Composite patch antenna device

Abstract

To provide a compact and thin composite patch antenna device configured to operate in multiple frequency bands. A composite patch antenna device includes a ground plate (10), a dielectric (20), a first patch element (30), a second patch element (40), and a filter part (50). The first patch element (30) is disposed on the dielectric (20), has a feeding part (31), and configured to operate in a first frequency band. The second patch element (40) is formed within the first patch element (30) so as to be separated therefrom by a slit (41) having a predetermined width, shares the feeding part (31) with the first patch element (30), and configured to operate in a second frequency band higher than the first frequency band. The filter part (50) is connected between the first patch element (30) and the second patch element (40) and configured to attenuate signals in the second frequency band while allowing signals in the first frequency band to pass therethrough.

Description

Technical Field

[0001] The present invention relates to a composite patch antenna device, and more particularly to a compact and thin composite patch antenna device configured to operate in multiple frequency bands.Background Art

[0002] Motorcycles are provided with headsets to enable communication between drivers or between a driver and a passenger. The headsets typically use Bluetooth (Registered Trademark) communication, and motorcycles have recently been provided with Bluetooth antennas. The headsets are further provided with wireless LAN antennas so as to enable wireless LAN communication, such as Wi-Fi (Registered Trademark) communication, with mobile information terminals (e.g., smartphones). Bluetooth communication uses a 2.4 GHz band, and wireless LAN communication also uses a 2.4 GHz band, so that they are likely to interfere with each other. Accordingly, Patent Document 1 discloses an antenna device in which a Bluetooth antenna element and a wireless LAN antenna element are disposed on the same plane, and a slit is formed in a ground layer so as to enhance isolation therebetween.

[0003] Also, for example, Patent Document 2 discloses a multilayer patch antenna device in which a planar antenna element is provided on each layer of multilayer substrates, with only a planar antenna element on the uppermost layer being provided with a feeding point and planar antenna elements on the lower layers being excited in a parasitic antenna system, so as to be operable in multiple frequency bands.Citation List Patent Document

[0004] Patent Document 1:JP 2021-184 593 APatent Document 2:JP 2003-283 240 A Disclosure of the Invention Problems to be Solved by the Invention

[0005] However, in wireless LAN communication, a 5 GHz band is used as well as a 2.4 GHz band, so that an antenna element supporting 5 GHz is separately required. For example, in a configuration as disclosed in the above-described Patent Document 1 in which a plurality of antenna elements are disposed on the same plane, a space is required for disposing 2.4 GHz-band Bluetooth antenna element and 2.4 GHz- and 5 GHz-band wireless LAN antenna elements on the same plane, inevitably resulting in an increase in antenna device size.

[0006] Further, in multilayer patch antenna devices using multilayer substrates as disclosed in Patent Document 2, although a mounting area is reduced, thickness inevitably increases. Further, a multilayer substrate structure is costly. Furthermore, excitation in a parasitic antenna system makes it difficult to achieve sufficient antenna characteristics.

[0007] Accordingly, there has been a demand for compact and thin patch antenna devices having circular polarization so as to enable communication regardless of orientation with respect to, for example, a motorcycle, and being operable in multiple frequency bands.

[0008] The present invention has been made in view of the above situation, and an object thereof is to provide a compact and thin composite patch antenna device configured to operate in multiple frequency bands.Means for Solving the Problems

[0009] To achieve the above object of the present invention, a composite patch antenna device according to the present invention may include: a ground plate; a dielectric disposed on the ground plate; a first patch element disposed on the dielectric, having a feeding part, and configured to operate in a first frequency band; a second patch element formed within the first patch element so as to be separated therefrom by a slit having a predetermined width, sharing the feeding part with the first patch element, and configured to operate in a second frequency band higher than the first frequency band; and a filter part connected between the first patch element and the second patch element and configured to attenuate signals in the second frequency band while allowing signals in the first frequency band to pass therethrough.

[0010] The filter part may be connected between the first patch element and the second patch element at a position spaced apart from the feeding part. the filter part may adjust impedance characteristics of the first patch element by a connection position of the filter part.

[0011] The filter part may be formed by a trap coil or a low-pass filter.

[0012] The filter part may be disposed on a side of the dielectric on which the ground plate is disposed and connected between the first patch element and the second patch element through a through hole.

[0013] The filter part may be formed by a meander pattern and disposed on a side of the dielectric on which the first patch element and the second patch element are disposed.

[0014] The first patch element may have a notch for adjusting impedance characteristics thereof.

[0015] The second patch element may be formed in a shape similar to that of the first patch element.

[0016] The feeding part may be a single-point feed or a two-point feed.

[0017] The composite patch antenna device may further include: a third patch element formed within the second patch element so as to be separated therefrom by a slit having a predetermined width, sharing the feeding part with the first patch element, and configured to operate in a third frequency band higher than the second frequency band; and a second filter part connected between the second patch element and the third patch element and configured to attenuate signals in the third frequency band while allowing signals in the first frequency band and the second frequency band to pass therethrough.Advantageous Effects of the Invention

[0018] The composite patch antenna device according to the present invention is compact and thin and is configured to operate in multiple frequency bands.Brief Description of the Drawings

[0019] FIG. 1 is a schematic top view for explaining the composite patch antenna device according to the present invention. FIG. 2 is a schematic cross-sectional side view taken along the line a-a for explaining the composite patch antenna device according to the present invention. FIG. 3 is a circuit diagram for explaining the filter part of the composite patch antenna device according to the present invention. FIG. 4 is a schematic enlarged top view for explaining another example of the filter part of the composite patch antenna device according to the present invention. FIG. 5 is a schematic top view for explaining another example of the first patch element of the composite patch antenna device according to the present invention. FIG. 6 is a schematic top view for explaining an example in which the feeding part of the composite patch antenna device according to the present invention is configured as a two-point feed. FIG. 7 is a schematic top view illustrating an example in which the composite patch antenna device according to the present invention is configured to operate in three frequency bands. Best Mode for Carrying Out the Invention

[0020] Hereinafter, an embodiment for practicing the present invention will be described with reference to the accompanying drawings. A composite patch antenna device according to the present invention is configured to operate in multiple frequency bands, specifically, a 2.4 GHz band for, for example, Bluetooth communication and a 5 GHz band for wireless LAN communication. However, the present invention is not limited thereto, and the composite patch antenna device according to the present invention may be configured to operate in any frequency bands in which patch antennas are operable. FIG. 1 is a schematic top view for explaining the composite patch antenna device according to the present invention. FIG. 2 is a schematic cross-sectional side view taken along the line a-a for explaining the composite patch antenna device according to the present invention.

[0021] In the drawing, the same reference numerals as those in FIG. 1 denote the same parts. As illustrated, the composite patch antenna device according to the present invention mainly includes a ground plate 10, a dielectric 20, a first patch element 30, a second patch element 40, and a filter part 50. The composite patch antenna device according to the present invention has a circularly polarized microstrip antenna structure so as to enable communication regardless of orientation.

[0022] The ground plate 10 is a conductor ground plate of the composite patch antenna device. It may be formed of a uniform conductor plate. A connection land separated from the ground plate 10 may be appropriately formed for connection to the filter part 50 to be described later and a signal line of a coaxial cable 1.

[0023] The dielectric 20 is disposed on the ground plate 10. The dielectric 20 acts as a dielectric of the composite patch antenna device, thereby providing a wavelength reduction effect depending on a dielectric constant thereof. The dielectric 20 may be formed of ceramics, or may be provided in the form of a printed circuit board or an air layer. When the dielectric 20 is a printed circuit board, a solid pattern on the back surface side of the printed circuit board may be used as the ground plate 10.

[0024] The first patch element 30 is configured to operate in a first frequency band. Specifically, the first frequency band may be a 2.4 GHz band used in, for example, Bluetooth communication or wireless LAN communication. The first patch element 30 is disposed on the dielectric 20. The first patch element 30 has a feeding part 31. The feeding part 31 is connected to a connection part of the coaxial cable 1 on the back surface side of the dielectric 20 through a through hole 32.

[0025] A resistor for connection detection or the like may be connected, as needed, between the connection part of the coaxial cable 1 and the feeding part 31. In the illustrated example, the feeding part 31 functions as a single-point feeder. Impedance characteristics can be adjusted by adjusting an offset of the feeding part 31 from the center of the first patch element 30. Further, in the illustrated example, degenerate separation elements 33 are respectively provided on the upper right side and the lower left side of the rectangular pattern of the first patch element 30, thereby allowing the first patch element 30 to generate circularly polarized waves.

[0026] However, the present invention is not limited thereto, and the degenerate separation elements may be formed by providing symmetrical cuts in a circular pattern. That is, the first patch element 30 may have any shape as long as it can generate circularly polarized waves. The first patch element 30 may be configured such that a length of one side thereof is λ / 2 of a wavelength corresponding to the first frequency band.

[0027] The second patch element 40 is configured to operate in a second frequency band higher than the first frequency band. Specifically, the second frequency band may be a 5 GHz band used in, for example, wireless LAN communication. The second patch element 40 is formed within the first patch element 30 so as to be separated therefrom by a slit (41) 41 having a predetermined width. That is, the second patch element 40 is formed by cutting out an inner portion of the first patch element 30 disposed on the dielectric 20 with the slit 41. In other words, a portion of the first patch element 30 is used as the second patch element 40. The second patch element 40 shares the feeding part 31 with the first patch element 30.

[0028] That is, signals in the first frequency band and the second frequency band may be separated as needed at a unit. In the illustrated example, degenerate separation elements 43 are respectively provided on the upper right side and the lower left side of the rectangular pattern of the second patch element 40, thereby allowing the second patch element 40 to generate circularly polarized waves. The second patch element 40 may be formed in a shape similar to that of the first patch element 30. However, the present invention is not limited thereto, and the second patch element 40 may be modified in shape, as needed, to adjust antenna characteristics thereof. The second patch element 40 may be configured such that a length of one side thereof is λ / 2 of a wavelength corresponding to the second frequency band.

[0029] The filter part 50 is configured to attenuate signals in the second frequency band while allowing signals in the first frequency band to pass therethrough. The filter part 50 is connected between the first patch element 30 and the second patch element 40. Specifically, the filter part 50 is disposed in the slit 41 formed between the first patch element 30 and the second patch element 40.

[0030] That is, the first patch element 30 functions as a microstrip antenna that resonates in the first frequency band together with the second patch element 40 via the filter part 50. On the other hand, the second patch element 40 functions as a microstrip antenna that resonates in the second frequency band alone, since signals in the second frequency band are attenuated by the filter part 50.

[0031] As illustrated, the filter part 50 is connected between the first patch element 30 and the second patch element 40 at a position spaced apart from the feeding part 31. That is, the filter part 50 is disposed in the slit 41 at a position that is offset downward from the center of the first patch element 30 and is farthest from the feeding part 31. The filter part 50 is connected in the vicinity of the upper left corner of the second patch element 40. This optimizes impedance characteristics of both the first patch element 30 and the second patch element 40.

[0032] However, the present invention is not limited thereto, and the filter part 50 may be connected at any position within a range from the upper left corner of the second patch element 40, which is farthest from the feeding part 31, to the upper right corner, which is not too close to the feeding part 31, as long as desired antenna characteristics are maintained. By adjusting the connection position of the filter part 50, impedance characteristics of the first patch element 30 can be adjusted, in particular.

[0033] Further, as illustrated in FIG. 2, the filter part 50 is disposed on a side of the dielectric 20 on which the ground plate 10 is disposed. The filter part 50 is connected between the first patch element 30 and the second patch element 40 through a through hole 21. With such a configuration, portions connecting the filter part 50 and the coaxial cable 1 are all provided at the side on which the ground plate 10 is disposed, so that soldering is required only on one side, thereby improving workability.

[0034] The ground plate 10, the dielectric 20, and the first patch element 30 and the second patch element 40 may be formed using, for example, a double-sided printed circuit board. That is, the first patch element 30 and the second patch element 40 may be patterned by etching.

[0035] FIG. 3 illustrates examples of the filter part 50. FIG. 3 is a circuit diagram for explaining the filter part of the composite patch antenna device according to the present invention. FIG. 3A illustrates an example in which the filter part 50 is formed by a trap coil 51. The trap coil may be a chip inductor. FIG. 3B illustrates an example in which the filter part 50 is formed by an LC filter including a coil 52 and a capacitor 53. The filter part 50 may be constituted by such a low-pass filter. Although the coil 52 and the capacitor 53 are illustrated in this example, such electronic circuit components are not necessarily provided, and an LC filter may be formed as an equivalent circuit by coupling capacitance or the like.

[0036] The thus configured filter part 50 attenuates signals in the second frequency band while allowing signals in the first frequency band to pass therethrough. However, the present invention is not limited thereto, and the filter part 50 may have any known configuration or any configuration to be developed in the future, as long as it can attenuate signals in the second frequency band while allowing signals in the first frequency band to pass therethrough.

[0037] The thus-configured composite patch antenna device according to the present invention operates as follows. In the first frequency band, the filter part 50 allows signals in the first frequency band to pass, and thus an entire structure extending from the second patch element 40 connected to the feeding part 31 to the first patch element 30 via the filter part 50 functions as a microstrip antenna for the first frequency band.

[0038] On the other hand, in the second frequency band, the second patch element 40 connected to the feeding part 31 resonates at λ / 2 of a wavelength corresponding to the second frequency band. The filter part 50 is connected between the first patch element 30 and the second patch element 40 and attenuates signals in the second frequency band. Accordingly, signals in the second frequency band do not propagate to the first patch element 30, so that only the second patch element 40 functions as a microstrip antenna. That is, due to the filter part 50, the first patch element 30 is not electrically seen from the second patch element 40. Thus, the filter part 50 also functions to enhance isolation between the first patch element 30 and the second patch element 40.

[0039] As described above, in the second frequency band, the filter part 50 functions as a trap coil that attenuates signals in the second frequency band, whereas in the first frequency band, the filter part 50 functions to allow excitation of the first patch element 30 as well.

[0040] According to the composite patch antenna device of the present invention, the second patch element 40 operating in the second frequency band can be disposed within an area of the first patch element 30 operating in the first frequency band. That is, since a portion of the first patch element 30 is used as the second patch element 40, the second frequency band can be covered using only a space for the first frequency band.

[0041] This eliminates the need to separately provide a space for the second frequency band, thereby enabling miniaturization of the antenna device. Further, a multilayer structure is not required for operation in the second frequency band, and the second patch element 40 has the same thickness as the first patch element 30, thereby enabling a reduction in thickness of the antenna device.

[0042] In the above illustrated example, the filter part 50 is disposed on a side of the dielectric 20 on which the ground plate 10 is disposed. However, the present invention is not limited thereto. FIG. 4 is a schematic enlarged top view for explaining another example of the filter part of the composite patch antenna according to the present invention. In the drawing, the same reference numerals as those in FIG. 1 denote the same parts. In FIG. 4, only a portion around the filter part 50 is illustrated, and other components are omitted.

[0043] As illustrated, the filter part 50 of the composite patch antenna device according to the present invention is disposed on a side of the dielectric 20 on which the first patch element 30 and the second patch element 40 are disposed. The filter part 50 is formed by a meander pattern 54. In this case, the filter part 50 can be patterned by etching simultaneously with the first patch element 30 and the second patch element 40. This eliminates the need to solder the filter part 50, thereby further improving assembling workability and reducing cost.

[0044] Further, the first patch element of the composite patch antenna according to the present invention may be modified in shape, as needed, for impedance adjustment. FIG. 5 is a schematic top view for explaining another example of the first patch element of the composite patch antenna device according to the present invention. In the drawing, the same reference numerals as those in FIG. 1 denote the same parts. The first patch element 30 may have a notch 34 for adjusting impedance characteristics thereof.

[0045] By changing a width and / or a length of the notch 34 as needed, impedance characteristics of the first patch element 30 can be adjusted. That is, impedance characteristics can be adjusted by using the notch 34 as well as by changing the connection position of the filter part 50. Although the notch 34 is formed only in the first patch element 30 in the illustrated example, the present invention is not limited thereto, and the notch may be formed in the second patch element 40.

[0046] In the illustrated examples described above, the feeding part is configured as a single-point feed. However, the present invention is not limited thereto. FIG. 6 is a schematic top view for explaining an example in which the feeding part of the composite patch antenna device according to the present invention is configured as a two-point feed. In the drawing, the same reference numerals as those in FIG. 1 denote the same parts.

[0047] As illustrated, the feeding part 31 of the composite patch antenna device according to the present invention may include a first feeding part 31a and a second feeding part 31b. In this case, circularly polarized waves are generated by two-point feeding, thereby eliminating the need to provide a degenerate separation element.

[0048] In a configuration in which two-point feeding is employed, the filter part 50 includes a filter part 50a and a filter part 50b. As in the case of single-point feeding, the filter part 50 (50a and 50b) are connected between the first patch element 30 and the second patch element 40 at positions spaced apart from the feeding part 31 (31a and 31b).

[0049] As described above, the feeding part 31 of the composite patch antenna device according to the present invention may be configured as a single-point feed or a two-point feed. The two-point feed is particularly effective when it is desired to broaden an axial ratio bandwidth, especially in the second frequency band.

[0050] Further, the composite patch antenna device according to the present invention may be configured to operate in additional frequency bands. FIG. 7 is a schematic top view illustrating an example in which the composite patch antenna device according to the present invention is configured to operate in three frequency bands. In the drawing, the same reference numerals as those in FIG. 1 denote the same parts. As illustrated, in this example, a third patch element 60 is additionally provided. The third patch element 60 is configured to operate in a third frequency band higher than the second frequency band.

[0051] The third patch element 60 is formed within the second patch element 40 so as to be separated therefrom by a second slit 61 having a predetermined width. That is, the third patch element 60 is formed by cutting out an inner portion of the second patch element 40 disposed on the dielectric 20 with the second slit 61. In other words, a portion of the second patch element 40 is used as the third patch element 60. The third patch element 60 shares the feeding part 31 with the first patch element 30. That is, signals in the first frequency band, the second frequency band, and the third frequency band may be separated as needed at a unit.

[0052] In the illustrated example, degenerate separation elements 63 are respectively provided on the upper right side and the lower left side of the rectangular pattern of the third patch element 60, thereby allowing the third patch element 60 to generate circularly polarized waves. The third patch element 60 may be formed in a shape similar to that of the first patch element 30 and the second patch element 40. However, the present invention is not limited thereto, and the third patch element 60 may be modified in shape, as needed, to adjust antenna characteristics thereof. The third patch element 60 may be configured such that a height thereof is λ / 2 of a wavelength corresponding to the third frequency band.

[0053] In this configuration, a second filter part 55 is provided. The second filter part 55 is configured to attenuate signals in the third frequency band while allowing signals in the first frequency band and the second frequency band to pass therethrough. The second filter part 55 is connected between the second patch element 40 and the third patch element 60.

[0054] Specifically, the second filter part 55 is disposed in the second slit 61 formed between the second patch element 40 and the third patch element 60. That is, the second patch element 40 functions as a microstrip antenna that resonates in the second frequency band together with the third patch element 60 via the second filter part 55. On the other hand, the third patch element 60 functions as a microstrip antenna that resonates in the third frequency band alone, since signals in the third frequency band are attenuated by the second filter part 55.

[0055] Although a configuration operable in three frequency bands is illustrated in the example, the present invention is not limited thereto, and a configuration operable in four or more frequency bands can be achieved by further separating an inner element with a slit and providing a filter part.

[0056] As described above, according to the present invention, there can be provided a compact and thin composite patch antenna device configured to operate in multiple frequency bands.

[0057] The composite patch antenna device according to the present invention is not limited to the above-described illustrated examples, and various modifications may be made without departing from the scope of the present invention.List of Reference Signs

[0058] 1:Coaxial cable 10:Ground plate 20:Dielectric 21:Through hole 30:First patch element 31:Feeding part 31a:Feeding part 31b:Feeding part 32:Through hole 33:Regenerate mode separator 34:Notch 40:Second patch element 41:Slit 43:Regenerate mode separator 50:Filter part 50a:Filter part 50b:Filter part 51:Trap coil 52:Coil 53:Capacitor 54:Meander pattern 55:Second filter part 60:Third patch element 61:Second slit 63:Regenerate mode separator

Claims

1. A composite patch antenna device configured to operate in multiple frequency bands, the composite patch antenna device comprising: a ground plate; a dielectric disposed on the ground plate; a first patch element disposed on the dielectric, having a feeding part, and configured to operate in a first frequency band; a second patch element formed within the first patch element so as to be separated therefrom by a slit having a predetermined width, sharing the feeding part with the first patch element, and configured to operate in a second frequency band higher than the first frequency band; and a filter part connected between the first patch element and the second patch element and configured to attenuate signals in the second frequency band while allowing signals in the first frequency band to pass therethrough.

2. The composite patch antenna device according to claim 1, wherein the filter part is connected between the first patch element and the second patch element at a position spaced apart from the feeding part.

3. The composite patch antenna device according to claim 1, wherein the filter part adjusts impedance characteristics of the first patch element by a connection position of the filter part.

4. The composite patch antenna device according to claim 1, wherein the filter part is formed by a trap coil or a low-pass filter.

5. The composite patch antenna device according to claim 1, wherein the filter part is disposed on a side of the dielectric on which the ground plate is disposed and connected between the first patch element and the second patch element through a through hole.

6. The composite patch antenna device according to claim 1, wherein the filter part is formed by a meander pattern and disposed on a side of the dielectric on which the first patch element and the second patch element are disposed.

7. The composite patch antenna device according to claim 1, wherein the first patch element has a notch for adjusting impedance characteristics thereof.

8. The composite patch antenna device according to claim 1, wherein the second patch element is formed in a shape similar to that of the first patch element.

9. The composite patch antenna device according to claim 1, wherein the feeding part is a single-point feed or a two-point feed.

10. The composite patch antenna device according to any one of claims 1 to 9, which further comprises: a third patch element formed within the second patch element so as to be separated therefrom by a slit having a predetermined width, sharing the feeding part with the first patch element, and configured to operate in a third frequency band higher than the second frequency band; and a second filter part connected between the second patch element and the third patch element and configured to attenuate signals in the third frequency band while allowing signals in the first frequency band and the second frequency band to pass therethrough.

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