Composite planar antenna device

Abstract

To provide a composite planar antenna device capable of reducing deterioration of antenna characteristics and supporting a plurality of frequency bands. A composite planar antenna device includes a first feeding part (10), a second feeding part (20), a first planar element (30), a second planar element (40), and a filter part (50). The first planar element (30) is disposed above a ground conductor surface (1) so as to face the ground conductor surface (1) and configured to support a first frequency band. The second planar element (40) is disposed on the same plane as the first planar element (30) above the ground conductor surface (1) so as to face the ground conductor surface (1) and to form a gap (G) of predetermined width with respect to the longitudinal edge portion of the first planar element (30). The second planar element (40) is used together with the first planar element (30) to support a second frequency band. The filter part (50) is connected to a gap (G) between the first planar element (30) and the second planar element (40) and configured to attenuate signals in the first frequency band and allow signals in the second frequency band to pass therethrough.

Description

Technical Field

[0001] The present invention relates to a composite planar antenna device, and more particularly to a composite planar antenna device disposed on a ground conductor surface and configured to support a plurality of frequency bands.Background Art

[0002] Vehicle-mounted antenna devices capable of supporting a plurality of frequency bands, for example, those supporting AM / FM bands include various types, such as pillar antennas, roof-mount antennas, and glass antennas. However, the pillar antennas have a large protrusion and are thus more likely to be bent due to unintended contact or the like. The roof-mount antennas have a high ground height and thus need to be tilted or removed in multi-story parking garages and automatic car washing machines. The glass antennas require development specific to each type, resulting in increased cost.

[0003] Recently, attention has also been paid to the design aspects of vehicles, and vehicle-mounted antenna devices are required to minimize any impairment to their appearance. In such circumstances, spoiler-integrated antennas and vehicle body-embedded antennas are now being developed.

[0004] For example, Patent Document 1 discloses a vehicle body-embedded antenna device filed by the same applicant as the present application. The vehicle-embedded antenna device disclosed in Patent Document 1 is configured such that a plate-like antenna element is disposed within a bathtub-shaped part provided in a vehicle metal body.

[0005] The plate-like antenna element is disposed at the uppermost position within the bathtub-shaped part, thereby making it possible to suppress deterioration of the signal reception performance of the antenna element. Further, since the antenna element is disposed within the bathtub-shaped part, it is shielded from noise radiated from electronic components inside the vehicle body, thereby eliminating the need for additional noise countermeasures.Citation List Patent Document

[0006] Patent Document 1: JP 2023 - 031 519 ADisclosure of the Invention Problems to be Solved by the Invention

[0007] In the conventional vehicle body-embedded antenna device that is disposed within the bathtub-shaped part, the bottom of the bathtub-shaped part is also formed of a metal body, so that the proportion of antenna current flowing through a grounding bracket or the like decreases. Therefore, under severe conditions where antenna sensitivity decreases within a limited space, it is difficult to provide a composite antenna device capable of supporting a plurality of frequency bands by using a plurality of plate-like antenna elements because of constraints on element size and isolation between elements.

[0008] When a plurality of elements are used within a limited space, the proximity of the elements causes coupling between them, resulting in deterioration of both elements. For example, in a case of elements with adjacent frequency bands (e.g., FM frequency band and DAB frequency band), a trade-off relationship occurs such that improvement in the characteristics of the DAB-band antenna element results in deterioration of the characteristics of the FM-band antenna element. These antenna characteristics depend on the efficiency of the element and the size of the element resulting from wavelength shortening.

[0009] On the other hand, in a case where a configuration is employed in which a common element is used and separated by a distributor to support a plurality of frequency bands, loss may occur due to the distributor. Therefore, compared with a single element of the same size, deterioration of antenna characteristics cannot be avoided in any conventional system.

[0010] The present invention has been made in view of the above situation, and an object thereof is to provide a composite planar antenna device capable of reducing deterioration of antenna characteristics and supporting a plurality of frequency bands even within a limited space.Means for Solving the Problems

[0011] To achieve the above object, a composite planar antenna device includes: a first feeding part for a first frequency band; a second feeding part for a second frequency band lower than the first frequency band; a first planar element disposed above the ground conductor surface so as to face the ground conductor surface, connected to the first feeding part, and configured to support the first frequency band; a second planar element disposed on the same plane as the first planar element above the ground conductor surface so as to face the ground conductor surface and connected to the second feeding part, wherein the longitudinal edge portion of the second planar element is arranged to form a gap of predetermined width with respect to the longitudinal edge portion of the first planar element, the second planar element being used together with the first planar element to support the second frequency band; and a filter part connected to the gap between the first planar element and the second planar element and configured to attenuate signals in the first frequency band and allow signals in the second frequency band to pass therethrough.

[0012] The filter part may be connected to a portion of the gap that is distant from the first feeding part of the first planar element and the second feeding part of the second planar element.

[0013] The filter part may be connected to a portion of the gap distant from the ground conductor surface when the distance from the first planar element and the second planar element to the ground conductor surface varies.

[0014] The second planar element may be connected to the second feeding part through a resonance coil.

[0015] The filter part may be formed of a trap coil, and the resonance coil may have an inductance lower than that of the trap coil.

[0016] The filter part may be formed of a trap coil or a low-pass filter circuit.Advantageous Effects of the Invention

[0017] The composite planar antenna device capable of supporting a plurality of frequency bands according to the present invention has the advantage of having reduced deterioration of antenna characteristics even within a limited space.Brief Description of the Drawings

[0018] FIG. 1 is a schematic plan view for explaining the composite planar antenna device according to the present invention. FIG. 2 is a circuit diagram for explaining the filter part of the composite planar antenna device according to the present invention. FIG. 3 is a schematic cross-sectional side view for explaining a specific example of the composite planar antenna device according to the present invention. FIG. 4 is a schematic cross-sectional side view for explaining a modification of the composite planar antenna device according to the present invention. FIG. 5 is a schematic plan view for explaining another example of the composite planar antenna device according to the present invention. FIG. 6 is a schematic plan view for explaining still another example of the composite planar antenna device according to the present invention. FIG. 7 is a schematic plan view for explaining another example of the first planar element of the composite planar antenna device according to the present invention. FIG. 8 is a schematic plan view for explaining another example of the second planar element of the composite planar antenna device according to the present invention. FIG. 9 is a schematic plan view for explaining another example of the arrangement of the first feeding part and the second feeding part of the composite planar antenna device according to the present invention. Best Mode for Carrying Out the Invention

[0019] An embodiment for practicing the present invention will be described with illustrated examples. FIG. 1 is a schematic plan view for explaining a composite planar antenna device according to the present invention. The composite planar antenna device according to the present invention is configured to support a plurality of frequency bands. Specifically, the composite planar antenna device may support, for example, an FM radio frequency band or a DAB radio frequency band.

[0020] However, the present invention is not limited thereto and may include combinations with other frequency bands, such as an UHF frequency band, provided that a plurality of frequency bands are supported. In particular, in a case of adjacent frequency bands, such as an FM frequency band and a DAB (Band III) frequency band, a coupling problem occurs between elements corresponding thereto. However, the composite planar antenna device according to the present invention provides high isolation and reduced deterioration of antenna characteristics and is thus suitably adaptable to such a case.

[0021] As illustrated, the composite planar antenna device according to the present invention mainly includes a first feeding part 10, a second feeding part 20, a first planar element 30, a second planar element 40, and a filter part 50. The composite planar antenna device according to the present invention is disposed on a ground conductor surface 1. More specifically, for example, the composite planar antenna device may be disposed within a bathtub-shaped part recessed from the metal body surface of a vehicle. That is, the composite planar antenna device according to the present invention can be provided as a vehicle body-embedded antenna device.

[0022] The first feeding part 10 is a feeding part for a first frequency band. The first frequency band may be, for example, a DAB frequency band, i.e., in the range of 174 MHz to 240 MHz. The first feeding part 10 may be disposed on, for example, a substrate 12.

[0023] The second feeding part 20 is a feeding part for a second frequency band which is lower than the first frequency band. The second frequency band may be, for example, an FM frequency band, i.e., in the range of 76 MHz to 95 MHz or in the range of 88 MHz to 108 MHz. The second feeding part 20 may also be disposed on, for example, the substrate 12.

[0024] The first planar element 30 is an element capable of supporting the first frequency band. The first planar element 30 is connected to the first feeding part 10. The first planar element 30 is disposed above the ground conductor surface 1 so as to face the ground conductor surface 1. The first planar element 30 may be formed of a conductor plate having, for example, a flat-plate portion. The first planar element 30 is a grounded-type antenna and functions like, for example, a monopole antenna.

[0025] Alternatively, the first planar element 30 may be configured to function as an inverted-F type antenna or an inverted-L type antenna. The first planar element 30 may have an antenna capacity to function as a capacitive antenna capable of supporting, for example, the DAB frequency band and the like. The first planar element 30 is formed by processing, for example, a metal plate. That is, it is sufficient that a rectangular flat-plate portion is formed by cutting the metal plate.

[0026] However, the present invention is not limited to this, and the first planar element 30 may be formed by processing the conductor foil of a printed circuit board or a flexible printed circuit board. Since it is sufficient that the flat-plate portion of the first planar element 30 has an antenna capacity to function as a capacitive antenna, the first planar element 30 may be replaced with a meander-shaped element having an antenna capacity substantially equivalent to that of the flat-plate portion. The first planar element 30 has a first feed line 31. The first feed line 31 may be a lead wire, or may be formed in a pin shape by bending the end portion of the flat-plate portion of the first planar element 30. That is, the first planar element 30 may be configured to function as an inverted-L type antenna. The first planar element 30 may be designed based on a quarter-wavelength (λ / 4) of the first frequency band.

[0027] The second planar element 40 is connected to the second feeding part 20. The second planar element 40 is disposed on the same plane as the first planar element 30 above the ground conductor surface 1 so as to face the ground conductor surface 1. Further, the longitudinal edge portion of the second planar element 40 is arranged to form a gap G of predetermined width with respect to the longitudinal edge portion of the first planar element 30.

[0028] That is, in the illustrated example, the second planar element 40 is disposed parallel to the first planar element 30 along the longitudinal direction. The second planar element 40 is used together with the first planar element 30, thereby supporting the second frequency band. The second planar element 40 may be formed of a conductor plate having, for example, a flat-plate portion. The second planar element 40 cooperates with the first planar element 30 through a filter part 50 to be described later so as to function like a loop antenna. The element length of the second planar element 40 may be designed such that the total element length adding with the first planar element 30 corresponds to an element length capable of supporting the FM frequency band or the like. The second planar element 40 may be formed by processing, for example, a metal plate.

[0029] That is, it is sufficient that, for example, a rectangular flat-plate portion is formed by cutting the metal plate. However, the present invention is not limited to this, and the second planar element 40 may be formed by processing, for example, the conductor foil of a printed circuit board or a flexible printed circuit board. At this time, the first planar element 30 and the second planar element 40 may be disposed on the same substrate. The second planar element 40 has a second feed line 41. The second feed line 41 may be a lead wire, or may be formed in a pin shape by bending the end portion of the flat-plate portion of the second planar element 40. That is, the second planar element 40 may be configured to function as an inverted-L type antenna while being configured as a loop antenna.

[0030] The filter part 50 attenuates signals in the first frequency band, while allows signals in the second frequency band pass therethrough. The filter part 50 is connected to the gap G between the first planar element 30 and the second planar element 40. As illustrated, the filter part 50 is connected to a portion of the gap G that is distant from the first feeding part 10 of the first planar element 30 and the second feeding part 20 of the second planar element 40. As a result, the loop of the element that can support the second frequency band becomes largest. However, the present invention is not limited to this, it is connected to a portion of the gap G that is near the first feeding part 10 and the second feeding part 20, provided that the antenna characteristics fall within an allowable range.

[0031] FIG. 2 illustrates the filter part 50. FIG. 2 is a circuit diagram for explaining the filter part of the composite planar antenna device according to the present invention. FIG. 2(a) illustrates an example in which the filter part 50 is formed of a trap coil 51. The trap coil may be implemented using an air-core coil. FIG. 2(b) illustrates an example in which the filter part 50 is formed of an LC filter that is composed of a coil 52 and a capacitor 53. The filter part 50 may be formed of such a low-pass filter.

[0032] Although, in this example, the coil 52 and the capacitor 53 are used, it is not always necessary to employ electronic circuit components, and the filter part 50 may be configured to function equivalent-circuitry as an LC filter through capacitive coupling. The thus configured filter part 50 is used to attenuate signals in the first frequency band and allow signals in the second frequency band to pass therethrough. The present invention is not limited to this, and any existing or future-developed configuration may be applied to the filter part 50, provided that it is configured to attenuate signals in the first frequency band and allow signals in the second frequency band to pass therethrough.

[0033] The thus configured composite planar antenna device according to the present invention operates as follows. That is, for the first frequency band, resonance is achieved in the first frequency band by using the first planar element 30 connected to the first feeding part 10. Although the filter part 50 is connected between the first planar element 30 and the second planar element 40, signals in the first frequency band are attenuated and are not propagated to the second planar element 40 side, and thus, only the first planar element 30 functions as an antenna element. The filter part 50 causes a state in which the second planar element 40 is not seen from the first planar element 30. Thus, the filter part 50 acts to enhance isolation between the first planar element 30 and the second planar element 40.

[0034] For the second frequency band, resonance is achieved at λ / 2 of the wavelength of the second frequency band by using the second planar element 40 connected to the second feeding part 20, the filter part 50, and the first planar element 30. Since the filter part 50 allows signals in the second frequency band to pass therethrough, the second planar element 40, the filter part 50, and the first planar element 30 collectively 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 collectively function as a loop antenna. Here, it can be seen that the leading end portion of the element configured like a loop antenna terminates at the first feeding part 10.

[0035] As described above, the filter part 50 acts as a trap coil for attenuating signals in the first frequency band and also as a resonance coil constituting a portion of an element with λ / 2 of the wavelength of the second frequency band.

[0036] The composite planar antenna device according to the present invention easily achieves isolation between elements by using the filter part 50. This allows the first planar element 30 with a large area and the second planar element 40 to be arranged such that their longitudinal edge portions are brought close to each other. As a result, the elements can be arranged within a minimum area in a limited space.

[0037] Further, the first planar element 30 and the second planar element 40 can be arranged through the gap G of predetermined width sufficient for capacitive coupling between the first planar element 30 and the second planar element 40, so that the first planar element 30 can be capacitively loaded onto the second planar element 40, thereby improving antenna characteristics of the second planar element 40. That is, even when the first planar element 30 and the second planar element 40 are arranged in close proximity, deterioration of antenna characteristics can be reduced as a whole.

[0038] The width of the gap G may be such that the first planar element 30 and the second planar element 40 are capacitively coupled. The width of the gap G sufficient for the capacitive coupling varies also depending on the length of the longitudinal opposing edge portions of the first planar element 30 and the second planar element 40. Specifically, for example, when the length of the longitudinal edge portion is 200 mm, the width of the gap G may be about 15 mm or less. The narrower the width of the gap G, for example 5 mm, the greater the capacitive loading, thereby further improving the antenna characteristics in the second frequency band.

[0039] Further, the longer the length of the longitudinal opposing edge portions of the first planar element 30 and the second planar element 40, the greater the capacitive loading, thereby still further improving the antenna characteristics in the second frequency band. As described above, since isolation is sufficiently high such that the second planar element 40 cannot be seen from the first planar element 30, the antenna characteristics of the first planar element 30 experiences little deterioration.

[0040] Assume here that the first frequency band is the DAB frequency band and the second frequency band is the FM frequency band, respectively, when the required level of the antenna characteristics in the DAB frequency band is high, the element shape and size can be configured to have a significant effect on the characteristics in the DAB frequency band, such as by reducing the area of the second planar element 40 and increasing the area of the first planar element 30. This increases design flexibility of the first planar element 30.

[0041] Further, the area ratio of the first planar element 30 and the second planar element 40 may be appropriately allocated within the same limited space. That is, the area ratio may be varied by vertically moving the position of the gap G in FIG. 1 to achieve an appropriate design. Thus, even within the same area, the area ratio of the first planar element 30 and the second planar element 40 can be appropriately designed by considering the antenna characteristics in the first frequency band and the second frequency band, so as to achieve optimal antenna performance.

[0042] FIG. 3 is a schematic cross-sectional side view for explaining a specific example of the composite planar antenna device according to the present invention. In the drawing, the same reference numerals as those in FIG. 1 denote the same parts. In this example, the first planar element 30 and the second planar element 40 are configured to function as inverted-L type antennas. However, as described above, the second planar element 40 is configured to function also as a loop antenna. In the illustrated example, the ground conductor surface 1 has a bathtub shape.

[0043] That is, the composite planar antenna device according to the present invention is disposed within the bathtub-shaped part. The first planar element 30 and the second planar element 40 are disposed in parallel, above the ground conductor surface 1, at the uppermost position within the bathtub-shaped part and are covered from above by a cover 3, such as a blind cover or a glass cover. Thus, the filter part 50 is disposed on the side of the first planar element 30 and the second planar element 40 that faces the ground conductor surface 1.

[0044] FIG. 4 is a schematic cross-sectional side view for explaining a modification of the composite planar antenna device according to the present invention. In the drawing, the same reference numerals as those in FIG. 3 denote the same parts. In the illustrated example, the composite planar antenna device according to the present invention is disposed within the bathtub-shaped part provided at the rear portion of the vehicle roof where the vehicle height decreases. The configuration illustrated in FIG. 4 differs from that illustrated in FIG. 3 in that the cover 3 is curved in conformity with the curvature of the vehicle roof, and its height relative to the ground conductor surface 1 gradually decreases.

[0045] In such a case, the first planar element 30 and the second planar element 40 may be curved in conformity with the outer shape 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 varies as described above, the filter part 50 may be connected not to the portion that is distant from the feeding parts, but to a portion distant from the ground conductor surface 1.

[0046] That is, as illustrated, the filter part 50 may be disposed adjacent a portion before which the surface facing the ground conductor surface 1 starts curving downward toward the ground conductor surface 1 from the parallel portion. This is because it is preferable that the filter part 50 be as distant from the ground conductor surface 1 as possible, since when a coil is used for the filter part 50, the Q value may decrease due to proximity to a conductor.

[0047] FIG. 5 illustrates another example of the composite planar antenna device according to the present invention. FIG. 5 is a schematic plan view for explaining another example of the composite planar antenna device according to the present invention. In the drawing, the same reference numerals as those in FIG. 1 denote the same parts. In this example, the second planar element 40 and the second feeding part 20 are connected through a resonance coil 54.

[0048] That is, for the second frequency band, resonance is achieved at λ / 2 of the wavelength of the second frequency band by using the resonance coil 54, the second planar element 40, the filter part 50, and the first planar element 30. The use of the resonance coil 54 enables finer adjustment, allowing the second frequency band to be supported. The resonance coil 54 exhibits narrowband characteristics when the Q value is high.

[0049] Therefore, it is preferable for the resonance coil 54 to use a chip inductor having a lower Q value than the air-core coil. The resonance coil 54 is disposed on the substrate 12, so that, when the chip inductor is used, the component cost can be reduced, and furthermore, the assembly man-hours can be reduced through automatic mounting.

[0050] When the second planar element 40 is connected to the second feeding part 20 through the resonance coil 54 as illustrated in FIG. 5, the inductance of the resonance coil 54 may be set as follows. That is, when the filter part 50 is formed of a trap coil, the resonance coil 54 may have an inductance lower than that of the filter part 50.

[0051] The following specifically describes the dimensions and inductances of the respective elements for a case where the first frequency band and the second frequency band are the DAB frequency band and 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 dimension of the gap G is 5 mm. In this case, the resonance coil 54 may have an inductance of 410 nH, and the trap coil of the filter part 50 may have an inductance of 870 nH. The specific numerical values are merely illustrative, and the present invention is not limited to these values.

[0052] FIG. 6 illustrates still another example of the composite planar antenna device according to the present invention. FIG. 6 is a schematic plan view for explaining still another example of the composite planar antenna device according to the present invention. In the drawing, the same reference numerals as those in FIG. 1 denote the same parts. In this example, the first planar element 30 is configured to function as an inverted-F type antenna.

[0053] Specifically, in the illustrated example, the first planar element 30 is connected to the ground through a short-circuit coil 55. The first planar element 30 may be connected to the ground not through the short-circuit coil 55 but through a load resistor, or may be connected directly, provided that the first planar element 30 is configured to function as an inverted-F type antenna. When the short-circuit coil 55 is used, the use of its inductance allows for impedance adjustment in the first frequency band.

[0054] More specifically, the area of the first planar element 30 is adjusted to match the first frequency, the longitudinal length of the first planar element 30 or the line length of the first feed line 31 is adjusted to adjust the entire first frequency band, and impedance is adjusted using the short-circuit coil 55. The short-circuit coil 55 may be, for example, a chip inductor. In a case where the space for disposing the composite planar antenna device according to the present invention is limited such that the size of the first planar element 30 cannot be increased and wavelength shortening may result in narrowband characteristics, adjustment is performed using the short-circuit coil 55, thereby enabling a wide bandwidth to be achieved.

[0055] For the first frequency band, antenna characteristics are improved further in an element configured to function as an inverted-F type antenna compared with an element configured to function as a monopole antenna. On the other hand, for the second frequency band, substantially no difference is observed in antenna characteristics irrespective of whether the leading end portion of the loop antenna is terminated at the first feeding part 10 or at the short-circuit coil 55.

[0056] Although the resonance coil 54 described using FIG. 5 is not illustrated in FIG. 6, it may be provided on the second planar element 40 side.

[0057] In all of the illustrated examples above, the second planar element 40 is disposed in parallel to the first planar element 30 along the longitudinal direction. However, the present invention is not limited to this. FIG. 7 is a schematic plan view for explaining another example of the first planar element of the composite planar antenna device according to the present invention. In the drawing, the same reference numerals as those in FIG. 1 denote the same parts. Only the first planar element 30, the second planar element 40, and the filter part 50 are illustrated, while other components are omitted.

[0058] As illustrated, in this example, the first planar element 30 is formed in an L-shape in a plan view. The first planar element 30 is arranged to wrap around the leading end portion of the second planar element 40. The filter part 50 may be connected to a portion of the gap G between the leading end portion of the second planar element 40 and the wrapping around portion of the first planar element 30. The shape of the first planar element 30 may be appropriately modified as illustrated in consideration of the antenna characteristics in the first frequency band and the second frequency band.

[0059] FIG. 8 is a schematic plan view for explaining another example of the second planar element of the composite planar antenna device according to the present invention. In the drawing, the same reference numerals as those in FIG. 1 denote the same parts. Only the first planar element 30, the second planar element 40, and the filter part 50 are illustrated, while other components are omitted. As illustrated, in this example, the second planar element 40 is formed in an L-shape in a plan view. The second planar element 40 is arranged to wrap around the leading end portion of the first planar element 30.

[0060] The filter part 50 may be connected to a portion of the gap G between the leading end portion of the first planar element 30 and the portion of the second planar element 40 facing the leading end portion of the first planar element 30. The shape of the second planar element 40 may be appropriately modified as illustrated in consideration of the antenna characteristics in the first frequency band and the second frequency band.

[0061] Provided that, as illustrated in FIGS. 7 and 8, the longitudinal edge portion of the first planar element and the longitudinal edge portion of the second planar element are arranged with at least a portion thereof disposed with a gap of predetermined width interposed therebetween, the same effects as described above can be obtained, that is, for the first frequency band, antenna characteristics are scarcely deteriorated due to coupling when the filter part 50 is employed, and for the second frequency band, capacitive loading enhances antenna characteristics.

[0062] Further, in all of the illustrated examples above, the first feeding part 10 and the second feeding part 20 are disposed on the same substrate 12. However, the present invention is not limited to this. FIG. 9 is a schematic plan view for explaining another example of the arrangement of the first feeding part and the second feeding part of the composite planar antenna device according to the present invention.

[0063] In the drawing, the same reference numerals as those in FIG. 1 denote the same parts. Only the first feeding part 10, the second feeding part 20, the first planar element 30, the second planar element 40, and the filter part 50 are illustrated, while other components are omitted. As illustrated, in this example, while the first planar element 30 and the second planar element 40 are arranged in parallel along the longitudinal direction as in FIG. 1, the first feeding part 10 and the second feeding part 20 are not located at the same end but are disposed separately on the left and right sides. The filter part 50 is connected to a portion of the gap G located near the center in the longitudinal direction in the illustrated example.

[0064] Even with such a configuration, as in the above-described illustrated examples, the first planar element 30 can function as a capacitive antenna, and the second planar element 40, the filter part 50, and the first planar element 30 can function as a loop antenna.

[0065] As described above, the composite planar antenna device according to the present invention can be variously modified depending on the arrangement space, and even in such cases, degradation of the antenna characteristics can be reduced.

[0066] The composite planar antenna device according to the present invention is not limited to the above-described illustrated examples, and various modifications may be made within the scope of the present invention.List of Reference Signs

[0067] 1:Ground conductor surface 3:Cover 10:First feeding part 12:Substrate 20:Second feeding part 30:First planar element 31:First feed line 40:Second planar element 41:Second feed line 50:Filter part 51:Trap coil 52:Coil 53:Capacitor 54:Resonance coil 55:Short-circuit coil G:Gap

Claims

1. A composite planar antenna device disposed on a ground conductor surface and configured to support a plurality of frequency bands, the composite planar antenna device comprising: a first feeding part for a first frequency band; a second feeding part for a second frequency band lower than the first frequency band; a first planar element disposed above the ground conductor surface so as to face the ground conductor surface, connected to the first feeding part, and configured to support the first frequency band; a second planar element disposed on the same plane as the first planar element above the ground conductor surface so as to face the ground conductor surface and connected to the second feeding part, wherein the longitudinal edge portion of the second planar element is arranged to form a gap of predetermined width with respect to the longitudinal edge portion of the first planar element, the second planar element being used together with the first planar element to support the second frequency band; and a filter part connected to the gap between the first planar element and the second planar element and configured to attenuate signals in the first frequency band and allow signals in the second frequency band to pass therethrough.

2. The composite planar antenna device according to claim 1, wherein the filter part is connected to a portion of the gap that is distant from the first feeding part of the first planar element and the second feeding part of the second planar element.

3. The composite planar antenna device according to claim 1, wherein the filter part is connected to a portion of the gap distant from the ground conductor surface when the distance from the first planar element and the second planar element to the ground conductor surface varies.

4. The composite planar antenna device according to claim 1, wherein the second planar element is connected to the second feeding part through a resonance coil.

5. The composite planar antenna device according to claim 4, wherein the filter part is formed of a trap coil, and the resonance coil has an inductance lower than that of the trap coil.

6. The composite planar antenna device according to any one of claims 1 to 4, wherein the filter part is formed of a trap coil or a low-pass filter circuit.

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