Composite planar antenna device

Abstract

Provided is a composite planar antenna device capable of handling a plurality of frequency bands with little deterioration of antenna characteristics even in a limited space.　The composite planar antenna device comprises a first power supply unit 10, a second power supply unit 20, a first planar element 30, a second planar element 40, and a filter unit 50. The first planar element 30 is disposed facing a ground conductor surface 1 from above, and can handle a first frequency band. The second planar element 40 is disposed on the same plane as the first planar element 30 so as to face the ground conductor surface from above, is disposed across a gap G of a predetermined width with respect to an edge portion in the longitudinal direction of the first planar element 30, and can handle a second frequency band by being used together with the first planar element 30. The filter unit 50 is connected in the gap G between the first planar element 30 and the second planar element 40, attenuates signals in the first frequency band, and passes signals in the second frequency band.

Description

Composite planar antenna device

[0001] The present invention relates to a composite planar antenna device, and more particularly to a composite planar antenna device that is disposed on a ground conductor plane and is compatible with a plurality of frequency bands.

[0002] There are various types of antenna devices that can be installed in vehicles and are compatible with multiple frequency bands, such as AM / FM band antennas, including pillar antennas, roof-mounted antennas, and glass antennas. However, pillar antennas that protrude significantly are more likely to bend due to contact or other factors. Furthermore, roof-mounted antennas are located high above the ground, so they must be easily folded or removed when entering multi-story parking garages or automatic car washes. Furthermore, glass antennas require unique development for each vehicle model, resulting in high development costs.

[0003] Recently, vehicle design has become more important, and vehicle-mounted antenna devices are required to minimize the vehicle's aesthetic appeal. To address this, spoiler-mounted antenna devices and vehicle body-embedded antenna devices have been developed.

[0004] For example, Patent Document 1 discloses a vehicle body-embedded antenna device by the same applicant as the present application. The vehicle body-embedded antenna device disclosed in Patent Document 1 has a plate-shaped antenna element disposed inside a bathtub-shaped portion provided in the metal body of the vehicle. By disposing the plate-shaped antenna element at the highest position possible inside the bathtub-shaped portion, it is possible to suppress deterioration of the signal reception performance of the plate-shaped antenna element. Furthermore, because the plate-shaped antenna element is disposed inside the bathtub-shaped portion, noise radiated from electrical equipment inside the vehicle is also shielded, eliminating the need for additional noise countermeasures.

[0005] Japanese Patent Application Laid-Open No. 2023-031519

[0006] In conventional vehicle body-embedded antenna devices installed inside a bathtub-shaped section, the bottom of the bathtub-shaped section is also made of a metal body, reducing the proportion of antenna current flowing to the pillar via a grounding bracket or the like. Therefore, in harsh environments where antenna sensitivity is reduced in a limited space, it has been difficult to realize a composite antenna device capable of supporting multiple frequency bands using multiple plate-shaped antenna elements due to issues such as element size and inter-element isolation. When using multiple elements in a limited space, placing the elements close to each other can result in inter-element coupling, resulting in degradation of both. For example, in the case of elements with close frequency bands, such as the FM and DAB frequency bands, improving the antenna performance in the DAB frequency band degrades the antenna performance in the FM frequency band, creating a contradictory relationship. These antenna characteristics depend on the efficiency of the elements due to wavelength shortening and the size of the elements. On the other hand, in configurations where a common element is used and separated by a divider to support multiple frequency bands, loss due to the divider can occur. Therefore, with all conventional methods, antenna performance inevitably deteriorates compared to a single element of the same size.

[0007] SUMMARY OF THE INVENTION In view of the above circumstances, the present invention provides a composite planar antenna device that can be used in a plurality of frequency bands with little deterioration of antenna characteristics even in a limited space.

[0008] In order to achieve the above-mentioned object of the present invention, a composite planar antenna apparatus according to the present invention comprises: a first feed section for a first frequency band; a second feed section for a second frequency band lower than the first frequency band; a first planar element arranged opposite to the first feed section on a ground conductor surface and compatible with the first frequency band; a second planar element arranged opposite to the ground conductor surface on the same plane as the first planar element and connected to the second feed section, wherein edges of the second planar element in the longitudinal direction are arranged relative to edges of the first planar element with a gap of a predetermined width therebetween, and the second planar element is compatible with the second frequency band when used together with the first planar element; and a filter section connected to the gap between the first and second planar elements, which attenuates signals of the first frequency band and passes signals of the second frequency band.

[0009] Here, the filter section may be connected to the gap between the vicinity of a position of the first planar element far from the first feeding section and the vicinity of a position of the second planar element far from the second feeding section.

[0010] Furthermore, when the distances from the first and second planar elements to the ground conductor surface change, the filter section may be connected to a gap near a position of the first and second planar elements far from the ground conductor surface.

[0011] The second planar element may be connected to the second power supply portion via a resonant coil.

[0012] The filter section may be made up of a trap coil, and the resonant coil may have an inductance lower than that of the trap coil.

[0013] The filter section may be made up of a trap coil or a low-pass filter circuit.

[0014] The composite planar antenna device of the present invention that is compatible with a plurality of frequency bands has the advantage that the deterioration of antenna characteristics is small even in a limited space, for example.

[0015] FIG. 1 is a schematic plan view illustrating a composite planar antenna device of the present invention. FIG. 2 is a circuit diagram illustrating a filter section of the composite planar antenna device of the present invention. FIG. 3 is a schematic side cross-sectional view illustrating a specific example of the composite planar antenna device of the present invention. FIG. 4 is a schematic side cross-sectional view illustrating a modified example of the specific example of the composite planar antenna device of the present invention. FIG. 5 is a schematic plan view illustrating another example of the composite planar antenna device of the present invention. FIG. 6 is a schematic plan view illustrating yet another example of the composite planar antenna device of the present invention. FIG. 7 is a schematic plan view illustrating another example of the first planar element of the composite planar antenna device of the present invention. FIG. 8 is a schematic plan view illustrating another example of the second planar element of the composite planar antenna device of the present invention. FIG. 9 is a schematic plan view illustrating another example of the arrangement of the first and second feed portions of the composite planar antenna device of the present invention.

[0016] Hereinafter, embodiments of the present invention will be described with reference to illustrative examples. FIG. 1 is a schematic plan view illustrating a composite planar antenna device of the present invention. The composite planar antenna device of the present invention is capable of supporting multiple frequency bands. Specifically, it may be capable of supporting, for example, the FM radio frequency band and the DAB radio frequency band. However, the present invention is not limited to this, and may also be capable of combining multiple frequency bands, such as UHF frequencies, with other frequency bands. In particular, when frequency bands are close to each other, such as the FM radio frequency band and the DAB (Band-III) radio frequency band, coupling problems between elements may occur. However, the present invention is suitable even in such cases because it provides high isolation and little degradation of antenna characteristics. As shown in the figure, the composite planar antenna device of the present invention is primarily composed of a first feed section 10, a second feed section 20, a first planar element 30, a second planar element 40, and a filter section 50. The composite planar antenna device of the present invention is disposed on a ground conductor surface 1. More specifically, it may be disposed within a bathtub-shaped recess formed in the metal body of a vehicle. That is, the composite planar antenna device of the present invention can also be provided as a vehicle body-embedded antenna device.

[0017] The first power supply unit 10 is a power supply unit for a first frequency band. Specifically, the first frequency band may be, for example, the DAB frequency band, i.e., the 174 MHz to 240 MHz band. The first power supply unit 10 may be provided on a substrate 12, for example.

[0018] The second power supply unit 20 is a power supply unit for a second frequency band that is lower than the first frequency band. Specifically, the second frequency band may be, for example, the FM frequency band, i.e., the 76 MHz to 95 MHz band or the 88 MHz to 108 MHz band. The second power supply unit 20 may also be provided on the substrate 12, for example.

[0019] The first planar element 30 is an element compatible with a first frequency band. The first planar element 30 is connected to the first feeding portion 10. The first planar element 30 is disposed on a ground conductor surface 1 so as to face the ground conductor surface 1. The first planar element 30 may be, for example, a conductor plate having a planar plate-like portion. The first planar element 30 is a grounded antenna that functions, for example, as a monopole antenna. It may also be configured to function as an inverted-F antenna or an inverted-L antenna. The first planar element 30 may have an antenna capacitance that functions as a capacitive antenna compatible with, for example, the DAB frequency band. The first planar element 30 is formed, for example, by processing a metal plate. That is, it is sufficient if a rectangular planar plate-like portion is formed by cutting the metal plate. However, the present invention is not limited thereto. For example, the first planar element 30 may be formed by processing a conductor foil of a printed circuit board or a flexible printed circuit board. Furthermore, the planar plate-like portion of the first planar element 30 may have any antenna capacitance that functions as a capacitive antenna, and may therefore be a meander-shaped element configured to have antenna capacitance substantially equivalent to that of the planar plate-like portion. The first planar element 30 is also provided with a first feed line 31. The first feed line 31 may be a lead wire, but may also be formed into a pin shape by, for example, bending the end of the planar plate-like portion of the first planar element 30. That is, the first planar element 30 may be configured as an inverted-L antenna. The first planar element 30 may be designed, for example, based on λ / 4 of the wavelength of the first frequency band.

[0020] The second planar element 40 is connected to the second feeding portion 20. The second planar element 40 is disposed on the same plane as the first planar element 30, facing the ground conductor surface 1. Furthermore, the second planar element 40 is disposed such that the longitudinal edges of the second planar element 40 are spaced apart from the longitudinal edges of the first planar element 30 via a gap G of a predetermined width. That is, in the illustrated example, the second planar element 40 is disposed so as to be parallel to the first planar element 30 in the longitudinal direction. The second planar element 40 is an element capable of supporting a second frequency band when used together with the first planar element 30. The second planar element 40 may be, for example, a conductor plate having a planar plate-like portion. The second planar element 40 functions like a loop antenna together with the first planar element 30 via a filter portion 50 (described later). The element length of the second planar element 40 may be such that the total element length, including the element length of the first planar element 30, is capable of supporting the FM frequency band, etc. The second planar element 40 may be formed by, for example, processing a metal plate. That is, a rectangular planar portion may be formed by cutting a metal plate. However, the present invention is not limited to this. For example, the second planar element 40 may be formed by processing a conductor foil of a printed circuit board or a flexible printed circuit board. In this case, the first planar element 30 and the second planar element 40 may be arranged on the same board. The second planar element 40 is provided with a second feeder line 41. The second feeder line 41 may be a lead wire, but may also be formed into a pin shape by, for example, bending the end of the planar portion of the second planar element 40. That is, the second planar element 40 may be configured as an inverted-L antenna while being configured as a loop antenna.

[0021] The filter section 50 attenuates signals in the first frequency band and passes signals in the second frequency band. The filter section 50 is connected to the gap G between the first planar element 30 and the second planar element 40. As shown in the figure, the filter section 50 is connected to the gap G between a position of the first planar element 30 far from the first feed portion 10 and a position of the second planar element 40 far from the second feed portion 20. This maximizes the loop of the element compatible with the second frequency band. However, the present invention is not limited to this, and the filter section 50 may be connected to the gap G between a position close to the first feed portion 10 or the second feed portion 20 as long as the antenna characteristics are within an acceptable range.

[0022] FIG. 2 shows an example of a filter unit 50. FIG. 2 is a circuit diagram illustrating the filter unit of the composite planar antenna device of the present invention. FIG. 2( a) shows an example in which the filter unit 50 is configured with a trap coil 51. The trap coil may be, for example, an air-core coil. FIG. 2( b) shows an example in which the filter unit 50 is configured with an LC filter consisting of a coil 52 and a capacitor 53. Such a low-pass filter circuit may also be used. Note that while the illustrated example shows a coil 52 and a capacitor 53, electronic circuit components are not necessarily required, and 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 first frequency band and passes signals in the second frequency band. Note that the present invention is not limited to this, and any existing or future configuration of the filter unit 50 can be applied as long as it is capable of attenuating signals in the first frequency band and passing signals in the second frequency band.

[0023] The composite planar antenna device of the present invention configured as described above operates as follows. That is, for a first frequency band, it resonates in the first frequency band using the first planar element 30 connected to the first feeding part 10. The filter section 50 is connected between the first planar element 30 and the second planar element 40, but since it attenuates signals in the first frequency band, they do not propagate to the second planar element 40 side, and only the first planar element 30 functions as an antenna element. The filter section 50 makes the second planar element 40 invisible from the first planar element 30. Therefore, the filter section 50 serves to increase the isolation between the first planar element 30 and the second planar element 40.

[0024] On the other hand, for the second frequency band, the second planar element 40 connected to the second feeding part 20, the filter part 50, and the first planar element 30 resonate at λ / 2 of the wavelength of the second frequency band. The filter part 50 passes signals of the second frequency band, so that the second planar element 40, the filter part 50, and the first planar element 30 function as an antenna element. That is, for the second frequency band, the second planar element 40, the filter part 50, and the first planar element 30 function as a loop antenna. Here, it can be seen that the tip of the element configured like a loop antenna is configured to terminate at the first feeding part 10.

[0025] In this way, the filter section 50 acts as a trap coil that attenuates signals in the first frequency band for the first frequency band, and acts as a resonant coil that forms part of an element with a wavelength of λ / 2 of the second frequency band for the second frequency band.

[0026] In the composite planar antenna device of the present invention, the filter section 50 facilitates ensuring isolation between elements. Therefore, the longitudinal edges of the first planar element 30 and the second planar element 40, which have large areas, can be arranged close to each other. This allows the elements to be arranged within a minimal range even in a limited space. Furthermore, since the first planar element 30 and the second planar element 40 can be arranged with a gap G of a predetermined width sufficient for capacitive coupling, the first planar element 30 can be capacitively loaded onto the second planar element 40, improving the antenna characteristics of the second planar element 40. In other words, even if the first planar element 30 and the second planar element 40 are arranged close to each other, overall degradation of the antenna characteristics can be reduced.

[0027] Here, the width of the gap G needs only to be large enough to allow capacitive coupling between the first planar element 30 and the second planar element 40. The width of the gap G that allows capacitive coupling also depends on the length of the opposing longitudinal edges of the first planar element 30 and the second planar element 40. To give a specific example, when the length of the longitudinal edges is 200 mm, the width of the gap G needs only to be approximately 15 mm or less. The narrower the width of the gap G, for example, when the width is 5 mm, the greater the capacitive loading, thereby further improving the antenna characteristics in the second frequency band. Furthermore, the longer the length of the opposing longitudinal edges of the first planar element 30 and the second planar element 40, the greater the capacitive loading, thereby further improving the antenna characteristics in the second frequency band. In this case, as described above, the second planar element 40 is not visible from the first planar element 30, resulting in high isolation, and therefore, the antenna characteristics of the first planar element 30 are less degraded.

[0028] For example, if the first frequency band is the DAB frequency band and the second frequency band is the FM frequency band, and the required level of antenna characteristics in the DAB frequency band is high, the area of ​​the second planar element 40 can be reduced and the area of ​​the first planar element 30 can be increased, thereby enabling the element shape and size to be significant for the antenna characteristics in the DAB frequency band. This increases the design flexibility of the first planar element 30. Furthermore, the area ratio between the first planar element 30 and the second planar element 40 can be appropriately distributed within the same limited space. That is, the design can be appropriately performed by changing the area ratio by moving the placement position of the gap G up or down in FIG. 1 . In this way, even within the same area, the area ratio between the first planar element 30 and the second planar element 40 can be appropriately designed to achieve optimal antenna characteristics by considering the antenna characteristics in the first frequency band and the second frequency band.

[0029] FIG. 3 is a schematic side cross-sectional view illustrating a specific example of a composite planar antenna device according to the present invention. In the figure, parts with the same reference numerals as those in FIG. 1 represent the same components. In this example, the first planar element 30 and the second planar element 40 are configured as an inverted-L antenna. However, as mentioned above, the second planar element 40 can also be configured as a loop antenna. In the illustrated example, the ground conductor surface 1 is bathtub-shaped. That is, this is an example in which the composite planar antenna device according to the present invention is embedded inside the bathtub-shaped portion. The first planar element 30 and the second planar element 40 are arranged parallel to the ground conductor surface 1 at the highest position possible inside the bathtub-shaped portion. They are then covered with a cover 3 such as a privacy cover or glass cover. Therefore, the filter section 50 is arranged on the side of the first planar element 30 and the second planar element 40 facing the ground conductor surface 1.

[0030] FIG. 4 is a schematic side cross-sectional view illustrating a modified example of the composite planar antenna device of the present invention. In the figure, parts with the same reference numerals as those in FIG. 3 represent the same components. In the illustrated example, the composite planar antenna device of the present invention is embedded in a bathtub-shaped section provided at the rear of a vehicle roof where the vehicle height is low. The difference from the example shown in FIG. 3 is that the vehicle roof is curved, and the cover 3 is also curved accordingly, gradually lowering the height to the ground conductor surface 1. In this case, the first planar element 30 and the second planar element 40 can be curved to match the appearance of the vehicle roof. When the distance from the first planar element 30 and the second planar element 40 to the ground conductor surface 1 changes in this way, the filter section 50 can be connected near a position far from the feeder, rather than near a position far from the ground conductor surface 1, of the first planar element 30 and the second planar element 40. That is, as shown in the figure, the filter section 50 can be disposed near the point where the surface facing the ground conductor surface 1 curves and hangs down from its parallel position, before approaching the ground conductor surface 1. This is because, for example, when a coil is used in the filter section 50, the Q value decreases when a conductor comes close, so it is better to keep it as far away from the ground conductor surface 1 as possible.

[0031] Next, FIG. 5 shows another example of a composite planar antenna device according to the present invention. FIG. 5 is a schematic plan view illustrating another example of a composite planar antenna device according to the present invention. In the figure, parts with the same reference numerals as those in FIG. 1 represent the same components. In this example, the second planar element 40 and the second feeder 20 are connected via a resonant coil 54. That is, for the second frequency band, the resonant coil 54, the second planar element 40, the filter section 50, and the first planar element 30 are used to resonate at λ / 2 of the wavelength of the second frequency band. Using the resonant coil 54 allows for more precise adjustments to accommodate the second frequency band. Here, a high Q factor of the resonant coil 54 results in narrowband characteristics. Therefore, the resonant coil 54 may be, for example, a chip inductor with a lower Q factor than an air-core coil. Because the resonant coil 54 is disposed on the substrate 12, using a chip inductor reduces the cost of the component itself and also reduces assembly man-hours through automated mounting.

[0032] 5 , when the second planar element 40 is connected to the second power supply unit 20 via a resonant coil 54, the inductance of the resonant coil 54 may be set as follows: That is, when the filter unit 50 is a trap coil, the resonant coil 54 may have a lower inductance than the trap coil of the filter unit 50.

[0033] For example, the dimensions and inductance of each element will be specifically described for a case where the first frequency band is the DAB frequency band and the second frequency band is the FM frequency band. The dimensions of the first planar element 30 are, for example, 200 mm in the longitudinal direction and 55 mm in the transverse direction. The dimensions of the second planar element 40 are, for example, 200 mm in the longitudinal direction and 20 mm in the transverse direction. The gap G is also 5 mm. With these dimensions, the resonant coil 54 may have an inductance of 410 nH, and the trap coil of the filter section 50 may have an inductance of 870 nH. Note that these specific values ​​are merely examples, and the present invention is not limited to these.

[0034] Next, FIG. 6 shows yet another example of a composite planar antenna device according to the present invention. FIG. 6 is a schematic plan view illustrating yet another example of a composite planar antenna device according to the present invention. In the figure, parts with the same reference numerals as in FIG. 1 represent the same components. In this example, the first planar element 30 is configured as an inverted-F antenna. Specifically, in the illustrated example, the first planar element 30 is connected to ground via a short-circuited coil 55. As long as it can be configured as an inverted-F antenna, it may be connected to ground via a load resistor without using the short-circuited coil 55, or it may be connected to ground directly. When the short-circuited coil 55 is used, the inductance enables impedance adjustment for the first frequency band. More specifically, the area of ​​the first planar element 30 is adjusted to match the first frequency band, while the longitudinal length of the first planar element 30 and the line length of the first feeder 31 are adjusted to adjust the entire first frequency band, and the short-circuited coil 55 adjusts the impedance. The short-circuited coil 55 may be, for example, a chip inductor. In cases where the space in which the composite planar antenna device of the present invention is arranged is narrow and the size of the first planar element 30 cannot be increased, and the band can be narrowed by shortening the wavelength, the band can be broadened by adjusting using the short-circuit coil 55.

[0035] For the first frequency band, the inverted-F antenna has better antenna characteristics than the monopole antenna, whereas for the second frequency band, there is almost no difference in antenna characteristics whether the tip of the loop antenna is terminated at the first feeding point 10 or at the short-circuit coil 55.

[0036] Although the resonance coil 54 described with reference to FIG. 5 is not shown in FIG. 6, it is of course possible to provide the resonance coil 54 on the second planar element 40 side.

[0037] In the above-described illustrated examples, the second planar element 40 is arranged parallel to the first planar element 30 in the longitudinal direction. However, the present invention is not limited to this. FIG. 7 is a schematic plan view illustrating another example of a first planar element of a composite planar antenna device of the present invention. In the figure, parts with the same reference numerals as in FIG. 1 represent the same components. Note that only the first planar element 30, the second planar element 40, and the filter section 50 are shown; the other components are omitted. As shown in the figure, in this example, the first planar element 30 is configured as an L-shape in a planar view. The first planar element 30 is configured to wrap around the tip of the second planar element 40. The filter section 50 may be connected to the gap G between the tip of the second planar element 40 and the wrapped-around portion of the first planar element 30. The shape of the first planar element 30 may be modified as shown in the figure, depending on the antenna characteristics in the first and second frequency bands.

[0038] 8 is a schematic plan view illustrating another example of the second planar element of the composite planar antenna device of the present invention. In the figure, parts with the same reference numerals as in FIG. 1 represent the same components. Note that only the first planar element 30, the second planar element 40, and the filter section 50 are shown; the other components are omitted. As shown in the figure, in this example, the second planar element 40 is configured as an L-shape in a planar view. The second planar element 40 is configured to wrap around the tip of the first planar element 30. The filter section 50 may be connected to the gap G between the tip of the first planar element 30 and the wrapped-around portion of the second planar element 40. The shape of the second planar element 40 may be modified as shown in the figure, depending on the antenna characteristics in the first and second frequency bands.

[0039] As shown in Fig. 7 and Fig. 8, if the longitudinal edge of the first planar element and a part of the longitudinal edge of the second planar element are arranged via a gap of a predetermined width, as described above, the filter unit 50 reduces the deterioration of the antenna characteristics due to coupling for the first frequency band, and the antenna characteristics are improved by capacitance loading for the second frequency band.

[0040] Furthermore, in the illustrated examples described above, the first and second feed portions 10 and 20 are arranged on the same substrate 12. However, the present invention is not limited to this. FIG. 9 is a schematic plan view illustrating another example of the arrangement of the first and second feed portions of the composite planar antenna device of the present invention. In the figure, parts with the same reference numerals as in FIG. 1 represent the same components. Note that only the first and second feed portions 10 and 20, the first and second planar elements 30 and 40, and the filter portion 50 are shown; the other components are omitted. As shown, in this example, the first and second planar elements 30 and 40 are arranged parallel to each other in the longitudinal direction, as in FIG. 1, but the first and second feed portions 10 and 20 are arranged separately on the left and right sides rather than at the same end. In the illustrated example, the filter portion 50 is connected to a gap G between the planar elements near the center in the longitudinal direction.

[0041] Even with such a configuration, similar to the illustrated example described above, it is possible to make the first planar element 30 function as a capacitive antenna, while making the second planar element 40, the filter section 50, and the first planar element 30 function as a loop antenna.

[0042] In this way, the composite planar antenna device of the present invention can be modified in various ways depending on the space in which it is to be placed, and even in such cases, it is possible to realize a device with little deterioration in antenna characteristics.

[0043] The composite planar antenna device of the present invention is not limited to the above-mentioned illustrated example, and it goes without saying that various modifications can be made without departing from the scope of the present invention.

[0044] REFERENCE SIGNS LIST 1 ground conductor surface 3 cover 10 first power supply section 12 substrate 20 second power supply section 30 first planar element 31 first power supply line 40 second planar element 41 second power supply line 50 filter section 51 trap coil 52 coil 53 capacitor 54 resonance coil 55 short-circuit coil G gap

Claims

1. A composite planar antenna device arranged on a ground conductor surface and capable of supporting a plurality of frequency bands, the composite planar antenna device comprising: a first feed section for a first frequency band; a second feed section for a second frequency band lower than the first frequency band; a first planar element arranged on the ground conductor surface facing each other, connected to the first feed section, and capable of supporting the first frequency band; a second planar element arranged on the ground conductor surface facing each other, on the same plane as the first planar element, and connected to the second feed section, the second planar element being arranged on the ground conductor surface facing each other and on the same plane as the first planar element, the second planar element being arranged with a gap of a predetermined width between the longitudinal edges of the second planar element and the longitudinal edges of the first planar element, the second planar element being capable of supporting the second frequency band when used together with the first planar element; and a filter section connected to the gap between the first and second planar elements, which attenuates signals in the first frequency band and passes signals in the second frequency band.

2. A composite planar antenna device according to claim 1, characterized in that the filter section is connected to a gap between the vicinity of a position far from the first power supply section of the first planar element and the vicinity of a position far from the second power supply section of the second planar element.

3. A composite planar antenna device according to claim 1, characterized in that the filter section is connected to a gap in the vicinity of a position of the first planar element and the second planar element far from the ground conductor surface when the distance between the first planar element and the second planar element and the ground conductor surface changes.

4. A composite planar antenna device according to claim 1, wherein the second planar element is connected to a second feeding portion via a resonant coil.

5. A composite planar antenna device according to claim 4, characterized in that the filter section comprises a trap coil, and the resonant coil has a lower inductance than the trap coil.

6. A composite planar antenna device according to any one of claims 1 to 4, wherein the filter section comprises a trap coil or a low-pass filter circuit.

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