Composite patch antenna device

Abstract

Provided is a compact, thin composite patch antenna device compatible with a plurality of frequency bands.　The composite patch antenna device comprises a ground plate 10, a dielectric 20, a first patch element 30, a second patch element 40, and a filter portion 50. The first patch element 30 is disposed on the dielectric 20, includes a power supply portion 31, and corresponds to a first frequency band. The second patch element 40 is formed within the first patch element 30 and is separated from the first patch element 30 by a slit 41 of a predetermined width, shares the power supply portion 31 of the first patch element 30, and corresponds to a second frequency band higher than the first frequency band. The filter portion 50 is connected between the first patch element 30 and the second patch element 40, attenuates signals in the second frequency band, and passes signals in the first frequency band.

Description

Composite patch antenna device

[0001] The present invention relates to a composite patch antenna device, and more particularly to a small and thin composite patch antenna device that is compatible with multiple frequency bands.

[0002] Motorcycles use headsets for communication between drivers and passengers. Headsets typically use Bluetooth (registered trademark) communication, and recently motorcycles have been equipped with Bluetooth antennas. Furthermore, wireless LAN antennas are also installed to enable wireless LAN communication, such as Wi-Fi (registered trademark), with mobile information terminals such as smartphones. Because Bluetooth communication uses the 2.4 GHz band and wireless LAN communication also uses the 2.4 GHz band, they are prone to interference with each other. For this reason, for example, Patent Document 1 discloses an antenna device in which an antenna element for Bluetooth communication and an antenna element for wireless LAN communication are arranged on the same plane and a slit is provided in the ground layer to improve isolation.

[0003] Furthermore, for example, Patent Document 2 discloses a stacked patch antenna device in which planar antenna elements are provided on each layer of a multilayer substrate to accommodate multiple frequency bands, with a feed point provided only on the planar antenna element on the top layer, and planar antenna elements on lower layers being excited using a non-feed method.

[0004] JP 2021-184593 A JP 2003-283240 A

[0005] However, since wireless LAN communication uses not only the 2.4 GHz band but also the 5 GHz band, a separate antenna element compatible with the 5 GHz band is required. For example, in an example in which multiple antenna elements are arranged on the same plane as disclosed in the above-mentioned Patent Document 1, an area is required to arrange on the same plane an antenna element for Bluetooth communication in the 2.4 GHz band and antenna elements for wireless LAN communication in the 2.4 GHz band and the 5 GHz band, respectively, and this inevitably results in an increase in the size of the antenna device.

[0006] In addition, in a laminated patch antenna device using a multilayer substrate as in Patent Document 2, although the projected area is small, the thickness is inevitably large. Also, the laminated substrate structure makes it expensive. Furthermore, since the structure is excited by a parasitic method, it is difficult to obtain sufficient antenna characteristics.

[0007] For this reason, there has been a demand for the development of a small, thin patch antenna device that is circularly polarized and compatible with multiple frequency bands so that communication is possible regardless of the orientation of the device relative to a motorcycle, for example.

[0008] SUMMARY OF THE INVENTION In view of the above circumstances, the present invention aims to provide a small and thin composite patch antenna device that is compatible with multiple frequency bands.

[0009] In order to achieve the above-mentioned object of the present invention, a composite patch antenna device according to the present invention may comprise: a ground plate; a dielectric disposed on the ground plate; a first patch element disposed on the dielectric, having a feeding portion and corresponding to a first frequency band; a second patch element formed within the first patch element and separated from the first patch element by a slit of a predetermined width, sharing the feeding portion of the first patch element, and corresponding to a second frequency band higher than the first frequency band; and a filter section connected between the first patch element and the second patch element, which attenuates signals in the second frequency band and passes signals in the first frequency band.

[0010] Here, the filter section may be connected between the first patch element and the second patch element in the vicinity of a position far from the power supply section.

[0011] The filter section may be any section that can adjust the impedance characteristics of the first patch element by changing the connection position thereof.

[0012] The filter section may be made up of a trap coil or a low-pass filter circuit.

[0013] The filter section may be arranged on the side where the dielectric ground plate is arranged, and may be connected between the first patch element and the second patch element via a through hole.

[0014] The filter section may also be formed of a meander pattern and arranged on the side of the dielectric where the first patch element and the second patch element are arranged.

[0015] The first patch element may also have a notch for adjusting the impedance characteristics of the first patch element.

[0016] The second patch element may be formed to have a shape similar to that of the first patch element.

[0017] The power supply section may be a one-point or two-point power supply.

[0018] Furthermore, the antenna may include a third patch element that is formed within the second patch element and separated from the second patch element by a slit of a predetermined width, shares the power supply section of the first patch element, and corresponds to a third frequency band that is higher than the second frequency band; and a second filter section that is connected between the second patch element and the third patch element and attenuates signals of the third frequency and passes signals of the first frequency band and the second frequency band.

[0019] The composite patch antenna device of the present invention has the advantage of being small and thin while being compatible with multiple frequency bands.

[0020] FIG. 1 is a schematic top view illustrating a composite patch antenna device of the present invention. FIG. 2 is a schematic a-a side cross-sectional view illustrating a composite patch antenna device of the present invention. FIG. 3 is a circuit diagram illustrating a filter section of a composite patch antenna device of the present invention. FIG. 4 is a schematic enlarged top view illustrating another example of a filter section of a composite patch antenna device of the present invention. FIG. 5 is a schematic top view illustrating another example of a first patch element of a composite patch antenna device of the present invention. FIG. 6 is a schematic top view illustrating an example of a composite patch antenna device of the present invention with a dual-point feed section. FIG. 7 is a schematic top view illustrating an example of a composite patch antenna device of the present invention adapted to three frequency bands.

[0021] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The composite patch antenna device of the present invention is compatible with multiple frequency bands. Specifically, it is compatible with the 2.4 GHz band for Bluetooth communication and the 5 GHz band for wireless LAN communication. However, the present invention is not limited to this, and any frequency band compatible with a patch antenna may be used. FIG. 1 is a schematic top view illustrating the composite patch antenna device of the present invention. FIG. 2 is a schematic side cross-sectional view taken along the line a-a illustrating the composite patch antenna device of the present invention. In the figures, parts designated with the same reference numerals as in FIG. 1 represent the same components. As shown, the composite patch antenna device of the present invention is primarily composed of a ground plate 10, a dielectric 20, a first patch element 30, a second patch element 40, and a filter section 50. The composite patch antenna device of the present invention has a circularly polarized microstrip antenna structure that enables communication regardless of the orientation.

[0022] The ground plate 10 serves as the conductive base plate of the composite patch antenna device. It may be made of a uniform conductive plate. Furthermore, it may be formed with connection lands separated from the ground plate 10 as appropriate to connect the filter section 50 (described later) and the signal line of the coaxial cable 1.

[0023] The dielectric 20 is disposed on the ground plate 10. The dielectric 20 serves as the dielectric of the composite patch antenna device, and the wavelength shortening effect is obtained depending on the dielectric constant of the dielectric. The dielectric 20 may be, for example, ceramics, a printed circuit board, or an air space. When the dielectric 20 is a printed circuit board, the solid pattern on the back side of the printed circuit board can be used as the ground plate 10.

[0024] The first patch element 30 corresponds to a first frequency band. Specifically, the first frequency band may be, for example, the 2.4 GHz band used in Bluetooth communication and wireless LAN communication. The first patch element 30 is disposed on the dielectric 20. The first patch element 30 includes a power feed 31. The power feed 31 is connected to the connection of the coaxial cable 1 on the back side of the dielectric 20 via a through hole 32. A resistor or the like for connection detection may be appropriately connected between the connection of the coaxial cable 1 and the power feed 31. In the illustrated example, the power feed 31 is a single-point power feed. The impedance characteristics can be adjusted by adjusting the offset position of the power feed 31 from the center of the first patch element 30. In the illustrated example, the first patch element 30 has degenerate separation elements 33 at the upper right and lower left of a rectangular pattern, and is configured to generate circularly polarized waves. However, the present invention is not limited to this. A circular pattern may also be provided with degenerate separation elements, such as notches, symmetrically arranged. That is, the shape of the first patch element 30 is not important as long as it is configured to generate circularly polarized waves. The dimensions of the first patch element 30 may be, for example, such that the length of one side is λ / 2 of the wavelength of the first frequency band.

[0025] The second patch element 40 corresponds to a second frequency band higher than the first frequency band. Specifically, the second frequency band may be, for example, the 5 GHz band used in wireless LAN communication. The second patch element 40 is formed within the first patch element 30 and separated from the first patch element 30 by a slit 41 of a predetermined width. That is, the second patch element 40 is formed by separating the inner side of the first patch element 30, which is disposed on the dielectric 20, by 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 power supply section 31 of the first patch element 30. That is, signals in the first frequency band and the second frequency band may be appropriately separated on the unit side. In the illustrated example, the second patch element 40 has a rectangular pattern and degenerate separation elements 43 are provided at the upper right and lower left of the second patch element 40, so that it generates circularly polarized waves. The second patch element 40 may be formed to have a similar shape to the first patch element 30. However, the present invention is not limited to this, and the shape may be changed as appropriate, for example, to adjust the antenna characteristics of the second patch element 40. The dimensions of the second patch element 40 may be, for example, such that the length of one side is λ / 2 of the wavelength of the second frequency band.

[0026] The filter unit 50 attenuates signals in the second frequency band and passes signals in the first frequency band. The filter unit 50 is connected between the first patch element 30 and the second patch element 40. Specifically, the filter unit 50 is disposed in a slit 41 between the first patch element 30 and the second patch element 40. 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 unit 50. Meanwhile, since signals in the second frequency band are attenuated by the filter unit 50, only the second patch element 40 functions as a microstrip antenna that resonates in the second frequency band.

[0027] As shown in the figure, the filter section 50 is connected between the first patch element 30 and the second patch element 40 near a position far from the power feed section 31. That is, the filter section 50 is disposed at the position of the slit 41, which is offset downward from the center of the first patch element 30 and farthest from the power feed section 31. Specifically, the filter section 50 is connected near the upper left corner of the second patch element 40. This maximizes the impedance characteristics of both the first patch element 30 and the second patch element 40. However, the present invention is not limited to this. As long as the antenna characteristics are within an acceptable range, the filter section 50 may be connected to a position not too close to the power feed section 31, such as the upper right corner, rather than the upper left corner of the second patch element 40, which is farthest from the power feed section 31. Adjusting the connection position of the filter section 50 makes it possible to adjust the impedance characteristics, particularly of the first patch element 30.

[0028] 2, the filter section 50 is arranged on the side of the dielectric 20 where the ground plate 10 is arranged. The filter section 50 is connected between the first patch element 30 and the second patch element 40 via through holes 21. With this configuration, all connections to the filter section 50 and the coaxial cable 1 are arranged on the side where the ground plate 10 is arranged, and therefore soldering is required only on one side, improving assembly workability.

[0029] The ground plane 10, the dielectric 20, and the first and second patch elements can be constructed using, for example, a double-sided printed circuit board, and the first and second patch elements 30 and 40 can be formed by patterning using etching.

[0030] FIG. 3 shows an example of a filter unit 50. FIG. 3 is a circuit diagram illustrating the filter unit of the composite patch antenna device of the present invention. FIG. 3( a) shows an example in which the filter unit 50 is configured with a trap coil 51. The trap coil may be, for example, a chip inductor. FIG. 3( b) shows an example in which the filter unit 50 is configured with an LC filter including a coil 52 and a capacitor 53. Such a low-pass filter circuit may also be used. While the illustrated example shows the coil 52 and the capacitor 53, electronic circuit components are not necessarily required. The filter unit 50 may be configured to function as an LC filter in terms of an equivalent circuit using coupling capacitance or the like. The filter unit 50 configured in this manner attenuates signals in the second frequency band and passes signals in the first frequency band. However, the present invention is not limited to this. Any existing or future configuration of the filter unit 50 may be applied as long as it is capable of attenuating signals in the second frequency band and passing signals in the first frequency band.

[0031] The composite patch antenna device of the present invention configured as described above operates as follows: For the first frequency band, the filter section 50 passes signals in the first frequency band, so that the entire structure from the second patch element 40 connected to the feed section 31 through the filter section 50 to the first patch element 30 functions as a microstrip antenna for the first frequency band.

[0032] On the other hand, for the second frequency band, resonance occurs at λ / 2 of the wavelength of the second frequency band using the second patch element 40 connected to the power supply unit 31. A filter unit 50 is connected between the first patch element 30 and the second patch element 40, but since it attenuates signals in the second frequency band, the signals do not propagate toward the first patch element 30, and only the second patch element 40 functions as a microstrip antenna. In other words, the filter unit 50 makes the first patch element 30 invisible to the second patch element 40. Therefore, the filter unit 50 also serves to increase the isolation between the first patch element 30 and the second patch element 40.

[0033] In this way, the filter section 50 acts as a trap coil that attenuates signals in the second frequency band for the second frequency band, and also acts to excite the first patch element 30 via the filter section 50 for the first frequency band.

[0034] According to the composite patch antenna device of the present invention, the second patch element 40 corresponding to the second frequency band can be arranged inside the range of the first patch element 30 corresponding to the first frequency band. That is, by using a portion of the first patch element 30 as the second patch element 40, it is possible to support up to the second frequency band using only the area for the first frequency band. Therefore, no additional area is required to support the second frequency band, which ultimately enables the antenna device to be made more compact. Furthermore, there is no need for a laminated structure to support the second frequency band, and the thickness remains the same as that of the first patch element 30 corresponding to the first frequency band, which ultimately enables the antenna device to be made thinner.

[0035] In the illustrated example described above, the filter section 50 is disposed on the side of the dielectric 20 where the ground plate 10 is disposed. However, the present invention is not limited to this. FIG. 4 is a schematic enlarged top view illustrating another example of the filter section of the composite patch antenna device of the present invention. In the figure, parts with the same reference numerals as in FIG. 1 represent the same components. FIG. 4 shows only the periphery of the filter section 50, and other parts are omitted. As shown, the filter section 50 of the composite patch antenna device of the present invention is disposed on the side of the dielectric 20 where the first patch element 30 and the second patch element 40 are disposed. The filter section 50 is formed of a meander pattern 52. If the filter section 50 is formed of a meander pattern 52, it can be patterned by etching simultaneously with the first patch element 30 and the second patch element 40. This eliminates the need for soldering the filter section 50, further improving assembly efficiency and reducing costs.

[0036] Furthermore, the shape of the first patch element of the composite patch antenna device of the present invention may be modified as needed to adjust the impedance. FIG. 5 is a schematic top view illustrating another example of the first patch element of the composite patch antenna device of the present invention. In the figure, parts with the same reference numerals as in FIG. 1 represent the same components. As shown in the figure, the first patch element 30 may have a cutout 34 for adjusting the impedance characteristics of the first patch element 30. The impedance characteristics of the first patch element 30 can be adjusted by appropriately adjusting the width and length of the cutout 34. In other words, the impedance characteristics can be adjusted using the cutout 34 in addition to the connection position of the filter section 50. Note that, while the illustrated example shows an example in which the cutout 34 is provided only in the first patch element 30, the present invention is not limited to this example, and a cutout may also be provided in the second patch element 40.

[0037] In the illustrated examples so far, examples of composite patch antenna devices with a single feed point have been shown. However, the present invention is not limited to this. Figure 6 is a schematic top view illustrating an example of a composite patch antenna device of the present invention with a two-point feed point. In the figure, parts with the same reference numerals as in Figure 1 represent the same items. As shown in the figure, the feed point 31 of the composite patch antenna device of the present invention may be composed of a first feed point 31a and a second feed point 31b. Note that, since circular polarization is generated by two-point feeding, a degenerate separation element is not required.

[0038] In this two-point feed configuration, filter section 50 is composed of filter section 50a and filter section 50b. As in the single-point feed configuration, filter section 50 (50a, 50b) is connected between first patch element 30 and second patch element 40 in the vicinity of a position far from feed section 31 (31a, 31b).

[0039] In this way, the feed section 31 of the composite patch antenna device of the present invention may be a single-point feed or a dual-point feed, which is particularly effective when it is desired to widen the axial ratio for the second frequency band.

[0040] Furthermore, the composite patch antenna device of the present invention can be made to support even more frequency bands. FIG. 7 is a schematic top view illustrating an example of a composite patch antenna device of the present invention that supports three frequency bands. In the figure, parts with the same reference numerals as in FIG. 1 represent the same components. As shown, this example includes a third patch element 60. The third patch element 60 supports a third frequency band, which is higher than the second frequency band. The third patch element 60 is formed within the second patch element 40, separated from the second patch element 40 by a second slit 61 of a predetermined width. That is, the third patch element 60 is formed by separating the inner side of the second patch element 40, which is disposed on the dielectric 20, by 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 feed portion 31 of the first patch element 30. That is, signals of the first, second, and third frequency bands can be appropriately separated on the unit side. In the illustrated example, the third patch element 60 has a rectangular pattern with degenerate separation elements 63 provided at the upper right and lower left, and is configured to generate circularly polarized waves. The third patch element 60 may be formed to have a shape similar to that of the first patch element 30 and the second patch element 40. However, the present invention is not limited to this, and the shape may be changed as appropriate, for example, to adjust the antenna characteristics of the third patch element 60. The dimensions of the third patch element 60 may be, for example, such that the height is λ / 2 of the wavelength of the third frequency band.

[0041] A second filter section 55 is also provided. The second filter section 55 attenuates signals in the third frequency band and passes signals in the first and second frequency bands. The second filter section 55 is connected between the second patch element 40 and the third patch element 60. Specifically, the second filter section 55 is disposed in a second slit 61 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 section 55. Meanwhile, since signals in the third frequency band are attenuated by the second filter section 55, only the third patch element 60 functions as a microstrip antenna that resonates in the third frequency band.

[0042] In the example shown in the figure, the filter is compatible with three frequency bands, but the present invention is not limited to this. It is also possible to provide a filter section by separating the inner element with a slit, thereby enabling the filter to be compatible with more frequency bands.

[0043] As described above, according to the present invention, it is possible to provide a small and thin composite patch antenna device that is compatible with multiple frequency bands.

[0044] The composite patch antenna device of the present invention is not limited to the above-described illustrated example, and it goes without saying that various modifications can be made without departing from the spirit of the present invention.

[0045] REFERENCE SIGNS LIST 1 coaxial cable 10 ground plate 20 dielectric 21 through hole 30 first patch element 31 power feed section 31a power feed section 31b power feed section 32 through hole 33 degenerate separation element 34 notch 40 second patch element 41 slit 43 degenerate separation element 50 filter section 50a filter section 50b filter section 50 filter section 51 trap coil 52 coil 52 meander pattern 53 capacitor 55 second filter section 60 third patch element 61 second slit 63 degenerate separation element

Claims

1. A composite patch antenna device compatible with a plurality of frequency bands, comprising: a ground plate; a dielectric arranged on the ground plate; a first patch element arranged on the dielectric, having a power feed portion and corresponding to a first frequency band; a second patch element formed within the first patch element and separated from the first patch element by a slit of a predetermined width, sharing the power feed portion of the first patch element, and corresponding to a second frequency band higher than the first frequency band; and a filter section connected between the first patch element and the second patch element, for attenuating signals in the second frequency band and passing signals in the first frequency band.

2. A composite patch antenna device as claimed in claim 1, characterized in that the filter section is connected between the first patch element and the second patch element in the vicinity of a position far from the power feed section.

3. A composite patch antenna device as claimed in claim 1, characterized in that the impedance characteristics of the first patch element of said filter section can be adjusted by changing the connection position of said filter section.

4. A composite patch antenna device according to claim 1, characterized in that the filter section comprises a trap coil or a low-pass filter circuit.

5. A composite patch antenna device as described in claim 1, characterized in that the filter section is arranged on the side where a dielectric ground plate is arranged, and is connected between the first patch element and the second patch element via a through hole.

6. A composite patch antenna device as claimed in claim 1, characterized in that the filter section is made of a meandering pattern arranged on the side of the dielectric on which the first patch element and the second patch element are arranged.

7. A composite patch antenna device as claimed in claim 1, characterized in that said first patch element has a notch for adjusting the impedance characteristics of the first patch element.

8. A composite patch antenna device as claimed in claim 1, wherein said second patch element is formed to be similar in shape to said first patch element.

9. A composite patch antenna device according to claim 1, characterized in that the feeding section is a single-point feeding section or a dual-point feeding section.

10. A composite patch antenna device as claimed in any one of claims 1 to 9, further comprising: a third patch element formed within the second patch element and separated from the second patch element by a slit of a predetermined width, sharing the power supply section of the first patch element, and corresponding to a third frequency band higher than the second frequency band; and a second filter section connected between the second patch element and the third patch element, for attenuating signals of the third frequency and passing signals of the first frequency band and the second frequency band.

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