Abstract
In an antenna device, when an AM/FM antenna as a first antenna and an SDARS antenna or a GPS antenna as a second antenna that have different frequency bands are provided in a common case, an additional conductor portion extends out from a conductor main body portion of a capacitive element, and the additional conductor portion includes a parallel strip-shaped portion having a length that is ¼ of an effective wavelength in a frequency band of the second antenna, and extending parallel to the conductor main body portion.
Claims
1. An antenna device comprising a first antenna and a second antenna that are provided in a common case and have different frequency bands, wherein an additional conductor portion extends out from a conductor main body portion of the first antenna, the additional conductor portion includes a predetermined-length portion extending at a distance along and parallel to an edge of the conductor main body portion and having a predetermined length corresponding to a frequency band of the second antenna, and the additional conductor portion facilitates a state of directionality of the second antenna by current of the additional conductor portion offsetting current of the first antenna.
2. The antenna device according to claim 1, wherein the predetermined-length portion of the additional conductor portion is arranged to correspond to a region having a high electric field of the conductor main body portion in the frequency band of the second antenna.
3. The antenna device according to claim 1, wherein the predetermined-length portion of the additional conductor portion has a length that is substantially 1/4 of an effective wavelength in the frequency band of the second antenna.
4. The antenna device according to claim 1, wherein a separation distance between the first antenna and the second antenna in a horizontal direction is substantially within 1/2 of a wavelength in the frequency band of the second antenna.
5. The antenna device according to claim 1, wherein the second antenna is omnidirectional in a horizontal plane, and a difference between a maximum gain and a minimum gain of the second antenna at a predetermined elevation angle is small as compared with a case where the additional conductor portion is not present.
6. The antenna device according to claim 1, further comprising a third antenna that is provided in the case, wherein the third antenna has a frequency band different from the frequencies of the first antenna and the second antenna, another additional conductor portion extends out from the conductor main body portion, and said another additional conductor portion includes a predetermined-length portion extending at a distance along an edge of the conductor main body portion and having a predetermined length corresponding to the frequency band of the third antenna.
7. The antenna device according to claim 6, wherein the predetermined-length portion of said another additional conductor portion is arranged to correspond to a region having a high electric field of the conductor main body portion in the frequency band of the third antenna.
8. The antenna device according to claim 6, wherein the predetermined-length portion of the other additional conductor portion has a length that is substantially 1/4 of an effective wavelength in the frequency band of the third antenna.
9. The antenna device according to claim 6, wherein a separation distance between the first antenna and the third antenna in a horizontal direction is substantially within 1/2 of a wavelength in the frequency band of the third antenna.
10. The antenna device according to claim 6, wherein the third antenna is omnidirectional in a horizontal plane, and a difference between a maximum gain and a minimum gain of the third antenna at a predetermined elevation angle is small as compared with a case where the additional conductor portion is not present.
11. The antenna device according to claim 1, wherein the additional conductor portion is a separate component from the conductor main body portion and is fixed to or integrated with the conductor main body portion.
12. The antenna device according to claim 1, wherein the first antenna is an AM/FM antenna, and a capacitive element of the AM/FM antenna includes the conductor main body portion and the additional conductor portion.
13. The antenna device according to claim 1, wherein the conductor main body portion extends in a horizontal direction, and the additional conductor portion extends in the horizontal direction or a vertical direction from a vicinity of an end portion of the conductor main body portion toward an outside thereof.
14. The antenna device according to claim 1, wherein the first antenna includes the conductor main body portion and the additional conductor portion.
15. The antenna device according to claim 1, wherein the additional conductor portion is provided between the first antenna and the second antenna.
16. The antenna device according to claim 1, wherein the additional conductor portion extends in parallel with the edge of the conductor main body portion.
17. The antenna device according to claim 1, wherein the second antenna is a satellite-type antenna.
18. The antenna device according to claim 1, wherein the additional conductor portion reduces a variation in directivity of the second antenna.
19. The antenna device according to claim 1, wherein the additional conductor portion is formed in a strip shape which extends in parallel with the edge of the conductor main body portion.
20. The antenna device according to claim 1, wherein the additional conductor portion includes an interconnection portion that connects to the conductor main body portion, in a vicinity of an end portion of the additional conductor portion.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) FIG. 1 is a right side cross-sectional view illustrating a structure of Embodiment 1 (case where an SDARS antenna is arranged in front of an AM/FM antenna) of an antenna device according to the present invention.
(2) FIG. 2A is an exploded right side view illustrating a case where a separate additional conductor portion is added to a conductor main body portion of a capacitively loaded plate as a capacitive element included in the AM/FM antenna in Embodiment 1.
(3) FIG. 2B is a right side view illustrating a state where a separate conductor portion is connected to and fixed to the conductor main body portion of the capacitively loaded plate in Embodiment 1.
(4) FIG. 3A is a rear view illustrating the alignment of major structural portions of Embodiment 1 (view when the antenna device is seen from the front side).
(5) FIG. 3B is a right side view under the same conditions.
(6) FIG. 3C is a diagram explaining a dimensional relationship between the major structural portions of Embodiment 1.
(7) FIG. 4A is a right side view illustrating an electric field distribution in the conductor main body portion of the capacitively loaded plate and the additional conductor portion integrated therewith when a radio wave in an SDARS band is transmitted from the SDARS antenna in Embodiment 1.
(8) FIG. 4B is a rear view under the same conditions.
(9) FIG. 4C is a left side view under the same conditions.
(10) FIG. 5A is a diagram explaining a current state (phase: 0°) on a right side surface of the additional conductor portion and the conductor main body portion of the capacitively loaded plate in Embodiment 1.
(11) FIG. 5B is a diagram explaining a current state (phase: 180°) on the right side surface of the conductor portion under the same conditions.
(12) FIG. 6 is a diagram explaining a measurement model for verifying effects of Embodiment 1.
(13) FIG. 7 is a directivity characteristic diagram illustrating a relationship between an azimuth and a gain (dBic) at an elevation angle of 20°, which is directivity in a horizontal plane (XY plane) of the SDARS antenna as a patch antenna in the measurement model for verifying the effects of Embodiment 1.
(14) FIG. 8 is a directivity characteristic diagram illustrating a case where the elevation angle is 40° under the same conditions.
(15) FIG. 9 is a directivity characteristic diagram illustrating a case where the elevation angle is 60° under the same conditions.
(16) FIG. 10 is a diagram illustrating a comparison in average gain (unit: dBic) at an elevation angle of 20° among the SDARS antenna alone, a standard model (example of the related art) where the conductor portion is not added, and Embodiment 1 (measurement model).
(17) FIG. 11 is a diagram illustrating a case where the elevation angle is 30° under the same conditions.
(18) FIG. 12 is a diagram illustrating a case where the elevation angle is 40° under the same conditions.
(19) FIG. 13 is a diagram illustrating a case where the elevation angle is 50° under the same conditions.
(20) FIG. 14 is a diagram illustrating a case where the elevation angle is 60° under the same conditions.
(21) FIG. 15 is a diagram illustrating a comparison in minimum gain (unit: dBic) at an elevation angle of 20° among the SDARS antenna alone, the standard model (example of the related art) where the conductor portion is not added, and Embodiment 1 (measurement model).
(22) FIG. 16 is a diagram illustrating a case where the elevation angle is 30° under the same conditions.
(23) FIG. 17 is a diagram illustrating a case where the elevation angle is 40° under the same conditions.
(24) FIG. 18 is a diagram illustrating a case where the elevation angle is 50° under the same conditions.
(25) FIG. 19 is a diagram illustrating a case where the elevation angle is 60° under the same conditions.
(26) FIG. 20 is a diagram illustrating a comparison in ripple (maximum gain-minimum gain) at an elevation angle of 20° among the SDARS antenna alone, the standard model (example of the related art) where the conductor portion is not added, and Embodiment 1 (measurement model).
(27) FIG. 21 is a diagram illustrating a comparison in ripple when the elevation angle is 30° under the same conditions.
(28) FIG. 22 is a diagram illustrating a comparison in ripple when the elevation angle is 40° under the same conditions.
(29) FIG. 23 is a diagram illustrating a comparison in ripple when the elevation angle is 50° under the same conditions.
(30) FIG. 24 is a diagram illustrating a comparison in ripple when the elevation angle is 60° under the same conditions.
(31) FIG. 25A is a rear view illustrating an electric field distribution in the conductor main body portion of the capacitively loaded plate and the additional conductor portion integrated therewith when a radio wave in a frequency band of a GPS antenna is transmitted in a measurement model where major structural portions of Embodiment 2 (case where the GPS antenna is arranged in front of the AM/FM antenna) according to the present invention are arranged on a ground plane.
(32) FIG. 25B is a right side view under the same conditions.
(33) FIG. 25C is a left side view under the same conditions.
(34) FIG. 26A is a diagram illustrating a current state (phase: 0°) in a left side surface of the capacitively loaded plate and the additional conductor portion integrated therewith in Embodiment 2.
(35) FIG. 26B is a diagram illustrating a current state (phase: 180°) in the left side surface of the conductor portion under the same conditions.
(36) FIG. 27 is a graph illustrating a relationship an elevation angle of 10° to 90° and an average gain in the GPS antenna alone as a patch antenna, the standard model (example of the related art) where the conductor portion is not added, and a measurement model of Embodiment 2.
(37) FIG. 28A is a rear view illustrating major structural portions of Embodiment 3 (case where the SDARS antenna is arranged behind the AM/FM antenna).
(38) FIG. 28B is a right side view under the same conditions.
(39) FIG. 28C is a left side view under the same conditions.
(40) FIG. 29A is a rear view illustrating major structural portions of Embodiment 4 (case where the GPS antenna is arranged behind the AM/FM antenna).
(41) FIG. 29B is a right side view under the same conditions.
(42) FIG. 29C is a left side view under the same conditions.
(43) FIG. 30A is a rear view illustrating major structural portions of Embodiment 5 (case where the SDARS antenna and the GPS antenna are arranged in front of the AM/FM antenna).
(44) FIG. 30B is a right side view under the same conditions.
(45) FIG. 30C is a left side view under the same conditions.
(46) FIG. 31A is a rear view illustrating major structural portions of Embodiment 6 (case where the SDARS antenna is arranged in front of the AM/FM antenna and the GPS antenna is arranged behind the AM/FM antenna).
(47) FIG. 31B is a right side view under the same conditions.
(48) FIG. 31C is a left side view under the same conditions.
(49) FIG. 32A is a rear view illustrating major structural portions of Embodiment 7 (case where the GPS antenna is arranged in front of the AM/FM antenna and the SDARS antenna is arranged behind the AM/FM antenna).
(50) FIG. 32B is a right side view under the same conditions.
(51) FIG. 32C is a left side view under the same conditions.
(52) FIG. 33A is a right side view illustrating a configuration of a capacitively loaded plate of the AM/FM antenna according to Embodiment 8.
(53) FIG. 33B is a left side view under the same conditions.
(54) FIG. 34A is a right side view illustrating a configuration of a capacitively loaded plate of the AM/FM antenna according to Embodiment 9.
(55) FIG. 34B is a left side view under the same conditions.
(56) FIG. 35A is a right side view illustrating a configuration of a capacitively loaded plate of the AM/FM antenna according to Embodiment 10.
(57) FIG. 35B is a left side view under the same conditions.
(58) FIG. 36A is a left side view illustrating an example of the related art of an antenna device when an SDARS antenna or a GPS antenna is arranged in front of an AM/FM antenna.
(59) FIG. 36B is a perspective view illustrating a standard model in which the AM/FM antenna of the example of the related art, and an SDARS antenna or a GPS antenna are arranged on a ground plane.
(60) FIG. 36C is a rear view under the same conditions.
(61) FIG. 36D is a right side view under the same conditions.
(62) FIG. 36E is a diagram explaining the dimensions of respective portions of the standard model.
(63) FIG. 37 is a diagram illustrating an antenna measurement system.
(64) FIG. 38 is a diagram explaining a reference model of the SDARS antenna alone as a patch antenna.
(65) FIG. 39 is a directivity characteristic diagram illustrating a relationship between an azimuth and a gain at an elevation angle of 20°, which is horizontal plane directivity of the reference model.
(66) FIG. 40 is a directivity characteristic diagram illustrating a case where the elevation angle is 40° under the same conditions.
(67) FIG. 41 is a directivity characteristic diagram illustrating a case where the elevation angle is 60° under the same conditions.
(68) FIG. 42 is a directivity characteristic diagram illustrating a relationship between an azimuth and a gain at an elevation angle of 20°, which is horizontal plane directivity of the SDARS antenna in the standard model of FIG. 33B.
(69) FIG. 43 is a directivity characteristic diagram illustrating a case where the elevation angle is 40° under the same conditions.
(70) FIG. 44 is a directivity characteristic diagram illustrating a case where the elevation angle is 60° under the same conditions.
(71) FIG. 45 is a graph illustrating a relationship between an elevation angle and an average gain at a frequency of 2332.5 MHz in the reference model of the SDARS antenna alone, and a case in which the distance between the capacitively loaded plate of the AM/FM antenna and the SDARS antenna is 0 mm to 64 mm (substantially λ/2).
(72) FIG. 46 is a graph illustrating a relationship between an elevation angle and an average gain at a frequency of 2338.75 MHz under the same conditions.
(73) FIG. 47 is a graph illustrating a relationship between an elevation angle and an average gain at a frequency of 2345 MHz under the same conditions.
(74) FIG. 48 is a graph illustrating a relationship between an elevation angle and a minimum gain at a frequency of 2332.5 MHz in the reference model of the SDARS antenna alone, and a case in which the distance between the capacitively loaded plate of the AM/FM antenna and the SDARS antenna is 0 mm to 64 mm.
(75) FIG. 49 is a graph illustrating a relationship between an elevation angle and a minimum gain at a frequency of 2338.75 MHz under the same conditions.
(76) FIG. 50 is a graph illustrating a relationship between an elevation angle and a minimum gain at a frequency of 2345 MHz under the same conditions.
(77) FIG. 51 is a graph illustrating a ripple (maximum gain-minimum gain) at each frequency in a frequency band of 2332.50 MHz to 2345.00 MHz when the elevation angle is 0°.
(78) FIG. 52 is a graph illustrating a relationship between an elevation angle and an average gain at a frequency of 1575.42 MHz in the reference model of the GPS antenna alone, and a case in which the distance between the capacitively loaded plate and the GPS antenna is 0 mm to 95 mm (substantially λ/2).
(79) FIG. 53A is a right side view illustrating an electric field distribution in the capacitively loaded plate in the standard model in which the AM/FM antenna and the SDARS antenna are combined.
(80) FIG. 53B is a rear view under the same conditions.
(81) FIG. 53C is a left side view under the same conditions.
(82) FIG. 54A is a rear view illustrating an electric field distribution in the capacitively loaded plate in the standard model in which the AM/FM antenna and the GPS antenna are combined.
(83) FIG. 54B is a right side view under the same conditions.
(84) FIG. 54C is a left side view under the same conditions.
DESCRIPTION OF EMBODIMENTS
(85) Hereinafter, preferable embodiments of the present invention will be described in detail with reference to the drawings. Identical or equivalent components, members, processes, and the like illustrated in each of the drawings are denoted by the same reference numerals, and the description thereof will be omitted. In addition, the embodiments are merely exemplary without limiting the present invention, and all the characteristics of the embodiments and combinations thereof are necessarily essential to the present invention.
Embodiment 1
(86) FIG. 1 illustrates Embodiment 1 of an antenna device according to the present invention where an SDARS antenna as a second antenna is arranged in front of an AM/FM antenna as a first antenna. In an antenna device 1, the AM/FM antenna 30 and an SDARS antenna 40 are accommodated in an internal space surrounded by an exterior case 5 which is constituted by a base 10 and a cover 20 covering the base 10 (for example, having a shark fin-shape). On the base 10, a circuit board 60 where an amplifier amplifying a received signal of the AM/FM antenna 30 and the like are mounted is fixed. The AM/FM antenna 30 includes: a capacitively loaded plate 35 as a capacitive element; and a coil element 32 of which one end (upper end) is connected to the capacitively loaded plate 35. The capacitively loaded plate 35 is supported in the vicinity of a ceiling (an upper side) of the cover 20, and the other end (lower end) of the coil element 32 is connected to the circuit board 60. The SDARS antenna 40 is fixed to the base 10 in front of the AM/FM antenna 30. The SDARS antenna 40 is a patch antenna. A hollow attachment bracket 7 that is attached through a vehicle roof is fixed to a bottom surface of the base 10, and cables (not illustrated in the drawing) for inputting received/transmitted signals of the AM/FM antenna 30 and the SDARS antenna 40 to a vehicle body side are led into the vehicle body through the attachment bracket 7.
(87) In FIG. 1, a right side and a left side in a left-right direction of the drawing are respectively a front side and a rear side of the antenna device, and an up-down direction of the drawing is an up-down direction of the antenna device. In addition, in FIG. 3A, a right side in a left-right direction of the drawing is a left side of the antenna device, and a right side is a left side of the antenna device. Here, a thin side of a capacitively loaded plate 35 is set as the front side of the antenna device. For convenience of description, a view illustrating the antenna device when seen from the front side is set as a rear view, a side surface on the left side when the antenna device is seen from the rear side is set as a left side surface, and a side surface on the right side when the antenna device is seen from the rear side is set as a right side surface. In addition, a front-rear direction may be expressed as a length direction, an up-down direction may be expressed as a height direction, and a left-right direction may be expressed as a width direction.
(88) Embodiment 1 is different from the example of the related art in that, as illustrated in FIGS. 2A and 2B, the capacitively loaded plate 35 formed of a conductor plate includes: a conductor main body portion 36 corresponding to the capacitively loaded plate 31 of the related art; and an additional conductor portion 37 including a parallel strip-shaped portion 37a that is formed in a strip shape with a predetermined width and extends in parallel to face a lower edge 36a of a right side surface of the conductor main body portion 36. The conductor main body portion 36 is formed of a conductor plate having a substantially U-shape in cross-section along the ceiling surface (upper side surface) of the cover 20. The additional conductor portion 37 includes an interconnection portion 37b that connects one end of the parallel strip-shaped portion 37a to the conductor main body portion 36 and allows the parallel strip-shaped portion 37a to face the front lower edge 36a of the right side surface of the conductor main body portion 36 at a short distance. The length of the parallel strip-shaped portion 37a along the lower edge 36a of the conductor main body portion 36 is set as a predetermined length corresponding to a frequency band of the SDARS antenna 40. Specifically, the length of the parallel strip-shaped portion 37a is set as a length that is ¼ of an effective wavelength in the frequency band of the SDARS antenna 40 (may be set as a length that is substantially ¼ of the effective wavelength). In addition, it is necessary that the predetermined-length portion of the additional conductor portion 37, that is, the parallel strip-shaped portion 37a is arranged to correspond to a region having a high electric field of the conductor main body portion 36 in the frequency band of the SDARS antenna 40. As described below, the front lower edge portion of the right side surface of the conductor main body portion 36 is the region having a high electric field. Therefore, the parallel strip-shaped portion 37a faces the front lower edge 36a of the right side surface of the conductor main body portion 36.
(89) In the capacitively loaded plate 35, the additional conductor portion 37 separate from the conductor main body portion 36 is prepared as illustrated in FIG. 2A, and the conductor main body portion 36 and the additional conductor portion 37 are electrically connected to each other by welding, soldering, riveting, spring contact, or the like on a connection portion 39 therebetween as illustrated in FIG. 2B. The conductor main body portion 36 and the additional conductor portion 37 may be formed and processed as an integrated product in advance.
(90) FIG. 3A is a rear view (view when the antenna device is seen from the front side) illustrating the alignment of the capacitively loaded plate 35 and the SDARS antenna 40, which are major structural portions according to Embodiment 1, on a ground plane 70. FIG. 3B is a right side view under the same conditions. FIG. 3C is a diagram illustrating a dimensional relationship of the additional conductor portion 37 included in the capacitively loaded plate 35 according to Embodiment 1. The coil element connected to the capacitively loaded plate 35 is not illustrated in the drawing. The ground plane 70 is a metal plate corresponding to the vehicle roof. A dimension of the conductor main body portion 36 of the capacitively loaded plate 35 and a height position thereof from the ground plane 70 are the same as those of the capacitively loaded plate 31 in the example of the related art. Regarding the parallel strip-shaped portion 37a of the additional conductor portion 37 illustrated in FIG. 3C, a length L2 is 28 mm, a width W2 is 3 mm, and a length G of the interconnection portion 37b (distance between the conductor main body portion 36 and the parallel strip-shaped portion 37a facing each other) is 3 mm. In consideration of a free space, the length L2 of the parallel strip-shaped portion 37a may be ¼ (≅32 mm) of a wavelength of an SDARS frequency. However, in the case of Embodiment 1, the parallel strip-shaped portion 37a is accommodated in the exterior case 5 including the base 10 and the cover 20 formed of a resin. Therefore, due to a wavelength shortening effect, L2 is 28 mm that is substantially ¼ of the effective wavelength and is shorter than that in the case of the free space. A dimensional relationship between structural components other than the additional conductor portion 37 is the same as that illustrated in FIG. 36E of the example of the related art.
(91) In the alignment and the dimensional relationship illustrated in FIGS. 3A to 3C, when a radio wave (left circularly polarized wave) in an SDARS band is transmitted from the SDARS antenna 40, an electric field distribution in the capacitively loaded plate 35 (the conductor main body portion 36 and the additional conductor portion 37) of the AM/FM antenna is illustrated in FIGS. 4A to 4C. FIG. 4A is a right side view, FIG. 4B is a rear view, and FIG. 4C is a left side view. In FIGS. 4A to 4C, a bright portion (light-colored portion) is a portion having a high electric field. It is understood from FIG. 4A that the electric field of the lower edge portion of the right side front surface of the conductor main body portion 36 is high, and the electric field of the additional conductor portion 37 facing the lower edge portion is also high (refer to the inside of frames in FIGS. 4A and 4B).
(92) In addition, FIG. 5A illustrates a current distribution (phase: 0°) of the right side surface of the capacitively loaded plate 35 (the conductor main body portion 36 and the additional conductor portion 37), and FIG. 5B illustrates a current distribution (phase: 180°) of the right side surface of the capacitively loaded plate. The size of an arrow represents the amount of a current, and the direction of an arrow represents a flowing direction of a current. In addition, the density of arrows represents the intensity of a current. It is understood from these drawings that the direction of a current flowing through a portion (in a rectangular frame P2) of the additional conductor portion 37 is opposite to the direction of a current flowing through the surface of the conductor main body portion of the lower edge portion (in a rectangular frame P1 of FIGS. 5A and 5B) of the right side front surface of the conductor main body portion 36 in the capacitively loaded plate 35. That is, the direction of the current in the lower edge portion (in the rectangular frame P1) of the right side front surface of the conductor main body portion 36 is opposite to the direction of the current flowing through the surface of the portion (in the rectangular frame P2) of the additional conductor portion 37 facing the lower edge portion, and the current in the rectangular frame P1 and the current in the rectangular frame P2 offset each other. As a result, disturbance (deviation) in directional characteristics caused by the high electric field in the lower edge portion of the right side front surface of the conductor main body portion 36 can be reduced. This verified data will be described below with reference to FIGS. 7 to 24.
(93) FIG. 6 is a diagram explaining a measurement model for verifying effects of Embodiment 1, in which the SDARS antenna 40 as a patch antenna, the capacitively loaded plate 35 (including the conductor main body portion 36 and the additional conductor portion 37), and the coil element (not illustrated in the drawing) are provided on the ground plane 70, and the three orthogonal axes X, Y, and Z are defined as illustrated in the drawing. The XY plane is positioned on the ground plane 70, the X axis is a front-rear direction of the capacitively loaded plate 35 (the rear direction is +), the Y axis is a left-right direction of the capacitively loaded plate 35, and the Z axis is a direction perpendicular to the ground plane 70. Dimensions and position relationships (mutual distances) of the respective members of the measurement model of FIG. 6 other than the additional conductor portion 37 are the same as those of the standard model of FIG. 36E.
(94) FIG. 7 is a directivity characteristic diagram illustrating a relationship between an azimuth and a circular polarization gain (dBic) at an elevation angle of 20°, which is directivity on a horizontal plane (XY plane) of the SDARS antenna as a patch antenna in the measurement model of FIG. 6. FIG. 8 is a directivity characteristic diagram illustrating a case where the elevation angle is 40° under the same conditions. FIG. 9 is a directivity characteristic diagram illustrating a case where the elevation angle is 60° under the same conditions. In particular, in the case of the elevation angle of 60° in FIG. 9, it is understood that the horizontal plane directional characteristics in a frequency band of 2332.5 MHz to 2345 MHz are similar to a circle. That is, it can be seen that the directivity can be improved to be equivalent to the directivity of the SDARS antenna alone.
(95) FIG. 10 is a diagram explaining a comparison in circular polarization average gain (unit: dBic) at an elevation angle of 20° among the SDARS antenna alone, the standard model (example of the related art) where the conductor portion is not added, and Embodiment 1 (measurement model). FIG. 11 is a diagram illustrating a case where the elevation angle is 30° under the same conditions. FIG. 12 is a diagram illustrating a case where the elevation angle is 40° under the same conditions. FIG. 13 is a diagram illustrating a case where the elevation angle is 50° under the same conditions. FIG. 14 is a diagram illustrating a case where the elevation angle is 60° under the same conditions. As seen in FIGS. 10 to 14, regarding the circular polarization average gain, there is no significant difference among the antenna alone, the standard model, and Embodiment 1 (measurement model) in a frequency band of 2332.5 MHz to 2345 MHz.
(96) FIG. 15 is a diagram explaining a comparison in circular polarization minimum gain (unit: dBic) at an elevation angle of 20° among the SDARS antenna alone, the standard model (example of the related art) where the conductor portion is not added, and Embodiment 1 (measurement model). FIG. 16 is a diagram illustrating a case where the elevation angle is 30° under the same conditions. FIG. 17 is a diagram illustrating a case where the elevation angle is 40° under the same conditions. FIG. 18 is a diagram illustrating a case where the elevation angle is 50° under the same conditions. FIG. 19 is a diagram illustrating a case where the elevation angle is 60° under the same conditions. As seen in FIGS. 15 to 19, the circular polarization minimum gain of Embodiment 1 (measurement model) is significantly improved as compared to that of the standard model and is equivalent to that of the SDARS antenna alone in a frequency band of 2332.5 MHz to 2345 MHz.
(97) FIG. 20 is a diagram explaining a comparison in ripple (maximum gain-minimum gain) at an elevation angle of 20° among the SDARS antenna alone, the standard model (example of the related art) where the conductor portion is not added, and Embodiment 1 (measurement model). FIG. 21 is a diagram illustrating a comparison in ripple when the elevation angle is 30° under the same conditions. FIG. 22 is a diagram illustrating a comparison in ripple when the elevation angle is 40° under the same conditions. FIG. 23 is a diagram illustrating a comparison in ripple when the elevation angle is 50° under the same conditions. FIG. 24 is a diagram illustrating a comparison in ripple when the elevation angle is 60° under the same conditions. As seen in FIGS. 20 to 24, the ripple of Embodiment 1 (measurement model) is significantly improved as compared to that of the standard model and is equivalent to that of the SDARS antenna alone in a frequency band of 2332.5 MHz to 2345 MHz. That is, it is possible to make a configuration that the presence of the capacitively loaded plate 35 does not have an adverse influence on the directional characteristic of the SDARS antenna.
(98) According to the embodiment, the following effects can be exhibited.
(99) (1) As illustrated in FIGS. 1 to 5A and 5B, when the first antenna (AM/FM antenna 30) and the second antenna (SDARS antenna 40) having different frequency bands are provided in the common exterior case 5, the additional conductor portion 37 extends out from the conductor main body portion 36 as the capacitively loaded plate of the AM/FM antenna 30, the parallel strip-shaped portion 37a of the additional conductor portion 37 is arranged to correspond to a region having a high electric field of the conductor main body portion 36 in the frequency band of the SDARS antenna 40, and the length of the parallel strip-shaped portion 37a is set as a length that is substantially ¼ of the effective wavelength in the frequency band of the SDARS antenna 40. Therefore, the horizontal plane directivity of the SDARS antenna 40 can be made to approach to theoretical non-directivity. That is, the current in a direction opposite to the current direction in the region having a high electric field of the conductor main body portion 36 is induced to the parallel strip-shaped portion 37a. As a result, the current in the region having a high electric field of the conductor main body portion 36 is canceled out, and a variation in directivity caused by the region can be reduced.
(100) (2) Accordingly, even when the separation distance between the AM/FM antenna 30 and the SDARS antenna 40 is not sufficiently large, excellent directional characteristics close to non-directivity in which a difference between the maximum gain and the minimum gain of the SDARS antenna 40 is small can be obtained. For example, even when the separation distance between the AM/FM antenna 30 and the SDARS antenna 40 is substantially within ½ of a wavelength λ.sub.SDARS in the frequency band of the SDARS antenna 40, excellent directional characteristics close to non-directivity can be secured, and the size of the exterior case 5 can be reduced. In the measurement model of FIG. 6, the distance G1 between the capacitively loaded plate of the AM/FM antenna and the SDARS antenna defined by FIG. 36A is 10.3 mm (shorter than λ.sub.SDARS/8), and antenna characteristics that are significantly shorter than the ½ wavelength of the SDARS band but are equivalent to those of the reference model of the SDARS antenna alone can be obtained.
Embodiment 2
(101) Embodiment 2 of the antenna device according to the present invention has a configuration in which the GPS antenna 50 as the second antenna is provided instead of the SDARS antenna according to Embodiment 1 illustrated in FIG. 1 (that is, the GPS antenna 50 is arranged in front of the AM/FM antenna). In this case, as illustrated in FIGS. 25A to 25C, the capacitively loaded plate 35 includes: the conductor main body portion 36; and an additional conductor portion 38 including a parallel strip-shaped portion 38a extending in parallel to face a front lower edge 36b of a left side surface of the conductor main body portion 36. The length of the parallel strip-shaped portion 38a along the front lower edge 36b of the conductor main body portion 36 is set as a length 45 mm) that is ¼ of an effective wavelength in the frequency band of the GPS antenna 50 (may be set as a length that is substantially ¼ of the effective wavelength). In addition, it is necessary that the parallel strip-shaped portion 38a is arranged to correspond to a region having a high electric field of the conductor main body portion 36 in the frequency band of the GPS antenna 50.
(102) FIG. 25A is a rear view (view when the antenna device is seen from the front side) illustrating an electric field distribution on the capacitively loaded plate (the conductor main body portion and the conductor portion) when a radio wave (right circularly polarized wave) in the frequency band of the GPS antenna is transmitted in a measurement model where major structural portions of Embodiment 2 are arranged on the ground plane 70. FIG. 25B is a right side view under the same conditions. FIG. 25C is a left side view under the same conditions. In FIGS. 25A to 25C, a bright portion (light-colored portion) is a portion having a high electric field. It is understood from FIGS. 25A to 25C that the electric field of a lower edge portion of a left side front surface of the conductor main body portion 36 is high, and the electric field of the additional conductor portion 38 facing the lower edge portion is also high.
(103) In addition, FIG. 26A illustrates a current distribution (phase: 0°) of the left side surface of the capacitively loaded plate 35 (the conductor main body portion 36 and the additional conductor portion 38), and FIG. 26B illustrates a current distribution (phase: 180°) of the left side surface of the capacitively loaded plate 35. It is understood from these diagrams that the direction of a current (current flowing through the surface of the conductor main body portion) of the lower edge portion (in a rectangular frame P3 of FIGS. 26A and 26B) of the left side front surface of the conductor main body portion 36 in the capacitively loaded plate 35 is opposite to the direction of a current (current flowing through the surface of the additional conductor portion) of a portion (in a rectangular frame P4 of FIGS. 26A and 26B) of the additional conductor portion 38 facing the lower edge portion. The current in the rectangular frame P3 and the current in the rectangular frame P4 offset each other, and thus disturbance (deviation) in directional characteristics caused by the high electric field in the lower edge portion of the left side front surface of the conductor main body portion 36 can be reduced.
(104) FIG. 27 is a graph illustrating a relationship an elevation angle of 10° to 90° and a circular polarization average gain (dBic) in the GPS antenna alone as a patch antenna, the standard model (example of the related art) where the conductor portion is not added, and Embodiment 2 (measurement model). It is understood from this diagram that the circular polarization average gain of the measurement model of Embodiment 2 is higher than that of the standard model and is a value close to that of the GPS antenna alone. In particular, it can be confirmed that the improvement degree becomes more significant at a larger evaluation angle and the circular polarization average gain is improved by 1.9 dBic at an elevation angle of 90°, by 1.5 dBic at an elevation angle of 80°, by 0.8 dBic at an elevation angle of 70°, and by 0.3 dBic at an elevation angle of 60°. In addition, at an elevation angle of 90° axis ratio, the average gain of the model of the GPS antenna alone is 1.5 dB as a target value, whereas the average gain of the standard model is 7.7 dB, and the average gain of Embodiment 2 is 2.0 dB. Therefore, it is confirmed that the average gain of Embodiment 2 is improved.
(105) As described above, it can be seen from FIG. 27 that, according to the Embodiment 2, even when the separation distance between the AM/FM antenna 30 and the GPS antenna 50 is substantially ½ or less of λ.sub.GPS, excellent antenna characteristic as the GPS antenna can be obtained.
Embodiment 3
(106) Embodiment 3 of the antenna device according to the present invention has a configuration in which the SDARS antenna is arranged behind the AM/FM antenna instead of being disposed in front of the AM/FM antenna as in Embodiment 1 illustrated in FIG. 1.
(107) FIG. 28A is a rear view (view when the antenna device is seen from the front side) illustrating a model in which major structural portions of Embodiment 3 of the antenna device according to the present invention are arranged on the ground plane 70, and the SDARS antenna is arranged behind the AM/FM antenna. FIG. 28B is a right side view under the same conditions. FIG. 28C is a left side view under the same conditions. In this antenna device, as illustrated in FIG. 1, the AM/FM antenna 30 and the SDARS antenna 40 therebehind are accommodated in an internal space surrounded by the exterior case 5 which is constituted by the base 10 and the cover 20 covering the base (for example, having a shark fin-shape).
(108) In this case, the capacitively loaded plate 35 formed of a conductor plate includes: the conductor main body portion 36; and the additional conductor portion 37 including the parallel strip-shaped portion 37a extending in parallel to a rear side lower edge 36c of the conductor main body portion 36. A region having a high electric field of the conductor main body portion 36 is the rear side lower edge portion of the right side surface of the conductor main body portion 36. Therefore, the parallel strip-shaped portion 37a of the additional conductor portion 37 is arranged to face the rear side lower edge 36c of the right side surface of the conductor main body portion 36 at a short distance. The length of the parallel strip-shaped portion 37a along the rear side lower edge 36c of the conductor main body portion 36 is set as a length that is ¼ of an effective wavelength in the frequency band of the SDARS antenna 40 (may be set as a length that is substantially ¼ of the effective wavelength).
(109) The other configurations are similar to those of Embodiment 1, and the similar effects as those of Embodiment 1 can be obtained.
Embodiment 4
(110) Embodiment 4 of the antenna device according to the present invention has a configuration in which the GPS antenna is arranged behind the AM/FM antenna instead of being disposed in front of the AM/FM antenna as in Embodiment 2 illustrated in FIGS. 25A to 25C.
(111) FIG. 29A is a rear view (view when the antenna device is seen from the front side) illustrating a model in which major structural portions of Embodiment 4 of the antenna device according to the present invention are arranged on the ground plane 70, and the GPS antenna is arranged behind the AM/FM antenna. FIG. 29B is a right side view under the same conditions. FIG. 29C is a left side view under the same conditions. In the antenna device, as illustrated in FIG. 1, the AM/FM antenna 30 and the GPS antenna 50 therebehind are accommodated in an internal space surrounded by the exterior case 5 which is constituted by the base 10 and the cover 20 covering the base (for example, having a shark fin-shape).
(112) In this case, the capacitively loaded plate 35 formed of a conductor plate includes: the conductor main body portion 36; and the additional conductor portion 38 including the parallel strip-shaped portion 38a extending in parallel to a rear side lower edge 36c of the conductor main body portion 36. A region having a high electric field of the conductor main body portion 36 is the rear side lower edge portion of the right side surface of the conductor main body portion 36. Therefore, the parallel strip-shaped portion 38a of the additional conductor portion 38 is arranged to face the rear side lower edge 36c of the right side surface of the conductor main body portion 36 at a short distance. The length of the parallel strip-shaped portion 38a along the rear side lower edge 36c of the conductor main body portion 36 is set as a length that is ¼ of an effective wavelength in the frequency band of the GPS antenna 50 (may be set as a length that is substantially ¼ of the effective wavelength).
(113) The other configurations are similar to those of Embodiment 2, and the similar effects as those of Embodiment 2 can be obtained.
Embodiment 5
(114) Embodiment 5 of the antenna device according to the present invention has a configuration in which the SDARS antenna of Embodiment 1 illustrated in FIG. 1 is arranged in front of the AM/FM antenna and the GPS antenna is additionally provided in front of the AM/FM antenna but behind the SDARS antenna.
(115) FIG. 30A is a rear view (view when the antenna device is seen from the front side) illustrating a model in which major structural portions of Embodiment 5 of the antenna device according to the present invention are arranged on the ground plane 70, and the SDARS antenna and the GPS antenna are arranged in front of the AM/FM antenna. FIG. 30B is a right side view under the same conditions. FIG. 30C is a left side view under the same conditions. In the antenna device, as illustrated in FIG. 1, the AM/FM antenna 30, and the SDARS antenna 40 and the GPS antenna 50 in front thereof are accommodated in an internal space surrounded by the exterior case 5 which is constituted by the base 10 and the cover 20 covering the base (for example, having a shark fin-shape). Here, the AM/FM antenna 30 corresponds to the first antenna, the SDARS antenna 40 corresponds to the second antenna, and the GPS antenna 50 corresponds to the third antenna. In Embodiment 5, the SDARS antenna 40, the GPS antenna 50, and the AM/FM antenna 30 are disposed in this order from the front side. However, the arrangement of the SDARS antenna 40 and the GPS antenna 50 may be reversed.
(116) The capacitively loaded plate 35 formed of a conductor plate includes: the conductor main body portion 36; the additional conductor portion 37 (corresponding to the SDARS antenna 40) including the parallel strip-shaped portion 37a extending in parallel to the front lower edge 36a of the right side surface of the conductor main body portion 36; and the additional conductor portion 38 (corresponding to the GPS antenna 50) including the parallel strip-shaped portion 38a extending in parallel to the front lower edge 36b of the left side surface of the conductor main body portion 36. The length of the parallel strip-shaped portion 37a along the front lower edge 36a of the conductor main body portion 36 is set as a length that is ¼ of an effective wavelength in the frequency band of the SDARS antenna 40 (may be set as a length that is substantially ¼ of the effective wavelength). The length of the parallel strip-shaped portion 38a along the front lower edge 36a of the conductor main body portion 36 is set as a length that is ¼ of an effective wavelength in the frequency band of the GPS antenna 50 (may be set as a length that is substantially ¼ of the effective wavelength).
(117) The other configurations may be considered to be similar to those of Embodiment 1. In Embodiment 5, even when the SDARS antenna 40 and the GPS antenna 50 are arranged in front of the AM/FM antenna 30, disturbance in the directional characteristics of the respective antennas 40 and 50 caused by the presence of both the SDARS antenna 40 and the GPS antenna 50 in the vicinity of the AM/FM antenna 30 can be reduced, excellent directional characteristics close to non-directivity can be secured, and the size of the case 5 can be reduced.
Embodiment 6
(118) Embodiment 6 of the antenna device according to the present invention has a configuration in which the SDARS antenna of Embodiment 1 illustrated in FIG. 1 is arranged in front of the AM/FM antenna and the GPS antenna is additionally provided behind the AM/FM antenna.
(119) FIG. 31A is a rear view (view when the antenna device is seen from the front side) illustrating a model in which major structural portions of Embodiment 6 of the antenna device according to the present invention are arranged on the ground plane 70, and the SDARS antenna is arranged in front of the AM/FM antenna, and the GPS antenna is arranged behind the AM/FM antenna. FIG. 31B is a right side view under the same conditions. FIG. 31C is a left side view under the same conditions. In the antenna device, as illustrated in FIG. 1, the AM/FM antenna 30, the SDARS antenna 40 in front thereof, and the GPS antenna 50 behind the AM/FM antenna 30 are accommodated in an internal space surrounded by the exterior case 5 which is constituted by the base 10 and the cover 20 covering the base (for example, having a shark fin-shape). That is, the SDARS antenna 40, the AM/FM antenna 30, and the GPS antenna 50 are arranged in this order from the front side. Here, the AM/FM antenna 30 corresponds to the first antenna, the SDARS antenna 40 corresponds to the second antenna, and the GPS antenna 50 corresponds to the third antenna.
(120) The capacitively loaded plate 35 formed of a conductor plate includes: the conductor main body portion 36; the additional conductor portion 37 (corresponding to the SDARS antenna 40) including the parallel strip-shaped portion 37a extending in parallel to the front lower edge 36a of the right side surface of the conductor main body portion 36; and the additional conductor portion 38 (corresponding to the GPS antenna 50) including the parallel strip-shaped portion 38a extending in parallel to the rear side lower edge 36c of the right side surface of the conductor main body portion 36. The length of the parallel strip-shaped portion 37a along the front lower edge 36a of the right side surface of the conductor main body portion 36 is set as a length that is ¼ of an effective wavelength in the frequency band of the SDARS antenna 40 (may be set as a length that is substantially ¼ of the effective wavelength). The length of the parallel strip-shaped portion 38a along the rear side lower edge 36c of the right side surface of the conductor main body portion 36 is set as a length that is ¼ of an effective wavelength in the frequency band of the GPS antenna 50 (may be set as a length that is substantially ¼ of the effective wavelength).
(121) The other configurations may be considered to be similar to those of Embodiment 1. In Embodiment 6, even when the SDARS antenna 40 is arranged in front of the AM/FM antenna 30 and the GPS antenna 50 is arranged behind the AM/FM antenna 30, disturbance in the directional characteristics of the respective antennas 40 and 50 caused by the presence of both the SDARS antenna 40 and the GPS antenna 50 in the vicinity of the AM/FM antenna 30 can be reduced, excellent directional characteristics close to non-directivity can be secured in both of the antennas 40 and 50, and the size of the case 5 can be reduced.
Embodiment 7
(122) Embodiment 7 of the antenna device according to the present invention has a configuration in which the SDARS antenna of Embodiment 1 illustrated in FIG. 1 is arranged behind the AM/FM antenna and the GPS antenna is additionally provided in front of the AM/FM antenna.
(123) FIG. 32A is a rear view (view when the antenna device is seen from the front side) illustrating a model in which major structural portions of Embodiment 7 of the antenna device according to the present invention are arranged on the ground plane 70, and the GPS antenna is arranged in front of the AM/FM antenna and the SDARS antenna is arranged behind the AM/FM antenna. FIG. 32B is a right side view under the same conditions. FIG. 32C is a left side view under the same conditions. In the antenna device, as illustrated in FIG. 1, the AM/FM antenna 30, the GPS antenna 50 in front thereof, and the SDARS antenna 40 behind the AM/FM antenna 30 are accommodated in an internal space surrounded by the exterior case 5 which is constituted by the base 10 and the cover 20 covering the base (for example, having a shark fin-shape). That is, the GPS antenna 50, the AM/FM antenna 30, and the SDARS antenna 40 are arranged in this order from the front side. Here, the AM/FM antenna 30 corresponds to the first antenna, the SDARS antenna 40 corresponds to the second antenna, and the GPS antenna 50 corresponds to the third antenna.
(124) The capacitively loaded plate 35 formed of a conductor plate includes: the conductor main body portion 36; the additional conductor portion 38 (corresponding to the GPS antenna 50) including the parallel strip-shaped portion 38a extending in parallel to the front lower edge 36b of the left side surface of the conductor main body portion 36; and the additional conductor portion 37 (corresponding to the SDARS antenna 40) including the parallel strip-shaped portion 37a extending in parallel to the rear side lower edge 36c of the right side surface of the conductor main body portion 36. The length of the parallel strip-shaped portion 38a along the front lower edge 36a of the left side surface of the conductor main body portion 36 is set as a length that is ¼ of an effective wavelength in the frequency band of the GPS antenna 50 (may be set as a length that is substantially ¼ of the effective wavelength). In addition, the length of the parallel strip-shaped portion 37a along the rear side lower edge 36c of the right side surface of the conductor main body portion 36 is set as a length that is ¼ of an effective wavelength in the frequency band of the SDARS antenna 40 (may be set as a length that is substantially ¼ of the effective wavelength).
(125) The other configurations may be considered to be similar to those of Embodiment 1. In Embodiment 7, even when the GPS antenna 50 is arranged in front of the AM/FM antenna 30 and the SDARS antenna 40 is arranged behind the AM/FM antenna 30, disturbance in the directional characteristics of the respective antennas 40 and 50 caused by the presence of both the SDARS antenna 40 and the GPS antenna 50 in the vicinity of the AM/FM antenna 30 can be reduced, excellent directional characteristics close to non-directivity can be secured, and the size of the case 5 can be reduced.
Embodiment 8
(126) FIG. 33A is a right side view illustrating a configuration of a capacitively loaded plate of the AM/FM antenna (first antenna) according to Embodiment 8. FIG. 33B is a left side view under the same conditions. In this case, the capacitively loaded plate 35 formed of a conductor plate includes: the conductor main body portion 36; and an additional conductor portion 371 (corresponding to the second antenna such as the SDARS antenna or the GPS antenna) including a parallel strip-shaped portion 371a extending in parallel to face a rear edge 36d of the right side surface. The length of the parallel strip-shaped portion 371a along the rear edge 36d of the right side surface of the conductor main body portion 36 is set as a length that is ¼ of an effective wavelength in the frequency band of the second antenna (may be set as a length that is substantially ¼ of the effective wavelength). Configurations other than the configuration of the capacitively loaded plate are similar to those of Embodiment 1.
(127) The configuration of Embodiment 8 is effective when a region having a high electric field of the conductor main body portion 36 in the frequency band of the second antenna is in the vicinity of the rear edge 36d of the right side surface of the conductor main body portion 36 and the parallel strip-shaped portion 371a is arranged to face the rear edge 36d. That is, disturbance in directional characteristic caused by the presence of the second antenna in the vicinity of the AM/FM antenna can be reduced.
Embodiment 9
(128) FIG. 34A is a right side view illustrating a configuration of a capacitively loaded plate of the AM/FM antenna (first antenna) according to Embodiment 9. FIG. 34B is a left side view under the same conditions. In this case, the capacitively loaded plate 35 formed of a conductor plate includes: the conductor main body portion 36; and an additional conductor portion 372 (corresponding to the second antenna such as the SDARS antenna or the GPS antenna) including a parallel strip-shaped portion 372a extending in parallel to face the rear side lower edge 36c of the right side surface of the conductor main body portion 36. Here, the additional conductor portion 372 is formed to be positioned further inside of the lower edge of the conductor main body portion 36. For example, by separating a part of the conductor main body portion 36 using an inverted L-shaped notch 370, the additional conductor portion 372 integrated with the conductor main body portion 36 can be formed. The length of the parallel strip-shaped portion 372a along the rear side lower edge 36c of the right side surface of the conductor main body portion 36 is set as a length that is ¼ of an effective wavelength in the frequency band of the second antenna (may be set as a length that is substantially ¼ of the effective wavelength). Configurations other than the configuration of the capacitively loaded plate are similar to those of Embodiment 1.
(129) The configuration of Embodiment 9 is effective when a region having a high electric field of the conductor main body portion 36 in the frequency band of the second antenna is in the vicinity of the rear side lower edge 36c of the right side surface of the conductor main body portion 36 and the parallel strip-shaped portion 372a is arranged to face the rear side lower edge 36c. That is, disturbance in directional characteristic caused by the presence of the second antenna in the vicinity of the AM/FM antenna can be reduced.
Embodiment 10
(130) FIG. 35A is a right side view illustrating a configuration of a capacitively loaded plate of the AM/FM antenna (first antenna) according to Embodiment 10. FIG. 35B is a left side view under the same conditions. In this case, the capacitively loaded plate 35 formed of a conductor plate includes: the conductor main body portion 36; and an additional conductor portion 373 (corresponding to the second antenna such as the SDARS antenna or the GPS antenna) including a parallel strip-shaped portion 373a extending in parallel to face the front lower edge 36a of the right side surface of the conductor main body portion 36. Here, the additional conductor portion 373 is formed to be positioned further inside of the lower edge of the conductor main body portion 36. For example, by separating a part of the conductor main body portion 36 using an inverted L-shaped notch 371, the additional conductor portion 373 integrated with the conductor main body portion 36 can be formed. The length of the parallel strip-shaped portion 373a along the front lower edge 36a of the right side surface of the conductor main body portion 36 is set as a length that is ¼ of an effective wavelength in the frequency band of the second antenna (may be set as a length that is substantially ¼ of the effective wavelength). Configurations other than the configuration of the capacitively loaded plate are similar to those of Embodiment 1.
(131) The configuration of Embodiment 10 is effective when a region having a high electric field of the conductor main body portion 36 in the frequency band of the second antenna is in the vicinity of the front lower edge 36a of the right side surface of the conductor main body portion 36 and the parallel strip-shaped portion 373a is arranged to face the front lower edge 36a. That is, disturbance in directional characteristics caused by the presence of the second antenna in the vicinity of the AM/FM antenna can be reduced.
(132) Hereinabove, the present invention has been described using the embodiments as examples. However, it is understood by those skilled in the art that the respective components or the respective treatment processes of the embodiments can be modified in various ways within the scope described in the claims. Hereinafter, modification examples will be simply described.
(133) In each of the embodiments of the present invention, the AM/FM antenna is used as an example of the first antenna, and the SDARS antenna or the GPS antenna is used as an example of the second antenna having a frequency band different from that of the first antenna. However, the present invention is also applicable to a case where antennas having different frequency bands are combined.
(134) The position where the additional conductor portion is extended out from the conductor main body portion of the first antenna is appropriately modifiable according to the positional relationship between the first antenna and the second antenna, and is not limited to the arrangement of each of the embodiments.
REFERENCE SIGNS LIST
(135) 1: antenna device 5: exterior case 7: attachment bracket 10: base 20: cover 30: AM/FM antenna 31, 35: capacitively loaded plate 32: coil element 36: conductor main body portion 37, 38, 371, 372, 373: additional conductor portion 37a, 38a, 371a, 372a, 373a: parallel strip-shaped portion 39: connection portion 40: SDARS antenna 50: GPS antenna 60: circuit board 70: ground plane
