Composite antenna device

Abstract

To provide a composite antenna device capable of resonating in a plurality of frequency bands in such a situation that a conductive cable connecting between an antenna element and a feeder circuit is long.SOLUTION: A composite antenna device 100 comprises: a first antenna 106 and a second antenna 108; a first conductive cable 110 and a second conductive cable 112 connected in parallel with the second antenna 108; and a feeder circuit 104 connected with the second conductive cable 112. Both the first conductive cable 110 and the second conductive cable 112 are formed by insulation-coating conductive wires. The second conductive cable 112 has an inductance larger than that of the first conductive cable 110.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an antenna device corresponding to a plurality of frequency bands.

Background Art

[0002] An antenna device mounted on an automobile is required to have a function of transmitting and receiving radio waves in a plurality of frequency bands such as AM, FM, and DAB (Digital Audio Broadcasting) with a single device. An antenna device capable of receiving radio waves in a plurality of frequency bands is called a "composite antenna device".

[0003] Patent Document 1 discloses a composite antenna device installed on a roof panel of an automobile. This composite antenna device is a so-called shark fin antenna, and two types of coils (a first tuning coil unit 10 and a second tuning coil unit 20) are connected in parallel to an antenna element (a common top capacitance unit 30) (see FIG. 1). The common top capacitance unit 30 receives radio waves in the AM frequency band, the common top capacitance unit 30 and the first tuning coil unit 10 resonate in the FM frequency band, and the common top capacitance unit 30 and the second tuning coil unit 20 resonate in the FM frequency band, so that it can correspond to three types of frequency bands.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In recent years, in automobiles, in addition to roof panels, there has been a demand for installing antenna devices on various exterior parts such as spoilers and door mirrors. A composite antenna device includes an antenna element and a power supply circuit, and it is desirable that the power supply circuit be connected to a structure with a stable ground potential. In exterior parts such as door mirrors, it is difficult to obtain a stable ground potential. Therefore, if an antenna element and a power supply circuit are built in such an exterior part together, the reception performance may be degraded due to the influence of noise generated by vehicle electrical components.

[0006] Therefore, if only the antenna element is built in the exterior part and the power supply circuit is built in a large structure such as a door body, it becomes easier to stabilize the ground potential of the power supply circuit. On the other hand, since the conductive cable connecting the antenna element and the power supply circuit becomes long, the influence of the inductance of the conductive cable cannot be ignored.

[0007] The present invention has been completed based on the above recognition of the problem, and its main object is to provide a composite antenna device capable of resonating in a plurality of frequency bands in a situation where the conductive cable connecting the antenna element and the power supply circuit becomes long.

Means for Solving the Problem

[0008] A composite antenna device according to an aspect of the present invention includes a planar first antenna, a first conductive cable and a second conductive cable connected in parallel to the first antenna, and a power supply circuit including a power supply connected to both or one of the first conductive cable and the second conductive cable. Both the first conductive cable and the second conductive cable are formed by insulating a conductive wire with an insulating coating. The second conductive cable has an inductance equal to or larger than the inductance of the first conductive cable.

Effect of the Invention

[0009] According to the present invention, it becomes easier to resonate a composite antenna device in which the antenna element and the power supply circuit are separated in a plurality of frequency bands.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Modes for Carrying Out the Invention

[0011] The antenna device in this embodiment is a composite antenna device capable of receiving radio waves in three frequency bands: the AM frequency band (520 - 1710 kHz), the FM frequency band (76 - 108 MHz or 88 - 108 MHz), and the DAB frequency band (174 - 240 MHz (terrestrial wave: Band-III)). Hereinafter, corresponding to the three configurations of the composite antenna device 100, it will be described separately in the first to third embodiments. When the first to third embodiments are not particularly distinguished, it is referred to as "this embodiment".

[0012] [First Embodiment] FIG. 1 is an external view of the composite antenna device 100 in the first embodiment. The composite antenna device 100 includes an antenna element 102 and a power supply circuit 104 (amplification circuit). The power supply circuit 104 supplies an alternating current to the antenna element 102 and amplifies the current when the antenna element 102 receives radio waves in a predetermined frequency band, thereby detecting the radio waves.

[0013] The composite antenna device 100 is required to satisfy the following three conditions. ·Condition 1: The power supply circuit 104 is directly connected to a structure with a stable ground potential (hereinafter referred to as "ground structure"). ·Condition 2: The antenna element 102 is separated from the ground structure as much as possible. ·Condition 3: The antenna element 102 is installed in the housing of the door mirror.

[0014] When the power supply circuit 104 is indirectly connected to the ground structure via a relay component such as a bracket, it becomes difficult to stabilize the ground potential of the power supply circuit 104 due to the resistance and inductance of the relay component. Therefore, it is desirable to keep the power supply circuit 104 as close as possible to the ground structure.

[0015] For example, when both the antenna element 102 and the power supply circuit 104 are housed in the housing of the door mirror, assume that a conductive component in the housing, for example, a hinge mechanism, is connected to the power supply circuit 104. In this case, the ground potential may become unstable due to the contact resistance of the hinge. Alternatively, it is also conceivable to use the vehicle body as the ground structure and connect the body and the power supply circuit 104 in the housing with an earth wire. In this case, the power supply circuit 104 will be far from the ground structure.

[0016] When the antenna element 102 is close to the ground structure, a parasitic capacitance may occur between the antenna element 102 and the ground structure. Since this parasitic capacitance degrades the reception performance of the antenna, it is desirable to separate the antenna element 102 from the ground structure (ground potential surface). This parasitic capacitance is also referred to as "stray capacitance".

[0017] Also, assume that incorporating the antenna element 102 into the door mirror is a requirement as a design requirement.

[0018] The antenna element 102 in the present embodiment includes a first antenna 106 and a second antenna 108. The first antenna 106 is a metal plate. The second antenna 108 is a metal plate provided in a direction perpendicular to the first antenna 106. Although the materials of the first antenna 106 and the second antenna 108 are arbitrary, in the present embodiment, they are formed of copper.

[0019] Depending on the country or region, mainly, FM radio waves are horizontally polarized and DAB radio waves are vertically polarized. Also, since there are radio waves reflected from buildings, the polarization direction is not uniform. The first antenna 106 and the second antenna 108 are arranged so as to be orthogonal to each other so as to easily correspond to both horizontal polarization and vertical polarization. Also, the second antenna 108 may be a wire or a metal plate.

[0020] The first conductive cable 110 and the second conductive cable 112 are connected to the first antenna 106 via the second antenna 108. The first conductive cable 110 and the second conductive cable 112 are general AV electric wires in which a metal conductor is coated with vinyl chloride. The first conductive cable 110 and the second conductive cable 112 are fixed to each other so as to be parallel. The end of the first conductive cable 110 is an open end (point A1 in FIG. 1), and the second conductive cable 112 is directly connected to the power supply circuit 104. The first conductive cable 110 and the second conductive cable 112 function as a resonance circuit (described later).

[0021] The power supply circuit 104 is an amplifier circuit including an AC power supply and is connected to the ground potential of the grounding structure. The power supply circuit 104 is a so-called LNA (Low Noise Amplifier).

[0022] FIG. 2 is a cross-sectional view when the composite antenna device 100 is installed on the door mirror 114. As described above, the composite antenna device 100 in the present embodiment is incorporated in the door mirror 114. The antenna element 102 is installed at the upper part of the housing 116 of the door mirror 114. The first antenna 106 is fixed to the ceiling surface of the housing 116. The first conductive cable 110 and the second conductive cable 112 extending from the second antenna 108 are led into the inside of the door 120 through a through hole 118 formed in advance in the housing 116.

[0023] The power supply circuit 104 is covered by a metal case. The power supply circuit 104 is directly connected to the inner wall 122 of the door of the door through the metal case. The inner wall 122 of the door is a steel plate (conductive), and like the roof panel, it is a relatively large metal and functions almost equivalently to a grounding structure. The power supply circuit 104 is set to the ground potential through the metal cover. The inner wall 122 of the door may be further connected to the frame of the vehicle, which is a larger and more stable grounding structure. In addition, a cable (not shown) for amplifier output is drawn out from the power supply circuit 104 and connected to a tuner in the vehicle interior.

[0024] Since the power supply circuit 104 is directly connected to the inner wall 122 of the door (grounding structure), condition 1 is satisfied. Also, since the antenna element 102 is incorporated in the door mirror 114, condition 3 is satisfied. Since the antenna element 102 and the inner wall 122 of the door (grounding structure) are sufficiently separated, condition 2 is satisfied.

[0025] FIG. 3 is an equivalent circuit diagram of 100 in the first embodiment. The second antenna 108 includes an inductance L1 as an internal inductance. One end of the first conductive cable 110 is connected to the second antenna 108, and the other end is an open end. The first conductive cable 110 includes an inductance L2 as an internal inductance. Also, the first conductive cable 110 includes a parasitic capacitance C1 due to capacitive coupling with the parallel second conductive cable 112. The second conductive cable 112 includes inductances L3 and L4 as internal inductances. The second conductive cable 112 is connected to the power supply circuit 104.

[0026] Since the first conductive cable 110 and the second conductive cable 112 are long conductive cables, their internal inductance becomes so large that it cannot be ignored. Also, since the first conductive cable 110 and the second conductive cable 112 are fixed to each other in a parallel state, the parasitic capacitance C1 is also greatly affected. Note that since the second conductive cable 112 is longer than the first conductive cable 110, L3 + L4 > L2. In this way, by bringing the first conductive cable 110 and the second conductive cable 112 close (parallel) to each other, the parasitic capacitance C1 is increased, and by utilizing the internal inductance of the first conductive cable 110 and the second conductive cable 112, a resonance circuit is formed by the first conductive cable 110 and the second conductive cable 112.

[0027] The antenna element 102 includes an AM power supply 124 that is a power supply corresponding to the AM frequency band and an FM / DAB power supply 126 that is a power supply corresponding to the FM / DAB frequency band. The second conductive cable 112 is connected to the AM power supply 124 and is also connected to the FM / DAB power supply 126 via a capacitor 128 (capacitance CX) installed on the power supply circuit 104. Note that the FM / DAB power supply 126 is connected to two systems of LC circuits, an LC circuit for detecting the FM frequency band and an LC circuit for detecting the DAB frequency band, as is known.

[0028] Radio waves in the AM frequency band are mainly detected by the first antenna 106 (capacitively loaded antenna). The antenna characteristics are adjusted so as to receive radio waves in the AM frequency band according to the shape and area of the first antenna 106. Radio waves in the FM frequency band are detected by the resonance of 102 (the first antennas 106 and 108), the first conductive cable 110 (inductance L2, capacitance C1), and the second conductive cable 112 (inductances L3, L4). Radio waves in the DAB frequency band are detected based on the resonance characteristics of the inductance L4 of the first antenna 106, the second antenna 108, and the second conductive cable 112. For the alternating current in the DAB frequency band (high frequency band), the parallel circuit portion of the first conductive cable 110 and the second conductive cable 112 serves as a filter.

[0029] By forming three resonance circuits corresponding to three resonance frequencies with the antenna element 102, the first conductive cable 110, and the second conductive cable 112, the composite antenna device 100 can detect radio waves in three frequency bands: AM, FM, and DAB. The capacitor 128 is for finely adjusting the resonance characteristics of the composite antenna device 100, and is not essential when the resonance characteristics can be adjusted only by the antenna element 102, the first conductive cable 110, and the second conductive cable 112.

[0030] The resonance frequency of the composite antenna device 100 can be adjusted by adjusting each element included in the composite antenna device 100. By adjusting the length of the first conductive cable 110, the inductance L1 and the parasitic capacitance C1 can be adjusted. By adjusting the length of the second conductive cable 112, the inductances L3 and L4 can be adjusted. By adjusting the length of the second antenna 108, the inductance L1 can be adjusted. Also, the resonance characteristics of the composite antenna device 100 can be adjusted by adjusting the capacitance of the capacitor 128 mounted on the power supply circuit 104.

[0031] FIG. 4 is a graph showing the frequency characteristics of the composite antenna device 100 in the first embodiment. The horizontal axis represents frequency, and the vertical axis represents antenna gain (reception performance). According to FIG. 4, high antenna gains are obtained in both the FM frequency band 130 and the DAB frequency band 134. Also, by making the first conductive cable 110 an open end, a notch 136 is formed, and it was confirmed that sufficient resonance can be obtained even in the wideband DAB frequency band 134.

[0032] [Second Embodiment] FIG. 5 is an external view of the composite antenna device 100 in the second embodiment. In the composite antenna device 100 of the second embodiment, instead of leaving one end of the first conductive cable 110 as an open end, it is directly connected to the power supply circuit 104. Both the first conductive cable 110 and the second conductive cable 112 are connected to the second antenna 108 and the power supply circuit 104. The lengths of the first conductive cable 110 and the second conductive cable 112 may be the same. Note that the installation method of the composite antenna device 100 in the second and third embodiments is the same as the installation method shown in FIG. 2.

[0033] FIG. 6 is an equivalent circuit diagram of the composite antenna device 100 in the second embodiment. The second antenna 108 includes an inductance L1 as an internal inductance. One end of the first conductive cable 110 is connected to the second antenna 108, and the other end is connected to the power supply circuit 104. The first conductive cable 110 includes inductances L2 and L5 as internal inductances. Also, the first conductive cable 110 includes a parasitic capacitance C2 due to capacitive coupling with the second conductive cable 112. Compared with the first embodiment, the parallel portion of the first conductive cable 110 and the second conductive cable 112 becomes longer, so the parasitic capacitance C2 is larger than the parasitic capacitance C1 (in the first embodiment). The second conductive cable 112 includes inductances L3 and L4 as internal inductances. The second conductive cable 112 is also connected to the power supply circuit 104.

[0034] The power supply circuit 104 includes an AM power supply 124 and an FM / DAB power supply 126. The second conductive cable 112 is connected to the AM power supply 124 and is also connected to the FM / DAB power supply 126 via a capacitor 128 (capacitance CX). The first conductive cable 110 is connected to the AM power supply 124 via a capacitor 138 installed on the power supply circuit 104 and is connected to the FM / DAB power supply 126 via the capacitor 138 and the capacitor 128.

[0035] Also in the second embodiment, by forming three types of resonance circuits corresponding to three types of resonance frequencies with the antenna element 102, the first conductive cable 110, and the second conductive cable 112, the composite antenna device 100 can detect radio waves in three frequency bands of AM, FM, and DAB. The capacitors 128 and 138 are for finely adjusting the resonance characteristics of the composite antenna device 100, and are not essential when the resonance characteristics can be adjusted only by the antenna element 102, the first conductive cable 110, and the second conductive cable 112.

[0036] The resonance frequency of the composite antenna device 100 of the second embodiment can also be adjusted by adjusting each element included in the composite antenna device 100. By adjusting the lengths of the first conductive cable 110 and the second conductive cable 112, the inductances L2, L3, L4, L5, and the parasitic capacitance C2 can be adjusted. By adjusting the length of the second conductive cable 112, the inductance L1 can be adjusted. Also, the resonance characteristics of the composite antenna device 100 can be adjusted by adjusting the capacitances of the capacitors 128 and 138 mounted on the power supply circuit 104.

[0037] [Third Embodiment] FIG. 7 is an external view of the composite antenna device 100 in the third embodiment. The third embodiment assumes a case where it is desired to particularly greatly separate the antenna element 102 and the power supply circuit 104. In the composite antenna device 100 of the third embodiment, one end of the first conductive cable 110 is an open end (point A1) as in the first embodiment. A third conductive cable 140 is further connected in parallel to the second conductive cable 112. The first antenna 106 side of the third conductive cable 140 is an open end (point A2). The second conductive cable 112 and the third conductive cable 140 are connected to the power supply circuit 104.

[0038] FIG. 8 is an equivalent circuit diagram of the composite antenna device 100 in the third embodiment. The second antenna 108 includes an inductance L1 as an internal inductance. The first conductive cable 110 includes an inductance L2 as an internal inductance. Also, the first conductive cable 110 includes a parasitic capacitance C1 due to capacitive coupling with the second conductive cable 112. The second conductive cable 112 includes inductances L3, L4, and L6 as internal inductances. That is, the total inductance of the second conductive cable 112 is L3 + L4 + L6. The second conductive cable 112 is connected to the power supply circuit 104.

[0039] As described above, one end of the third conductive cable 140 on the antenna element 102 side is an open end (point A2), and the other end is connected to the power supply circuit 104. The third conductive cable 140 includes an inductance L7 as an internal inductance. Also, the third conductive cable 140 includes a parasitic capacitance C3 due to capacitive coupling with the second conductive cable 112.

[0040] In the third embodiment, the second conductive cable 112 is mutually fixed in a state parallel to the first conductive cable 110 on the antenna element 102 side and mutually fixed in a state parallel to the third conductive cable 140 on the power supply circuit 104 side.

[0041] The second conductive cable 112 is connected to the AM power supply 124 and is also connected to the FM / DAB power supply 126 via a capacitor 128 (capacitance CX) installed on the power supply circuit 104. The third conductive cable 140 is connected to the AM power supply 124 via a capacitor 138 and is connected to the FM / DAB power supply 126 via the capacitor 138 and the capacitor 128.

[0042] In the third embodiment, the composite antenna device 100 can detect radio waves in three frequency bands of AM, FM, and DAB by forming three resonance circuits corresponding to three types of resonance frequencies with the antenna element 102, the first conductive cable 110, the second conductive cable 112, and the third conductive cable 140. The capacitors 128 and 138 are for fine-tuning the resonance characteristics of the composite antenna device 100, and are not essential when the resonance characteristics can be adjusted only by the antenna element 102, the first conductive cable 110, the second conductive cable 112, and the third conductive cable 140.

[0043] The resonance frequency of the composite antenna device 100 in the third embodiment can also be adjusted by adjusting each element included in the composite antenna device 100. By adjusting the lengths of the first conductive cable 110, the second conductive cable 112, and the third conductive cable 140, the inductances L2, L3, L4, L6, L7 and the parasitic capacitances C1, C2 can be adjusted. The resonance characteristics of the composite antenna device 100 can also be adjusted by adjusting the capacitances of the capacitors 128 and 138 mounted on the power supply circuit 104.

[0044] Actually, as in the first embodiment, it is desirable to form a resonance circuit corresponding to the FM frequency band with the first conductive cable 110 and the second conductive cable 112. On the other hand, it is desirable to suppress the influence of the inductances L6, L7 and the parasitic capacitance C3 on the resonance characteristics of the AM frequency band, FM frequency band and DAB frequency band. The resonance circuit formed by the inductances L6, L7 and the parasitic capacitance C3 preferably functions as a low-pass filter that passes low-frequency currents in the AM frequency band and FM frequency band.

[0045] [Summary] The composite antenna device 100 has been described based on the embodiments above. In the composite antenna device 100 according to this embodiment, while satisfying the design requirement of installing the antenna element 102 on an exterior part such as a door mirror, the power supply circuit 104 can be directly connected to a grounding structure such as the inner wall 122 of the door. Also, the antenna element 102 and the grounding structure can be sufficiently separated from each other.

[0046] The housing 116 of the door mirror 114 has a through hole 118 for wiring. Since the first conductive cable 110, the second conductive cable 112, and the third conductive cable 140 are all thin AV cables that are easy to handle, the antenna element 102 inside the door mirror 114 and the power supply circuit 104 inside the door 120 can be connected using the existing through hole 118.

[0047] When the power supply circuit 104 is provided in the housing 116, waterproof measures for the power supply circuit 104 are required. In this embodiment, since the power supply circuit 104 can be installed inside the vehicle compartment such as the door 120, it is easy to ensure the waterproofness of the power supply circuit 104. As a result of adopting the above configuration, conductive cables such as the first conductive cable 110 and the second conductive cable 112 become relatively long. Generally, when the conductive cable connecting the antenna element 102 and the power supply circuit 104 becomes long, the internal inductance of the conductive cable may cause a decrease in the antenna gain. In this embodiment, the internal inductance of the first conductive cable 110 and the like is actively utilized. In particular, the first conductive cable 110 and the second conductive cable 112 are made parallel, and a resonance circuit is formed by the first conductive cable 110 and the second conductive cable 112 by utilizing the parasitic capacitance generated between the first conductive cable 110 and the second conductive cable 112. The resonance frequency by the first conductive cable 110 and the second conductive cable 112 can be adjusted not only by the lengths of the first conductive cable 110 and the second conductive cable 112 but also by additional capacitors such as the capacitor 128.

[0048] Note that the present invention is not limited to the above-described embodiments and modifications, and the components can be modified and embodied without departing from the gist. Various inventions may be formed by appropriately combining a plurality of components disclosed in the above embodiments and modifications. Also, some components may be deleted from all the components shown in the above embodiments and modifications.

[0049] [Modification Example] The first antenna 106 has been described as a flat metal plate. The first antenna 106 may be a planar conductor, and is not limited to a plane, and may be partially or entirely curved. For example, the first antenna 106 may be curved according to the shape of the housing 116. The first antenna 106 only needs to be a planar antenna having at least a certain extent.

[0050] The internal inductance of the first conductive cable 110, the second conductive cable 112, and the third conductive cable 140 can also be adjusted by the material of the conductor or the coating of the conductor. For example, the internal inductance of the conductive cable may be increased by mixing ferrite into the coating. Also, the internal inductance may be adjusted by adding a coil to a part of the first conductive cable 110, the second conductive cable 112, and the third conductive cable 140.

[0051] In the first embodiment, it has been described that the first conductive cable 110 and the second conductive cable 112 are fixed to each other in parallel. It is not necessary for the entire first conductive cable 110 to be parallel to the second conductive cable 112, and a part of the first conductive cable 110 may be parallel to the second conductive cable 112. Also, instead of completely fixing the first conductive cable 110 and the second conductive cable 112 to each other, the first conductive cable 110 and the second conductive cable 112 may be capacitively coupled by twisting the first conductive cable 110 and the second conductive cable 112 in a spiral shape. Alternatively, instead of parallelizing the first conductive cable 110 and the second conductive cable 112, the first conductive cable 110 and the second conductive cable 112 may be capacitively coupled by fixing a part or all of the first conductive cable 110 and the second conductive cable 112 in a state where they are close to each other. The same applies to the second conductive cable 112 and the third conductive cable 140.

[0052] In the second embodiment, it has been described that the second conductive cable 112 is directly connected to the AM power supply 124. As a modification, the second conductive cable 112 may be connected to the AM power supply 124 via a capacitor Z (not shown) installed on the power supply circuit 104. In this case, the resonance frequency may be adjusted by making the capacitance of the capacitor Z different from the capacitance of the capacitor 138.

[0053] The second antenna 108 does not necessarily have to be strictly perpendicular to the first antenna 106, and the angle formed by the first antenna 106 and the second antenna 108 may be substantially perpendicular. The term "substantially perpendicular" as used herein means within a range of 75 to 105 degrees, more preferably about 85 to 95 degrees.

[0054] In this embodiment, it has been described that the antenna element 102, which is a part of the first conductive cable 110, is installed on the door mirror 114, but it may be installed at other positions on the vehicle body such as a spoiler or a trunk panel.

Description of Reference Numerals

[0055] 100 Composite antenna device, 102 Antenna element, 104 Feeding circuit, 106 First antenna, 108 Second antenna, 110 First conductive cable, 112 Second conductive cable, 114 Door mirror, 116 Housing, 118 Through hole, 120 Door, 122 Inner wall of the door, 124 AM power supply, 126 FM / DAB power supply, 128 Capacitor, 130 FM frequency band, 134 DAB frequency band, 136 Notch, 138 Capacitor, 140 Third conductive cable

Claims

1. A planar first antenna, a first conductive cable and a second conductive cable connected in parallel to the first antenna, a power supply circuit including a capacitor and connected through the second conductive cable and the capacitor, characterized in that: both the first conductive cable and the second conductive cable are formed by insulating a conductive wire with an insulating coating, the end of the first conductive cable on the side opposite to the antenna side is an open end, the second conductive cable is longer than the first conductive cable and has an inductance equal to or greater than that of the first conductive cable.

2. A planar first antenna, a first conductive cable and a second conductive cable connected in parallel to the first antenna, a power supply circuit including a capacitor and connected to both the first conductive cable and the second conductive cable, characterized in that: both the first conductive cable and the second conductive cable are formed by insulating a conductive wire with an insulating coating, the first conductive cable is connected to the power supply through the capacitor, the second conductive cable is connected to the power supply without passing through the capacitor, the second conductive cable has an inductance equal to or greater than that of the first conductive cable.

3. A planar first antenna, a first conductive cable and a second conductive cable connected in parallel to the first antenna, a third conductive cable parallel to the second conductive cable, a power supply circuit including a power supply connected to both the second conductive cable and the third conductive cable, characterized in that: both the first conductive cable and the second conductive cable are formed by insulating a conductive wire with an insulating coating, the end of the first conductive cable on the side opposite to the antenna side is an open end, the end of the third conductive cable on the antenna side is an open end, the second conductive cable has an inductance equal to or greater than that of the first conductive cable.

4. A planar first antenna, a first conductive cable and a second conductive cable connected in parallel to the first antenna, A power supply circuit including a first power supply corresponding to a first frequency, a second power supply corresponding to a second frequency, and a capacitor for resonance adjustment inserted between the first power supply and the second power supply. Both the first conductive cable and the second conductive cable are connected to the first power supply without passing through the capacitor, and are connected to the second power supply through the capacitor. Both the first conductive cable and the second conductive cable are formed by insulating a conductive wire with an insulating coating. The composite antenna device, wherein the second conductive cable has an inductance equal to or greater than that of the first conductive cable.

5. The composite antenna device according to any one of claims 1 to 4, wherein the first conductive cable and the second conductive cable are fixed to each other such that at least a part of the first conductive cable and at least a part of the second conductive cable are parallel.

6. Comprising a second antenna connected to the first antenna. The composite antenna device according to any one of claims 1 to 4, wherein the first antenna is connected to both the first conductive cable and the second conductive cable through the second antenna.

7. The composite antenna device according to claim 6, wherein the relative angle between the first antenna and the second antenna is formed to be 75 degrees or more and 105 degrees or less.

8. The first antenna is installed inside the housing of a vehicle door mirror. The first conductive cable and the second conductive cable are drawn into the vehicle interior from the housing. The composite antenna device according to any one of claims 1 to 4, wherein the power supply circuit is installed in the vehicle interior and is connected to the vehicle body as a conductor of a reference potential.

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