Antenna device

Abstract

To prevent a decrease in gain when a resonance frequency is adjusted.SOLUTION: An antenna device 1 includes: an antenna substrate 22 as a dielectric substrate; a radiation conductor 21 as a radiation conductor provided on one surface of the dielectric substrate; and feeding parts 23A and 23B for feeding power to the radiation conductor 21. The radiation conductor 21 includes a T-shaped slit 211 having: a slit 211A provided in the center direction from one side of the radiation conductor 21; and a slit 211B provided parallel to one side of the radiation conductor 21 and connected to one end of the slit 211A on the center side.SELECTED DRAWING: Figure 2

Description

Technical Field

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

Background Art

[0002] Conventionally, patch antennas installed on the rooftops of vehicles such as automobiles, inside the IP (Instrument Panel), etc. are known. The patch antenna receives, for example, circularly polarized radio waves from GNSS (Global Navigation Satellite System) satellites. The patch antenna includes a radiating conductor, a feeding pin, an antenna substrate of a dielectric such as ceramic, and a ground (GND (Ground)) conductor.

[0003] The resonance frequency of the patch antenna is determined by the dielectric constant, thickness (thickness in the direction parallel to the radiating conductor), size, and outer periphery of the radiating conductor of the dielectric. However, when aiming for miniaturization or weight reduction by changing the dielectric (for example, from ceramic to resin), the resonance frequency becomes higher than the desired resonance frequency.

[0004] When the resonance frequency becomes higher than the desired value, it is known to perform frequency adjustment by inserting an I-shaped slit in the radiating conductor of the patch antenna. For example, a patch antenna having first, second, and third I-shaped slits extending from each side toward the center in a substantially rectangular radiating conductor is known (see Patent Document 1).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in the patch antenna of Patent Document 1, the impedance is more likely to change as the first to third slits approach the feeding pin. For this reason, in the patch antenna of Patent Document 1, the impedance changes drastically, the range of the resonance frequency to be adjusted becomes wide, and the gain decreases as the first to third slits are made longer.

[0007] An object of the present invention is to prevent a decrease in gain when adjusting the resonance frequency.

Means for Solving the Problems

[0008] To solve the above problems, the antenna device of the present invention includes a dielectric substrate, a radiation conductor provided on one surface of the dielectric substrate, a feeding unit that feeds power to the radiation conductor, The radiation conductor has a first slit provided from one side of the radiation conductor toward the center, and a second slit provided parallel to one side of the radiation conductor and connected to one end on the center side of the first slit.

Effects of the Invention

[0009] According to the present invention, it is possible to prevent a decrease in gain when adjusting the resonance frequency.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments and modified examples according to the present invention will be described in detail in order with reference to the accompanying drawings. However, the scope of the invention is not limited to the illustrated examples.

[0012] (Embodiment) Referring to FIGS. 1 to 7, an embodiment according to the present invention will be described. First, referring to FIGS. 1 to 3, the device configuration of the present embodiment will be described. FIG. 1 is a perspective view showing an antenna device 1 of the present embodiment. FIG. 2 is a top view showing the antenna device 1. FIG. 3 is a top view showing a virtual radiation conductor 21C.

[0013] As shown in FIG. 1, the antenna device 1 of the present embodiment is a patch antenna, and is installed, for example, inside the IP of a vehicle such as an automobile or inside a device such as a so-called shark fin antenna on the roof. The antenna device 1 is, for example, an antenna device for GNSS as a wireless communication method. The antenna device 1 receives radio waves from GNSS satellites in order to measure the position of the vehicle. A control unit (not shown) inside the vehicle performs positioning of the vehicle based on the received signal from the antenna device 1. Also, in FIG. 1, three-dimensional X-axis, Y-axis, and Z-axis are taken, and the same applies to other figures.

[0014] GNSS includes communication standards such as GPS (Global Positioning System), QZSS (Quasi-Zenith Satellite System), GLONASS (Global Navigation Satellite System), and Galileo. In particular, it is assumed that the antenna device 1 is designed to resonate at the L1 band of GPS (center frequency: 1575.42 [MHz]).

[0015] The antenna device 1 includes a radiating conductor 21, an antenna substrate (base) 22, feeding parts 23A and 23B, and a ground conductor 24. The radiating conductor 21 is an electrode of a conductor such as a silver foil formed on the upper surface (+Z-direction surface, surface) of the antenna substrate 22. The radiating conductor 21 is, for example, a substantially square silver foil smaller than the upper surface of the antenna substrate 22 and patterned on the antenna substrate 22. The feeding parts 23A and 23B are electrically connected to the radiating conductor 21. No perturbation element (notch, protrusion) is formed in the radiating conductor 21. Note that the radiating conductor 21 may be configured to have a perturbation element formed therein.

[0016] As shown in FIG. 2, the radiating conductor 21 has a planar portion 210 and a T-shaped slit 211. The planar portion 210 is a planar portion of a substantially square conductor having four sides and extends in the XY plane. The feeding parts 23A and 23B are connected, for example, on the center side of the planar portion 210 and at positions that are line-symmetric with respect to the diagonal of the planar portion 210.

[0017] The T-shaped slit 211 is a T-shaped slit disposed on each of the four sides of the planar portion 210. That is, the four T-shaped slits 211 are disposed on the +X side edge, -X side edge, +Y side edge, and -Y side edge of the planar portion 210. The T-shaped slit 211 has slits 211A and 211B. The slit 211A is a linear strip-shaped slit connected to the central portion of the edge of the planar portion 210 and extending in the central direction of the planar portion 210 perpendicular to the edge. The slit 211B is a linear strip-shaped slit connected to the tip of the slit 211A and extending in a direction perpendicular to the extending direction of the slit 211A. For example, in the T-shaped slit 211 connected to the +X side edge of the planar portion 210, the slit 211A extends from the edge in the -X direction. The slit 211B extends in the Y-axis direction. Thereby, the T-shaped slit 211 is formed in a T shape.

[0018] The resonance frequency of the radiating conductor is determined by the outer periphery of the radiating conductor, and the longer the outer periphery is, the lower it is. If there is no slit 211A, the radiating conductor 21 becomes the radiating conductor 21C shown in FIG. 3. Since the slit 211B is connected to the outer periphery of the radiating conductor in the radiating conductor 21C, the outer periphery is shorter than that of the radiating conductor 21 having the slit 211A, and the resonance frequency is less likely to decrease. Therefore, in order to easily lower the resonance frequency, the slit 211A is provided in the radiating conductor 21 (T-shaped slit 211).

[0019] The antenna substrate 22 is a plate formed of a resin such as PPE (Polyphenyleneether) (such as polypropylene) material or PC (PolyCarbonate) material as a dielectric having a predetermined dielectric constant (relative permittivity). Using the above resin can make the antenna substrate 22 and the antenna device 1 lighter than using a ceramic as a dielectric. Due to the wavelength shortening effect by this relative dielectric constant, the antenna device 1 can be miniaturized. The material of the antenna substrate 22 is not limited to a dielectric, and may be a magnetic material having a predetermined relative permeability μr or a composite material having a predetermined relative dielectric constant εr and relative permeability μr. The wavelength shortening effect also occurs with the relative permeability μr.

[0020] The power supply units 23A and 23B are, for example, power supply pins made of a metal conductor. One end of the power supply pins is electrically connected to the radiation conductor 21, penetrates through the antenna substrate 22 and the ground conductor 24, and the other end is connected to a circuit unit for power supply (not shown). The power supply units 23A and 23B serve as two power supply points. The power supply units 23A and 23B may be constituted by through holes penetrating the antenna substrate 22.

[0021] The ground conductor 24 is an electrode of a metal conductor formed on the lower surface (-Z direction side surface, back surface) of the antenna substrate 22 and grounded. The ground conductor 24 is, for example, a substantially square silver foil smaller than the outer shape of the lower surface of the antenna substrate 22 and patterned on the lower surface of the antenna substrate 22.

[0022] Next, with reference to FIGS. 4 to 7, the antenna characteristics of the antenna device 1 will be described. FIG. 4 is a diagram showing the frequency characteristics of the gain of an antenna device having a radiation conductor without a T-shaped slit. FIG. 5 is a diagram showing the frequency characteristics of the gain of the antenna device 1. FIG. 6 is a top view showing the antenna device 1a having the radiation conductor 21a having the I-shaped slit 211a. FIG. 7 is a diagram showing the frequency characteristics of the gain of the antenna device 1a.

[0023] First, in the radiation conductor 21 of the antenna device 1, consider an antenna device having a radiation conductor without a T-shaped slit 211 (hereinafter referred to as an antenna device without a T-shaped slit). However, it is assumed that the parts other than the radiation conductor of the antenna device without a T-shaped slit are the same as those of the antenna device 1.

[0024] As shown in FIG. 4, the gain [dBi] of the antenna device without a T-shaped slit with respect to the frequency [GHz] was measured. The gain [dBi] of the antenna device without a T-shaped slit takes the maximum value M01 at 1758 [MHz]. That is, the resonance frequency of the antenna device without a T-shaped slit is 1758 [MHz]. This resonance frequency is intended to be lowered by about 183 [MHz] to the center frequency (1575 [MHz]) of the L1 band of GPS.

[0025] Next, as shown in FIG. 5, the gain [dBi] of the antenna device 1 (with the T-shaped slit 211) with respect to the frequency [GHz] was measured. The gain [dBi] of the antenna device 1 takes the maximum value M02 at 1575 [MHz]. That is, the resonance frequency of the antenna device 1 is 1575 [MHz]. Therefore, by adding the T-shaped slit 211 to the radiation conductor 21, the resonance frequency can be lowered from 1758 [MHz] to the center frequency of the GPS L1 band.

[0026] Here, as shown in FIG. 6, consider an antenna device 1a in which the radiation conductor 21 of the antenna device 1 is replaced with a radiation conductor 21a having an I-shaped slit 211a. However, it is assumed that the parts of the antenna device 1a other than the radiation conductor 21a are the same as those of the antenna device 1.

[0027] The radiation conductor 21a has a planar portion 210 and an I-shaped slit 211a. The I-shaped slit 211a is an I-shaped (linear strip-shaped) slit arranged in four each on the four sides of the planar portion 210. That is, 16 I-shaped slits 211a are arranged in four each on the +X side, -X side, +Y side, and -Y side of the planar portion 210. The I-shaped slit 211a is connected near the center of the side of the planar portion 210 and extends in the direction of the center of the planar portion 210 perpendicular to the side. For example, the I-shaped slit 211a connected to the +X side of the planar portion 210 extends in the -X direction.

[0028] As shown in FIG. 7, the gain [dBi] of the antenna device 1a with respect to the frequency [GHz] was measured. The gain [dBi] of the antenna device 1a takes the maximum value M03 at 1575 [MHz]. That is, the resonance frequency of the antenna device 1a is 1575 [MHz]. Therefore, by adding the I-shaped slit 211a to the radiation conductor 21, the resonance frequency can be lowered from 1758 [MHz] to the center frequency of the GPS L1 band.

[0029] However, the gain [dBi] of the maximum value M03 of the antenna device 1a drops by as much as 0.693 [dB] from the gain [dBi] of the maximum value M01 of the antenna device without the T-shaped slit.

[0030] On the other hand, the gain [dBi] of the maximum value M02 of the antenna device 1 drops by only 0.196 [dB] from the gain [dBi] of the maximum value M01 of the antenna device without the T-shaped slit. Therefore, the antenna device 1 can lower the resonance frequency while maintaining the antenna performance by the T-shaped slit 211 as compared with the antenna device 1a.

[0031] As described above, according to the present embodiment, the antenna device 1 includes an antenna substrate 22, a radiation conductor 21 provided on one upper surface of the antenna substrate 22, and power feeding units 23A and 23B for feeding power to the radiation conductor 21. The radiation conductor 21 includes a T-shaped slit 211 having a slit 211A provided from one side of the radiation conductor 21 toward the center direction, and a slit 211B provided in parallel with one side of the radiation conductor 21 and connected to one end on the center side of the slit 211A. The antenna device 1 includes a ground conductor 24 provided on the lower surface facing one upper surface (the surface on the radiation conductor 21 side) of the antenna substrate 22.

[0032] Therefore, when adjusting the resonance frequency, the slit can be separated from the power feeding units 23A and 23B by the T-shaped slit 211, and a decrease in gain can be prevented.

[0033] (Modification example) With reference to FIG. 8, a modification example of the above embodiment will be described. FIG. 8 is a top view showing the antenna device 1b of this modification example.

[0034] The antenna device 1 of the above embodiment has a configuration in which the radiation conductor 21 has a T-shaped slit 211. The antenna device 1b of this modification example has a configuration in which a slit for folding back is further added to the T-shaped slit 211.

[0035] As shown in FIG. 8, the antenna device 1b of this modification is obtained by replacing the radiation conductor 21 of the antenna device 1 with a radiation conductor 21b. However, it is assumed that the parts of the antenna device 1b other than the radiation conductor 21b are the same as those of the antenna device 1.

[0036] The radiation conductor 21b has a planar portion 210 and a T-shaped slit 211b. The T-shaped slit 211b is a substantially T-shaped slit disposed on each of the four sides of the planar portion 210. That is, the four T-shaped slits 211b are disposed on the +X side edge, -X side edge, +Y side edge, and -Y side edge of the planar portion 210. The T-shaped slit 211b has slits 211A, 211B, 211C, and 211D. The slit 211C is a linear strip-shaped slit that is connected to the tip of the slit 211B and extends in the direction toward the center of the planar portion 210, which is orthogonal to the extending direction of the slit 211B. The slit 211D is a linear strip-shaped slit that is connected to the tip of the slit 211C and extends in the direction toward the center of the planar portion 210, which is orthogonal to the extending direction of the slit 211C. For example, in the T-shaped slit 211b connected to the +X side edge of the planar portion 210, the slit 211A extends from the side in the -X direction. The slit 211B extends in the Y-axis direction. The slit 211C extends in the -X direction. The slit 211D extends in the -Y direction (or +Y direction).

[0037] The slit 211D is disposed in parallel in the vicinity of the slit 211B. Therefore, the slits 211C and 211D extend in a folding-back direction that is at a distance from the power supply portions 23A and 23B.

[0038] As a result, the T-shaped slit 211 has the folded-back slits 211C and 211D added thereto in a T shape, and the length of the resonating slit is extended. For this reason, the antenna device 1b has a lower resonance frequency than the antenna device 1.

[0039] As described above, according to this modification example, the radiation conductor 21b (T-shaped slit 211b) is connected to one end of the slit 211B and has slits 211C and 211D whose connection destination and extending direction are changed. Therefore, the slit lengths of the slit 211B of the T-shaped slit 211b can be extended by the slits 211C and 211D, and the resonance frequency can be made lower (than the T-shaped slit 211).

[0040] In addition, the slits 211C and 211D extend in a direction away from the power feeding portions 23A and 23B. Therefore, the resonance frequency can be made lower, and a decrease in gain can be further prevented.

[0041] Note that the descriptions in the above embodiments and modification examples are merely examples of the antenna device according to the present invention and are not limited thereto. For example, a configuration in which the above embodiments and modification examples are appropriately combined may be adopted.

[0042] In the above embodiments and modification examples, the frequency band of the antenna devices 1 and 1b is configured to be the frequency band of GNSS. However, the present invention is not limited thereto, and other wireless communication system frequency bands may be used.

[0043] In the above embodiments and modification examples, the antenna devices 1 and 1b are patch antennas having a single-layer antenna substrate 22 with two-point power feeding by the power feeding portions 23A and 23B. However, the present invention is not limited thereto. For example, the antenna devices 1 and 1b may be patch antennas with single-point power feeding. Further, the antenna devices 1 and 1b may be patch antennas having a multi-layer antenna substrate.

[0044] In the above modification example, the antenna device 1b is configured to have a T-shaped slit 211b having slits 211C and 211D in addition to the slits 211A and 211B. However, the present invention is not limited thereto. For example, the T-shaped slit 211b may be configured by adding the slit 211C to the slits 211A and 211B, or may be configured by adding three or more series of mutually connected slits in the same manner.

[0045] Further, in the above-described modification, the folding direction of the T-shaped slit 211b is configured to be the central direction of the flat portion 210, but the present invention is not limited thereto. For example, the folding direction of the T-shaped slit 211b may be configured to be the outer direction of the flat portion 210. For example, in the T-shaped slit 211b connected to the side on the +X direction side of the flat portion 210, within the range of the flat portion 210, the slit 211C is connected to one end of the slit 211B, extends in the +X direction from the connection end, the slit 211D is connected to one end on the +X direction side of the slit 211C, and extends in the -Y direction or +Y direction from the connection end.

[0046] In addition, regarding the detailed configuration and detailed operation of the antenna devices 1 and 1b in the above embodiment, appropriate changes can be made without departing from the spirit of the present invention.

Explanation of Reference Numerals

[0047] 1, 1a, 1b Antenna device 21, 21a, 21b Radiating conductor 210 Flat portion 211, 211b T-shaped slit 211a I-shaped slit 211A, 211B, 211C, 211D Slit 22 Antenna substrate 23A, 23B Feeding portion 24 Ground conductor

Claims

1. A dielectric substrate, a radiation conductor provided on one surface of the dielectric substrate, and a power feeding unit for feeding power to the radiation conductor, wherein the radiation conductor has a first slit provided from one side of the radiation conductor toward the center, and a second slit provided parallel to one side of the radiation conductor and connected to one end of the first slit on the center side, and the antenna device.

2. The antenna device according to claim 1, further comprising a ground conductor provided on a surface facing the one surface of the dielectric substrate.

3. The antenna device according to claim 1 or 2, wherein the radiation conductor has at least one third slit connected to one end of the second slit and having a changed connection destination and extending direction.

4. The antenna device according to claim 3, wherein the third slit extends in a direction away from the power feeding unit.

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