Antenna device

Abstract

This antenna device (1) comprises a radiator (10) that includes at least one antenna element (12-1, 12-2), a housing (20) that includes a plate-shaped region composed of a dielectric, and a plurality of strip conductors (21) that are positioned in the plate-shaped region of the housing (20). The antenna elements (12-1, 12-2) have power supply points (F1, F2) at positions shifted in a first direction from the centers of the antenna elements (12-1, 12-2) . Each of the plurality of strip conductors (21) is disposed such that the longitudinal direction of the strip conductor (21) intersects the first direction.

Description

Antenna device

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

[0002] An antenna device is generally used while being housed in some kind of housing for protection from the surrounding environment.

[0003] For example, Patent Documents 1 and 2 disclose exemplary antenna devices.

[0004] Japanese Unexamined Patent Application Publication No. 2004 - 135284, Patent No. 4727884

[0005] When an antenna device provided inside a housing radiates radio waves, the radio waves not only pass through the housing and propagate in a desired direction, but also propagate along the surface of the housing. The radio waves propagating along the surface of the housing become interference waves, which may cause fluctuations in antenna gain that vary depending on the direction. Therefore, even when an antenna device is housed in a housing, it is required to reduce the influence of the housing on the radiation characteristics of the antenna device more than in the past.

[0006] An object of the present disclosure is to provide an antenna device provided with a housing, in which the influence of the housing on radiation characteristics is reduced more than in the past.

[0007] The antenna device according to the first aspect of the present disclosure includes: a radiator including at least one antenna element; a housing including a plate - like region made of a dielectric; and a plurality of strip conductors arranged in the plate - like region of the housing. The antenna element has a first feeding point at a position shifted from the center of the antenna element in a first direction. Each of the plurality of strip conductors is arranged such that the longitudinal direction of the strip conductor intersects the first direction.

[0008] According to the antenna device according to the second aspect of the present disclosure, in the antenna device according to the first aspect, each of the plurality of strip conductors has a longitudinal length larger than the dimension of the radiator in the longitudinal direction with respect to the longitudinal direction of the strip conductor.

[0009] According to an antenna device of a third aspect of the present disclosure, in an antenna device of a first or second aspect, the plurality of strip conductors are arranged such that the two strip conductors closest to the radiator are spaced further apart than the dimensions of the radiator.

[0010] According to the fourth aspect of the present disclosure, in the antenna device according to one of the first to third aspects, each of the plurality of strip conductors is arranged such that the longitudinal direction of the strip conductor is perpendicular to the first direction.

[0011] According to the fifth aspect of the present disclosure, in the antenna device according to one of the first to fourth aspects, the plurality of strip conductors have a longitudinal length that increases as the distance from the radiator increases.

[0012] According to the sixth aspect of the present disclosure, in the antenna device according to one of the first to fifth aspects, each of the plurality of strip conductors is curved or bent such that the end of the strip conductor approaches the radiator.

[0013] According to the seventh aspect of the present disclosure, in the antenna device according to one of the first to sixth aspects, the plurality of strip conductors are embedded in the plate-shaped region of the housing.

[0014] According to an antenna device according to the eighth aspect of the present disclosure, in an antenna device according to one of the first to seventh aspects, the antenna element has a second feed point at a position shifted from the center of the antenna element in a second direction different from the first direction, and the plurality of strip conductors include a plurality of first strip conductors arranged to intersect the first direction and a plurality of second strip conductors arranged to intersect the second direction.

[0015] According to one aspect of the present disclosure, the influence of the housing on the radiation characteristics can be reduced compared to conventional designs.

[0016] This is a top view showing the configuration of the antenna device 1 according to the first embodiment. This is a cross-sectional view of the antenna device 1 in Figure 1 along the line A-A'. This is a top view showing the configuration of the radiator 10 in Figure 1. This is a diagram illustrating the suppression of interference waves by the antenna device 1 in Figure 1. This is a diagram illustrating the suppression of interference waves by the antenna device 1 in Figure 1. This is a diagram showing the electric field distribution on the housing of an antenna device according to a comparative example. This is a diagram showing the electric field distribution on the housing 20 when the antenna device 1 in Figure 1 has a configuration of d0 = 15 mm, d1 = 10 mm, d2 = 10 mm. This is a diagram showing the electric field distribution on the housing 20 when the antenna device 1 in Figure 1 has a configuration of d0 = 15 mm, d1 = 5 mm, d2 = 10 mm. This is a diagram showing the electric field distribution on the housing 20 when the antenna device 1 in Figure 1 has a configuration of d0 = 15 mm, d1 = 15 mm, d2 = 10 mm. This is a diagram showing the electric field distribution on the housing 20 when the antenna device 1 in Figure 1 has a configuration of d0 = 15 mm, d1 = 10 mm, d2 = 3 mm. This figure shows the electric field distribution on the housing 20 when the antenna device 1 in Figure 1 has a configuration of d0 = 5 mm, d1 = 10 mm, and d2 = 10 mm. This figure shows the electric field distribution on the housing 20 when the antenna device 1 in Figure 1 has a configuration of d0 = 10.7 mm, d1 = 10 mm, and d2 = 10 mm. This is a top view showing the configuration of the antenna device 1A according to the first modification of the first embodiment. This is a top view showing the configuration of the antenna device 1B according to the second modification of the first embodiment. This is a top view showing the configuration of the antenna device 1C according to the third modification of the first embodiment. This is a top view showing the configuration of the antenna device 1D according to the second embodiment. This is a top view showing the configuration of the radiator 10D in Figure 16. This is a top view showing the configuration of the antenna device 1E according to a modification of the second embodiment.

[0017] Hereinafter, antenna devices according to each embodiment of the present invention will be described with reference to the drawings. Throughout the drawings, the same reference numerals indicate the same components.

[0018] [First Embodiment] [Configuration of the First Embodiment] Figure 1 is a top view showing the configuration of the antenna device 1 according to the first embodiment. Figure 2 is a cross-sectional view of the antenna device 1 in Figure 1 along the line A-A'.

[0019] The antenna device 1 comprises a radiator 10, a housing 20, and a plurality of strip conductors 21.

[0020] Figure 3 is a top view showing the configuration of the radiator 10 in Figure 1. The radiator 10 comprises a dielectric substrate 11 having dimensions d11 × d12, a ground conductor (not shown) formed on one surface of the dielectric substrate 11, and at least one antenna element 12-1, 12-2 formed on the other surface of the dielectric substrate 11. In the example in Figure 3, the radiator 10 is configured as a microstrip antenna comprising two antenna elements 12-1, 12-2. The antenna elements 12-1, 12-2 each have feed points F1, F2, respectively, shifted from the center of the antenna elements 12-1, 12-2 in the direction along the X-axis. The antenna elements 12-1, 12-2 are excited via the feed points F1, F2, respectively, and transmit or receive radio waves with polarization along the X-axis. In Figure 3, the direction of polarization is shown by a thick dashed line. Here, since the feed points F1 and F2 are shifted along the X-axis from the centers of the antenna elements 12-1 and 12-2, the polarization direction is parallel to the X-axis. The feed point is the point where a high-frequency signal is transmitted to the antenna elements 12-1 and 12-2, for example, via feed wiring (not shown).

[0021] The radiator 10 has dimensions d11 and d12 that are less than or equal to the operating wavelength λ0 in air.

[0022] Referring again to Figures 1 and 2, the housing 20 is positioned at a predetermined distance d3 from the radiator 10. The housing 20 is made of a dielectric material such as plastic. The housing 20 may be configured to surround the radiator 10 and other circuits (e.g., wireless communication circuits), but in this application, for the sake of simplicity in illustration, only the plate-like region above the radiator 10 is shown. There are no other dielectric or metal components between the radiator 10 and the housing 20; only air exists.

[0023] Multiple strip conductors 21 are arranged in a plate-shaped region of the housing 20. For example, four or more strip conductors 21 may be provided, including two or more strip conductors 21 on the +X side of the radiator 10 and two or more strip conductors 21 on the -X side of the radiator 10.

[0024] Each strip conductor 21 is arranged such that its longitudinal direction intersects the polarization direction of the radiator 10 (shown by the thick dashed line in Figure 1). For example, each strip conductor 21 may be arranged such that, in a plan view, its longitudinal direction is perpendicular to the polarization direction of the radiator 10.

[0025] Each strip conductor 21 has a longitudinal length greater than the dimension d11 of the radiator 10 in the longitudinal direction of the strip conductor 21. In the example in Figure 1, each strip conductor 21 has a linear shape and the same longitudinal length d0 (i.e., d0 > d11).

[0026] The two strip conductors 21 closest to the radiator 10 are arranged with a spacing d1 greater than the dimensions of the radiator 10 (i.e., d1 > d12). The remaining strip conductors 21 are arranged with a spacing d2 that is the same as or different from the spacing d1.

[0027] The multiple strip conductors 21 may be arranged on the top or bottom surface of the housing 20, or they may be embedded inside the housing 20 without being exposed on the surface of the housing 20. The multiple strip conductors 21 may be metal plates or metal rods, may be formed by attaching metal tape, or may be formed by applying ink containing metal.

[0028] The parameters d0, d1, and d2 relating to the dimensions and arrangement of the strip conductor 21 may be set to values ​​within the following ranges with respect to the operating wavelength λ0 in air, for example.

[0029] λ0 ≤ d0 ≤ 2 × λ0 0.9 × λ0 ≤ d1 ≤ 1.1 × λ0 0.5 × λ0 ≤ d2 ≤ λ0

[0030] Figures 4 and 5 illustrate the suppression of interference waves by the antenna device 1 shown in Figure 1. When the radiator 10 radiates radio waves, the radio waves not only propagate through the housing 20 in the desired direction, but also propagate along the surface of the housing 20. Conventionally, there was a risk that radio waves propagating along the surface of the housing 20 would become interference waves. On the other hand, according to this embodiment, by providing multiple strip conductors 21 on the housing 20, the radio waves propagating along the surface of the housing 20 can be attenuated, and interference waves can be suppressed. Therefore, the influence of the housing 20 on the radiation characteristics of the antenna device 1 can be reduced compared to conventional methods.

[0031] [Operation of the First Embodiment] A simulation was performed on the antenna device 1 according to this embodiment.

[0032] The operation of the antenna device 1 according to this embodiment will be described with reference to Figures 6 and 7.

[0033] Figure 6 shows the electric field distribution on the housing of the antenna device according to the comparative example. The antenna device according to the comparative example has a configuration in which the strip conductor 21 is removed from the antenna device 1 of Figure 1. The operating frequency of the radiator 10 was 28 GHz, and the operating wavelength λ0 in air was 10.7 mm. Figure 6 shows that radio waves propagate along the surface of the housing 20 in the ±X direction.

[0034] Figure 7 shows the electric field distribution on the housing 20 when the antenna device 1 in Figure 1 has a configuration of d0 = 15 mm, d1 = 10 mm, and d2 = 10 mm. Comparing Figures 6 and 7, it can be seen that by providing multiple strip conductors 21 on the housing 20, the radio waves propagating along the surface of the housing 20 can be significantly attenuated.

[0035] Next, referring to Figures 8 to 12, preferred ranges for parameters d0, d1, and d2 related to the dimensions and arrangement of the strip conductor 21 will be described.

[0036] Figure 8 shows the electric field distribution on the housing 20 when the antenna device 1 in Figure 1 has a configuration of d0 = 15 mm, d1 = 5 mm, and d2 = 10 mm. It can be seen that when the distance d1 = 5 mm between the two strip conductors 21 closest to the radiator 10 is significantly smaller than the operating wavelength λ0 = 10.7 mm in air, the radio waves propagating along the surface of the housing 20 become stronger compared to the case in Figure 7.

[0037] Figure 9 shows the electric field distribution on the housing 20 when the antenna device 1 in Figure 1 has a configuration of d0 = 15 mm, d1 = 15 mm, and d2 = 10 mm. It can be seen that when the distance d1 = 15 mm between the two strip conductors 21 closest to the radiator 10 is significantly larger than the operating wavelength λ0 = 10.7 mm in air, the radio waves propagating along the surface of the housing 20 become stronger compared to the case in Figure 7.

[0038] Figure 10 shows the electric field distribution on the housing 20 when the antenna device 1 in Figure 1 has a configuration of d0 = 15 mm, d1 = 10 mm, and d2 = 3 mm. It can be seen that when the spacing d2 = 3 mm between the remaining strip conductors 21, excluding the two strip conductors 21 closest to the radiator 10, is significantly smaller than λ0 / 2, the radio waves propagating along the surface of the housing 20 become stronger compared to the case in Figure 7.

[0039] Figure 11 shows the electric field distribution on the housing 20 when the antenna device 1 in Figure 1 has a configuration of d0 = 5 mm, d1 = 10 mm, and d2 = 10 mm. It can be seen that when the longitudinal length d0 = 5 mm of the strip conductor 21 is significantly smaller than the operating wavelength λ0 = 10.7 mm in air, the radio waves propagating along the surface of the housing 20 become stronger compared to the case in Figure 7.

[0040] FIG. 12 is a diagram showing the electric field distribution on the housing 20 when the antenna device 1 in FIG. 1 has a configuration with d0 = 10.7 mm, d1 = 10 mm, and d2 = 10 mm. Even when the length d0 in the longitudinal direction of the strip conductor 21 matches the operating wavelength λ0 = 10.7 mm in air, it can be seen that the radio wave propagating along the surface of the housing 20 becomes stronger compared to the case of FIG. 7. This is considered to be because the strip conductor 21 is excited by resonating with the radio wave propagating along the surface of the housing 20.

[0041] Referring to FIGS. 7 to 12, it was found that in the case of FIG. 7, the radio wave propagating along the surface of the housing 20 can be most effectively attenuated. It was found that when the parameters d0, d1, and d2 are set within the above-described ranges, practically favorable results can be obtained.

[0042] [Effect of the First Embodiment] According to the antenna device 1 according to the first embodiment, by providing a plurality of strip conductors 21 on the housing 20, the influence of the housing 20 on the radiation characteristics of the antenna device 1 can be reduced more than before.

[0043] The applicant of the present application performed simulations for the cases where the relative permittivity of the housing 20 is 3 and 6, and confirmed in both cases that the influence of the housing 20 on the radiation characteristics of the antenna device 1 can be reduced more than before. According to the present embodiment, even when the relative permittivity of the housing 20 is not too low, the influence of the housing 20 on the radiation characteristics of the antenna device 1 can be reduced more than before.

[0044] The applicant of the present application confirmed that when the plurality of strip conductors 21 are embedded inside the housing 20, the influence of the housing 20 on the radiation characteristics of the antenna device 1 can be reduced more than when the plurality of strip conductors 21 are exposed on the surface of the housing 20.

[0045] According to this embodiment, in order to attenuate radio waves propagating along the surface of the housing 20, it is only necessary to arrange a plurality of strip conductors 21 in the housing, and it is unnecessary to provide other parts and / or other housings. Furthermore, the distance d3 from the radiator 10 to the housing 20 is independent of the operating wavelength λ0 and can be adjusted arbitrarily. Therefore, it is possible to provide a small antenna device 1 that does not include extra parts and housings and has no dimensional constraints.

[0046] The antenna device 1 according to this embodiment can be used, for example, in frequency bands of 24 GHz or higher. In high frequency bands such as millimeter waves to subterahertz waves, the influence of radio waves propagating along the surface of the housing on the radiation characteristics becomes significant. According to this embodiment, in such frequency bands, the influence of the housing 20 on the radiation characteristics of the antenna device 1 can be reduced compared to conventional designs.

[0047] [Modification of the First Embodiment] Figure 13 is a top view showing the configuration of an antenna device 1A according to a first modification of the first embodiment. The antenna device 1A includes a plurality of strip conductors 21A instead of the plurality of strip conductors 21 in Figure 1. The plurality of strip conductors 21A have a longitudinal length that increases as the distance from the radiator 10 increases. In addition, each strip conductor 21A is curved so that its end approaches the radiator 10. As can be seen from Figure 6, radio waves propagating along the surface of the housing 20 generally spread out concentrically from a point directly above the radiator 10. By using strip conductors 21A formed to match the shape of the wavefront of the radio waves, the radio waves propagating along the surface of the housing 20 can be attenuated more effectively than in the case of Figure 1.

[0048] FIG. 14 is a top view showing the configuration of the antenna device 1B according to the second modification of the first embodiment. The antenna device 1B includes a plurality of strip conductors 21B instead of the plurality of strip conductors 21 in FIG. 1. The plurality of strip conductors 21B have a longitudinal length that increases as the distance from the radiator 10 increases. Further, each strip conductor 21B is bent so that the end of the strip conductor 21B approaches the radiator 10. By using the strip conductor 21B bent as shown in FIG. 14, not limited to the strip conductor 21A curved as shown in FIG. 13, the radio wave propagating along the surface of the housing 20 can be attenuated more effectively than in the case of FIG. 1.

[0049] FIG. 15 is a top view showing the configuration of the antenna device 1C according to the third modification of the first embodiment. The antenna device 1C includes a plurality of strip conductors 21C instead of the plurality of strip conductors 21 in FIG. 1. The plurality of strip conductors 21C have a longitudinal length that increases as the distance from the radiator 10 increases. By using the straight strip conductor 21C, not limited to the curved or bent strip conductors 21A and 21B, the radio wave propagating along the surface of the housing 20 can be attenuated more effectively than in the case of FIG. 1.

[0050] [Second Embodiment] FIG. 16 is a top view showing the configuration of the antenna device 1D according to the second embodiment.

[0051] The antenna device 1D includes a radiator 10D, a housing 20, a plurality of first strip conductors 21-1, and a plurality of second strip conductors 21-2.

[0052] Figure 17 is a top view showing the configuration of the radiator 10D in Figure 16. The radiator 10D comprises a dielectric substrate 11D, a ground conductor (not shown) formed on one surface of the dielectric substrate 11D, and antenna elements 12-1 to 12-4 formed on the other surface of the dielectric substrate 11D. Antenna element 12-1 has a feed point F1a at a position shifted from the center of antenna element 12-1 in the direction along the X axis, and a feed point F1b at a position shifted from the center of antenna element 12-1 in the direction along the Y axis. Antenna element 12-1 is excited via feed point F1a or F1b, and when excited via feed point F1a, it transmits or receives radio waves with polarization direction along the X axis, and when excited via feed point F1b, it transmits or receives radio waves with polarization direction along the Y axis. Antenna elements 12-2 to 12-4 are also excited via one of two feed points, similar to antenna element 12-1, and transmit or receive radio waves with polarization directions along the X or Y axis.

[0053] Referring again to Figure 16, each strip conductor 21-1 is positioned such that its longitudinal direction intersects the polarization direction along the X-axis of the radiator 10D. For example, each strip conductor 21-1 may be positioned so that its longitudinal direction is perpendicular to the polarization direction along the X-axis of the radiator 10D. Similarly, each strip conductor 21-2 is positioned such that its longitudinal direction intersects the polarization direction along the Y-axis of the radiator 10D. For example, each strip conductor 21-2 may be positioned so that its longitudinal direction is perpendicular to the polarization direction along the Y-axis of the radiator 10D.

[0054] Each strip conductor 21-1 has a longitudinal length greater than the dimensions of the radiator 10D in the longitudinal direction of the strip conductor 21-1. Similarly, each strip conductor 21-2 has a longitudinal length greater than the dimensions of the radiator 10D in the longitudinal direction of the strip conductor 21-2. In the example of Figure 16, each strip conductor 21-1 and 21-2 has a linear shape and the same longitudinal length.

[0055] The two strip conductors 21-1 closest to the radiator 10D are spaced further apart than the dimensions of the radiator 10D. The remaining strip conductors 21-1 are spaced at the same or different intervals. Also, the two strip conductors 21-2 closest to the radiator 10D are spaced further apart than the dimensions of the radiator 10D. The remaining strip conductors 21-2 are spaced at the same or different intervals.

[0056] Antenna device 1D transmits or receives radio waves with polarization direction along the X-axis or Y-axis. By providing multiple strip conductors 21-1 and multiple strip conductors 21-2 on the housing 20, antenna device 1D can attenuate radio waves propagating along the surface of the housing 20 and suppress interference waves, regardless of the polarization direction of the radio waves. Therefore, the influence of the housing 20 on the radiation characteristics of antenna device 1D can be reduced compared to conventional designs.

[0057] Figure 18 is a top view showing the configuration of an antenna device 1E according to a modified example of the second embodiment. The antenna device 1E includes multiple strip conductors 21A-1 and multiple strip conductors 21A-2 instead of the multiple strip conductors 21-1 and multiple strip conductors 21-2 in Figure 16. According to this modified example, as explained with reference to Figure 13, by using strip conductors 21A-1 and 21A-2 formed to match the shape of the wavefront of the radio wave, the radio wave propagating along the surface of the housing 20 can be attenuated more effectively than in the case of Figure 16.

[0058] The antenna device according to the second embodiment may include strip conductor 21B in Figure 14 or strip conductor 21C in Figure 15 instead of strip conductors 21-1 and 21-2 in Figure 16.

[0059] [Other Embodiments] Antenna elements 12-1 to 12-4 may have shapes other than rectangular, for example, circular shapes. Also, the radiator is not limited to microstrip antennas, but may include any antenna elements having polarization in a predetermined direction.

[0060] The antenna device may include any number and / or strip conductors of any shape.

[0061] The portion of the housing on which the strip conductor is installed is not limited to a flat plate; it may also be curved.

[0062] An antenna device according to one aspect of this disclosure may be used, for example, in a base station of a mobile communication system or in a mobile station.

[0063] 1, 1A to 1E Antenna device 10, 10D Radiator 11, 11D Dielectric substrate 12-1 to 12-4 Antenna element 20 Housing 21, 21A to 21C, 21-1, 21-2, 21A-1, 21A-2 Strip conductor F1, F2, F1a, F1b Feed point

Claims

1. An antenna device comprising: a radiator including at least one antenna element; a housing including a plate-shaped region made of a dielectric; and a plurality of strip conductors arranged in the plate-shaped region of the housing, wherein the antenna element has a first feed point at a position shifted in a first direction from the center of the antenna element, and each of the plurality of strip conductors is arranged such that the longitudinal direction of the strip conductor intersects the first direction.

2. The antenna device according to claim 1, wherein each of the plurality of strip conductors has a longitudinal length greater than the dimensions of the radiator with respect to the longitudinal direction of the strip conductor.

3. The antenna device according to claim 1 or 2, wherein the plurality of strip conductors are arranged such that the two strip conductors closest to the radiator are spaced further apart than the dimensions of the radiator.

4. The antenna device according to one of claims 1 to 3, wherein each of the plurality of strip conductors is arranged such that the longitudinal direction of the strip conductor is perpendicular to the first direction.

5. The antenna device according to one of claims 1 to 4, wherein the plurality of strip conductors have a longitudinal length that increases as the distance from the radiator increases.

6. The antenna device according to one of claims 1 to 5, wherein each of the plurality of strip conductors is curved or bent so that the end of the strip conductor approaches the radiator.

7. The antenna device according to one of claims 1 to 6, wherein the plurality of strip conductors are embedded in a plate-shaped region of the housing.

8. The antenna device according to one of claims 1 to 7, wherein the antenna element has a second feed point at a position shifted from the center of the antenna element in a second direction different from the first direction, and the plurality of strip conductors include a plurality of first strip conductors arranged to intersect in the first direction and a plurality of second strip conductors arranged to intersect in the second direction.

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