Antenna device

Abstract

Provided is an antenna device having a wider band due to adjustment in the center angles of a pair of fan-shaped radiation electrodes.　This antenna device includes a substrate, a pair of radiation electrodes formed on a first surface of the substrate, and a pair of transmission lines respectively connected to the pair of radiation electrodes. Each radiation electrode has a fan shape in a plan view. The pair of radiation electrodes are arranged so that the centers of the fan shapes thereof face each other in a plan view. The pair of transmission lines are respectively connected to feed points located at the centers of the pair of radiation electrodes. The center angles of the fan shapes of the pair of radiation electrodes are each set to 120 to 170 degrees.

Description

Antenna device

[0001] The present disclosure relates to an antenna device.

[0002] Conventionally, there has been an ultra-wideband antenna comprising a dielectric substrate, a plurality of antenna conductors arranged on one side of the dielectric substrate and quasi-self-complementary on that side, and a plurality of feed conductors symmetrical with respect to the plane of symmetry of the antenna conductors, with a gap of 1 / 10 or less of the wavelength in vacuum of the operating frequency at the center of rotational symmetry between the plurality of antenna conductors (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2005-130292

[0004] Conventional ultra-wideband antennas (antenna devices) have gaps between the centers of rotational symmetry between a plurality of antenna conductors (radiation electrodes), but there is room for improvement in terms of bandwidth.

[0005] Therefore, an object of the present invention is to provide an antenna device that achieves a broader bandwidth by setting the central angle of a pair of sector-shaped radiation electrodes.

[0006] An antenna device according to an embodiment of the present disclosure includes a substrate, a pair of radiation electrodes formed on a first surface of the substrate, and a pair of transmission lines respectively connected to the pair of radiation electrodes, each radiation electrode being fan-shaped in a planar view, the pair of radiation electrodes being arranged such that the centers of the fan shapes face each other in a planar view, the pair of transmission lines being respectively connected to feeding points located at the centers of the pair of radiation electrodes, and the pair of radiation electrodes having a central angle of 120 degrees to 170 degrees.

[0007] By setting the central angle of the pair of sector-shaped radiation electrodes, it is possible to provide an antenna device with a wide bandwidth.

[0008] 1 is a diagram illustrating an example of the configuration of an antenna device of an embodiment. FIG. 2 is a diagram illustrating an example of the configuration of an antenna device of an embodiment. FIG. 3 is a diagram illustrating an example of the configuration of an antenna device of an embodiment. FIG. 4 is a diagram illustrating an example of the circuit configuration of an antenna device of an embodiment. FIG. 5 is a diagram illustrating an example of the circuit configuration of an antenna device of an embodiment. FIG. 6 is a diagram illustrating an example of a simulation result of the S11 parameter of the antenna device of an embodiment. FIG. 7 is a diagram illustrating an example of a simulation result of the fractional bandwidth of the antenna device of an embodiment. FIG. 8 is a diagram illustrating another example of the configuration of the antenna device of an embodiment.

[0009] Hereinafter, embodiments to which the antenna device of the present disclosure is applied will be described. In the following, the same elements will be given the same reference numerals, and duplicated descriptions may be omitted.

[0010] In the following description, the XYZ coordinate system is defined. The direction parallel to the X axis (X direction), the direction parallel to the Y axis (Y direction), and the direction parallel to the Z axis (Z direction) are perpendicular to each other. The XYZ coordinate system is an example of a Cartesian coordinate system. Viewing the XY plane is referred to as planar view. In the following, the X direction may be referred to as left and right, the +Z direction as up, and the −Z direction as down, but these do not represent the universal left and right directions and up and down directions. In the following, the length, width, thickness, etc. of each part may be exaggerated to make the configuration easier to understand. Furthermore, terms such as parallel, right angle, orthogonal, horizontal, vertical, up and down, etc., are intended to allow for deviations to the extent that they do not impair the effects of the embodiments.

[0011] 1A to 1C are diagrams illustrating an example of the configuration of an antenna device 100 according to an embodiment. Fig. 1A is a perspective view, Fig. 1B is a plan view, and Fig. 1C is a side view. Figs. 2A and 2B are diagrams illustrating an example of the circuit configuration of the antenna device 100 according to an embodiment.

[0012] The antenna device 100 includes a substrate 101, a pair of radiation electrodes 110A and 110B, a pair of transmission lines 115A and 115B, and a ground layer 120. The radio waves transmitted and received by the antenna device 100 are, for example, radio waves in the millimeter wave band. Millimeter waves are radio waves in a frequency band of 30 GHz to 300 GHz. However, the radio waves transmitted and received by the antenna device 100 may be radio waves with a frequency belonging to a band other than the millimeter wave band.

[0013] <Substrate 101> The substrate 101 is a thin plate-like substrate that is parallel to the XY plane and has a surface 101A on the +Z direction side and a surface 101B on the −Z direction side. The surface 101A is an example of a first surface, and the surface 101B is an example of a second surface.

[0014] Any wiring board capable of mounting a conductive layer may be used as the substrate 101. As an example, a pair of radiation electrodes 110A and 110B are provided on a surface 101A on the +Z direction side of the substrate 101, and a ground layer 120 is provided on a surface 101B on the −Z direction side of the substrate 101.

[0015] The pair of radiation electrodes 110A, 110B, the transmission lines 115A, 115B, and the ground layer 120 are realized by conductive layers provided on both sides of the substrate 101, so it is possible to use a printed circuit board with a simple configuration that does not have an inner layer. The conductive layer is made of copper, for example, but may be made of a metal other than copper, such as aluminum.

[0016] The substrate 101 may also be a flexible substrate. As an example of a flexible substrate, a substrate having flexibility made of polyimide resin or the like can be used. When the substrate 101 is flexible, the antenna device 100 can be attached to a curved surface of an object, such as a curved surface. The substrate 101 may also be a multilayer substrate having an inner layer.

[0017] <Radiation electrodes 110A, 110B> The radiation electrodes 110A, 110B are provided on the surface 101A on the +Z direction side of the substrate 101, and have the same size. The radiation electrodes 110A, 110B are arranged symmetrically in a planar view. The radiation electrodes 110A, 110B are fan-shaped in a planar view, and are arranged so that the centers of the fan shapes face each other in a planar view.

[0018] The radiation electrodes 110A and 110B have feed points 111A and 111B, respectively, which are located at the centers of the radiation electrodes 110A and 110B. Therefore, the radiation electrodes 110A and 110B are arranged so that the feed points 111A and 111B face each other in a plan view. A line A connecting the feed points 111A and 111B is parallel to the X-axis. Transmission lines 115A and 115B are connected to the feed points 111A and 111B of the radiation electrodes 110A and 110B, respectively.

[0019] 2A , the radiation electrodes 110A and 110B may be connected to a differential signal source 150 via transmission lines 115A and 115B. In this case, a differential signal is supplied to the radiation electrodes 110A and 110B from the differential signal source 150 via the transmission lines 115A and 115B, and the radiation electrodes 110A and 110B are differentially excited. The differential signal source 150 is a balanced circuit, and the transmission lines 115A and 115B are balanced lines.

[0020] Furthermore, instead of being connected to the differential signal source 150, the radiation electrodes 110A and 110B may be fed using a circuit configuration shown in FIG. 2B . In FIG. 2B , the radiation electrodes 110A and 110B are connected to a balun 150A via transmission lines 115A and 115B. The balun 150A is connected to a signal source 150C via a coaxial cable 150B. That is, the radiation electrodes 110A and 110B are connected to the signal source 150C via the transmission lines 115A and 115B, the balun 150A, and the coaxial cable 150B. The signal source 150C outputs an AC signal. A differential signal is supplied to the radiation electrodes 110A and 110B from the balun 150A via the transmission lines 115A and 115B, and the radiation electrodes 110A and 110B are differentially excited. In this case, the transmission lines 115A and 115B are balanced lines, and the balun 150A, the coaxial cable 150B, and the signal source 150C are unbalanced circuits. Note that the transmission lines 115A and 115B may be unbalanced transmission lines such as microstrip lines.

[0021] The radiating electrodes 110A and 110B both have the same central angle θ. 1A, 1B, 2A, and 2B show, as an example, the radiating electrodes 110A and 110B whose central angle θ is 140 degrees. The radiating electrodes 110A and 110B are arranged so that a line A connecting the power feed points 111A and 111B bisects the central angle θ. In other words, the radiating electrode 110A is line-symmetric with respect to the line A, and the radiating electrode 110B is line-symmetric with respect to the line A.

[0022] The radius R of the sector shape of the radiation electrodes 110A, 110B is approximately λe / 4, where λe is the electrical length of the wavelength of the radio waves transmitted and received by the radiation electrodes 110A, 110B. Because the radiation electrodes 110A, 110B are sector-shaped, the radius R is constant at any angle within the central angle θ. The sector-shaped radiation electrodes 110A, 110B are the portion of the circle of radius R that corresponds to the central angle θ.

[0023] Such radiation electrodes 110A, 110B operate like dipole antennas. The resonant frequency of the radiation electrodes 110A, 110B is, for example, 60 GHz. The radiation electrodes 110A, 110B radiate radio waves in the +Z direction and the -Z direction. However, since the ground layer 120 is provided on the surface 101B on the -Z direction side of the substrate 101, the antenna device 100 has directivity that radiates in the +Z direction. Note that the antenna device 100 may be configured without including the ground layer 120.

[0024] In order to achieve a broadband, the central angle θ of the radiation electrodes 110A and 110B of the antenna device 100 is set to an angle within a range of 120 degrees to 170 degrees. The central angle θ may be within a range of 120 degrees to 170 degrees, more preferably within a range of 130 degrees to 160 degrees, and even more preferably within a range of 140 degrees ±10 degrees.

[0025] <Transmission lines 115A, 115B> The transmission lines 115A, 115B are connected to the feed points 111A, 111B of the radiation electrodes 110A, 110B, respectively. In a plan view, the transmission lines 115A, 115B extend parallel to each other on the side (−Y direction side) of the extension direction of a straight line A connecting the feed points 111A, 111B of the radiation electrodes 110A, 110B. As an example, the transmission lines 115A, 115B extend parallel to each other in the −Y direction.

[0026] <Ground Layer 120> The ground layer 120 is provided on the surface 101B on the −Z direction side of the substrate 101. The ground layer 120 overlaps with the radiation electrodes 110A and 110B in a plan view, and also overlaps with most of the transmission lines 115A and 115B. The ground layer 120 is a reflective layer that reflects radio waves emitted from the radiation electrodes 110A and 110B toward the +Z direction.

[0027] 3 is a diagram showing an example of a simulation result of the S11 parameter of the antenna device 100. As conditions for the simulation, the frequency of the AC signal generated by the signal source 150C was set to the 60 GHz band, and the thickness of the substrate 101 was set to 0.35 mm.

[0028] When the S11 parameter of the antenna device 100 was calculated, the results shown in Figure 3 were obtained. As an example, if the reference for the S11 parameter is -10 dB, a wide bandwidth of 6.8 GHz, from 56.70 GHz to 63.50 GHz, was obtained as a band below -10 dB. In this way, it was confirmed that the antenna device 100 can achieve a wide bandwidth.

[0029] 4A and 4B are diagrams showing an example of simulation results of the fractional bandwidth of the antenna device 100. Since the simulation results of Fig. 3 show that the antenna device 100 can achieve a broadband, the fractional bandwidth of the antenna device 100 was calculated by setting the central angle θ and the thickness t of the substrate 101 to various values. Furthermore, simulations were performed for the frequency of the AC signal generated by the differential signal source 150 in the 30 GHz band in addition to the 60 GHz band.

[0030] A simulation was performed on the antenna device 100 including the radiation electrodes 110A, 110B in which the central angle θ of the sector shape of the radiation electrodes 110A, 110B varied in 10-degree increments from 60 degrees to 180 degrees. Four combinations of the resonant frequency bands of the radiation electrodes 110A, 110B and the thickness t of the substrate 101 were prepared: 0.35 mm for a frequency in the 60 GHz band, 0.3 mm for the 60 GHz band, 0.25 mm for the 60 GHz band, and 0.5 mm for the 30 GHz band.

[0031] 4A and 4B , the fractional bandwidth was greatest for all four combinations when the central angle θ was 140 degrees. Specifically, the fractional bandwidth was 18.6% for 0.35 mm in the 60 GHz band, 16.4% for 0.3 mm in the 60 GHz band, 12.6% for 0.25 mm in the 60 GHz band, and 12.0% for 0.5 mm in the 30 GHz band. Among the four combinations where the central angle θ was 140 degrees, the fractional bandwidth was greatest for the combination of 0.35 mm in the 60 GHz band, and decreased as the thickness of the substrate 101 became thinner, with the fractional bandwidth being smallest for 0.5 mm in the 30 GHz band.

[0032] In all four combinations, the relative bandwidth when the central angle θ was 140 degrees was a good value of 12.0% or more.

[0033] Furthermore, in all four combinations, a fractional bandwidth of approximately 10% or more was obtained when the central angle θ was in the range of 120 degrees to 170 degrees. From these results, it was confirmed that a good fractional bandwidth value can be obtained and a broadband can be achieved if the central angle θ is in the range of 120 degrees to 170 degrees.

[0034] <Radiation electrodes 110A and 110B with central angles θ of 120 degrees and 170 degrees> Fig. 5A is a diagram showing an example of the configuration of the antenna device 100 including the radiation electrodes 110A and 110B with a central angle θ of 120 degrees. Fig. 5B is a diagram showing an example of the configuration of the antenna device 100 including the radiation electrodes 110A and 110B with a central angle θ of 170 degrees. The radiation electrodes 110A and 110B with a central angle θ of 120 degrees shown in Fig. 5A are smaller than the radiation electrodes 110A and 110B with a central angle θ of 140 degrees shown in Fig. 1B, and the radiation electrodes 110A and 110B with a central angle θ of 170 degrees shown in Fig. 5B are larger than the radiation electrodes 110A and 110B with a central angle θ of 140 degrees shown in Fig. 1B.

[0035] <Effects> The antenna device 100 includes a substrate 101, a pair of radiation electrodes 110A, 110B formed on a surface 101A of the substrate 101, and a pair of transmission lines 115A, 115B connected to the pair of radiation electrodes 110A, 110B, respectively. Each radiation electrode is fan-shaped in a planar view. The pair of radiation electrodes 110A, 110B are arranged so that the centers of the fan shapes face each other in a planar view. The pair of transmission lines 115A, 115B are connected to feed points 111A, 111B located at the centers of the pair of radiation electrodes 110A, 110B, respectively. The central angle of each fan shape of the radiation electrodes 110A, 110B is 120 degrees to 170 degrees. In this way, by setting the central angle θ within the range of 120 degrees to 170 degrees, a broadband can be achieved.

[0036] Therefore, by setting the central angle of the pair of sector-shaped radiation electrodes 110A and 110B, it is possible to provide the antenna device 100 with a wide bandwidth.

[0037] The antenna device 100 may further include a ground layer 120 formed on the second surface (surface 101B) of the substrate 101. It is possible to provide an antenna device 100 that has directivity on the surface 101A side of the substrate 101 and has unidirectionality over a wide band.

[0038] Furthermore, the pair of transmission lines 115A, 115B may extend in parallel in a direction away from the feed points 111A, 111B of the pair of radiation electrodes 110A, 110B on the side of the extension direction of the straight line connecting the feed points 111A, 111B of the pair of radiation electrodes 110A, 110B in a plan view. By having the transmission lines 115A, 115B extend in the same direction, it is possible to provide a wideband antenna device 100 with a simplified configuration.

[0039] Furthermore, the fan-shaped portions of the pair of radiation electrodes 110A and 110B may each have a constant radius from the center. By including the radiation electrodes 110A and 110B each having a fan-shaped portion with a constant radius from the center, it is possible to provide the antenna device 100 that can more reliably achieve a broadband.

[0040] Furthermore, the pair of transmission lines 115A and 115B may be balanced lines connected to the differential signal source 150. This allows power to be fed with low loss without using a balun 150A.

[0041] The above describes an antenna device according to an exemplary embodiment of the present disclosure, but the present disclosure is not limited to the specifically disclosed embodiment, and various modifications and variations are possible without departing from the scope of the claims.

[0042] This international application claims priority based on Japanese Patent Application No. 2024-069933, filed on April 23, 2024, the entire contents of which are incorporated herein by reference.

[0043] REFERENCE SIGNS LIST 100 Antenna device 101 Substrate 110A, 110B Radiation electrodes 111A, 111B Feeding points 115A, 115B Transmission lines 120 Ground layer 150 Differential signal source 150A Balun 150B Coaxial cable 150C Signal source

Claims

1. An antenna device comprising: a substrate; a pair of radiation electrodes formed on a first surface of the substrate; and a pair of transmission lines respectively connected to the pair of radiation electrodes, wherein each radiation electrode is fan-shaped in a planar view; the pair of radiation electrodes are arranged so that the centers of the fan shapes face each other in a planar view; the pair of transmission lines are respectively connected to feeding points located at the centers of the pair of radiation electrodes; and the central angle of each fan shape of the pair of radiation electrodes is 120 degrees to 170 degrees.

2. The antenna device according to claim 1, further comprising a ground layer formed on the second surface of the substrate.

3. An antenna device according to claim 1 or 2, wherein the pair of transmission lines extend in parallel in a direction away from the feed points of the pair of radiation electrodes, on the side of the extension direction of a straight line connecting the feed points of the pair of radiation electrodes, in a plan view.

4. The antenna device according to any one of claims 1 to 3, wherein the sector shape of each of the pair of radiation electrodes has a constant radius from the center.

5. The antenna device according to any one of claims 1 to 4, wherein the pair of transmission lines are balanced lines connected to a differential signal source.

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