Antenna device

Abstract

To ensure excellent antenna performance and miniaturize an antenna device.SOLUTION: An antenna device 1 includes capacitance loading elements 41a and 41b, tuning coils 42a and 42b, and a filter 44. The capacitance loading element 41a receives a first frequency band. The capacitance loading element 41b receives a second frequency band that is higher or lower than the first frequency band. One end of the tuning coil 42a is connected to the capacitance loading element 41a. One end of the tuning coil 42b is connected to the capacitance loading element 41b. The filter 44 is connected to the capacitance loading elements 41a and 41b, and passes the first frequency band and attenuates the second frequency band.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an antenna device. [Background technology]

[0002] Conventionally, there is known an antenna device that receives signals in two different adjacent frequency bands. In this antenna device, the antenna performance for receiving the higher frequency band affects the antenna performance for receiving the lower frequency band, resulting in reduced sensitivity at the higher end of the lower frequency band.

[0003] To solve the above problems, a composite antenna device is known that includes one common top capacitance section, and first and second tuning coil sections connected in parallel to the common top capacitance section (see Patent Documents 1 and 2). The composite antenna device uses two tuning coil sections to resonate in a first frequency band and a second frequency band that is higher than the first frequency band. The first tuning coil section functions as a filter that attenuates frequency bands other than the first frequency band. The second tuning coil section functions as a filter that attenuates frequency bands other than the second frequency band.

[0004] Also known is an antenna device having a radio antenna and a DAB (Digital Audio Broadcasting) antenna (see Patent Document 3). The radio antenna has a first capacitance loading element and a coil element. The DAB antenna has a second capacitance loading element and a coil element, and has a higher frequency band than the radio antenna. The relative positions of the radio antenna and the DAB antenna ensure isolation performance between them. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-133692 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-115742 [Patent Document 3] Japanese Patent Publication No. 2023-110193 Summary of the Invention [Problem to be solved by the invention]

[0006] In the composite antenna devices of Patent Documents 1 and 2, the tuning coil must have two functions: a resonance function achieved by connecting the common top capacitance section and the tuning coil section in series, and a filter function that attenuates frequencies other than the desired frequency band. In this case, this narrows the tuning coil options (such as changing the resonance frequency within the desired frequency band), and there is a risk that good antenna performance cannot be ensured.

[0007] The antenna device of Patent Document 3 is not suitable for reducing the product size when ensuring isolation performance through positional relationships.

[0008] An object of the present invention is to ensure good antenna performance and reduce the size of an antenna device. [Means for solving the problem]

[0009] In order to solve the above problems, the antenna device of the present invention comprises: a first capacitive loading element for receiving a first frequency band; a second capacitive loading element for receiving a second frequency band that is higher or lower than the first frequency band; a first tuning coil having one end connected to the first capacitive loading element; a second tuning coil having one end connected to the second capacitive loading element; a filter connected to the first capacitive loading element and the second capacitive loading element, the filter passing the first frequency band and attenuating the second frequency band. [Effects of the Invention]

[0010] According to the present invention, good antenna performance can be ensured and the antenna device can be made smaller. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is an external perspective view showing an antenna device according to an embodiment of the present invention; [Figure 2] FIG. 2 is a partially see-through schematic view showing the internal configuration of the antenna device. [Figure 3] FIG. 2 is an equivalent circuit diagram of an antenna unit according to the embodiment. [Figure 4] 1(a) is an equivalent circuit diagram of the antenna as viewed from the first frequency band, and FIG. 1(b) is an equivalent circuit diagram of the antenna as viewed from the second frequency band. [Figure 5] FIG. 4 is a diagram illustrating frequency characteristics of gain of the antenna unit according to the embodiment. [Figure 6] FIG. 10 is an equivalent circuit diagram of an antenna unit of a first modified example. [Figure 7] FIG. 10 is an equivalent circuit diagram of an antenna unit of a second modified example. [Figure 8] FIG. 10 is an equivalent circuit diagram of an antenna unit according to a third modified example. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment and first and second modifications of the present invention will be described in detail with reference to the accompanying drawings, although the scope of the invention is not limited to the illustrated examples.

[0013] (Embodiment) An embodiment of the present invention will be described with reference to Fig. 1 to Fig. 5. First, the device configuration of this embodiment will be described with reference to Fig. 1 and Fig. 2. Fig. 1 is an external perspective view showing an antenna device 1 of this embodiment. Fig. 2 is a partially see-through schematic view showing the internal configuration of the antenna device 1.

[0014] The antenna device 1 of this embodiment is an in-vehicle antenna device of a so-called shark fin antenna that is attached to a fixing opening (not shown) in the installation surface of the roof of a vehicle such as an automobile. The antenna device 1 is a composite antenna device that receives at least FM radio broadcasts (frequency band: VHF band) and DAB broadcasts.

[0015] As shown in Fig. 1, the antenna device 1 includes an antenna cover 10, and is configured to house the antenna main body and other components inside the antenna cover 10. The antenna cover 10 is attached to an antenna base 20 (described later) and is formed to protrude in a streamlined shape from front to rear, forming a low-profile shark fin shape so as not to spoil the appearance of the vehicle. The antenna cover 10 is made of a synthetic resin such as ABS (Acrylonitrile Butadiene Styrene) resin that is radio wave transparent and insulating, and is a molded product with an open bottom.

[0016] As shown in FIG. 2, the antenna device 1 includes an antenna cover 10, an antenna base 20, a substrate 30, and an antenna section 40A.

[0017] The opening on the bottom surface of the antenna cover 10 is configured to form a storage space for the substrate 30, the antenna section 40A, etc. when the antenna base 20 and the like are attached.

[0018] The antenna base 20 is the base of the antenna device 1, supports the substrate 30, and is configured to be attached to a fixing opening on the installation surface of the roof of a vehicle. The antenna base 20 has a flat plate 21 and a protruding portion 22. The flat plate 21 is a substantially flat base body made of die-cast metal such as aluminum or zinc, and is integrated with the protruding portion 22. The flat plate 21 may also be made of sheet metal such as a steel plate.

[0019] The protrusion 22 is provided on the underside of the flat plate 21, and has a hole for a cable for the board 30 formed in the center of the shaft, as well as a male screw. A vehicle mounting fixture such as a nut (not shown) is attached to the protrusion 22 while it is inserted into a fixing opening in the vehicle. This fixes the antenna device 1 to the vehicle. In addition, a packing (not shown) is attached to the periphery of the flat surface of the flat plate 21 to prevent water and dust from entering the antenna device 1 and the interior of the vehicle.

[0020] The substrate 30 includes a main substrate 31 and an antenna substrate 32. The main substrate 31 is a PCB (Printed Circuit Board) provided on the flat plate 21 with its plane oriented horizontally, and has electronic components mounted thereon and a circuit pattern formed thereon. The main substrate 31 or the antenna substrate 32 is provided with power supply portions 43a and 43b, which will be described later.

[0021] Antenna substrate 32 is a substrate such as a PCB that is erected on main substrate 31. Capacitive loading elements 41a and 41b (described later) are electrically connected to the upper part of antenna substrate 32, and tuning coils 42a and 42b and a filter 44 (described later) are also mounted on antenna substrate 32.

[0022] Antenna section 40A includes antennas 4a and 4b and a filter 44. Antenna 4a includes a capacitance loading element 41a, a tuning coil 42a, and a power supply section 43a. Antenna 4b includes a capacitance loading element 41b, a tuning coil 42b, and a power supply section 43b.

[0023] The capacitance loading elements 41a and 41b are each made of metal such as tinplate and arranged near the inside of the antenna cover 10 using an inner cover (not shown). The capacitance loading elements 41a and 41b are arranged at a predetermined distance from each other in the front-to-rear direction of the vehicle.

[0024] Tuning coil 42a has one end electrically connected to capacitive loading element 41a and filter 44, and the other end electrically connected to power supply 43a. Tuning coil 42b has one end electrically connected to capacitive loading element 41b and filter 44, and the other end electrically connected to power supply 43b. Tuning coils 42a and 42b are each provided on antenna substrate 32 and are distributed constant coils made of wound conductor wires such as enamel-coated copper wire or nickel-coated copper wire. Note that tuning coils 42a and 42b are not limited to being wound distributed constant coils (inductors). Tuning coils 42a and 42b may also be configured as distributed constant coils of other shapes, such as meandering or zigzag, or as chip or lead components of lumped constant coils (inductors) mounted on antenna substrate 32.

[0025] In antenna 4a, tuning coil 42a resonates with capacitive loading element 41a at a predetermined frequency. The frequency band of resonance of antenna 4a is defined as a first frequency band. Similarly, in antenna 4b, tuning coil 42b resonates with capacitive loading element 41b at a predetermined frequency. The frequency band of resonance of antenna 4b is defined as a second frequency band. The first frequency band is defined as a lower frequency band than the second frequency band.

[0026] In this embodiment, the antenna 4a for the first frequency band is an antenna for receiving FM broadcasts, and the antenna 4b for the second frequency band is an antenna for receiving DAB broadcasts.

[0027] The filter 44 is made up of a coil (inductor) as a circuit element. The filter 44 is a chip component or lead component of a lumped constant coil mounted on the antenna substrate 32. Note that the filter 44 is not limited to a lumped constant coil, and may be configured as a distributed constant coil.

[0028] Power supply unit 43a is a power supply unit to which an antenna current resulting from radio wave reception by antenna 4a is input, and power supply unit 43b is a power supply unit to which an antenna current resulting from radio wave reception by antenna 4b is input.

[0029] Next, the circuit configuration and antenna characteristics of the antenna unit 40A will be described with reference to Fig. 3 to Fig. 5. Fig. 3 is an equivalent circuit diagram of the antenna unit 40A. Fig. 4(a) is an equivalent circuit diagram of the antenna 40a as viewed from the first frequency band. Fig. 4(b) is an equivalent circuit diagram of the antenna 40b as viewed from the second frequency band. Fig. 5 is a diagram showing the frequency characteristics of the gain of the antenna unit 40A.

[0030] As shown in Fig. 3, antenna 4a is a physical antenna in which a capacitance loading element 41a and a tuning coil 42a are connected in series, and a power supply unit 43a is electrically connected to tuning coil 42a. Antenna 4b is a physical antenna in which a capacitance loading element 41b and a tuning coil 42b are connected in series, and a power supply unit 43b is electrically connected to tuning coil 42b. Filter 44 is electrically connected between a point between capacitance loading element 41a and tuning coil 42a and a point between capacitance loading element 41b and tuning coil 42b. The inductance of the coil of filter 44 is adjusted so that it functions as a low-pass filter that passes a frequency band (first frequency band) lower than the second frequency band.

[0031] Here, consider antenna unit 40A as seen from the first frequency band (when receiving radio waves in the first frequency band), as shown in Figure 4(a). In this case, capacitive loading element 41b does not resonate and therefore does not function. In Figures 4(a) and 4(b), of the elements of antenna unit 40A, those that are functioning are indicated by solid lines, and those that are not functioning are indicated by dotted lines.

[0032] When viewed from the first frequency band, capacitance loading element 41a and tuning coil 42a resonate, causing antenna 4a to function. At the same time, filter 44 causes antenna current in the first frequency band to flow toward tuning coil 42b, causing tuning coil 42b to function as a GND impedance adjustment coil, and power supply unit 43b to function as GND. Thus, when viewed from the first frequency band, antenna unit 40A functions as antenna 40a. Antenna 40a includes antenna 4a, filter 44, tuning coil 42b, and power supply unit 43b. Antennas 4a and 4b are capacitance-loaded monopole antennas. Antenna 40a functions as a grounded antenna (capacitance-loaded inverted-F antenna) in the first frequency band.

[0033] Next, consider antenna unit 40A as viewed from the second frequency band (when receiving radio waves in the second frequency band), as shown in Figure 4(b). When viewed from the second frequency band, capacitive loading element 41b and tuning coil 42b resonate, and antenna 4b functions. However, no antenna current in the second frequency band flows through filter 44. Therefore, antenna 4a does not function when viewed from the second frequency band.

[0034] In this way, when viewed from the second frequency band, the antenna section 40A functions as the antenna 40b. The antenna 40b is equivalent to the antenna 4b, and functions as a capacitance-loaded monopole antenna for the second frequency band.

[0035] Regarding the first frequency band, the frequency band for FM broadcasting is 76 to 95 MHz (for Japan) and 88 to 108 MHz (for overseas countries), which has a bandwidth of only about 20 MHz. Regarding the second frequency band, the frequency band for DAB broadcasting is 174 to 240 MHz, which has a bandwidth of nearly 70 MHz. Therefore, by using antenna 40a, a grounded antenna with a narrow bandwidth, as the antenna for the first frequency band, the reception bandwidth of the antenna for the first frequency band is narrowed.

[0036] In Figure 5, the gain of antenna 40a in the first frequency band and the gain of antenna 40b in the second frequency band are shown by solid lines, and the gain of the capacitance-loaded monopole antenna in the first frequency band is shown by dotted lines. As shown in Figure 5, there are frequencies at which the gain of the capacitance-loaded monopole antenna in the first frequency band interferes with the gain of antenna 40b (4b) in the second frequency band. However, by replacing the capacitance-loaded monopole antenna with antenna 40a, which has a narrowband bandwidth for the first frequency band, the mutual interference between the gain in the first frequency band and the gain in the second frequency band can be suppressed, ensuring antenna isolation performance.

[0037] In this way, the antenna unit 40A includes a capacitance loading element and a tuning coil for each of the desired first and second frequency bands, allowing for fine tuning of the resonance point within each frequency band. At the same time, the antenna unit 40A sets the impedance of the filter 44 to a predetermined value, allowing the antenna 40b for the first frequency band to function as a grounded antenna and the antenna for the second frequency band to function as a capacitance-loaded monopole antenna. This ensures isolation performance.

[0038] As described above, according to the present embodiment, antenna device 1 includes, as antenna section 40A, capacitance loading elements 41a and 41b, tuning coils 42a and 42b, and filter 44. Capacitance loading element 41a receives a first frequency band. Capacitance loading element 41b receives a second frequency band higher than the first frequency band. One end of tuning coil 42a is connected to capacitance loading element 41a. One end of tuning coil 42b is connected to capacitance loading element 41b. Filter 44 is connected to capacitance loading elements 41a and 41b, and passes the first frequency band and attenuates the second frequency band. The other end of tuning coil 42a is connected to power feeding section 43a. The other end of tuning coil 42b is connected to power feeding section 43b.

[0039] Therefore, when receiving radio waves in the first frequency band, the antenna unit 40A functions as antenna 40a, a narrow-band grounded antenna, and when receiving radio waves in the second frequency band, it functions as antenna 40b, a capacitance-loaded monopole antenna. Therefore, antennas 40a and 40b can receive either the first or second frequency band, ensuring good antenna performance. Furthermore, the filter 44 allows the components of the antenna unit 40A to be standardized, reducing the number of components, thereby enabling the antenna device 1 to be made smaller and less expensive.

[0040] Furthermore, filter 44 is a low-pass filter that passes the first frequency band and attenuates at least the second frequency band, so that when receiving radio waves in the first frequency band, antenna 40a can function as a narrow-band grounded antenna, and when receiving radio waves in the second frequency band, antenna 40b can function as a capacitance-loaded monopole antenna, ensuring good antenna performance.

[0041] Furthermore, the filter 44 has a coil (inductor), which reduces the number of components in the filter 44, allowing the antenna device 1 to be made smaller and at lower costs.

[0042] (First Modification) A first modification of the above embodiment will be described with reference to Fig. 6. Fig. 6 is an equivalent circuit diagram of the antenna unit 40B.

[0043] The device configuration of this modified example is such that, in the antenna device 1 of the above embodiment, antenna section 40A of Fig. 2 and Fig. 3 is replaced with antenna section 40B shown in Fig. 6. Antenna section 40B has antennas 4a and 4b and filter 45. Filter 45 is electrically connected between a point between capacitive loading element 41a and tuning coil 42a and a point between capacitive loading element 41b and tuning coil 42b.

[0044] The filter 45 has a coil 451 and a capacitor 452 connected in series. The coil and capacitor connected in series function as a band-pass filter. Therefore, the inductance of the coil 451 and the capacitance of the capacitor 452 are adjusted so that the filter 45 functions as a band-pass filter that passes a first frequency band and attenuates at least a second frequency band.

[0045] Antenna unit 40B has antennas 40c and 40d similar to antennas 40a and 40b of antenna unit 40A. Antenna 40c has antenna 4a, filter 45, tuning coil 42b, and power supply unit 43b. Antenna 40c functions as a grounded antenna for the first frequency band. Antenna 40d is antenna 4b and functions as a capacitance-loaded monopole antenna for the second frequency band.

[0046] As described above, according to this modification, filter 45 is a bandpass filter that passes the first frequency band, and therefore filter 45 allows antenna 40c, which is a narrowband grounded antenna, to function when receiving radio waves in the first frequency band, and antenna 40d, which is a capacitance-loaded monopole antenna, to ensure good antenna performance.

[0047] Furthermore, filter 45 has coil 451 and capacitor 452 connected in series to coil 451. This allows a bandpass filter to be easily configured, the number of components of filter 45 to be reduced, and antenna device 1 to be miniaturized and reduced in cost.

[0048] (Second Modification) A second modification of the above embodiment will be described with reference to Fig. 7. Fig. 7 is an equivalent circuit diagram of an antenna unit 40C.

[0049] The device configuration of this modified example is such that, in the antenna device 1 of the above embodiment, the antenna section 40A of Fig. 2 and Fig. 3 is replaced with an antenna section 40C shown in Fig. 7. The antenna section 40C has antennas 4a and 4b and a filter 46. The filter 46 is electrically connected between a point between the capacitance loading element 41a and the tuning coil 42a and a point between the capacitance loading element 41b and the tuning coil 42b.

[0050] The filter 45 has a coil 461 and a capacitor 462 connected in parallel. The coil and capacitor connected in parallel function as a band-stop filter. Therefore, the inductance of the coil 461 and the capacitance of the capacitor 462 are adjusted so that the filter 45 functions as a band-stop filter that attenuates the second frequency band and passes at least the first frequency band.

[0051] Antenna unit 40C includes antennas 40e and 40f similar to antennas 40a and 40b of antenna unit 40A. Antenna 40e includes antenna 4a, filter 46, tuning coil 42b, and power supply unit 43b. Antenna 40e functions as a grounded antenna for the first frequency band. Antenna 40f is antenna 4b and functions as a capacitance-loaded monopole antenna for the second frequency band.

[0052] As described above, according to this modification, filter 46 is a bandstop filter that attenuates the second frequency band. Therefore, filter 46 allows antenna 40e, which is a narrowband grounded antenna, to function when receiving radio waves in the first frequency band, and antenna 40f, which is a capacitance-loaded monopole antenna, to ensure good antenna performance.

[0053] Furthermore, filter 46 has coil 461 and capacitor 462 connected in parallel to coil 461. This makes it possible to easily configure a bandstop filter, reduce the number of components in filter 46, and reduce the size and cost of antenna device 1.

[0054] The above description of the embodiment is merely an example of the antenna device according to the present invention, and the present invention is not limited to this.

[0055] For example, in the above-described embodiment and modified example, the first frequency band of the antenna units 40A, 40B, and 40C is the FM broadcast frequency band, and the second frequency band is the DAB broadcast frequency band, but this is not limited to this. The second frequency band may be a frequency band higher than the first frequency band, such as the DTV (Digital Television) broadcast frequency band (470 to 710 MHz). Furthermore, the first frequency band may be a frequency band lower than the second frequency band.

[0056] 3, the first frequency band of antenna 4a may be higher than the second frequency band of antenna 4b. In antenna unit 40A of the third modification, filter 44 of the third modification is configured with a coil having an impedance that passes the first frequency band and attenuates at least the second frequency band (having a resistance band in the second frequency band). In filter 44 of the third modification, the inductance of the coil is adjusted so that it functions as a high-pass filter that passes the first frequency band and attenuates at least the second frequency band.

[0057] Furthermore, an antenna unit according to a third modified example in which the first frequency band of the antenna 4a is higher than the second frequency band of the antenna 4b may be configured as an antenna unit 40D shown in Fig. 8. Fig. 8 is an equivalent circuit diagram of the antenna unit 40D.

[0058] The antenna unit 40D includes antennas 4a and 4b and a filter 47. The filter 47 is formed of, for example, a capacitor. The capacitance of the capacitor is adjusted so that the filter 47 functions as a high-pass filter that passes a first frequency band and attenuates at least a second frequency band.

[0059] When viewed from the first frequency band, antenna units 40A and 40D of the third modified example function as antenna 40a of Fig. 4(a). Antenna 40a of the third modified example includes antenna 4a, filter 44 of the third modified example, tuning coil 42b, and power supply unit 43b. Antenna 40a of the third modified example functions as a grounded antenna (capacitor-loaded inverted-F antenna) for the first frequency band.

[0060] When viewed from the second frequency band, the antenna units 40A and 40B of the third modified example function as the antenna 40b in Fig. 4(b) The antenna 40b functions as a capacitance-loaded monopole antenna for the second frequency band.

[0061] The antenna device of the third modification includes the antenna unit 40A or 40D of the third modification. The antenna device of the third modification is applied to, for example, transmitting and receiving radio waves of a medium in which the first frequency band is higher than the second frequency band and the band is narrower.

[0062] As described above, the antenna device of the third modification can be configured to use any first and second frequency bands such that the first frequency band is greater than the second frequency band, as in the above-described embodiment. Furthermore, when receiving radio waves in the first frequency band, antenna 40a can function as a narrow-band grounded antenna, and when receiving radio waves in the second frequency band, antenna 40b can function as a capacitance-loaded monopole antenna, ensuring good antenna performance. Furthermore, filters 44 and 47 of the third modification allow for the sharing of components in antenna section 40A of the third modification, reducing the number of components, thereby enabling antenna device 1 to be miniaturized and cost-effective.

[0063] Furthermore, the filters 44 and 47 of the antenna units 40A and 40D of the third modified example are high-pass filters that pass the first frequency band and attenuate at least the second frequency band, allowing the antenna 40a to function as a narrow-band grounded antenna when receiving radio waves in the first frequency band, and as an antenna 40b as a capacitance-loaded monopole antenna when receiving radio waves in the second frequency band, ensuring good antenna performance.

[0064] Furthermore, filter 44 of the third modified example has a coil, and filter 47 has a capacitor. This allows the number of components in filters 44 and 47 to be reduced, allowing the antenna device of the third modified example to be made smaller and more cost-effective.

[0065] Furthermore, as a third modified example, in antenna unit 40B of Fig. 6, the first frequency band of antenna 4a may be higher than the second frequency band of antenna 4b. In antenna unit 40B of the third modified example, filter 45 of the third modified example has coil 451 and capacitor 452. However, the inductance of coil 451 and the capacitance of capacitor 452 are adjusted so that filter 45 functions as a bandpass filter that passes the first frequency band and attenuates at least the second frequency band. This configuration achieves the same effects as the first modified example.

[0066] Furthermore, as a third modified example, in antenna unit 40C of Fig. 7, the first frequency band of antenna 4a may be configured to be higher than the second frequency band of antenna 4b. In antenna unit 40B of the third modified example, filter 46 of the third modified example has coil 461 and capacitor 462. However, the inductance of coil 461 and the capacitance of capacitor 462 are adjusted so that filter 46 functions as a bandstop filter that attenuates the second frequency band and passes at least the first frequency band. This configuration provides the same effects as the second modified example.

[0067] Furthermore, the detailed configuration and detailed operation of the antenna device 1 in the above-described embodiment can also be modified as appropriate without departing from the spirit of the present invention. [Explanation of symbols]

[0068] 1 Antenna device 10 Antenna cover 20 Antenna base 21 flat plate 22 Convex part 30 boards 31 Main board 32 Antenna board 40A, 40B, 40C, 40D Antenna section 4a, 4b, 40a, 40b, 40c, 40d, 40e, 40f antennas 41a, 41b Capacitive loading element 42a, 42b Tuning coil 43a, 43b Power supply section 44, 45, 46, 47 Filters 451,461 coils 452,462 capacitors

Claims

1. a first capacitive loading element for receiving a first frequency band; a second capacitive loading element for receiving a second frequency band that is higher or lower than the first frequency band; a first tuning coil having one end connected to the first capacitive loading element; a second tuning coil having one end connected to the second capacitive loading element; a filter connected to the first capacitive loading element and the second capacitive loading element, the filter passing the first frequency band and attenuating the second frequency band.

2. the other end of the first tuning coil is connected to a first power supply portion; 2. The antenna device according to claim 1, wherein the other end of the second tuning coil is connected to a second power supply portion.

3. the first frequency band is lower than the second frequency band; 3. The antenna device according to claim 1, wherein the filter is a low-pass filter that passes the first frequency band and attenuates at least the second frequency band.

4. The antenna device according to claim 3 , wherein the filter comprises a coil.

5. the first frequency band is higher than the second frequency band; 3. The antenna device according to claim 1, wherein the filter is a high-pass filter that passes the first frequency band and attenuates at least the second frequency band.

6. The antenna device according to claim 5 , wherein the filter comprises a coil or a capacitor.

7. 3. The antenna device according to claim 1, wherein the filter is a band-pass filter that passes the first frequency band.

8. The antenna device according to claim 5 , wherein the filter comprises a coil and a capacitor connected in series with the coil.

9. 3. The antenna device according to claim 1, wherein the filter is a band-stop filter that attenuates the second frequency band.

10. The antenna device according to claim 7 , wherein the filter comprises a coil and a capacitor connected in parallel to the coil.

Images