity with respect to the elevation angle.

[0140] In Figures 24A and 24B, the analysis frequency is 2 GHz, the SNR is 30 dB, and the XPR is 10 dB. Note that a line-of-sight (LOS) propagation environment is expected for communication between flying vehicles. Therefore, a propagation environment in which the vertical polarization component is more dominant than the horizontal polarization component is assumed, and the XPR, which represents the cross-polarization power ratio, is set to 10 dB.

[0141] In addition, in sandwich array device 100, as a MIMO array antenna, upper antenna device 10A is selected for an elevation angle target of 0 degrees to 90 degrees, and lower antenna device 10B is selected for a depression angle target of -90 degrees to 0 degrees.

[0142] 24A, the transmission capacity of the MIMO array antenna is almost constant in all azimuth directions for any spread angle. This shows that a stable transmission capacity can be achieved by controlling the beam (directivity) of the MIMO array antenna using the sandwich array device 100 to the azimuth angle of the arriving wave.

[0143] Also, from Fig. 24B, it can be seen that the transmission capacity of the MIMO array antenna has symmetric characteristics with respect to an elevation angle of 0 degrees due to the switching operation between the upper antenna device 10A and the lower antenna device 10B. Also, from Fig. 24B, it can be seen that the fluctuation of the transmission capacity of the MIMO array antenna with respect to the elevation angle is small. This shows that a stable transmission capacity can be achieved by controlling the beam (directivity) of the MIMO array antenna using the sandwich array device 100 to the elevation angle of the arriving wave.

[0144] Comparing the transmission capacity when the elevation angle is 0 degrees in Fig. 23 with Fig. 24A and Fig. 24B, the following can be seen: That is, it can be seen that the transmission capacity of the MIMO array antenna using sandwich array device 100 almost maintains the maximum transmission capacity of the MIMO array antenna using half-wavelength dipole array antennas.

[0145] As a result, in the above embodiment, for the purpose of full solid angle irradiation, the radius r of the base plate 2 selected from FIG. g It can be seen that the choice of 10 cm is appropriate.

[0146] Fig. 25 is a diagram showing the three-dimensional transmission capacity over the entire solid angle of a MIMO array antenna using half-wavelength dipole array antennas in a comparative example. Fig. 26 is a diagram showing the three-dimensional transmission capacity over the entire solid angle of a MIMO array antenna using sandwich array device 100 in this embodiment.

[0147] As can be seen from Fig. 25, the transmission capacity of the MIMO array antenna using half-wavelength dipole array antennas has deep nulls in the zenith and nadir directions. On the other hand, as shown in Fig. 26, the transmission capacity of the MIMO array antenna using sandwich array device 100 of this embodiment has a spherical shape with an equal radius. This shows that the MIMO array antenna using sandwich array device 100 of this embodiment has the ability to connect to a target in any direction.

[0148] The above-mentioned characteristics of the transmission capacity of the MIMO array antenna using the sandwich array device 100 in this embodiment are obtained by appropriate power synthesis of the θ component and φ component of the radiation directivity. In particular, the φ component is generated from the current distribution induced in the ground plate 2. For this reason, the φ component does not exist in principle in a half-wavelength dipole array antenna formed of dipole antennas.

[0149] <Verifying that high-speed communication is possible> Next, it has been confirmed that high-speed communication is possible when sandwich array device 100 in this embodiment is operated as a MIMO array antenna by using outage probability based on transmission capacity, as will be described below.

[0150] First, the communication outage probability is defined as the probability that the transmission capacity falls below a specified threshold, as shown in the following (Equation 15).

[0151]

number

[0152] In (Equation 15), p(θ, φ) denotes the probability density function (PDF) of the transmission capacity over the entire solid angle. th denotes the threshold of transmission capacity. th is C th indicates the azimuth angle corresponding to θ th is C th The elevation angles corresponding to the above values ​​are shown.

[0153] FIG. 27 is a diagram showing the communication outage probability over the entire solid angle of a MIMO array antenna using sandwich array device 100 according to this embodiment. The present disclosure shown in FIG. 27 represents a MIMO array antenna using sandwich array device 100. The comparative example shown in FIG. 27 represents a MIMO array antenna using the above-mentioned half-wavelength dipole array antenna. In addition, in FIG. 27, the horizontal axis represents the maximum value C max This is the transmission capacity standardized by.

[0154]

number

[0155] 27, in the comparative example, when the spread angle is 10 degrees (σ=10 degrees), the normalized transmission capacity r at which the communication outage probability becomes zero is 22%. On the other hand, in the present disclosure, when the spread angle is 10 degrees, the normalized transmission capacity r at which the communication outage probability becomes zero is 87%.

[0156] This shows that a MIMO array antenna using sandwich array device 100 according to this disclosure, that is, this embodiment, enables high-speed communication at 87% of the maximum transmission capacity in all directions in a three-dimensional space.

[0157] From the above confirmations, it has become clear that sandwich array device 100 of this embodiment 1) can form monopulse directivity by the space division monopulse method, 2) can estimate the direction of arrival waves over the entire solid angle, and 3) has the function of a MIMO array antenna. Furthermore, in sandwich array device 100 of this embodiment, when forming monopulse directivity and when estimating the direction of arrival waves over the entire solid angle, the radius r of base plate 2 is different. g is 7 cm, and to realize the function of the MIMO array antenna, the radius r g In other words, in the sandwich array device 100 of the present embodiment, in order to realize all of the functions 1) to 3) in one device, the radius r g Switch between.

[0158] (Modification) In the above embodiment, a case has been described in which one sandwich array device 100 composed of two antenna devices 10 is used as a MIMO array antenna, but this is not limiting. A multi-element MIMO array antenna may be formed by modularizing and combining sandwich array device 100. This case will be described below.

[0159] Fig. 28 is a diagram showing an example of a multi-element MIMO array antenna in a modified example, in which five sandwich array devices 100a, 100b, 100c, 100d, and 100e are combined to form a multi-element MIMO array antenna.

[0160] In the above embodiment, the antenna device 10 is used as a MIMO array antenna, but the present invention is not limited to this. The antenna device 10 may be modularized and combined to form a multi-element MIMO array antenna. This case will be described below.

[0161] Fig. 29A is a diagram showing an example of a 4×4 MIMO array antenna in a modified example. Fig. 29B is a diagram showing an example of an 8×8 MIMO array antenna in a modified example. Fig. 29C is a diagram showing an example of a 16×16 MIMO array antenna in a modified example. Fig. 29D is a diagram showing an example of a 32×32 MIMO array antenna in a modified example. Fig. 29E is a diagram showing an example of a 64×64 MIMO array antenna in a modified example. Fig. 29F is a diagram showing an example of a 128×128 MIMO array antenna in a modified example. Fig. 29G is a diagram showing an example of a 256×256 MIMO array antenna in a modified example. Each of Figs. 29A to 29G shows a combination of antenna devices 10 when the multi-element MIMO array antenna is viewed from above.

[0162] In this way, by modularizing and combining sandwich array device 100 or antenna device 10, it can be easily expanded into a multi-element MIMO array antenna.

[0163] (Other embodiments) The present invention is not limited to the above-described embodiment. Various modifications and variations can be made to the above-described embodiment within the same scope as the present invention or within an equivalent scope.

[0164] In the above-described embodiment, each component may be configured by dedicated hardware, or a component that can be realized by software may be realized by executing a program.

[0165] Also, for example, the modules constituting the antenna device 10 may be realized in the form of IC (integrated circuit), ASIC (application specific integrated circuit), and LSI (large scale integration), or may be realized by a processor based on a CPU such as ARM and a machine such as a PC (personal computer). Each of these modules may be included in many single-function LSIs or one LSI. Although the name used here is LSI, it may be called IC, system LSI, super LSI, or ultra LSI depending on the degree of integration. Furthermore, the integration method is not limited to LSI, and integration can also be done by dedicated circuits or general-purpose processors. This includes special microprocessors such as DSP (digital signal processors) that can be instructed by program instructions. FPGA (field programmable gate arrays) that can be programmed after LSI manufacturing or reconfigurable processors that can reconfigure the connection or arrangement of LSIs can be used for the same purpose. In the future, as manufacturing and processing technologies develop, completely new technologies may replace LSIs. Integration can be realized by such technologies. [Industrial Applicability]

[0166] The present invention can be used in antenna devices and the like that estimate the direction of arrival of received radio waves and control directivity to the estimated direction of arrival of the waves to achieve highly reliable communication, and can be particularly used in antenna devices and the like used in flying vehicles, MIMO antennas, etc. [Explanation of symbols]

[0167] 1, 1A, 1B Circularly arranged phased array antenna 2, 2A, 2B, 2a, 2b main plate 3. Control Unit 4 Arithmetic section 10, 10A, 10B Antenna device 100, 100a, 100b, 100c, 100d, 100e Sandwich array device 301 Diode 302 Choke coil

Claims

1. a circularly arranged phased array antenna including N first antenna elements (N being a natural number of 3 or more) arranged at equal intervals on a circle and one second antenna element arranged approximately at the center of the circle; A circular base plate whose radius can be changed by switching control; a subarray control unit that divides the N first antenna elements into the N / 2 subarrays orthogonal to a direction of an incoming wave arriving at the circularly arranged phased array antenna, the direction being parallel to the ground plane, and controls directivities of the subarrays to independently form the N / 2 beams directed in the direction of the incoming wave, The first antenna element and the second antenna element are configured as monopole antennas mounted on the ground plane. Antenna device.

2. The first antenna element and the second antenna element are configured as 1 / 4 wavelength monopole antennas.

2. The antenna device according to claim 1.

3. Each of the N / 2 subarrays is composed of a combination of two antenna elements whose arrangement directions are parallel to each other, The combination is changed depending on the direction of arrival of the wave.

3. The antenna device according to claim 1 or 2.

4. A circularly arranged phased array antenna comprising N first antenna elements (N is a natural number equal to or greater than 3) arranged at equal intervals on a circle and one second antenna element disposed approximately at the center of the circle; A circular base plate whose radius can be changed by switching control; a directivity control unit that controls the directivity of the circularly arranged phased array antenna within a predetermined angle range including the elevation angle direction by providing phases to two of the first antenna elements that are closest to a desired communication direction in order to form delta directivity and sigma directivity, the phases being calculated using a path difference in an elevation angle direction, which is a direction of an incoming wave arriving at the circularly arranged phased array antenna and the ground plane, the first antenna element and the second antenna element are configured as monopole antennas mounted on the ground plane, The delta directivity is a directivity that reduces a radiation gain by realizing anti-phase excitation in the elevation angle direction, The sigma directivity is a directivity that increases radiation gain by realizing in-phase excitation in the elevation angle direction. Antenna device.

5. A circularly arranged phased array antenna comprising N first antenna elements (N is a natural number equal to or greater than 3) arranged at equal intervals on a circle and one second antenna element disposed approximately at the center of the circle; A circular base plate whose radius can be changed by switching control; a calculation unit that performs statistical analysis on a first signal and a second signal obtained by multiplying a received signal of each of the first antenna elements by two weights corresponding to an arrangement of the first antenna elements and summing the result, and a third signal which is a received signal of the second antenna element, and calculates a phase difference between the first signal and the third signal, thereby estimating an arrival wave direction which is a direction of an arrival wave arriving at the circularly arranged phased array antenna relative to the ground plane, the first antenna element and the second antenna element are configured as monopole antennas mounted on the ground plane, the calculation unit calculates a phase angle of the voltage of the third signal by averaging a phase angle of the voltage of the first signal and a phase angle of the voltage of the second signal, thereby calculating a phase difference between the first signal and the third signal; The phase difference is approximately proportional to the direction of the incoming wave. Antenna device.

6. A radio communication system comprising a first antenna device and a second antenna device, Each of the first antenna device and the second antenna device a circularly arranged phased array antenna including N first antenna elements (N being a natural number of 3 or more) arranged at equal intervals on a circle and one second antenna element arranged approximately at the center of the circle; A circular base plate whose radius is variable by switching control; the first antenna element and the second antenna element are configured as monopole antennas mounted on the ground plane, The first antenna device is disposed at the zenith of the flying vehicle; The second antenna device is disposed at the nadir of the flying vehicle; The first antenna device and the second antenna device have opposite directions of the circularly arranged phased array antenna as viewed from the ground plane. Sandwich array device.

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