JP4594879B2 - Automotive antenna - Google Patents

Description

  The present invention relates to a structure of an in-vehicle antenna.

  Vehicles are equipped with antennas for receiving amplitude modulation (AM) and frequency modulation (FM) broadcasts from various radio stations. In many cases, such an antenna is used as a rod antenna mounted on a vehicle fender, a vehicle roof, or a certain location on the vehicle. However, such a rod antenna has a problem of deteriorating the appearance of the vehicle (see, for example, Patent Documents 1 to 3).

  Therefore, a glass antenna in which these antennas are arranged on a glass surface has been proposed (for example, see Patent Document 1). Such a glass antenna is disposed on the surface of the rear glass 4 of the vehicle 1 shown in FIG. 14, and the appearance of the antenna is shown in FIG. The rear glass 4 is provided with an AM glass antenna 100 having a grid-like antenna pattern, a defogger line 5 for fogging, and an antenna corresponding to a frequency other than AM, such as an FM antenna, on the same surface of the rear glass 4. ing. The fogging defogger line 5 is arranged over a considerable area of the rear glass 4. The AM glass antenna 100 is placed in the upper space, and the antennas other than AM are placed in the empty space 102 on the surface of the rear glass 4 so that the defogger line 5 for fogging and the AM glass antenna 100 do not overlap with the antenna pattern. Each is arranged.

  On the other hand, in Japan, AM radio broadcasts use frequencies of 522 to 1629 kHz, and their wavelengths are very long compared to FM radio broadcasts, TV broadcasts, etc., and the required antenna length is the same as that of TV antennas. It becomes very long compared to it. Since it is difficult to install such a long antenna on the surface of the rear glass 4 of the vehicle 1, the size of the AM glass antenna 100 necessarily functions as a very small antenna with respect to the wavelength. It becomes. In a minute antenna whose length is very short compared to such a wavelength, the induced reception voltage is proportional to the effective area of the antenna. Therefore, when the AM glass antenna 100 is disposed on the surface of the rear glass 4, it is necessary to secure an antenna area that can satisfy the required performance.

  However, since it is necessary for the antenna element not to obstruct the field of view from the rear glass 4, the arrangement position and area of the AM glass antenna 100 are limited, and the surface of the rear glass 4 is required by the design of the vehicle. If the distance cannot be increased, the area of the AM glass antenna 100 is further limited, and the required performance cannot be satisfied. This problem is particularly noticeable when an antenna corresponding to another frequency such as an FM antenna or a TV antenna is arranged on the same surface of the rear glass 4 as well as the AM glass antenna 100. There is a problem that antennas corresponding to frequencies other than the antenna 100 and the AM antenna cannot be arranged on the surface of the rear glass 4.

  Accordingly, a proposal has been made to arrange these antennas inside the rear spoiler 2 of the vehicle shown in FIG. 14 (see, for example, Patent Document 3). When a plurality of antennas corresponding to different frequencies are housed in the rear spoiler 2, the antennas must be arranged on the same plane in order to prevent electromagnetic interference between the antennas. It was. There is no problem if the rear spoiler 2 is large and the antennas can be arranged in the same plane inside the rear spoiler 2 in this way, but if the size of the rear spoiler 2 is small due to vehicle design requirements, Each antenna cannot be arranged on the same plane. Further, in recent years, with the development of electronics, it is required to accommodate not only conventional AM antennas and FM antennas but also more antennas corresponding to more frequencies than analog TV antennas, digital TV antennas, and the like. As a result, it becomes increasingly difficult for an AM antenna as a minute antenna to secure an area necessary for performance (see, for example, Patent Documents 4 and 5).

Japanese Patent Laid-Open No. 9-172315 JP-A-10-329615 JP 2001-102826 A JP 2003-309212 A JP 2004-179790 A

  To solve this problem, as shown in FIG. 11, the AM antenna 50 having a grid-like antenna pattern inside the rear spoiler 2 and the ultra-short wave antenna 30 such as an FM antenna and a TV antenna have a distance H. It is possible to arrange them in a stack. FIG. 10 shows the planar shapes of the AM antenna 50 and the ultrahigh frequency antenna 30 that are arranged so as to overlap inside the rear spoiler 2. As shown in FIG. 10, the AM antenna 50 is an antenna pattern in which a plurality of long side direction elements 52 and a plurality of short side direction elements 54 are combined in a lattice shape, and one end of the AM antenna 50 is a grounding body at a feeding point 56. It is connected to the roof 6 of the vehicle 1. The AM antenna 50 is a necessary area for securing a reception voltage in which the area of the grating formed by the long side direction element 52 and the short side direction element 54 is induced, and it is necessary to increase this area in terms of performance. It becomes. For this reason, the AM antenna 50 occupies a large area. On the other hand, the ultrahigh frequency antenna 30 has a linear shape in which linear ultrahigh frequency elements 32 are connected to both sides of the feeding point 34. The ultra-short wave element 32 is arranged in parallel with the long-side direction element 52 of the AM antenna 50, and the length thereof is a certain length determined by the frequency of the received radio wave. Since the wavelength of the received radio wave is short, the length of the ultrashort wave antenna 30 is considerably smaller than that of the AM antenna 50. For this reason, when the AM antenna 50 and the ultrahigh frequency antenna 30 are arranged so as to overlap each other as shown in FIGS. 10 and 11, the large AM antenna 50 covers the small ultrahigh frequency antenna 30, so This causes a problem that the performance of the ultrashort-wave antenna 30 is degraded due to a wall that hinders transmission / reception of 30 radio waves.

  The arrows in FIG. 12 indicate the directions of currents flowing through the AM antenna 50 and the ultrahigh frequency antenna 30. At the time of transmission (or reception) of radio waves, in the AM antenna 50, the current from the feeding point 56 flows through the long side direction element 52 and the short side direction element 54 formed in a lattice shape to generate an electromagnetic field. Is emitted. On the other hand, in the ultrahigh frequency antenna 30, the current from the feeding point 34 flows to the ultrahigh frequency element 32, and an electromagnetic field is generated in the same manner as the AM antenna 50 to radiate radio waves. At this time, a current flows in parallel to the long-side element 52 of the AM antenna 50 and the ultrashort-wave element 32 of the ultrashort-wave antenna 30. However, when the directions of the currents flowing through the antenna elements parallel to each other in this way match, the electromagnetic fields generated by the respective antennas interfere with each other, causing a performance degradation due to the disturbance of the electromagnetic fields. In particular, since the performance of the ultra-short wave antenna 30 that is small in size and is covered by the AM antenna 50 is greatly deteriorated, the AM antenna 50 and the ultra-short wave antenna 30 cannot be stacked and stored in the rear spoiler 2 as described above. There was a problem.

  Therefore, the present invention provides an in-vehicle antenna capable of maintaining good performance even when a plurality of antennas corresponding to different frequencies are aggregated inside an exterior product such as a rear spoiler of a vehicle. Objective.

  An object of the present invention is a vehicle-mounted antenna in which a plurality of antennas corresponding to different frequency bands are arranged in a vehicle exterior made of a hollow body, and a linear feeding element having one end connected to the vehicle body, And a comb-shaped AM antenna having a plurality of comb-shaped elements arranged in parallel with the feed element in an orthogonal direction, and an ultra-high-frequency antenna having a linear ultra-high frequency element. The tooth elements extend in directions perpendicular to each other, and the ultra-short wave element is arranged at a predetermined distance from the feeding element and each comb-tooth element. Here, the ultra-short wave antenna may be a digital TV antenna, an analog TV antenna, or an FM antenna.

  INDUSTRIAL APPLICABILITY The present invention has an effect that each antenna can maintain good performance even when a plurality of antennas corresponding to different frequencies are gathered inside a hollow body exterior such as a rear spoiler of a vehicle.

  Hereinafter, embodiments of the invention will be described with reference to the drawings. Parts similar to those of the prior art are denoted by the same reference numerals, and description thereof is omitted.

FIG. 1 is a plan sectional view of a vehicle-mounted antenna according to a first embodiment of the present invention, and FIG. 2 is a side sectional view. As shown in FIG. 2, the AM antenna 10 and the ultrashort-wave antenna 30 are arranged so as to overlap in the vertical direction inside the hollow rear spoiler 2. The AM antenna 10 is disposed in an upper portion having a large internal space, and the ultrashort wave antenna 30 is disposed in a lower portion of the AM antenna 10. As shown in FIG. 1, the AM antenna 10 is connected to a linear feeding element 12 having a length L ₁ and a plurality of comb-tooth elements 14 having a length d ₂ arranged in parallel to the feeding element 12 in a direction orthogonal to the feeding element 12. The comb-teeth antenna 14 extends in the direction opposite to the vehicle body 1. One end of the AM antenna 10 is connected to the roof 6 of the vehicle 1 serving as a grounding body at a feeding point 16, and the feeding element 12 is arranged away from the roof 6 by a distance d ₁ . The AM antenna 10 has an antenna area of L ₁ × d ₂ so that radio waves can be received at a necessary reception voltage as a minute antenna. As shown in FIG. 3, the comb-shaped AM antenna 10 functions as an antenna in which the comb-tooth element 14 extends in the direction opposite to the GND with respect to the GND 20.

On the other hand, very high frequency antenna 30 has a linear ultra short element 32 is connected to the overall length L ₂ of the linear shape on both sides of the feeding point 34. The total length _{L 2} of the VHF antenna 30 is shorter than the total length _{L 1} of the AM antenna 10. The ultra-short wave element 32 is disposed in a direction orthogonal to the comb-tooth element 14 of the AM antenna 10, and is disposed substantially parallel to the feed element 12 at a distance d ₃ parallel to the feed element 12 of the AM antenna 10. Further, as shown in FIG. 2, since the ultrashort wave antenna 30 and the AM antenna 10 are arranged with a certain distance H in the vertical direction, the ultrashort wave element 32 and the comb element 14 are also constant in the vertical direction. They are arranged with a distance H.

The arrows in FIG. 4 indicate the directions of currents flowing through the AM antenna 10 and the ultrahigh frequency antenna 30. At the time of transmission (or reception) of radio waves, in the AM antenna 10, current from the feeding point 16 flows from the feeding element 12 to each comb element 14 to generate an electromagnetic field, and radio waves are radiated. On the other hand, in the ultra-short wave antenna 30, the current from the feeding point 34 flows to the ultra-short wave element 32 to generate an electromagnetic field and radiate radio waves, as in the prior art. At this time, current flows through the comb-tooth element 14 of the AM antenna 10 and the ultrashort-wave element 32 of the ultrahigh-frequency antenna 30 in directions orthogonal to each other, so that interference of the electromagnetic fields of the antennas as in the prior art is reduced. Also, VHF element 32 and the feeding element 12 of the VHF antenna of the AM antenna 10 is electromagnetically by the current flows parallel to the respective elements from the fact that have been arranged parallel to one another, by a distance d ₃ km Field interference is also reduced. Furthermore, each comb-tooth element 14 and the ultrahigh frequency element 32 are separated from each other by a distance H in the vertical direction, thereby preventing the influence of the mutual electromagnetic field on each antenna performance. For this reason, the AM antenna 10 is less likely to affect the performance of the ultrashort-wave antenna 30.

The distance d ₁ from the roof 6 of the feeding element 12 of the AM antenna 10 is 10 mm or more, and the parallel distance d ₃ between the feeding element 12 of the AM antenna 10 and the ultrahigh frequency element 32 of the ultrahigh frequency antenna 30 is 25 mm or more. The vertical distance H is preferably 5 mm or more when the ultra-short wave antenna 30 is a digital TV antenna, and is preferably 10 mm or more when the ultra-short wave antenna 30 is an FM antenna. Further, the AM antenna 10 and the ultra-short wave antenna 30 only need to be made of a conductive material, and the material, thickness, etc., such as a plate shape or a film shape, need not be particularly limited.

  5 and 6 show a comparison of the performance of the vehicle-mounted antenna according to the present invention and the vehicle-mounted antenna according to the prior art. Each figure shows the backward average gain (dBd) and the F / B ratio (gain ratio in the opposite direction to the maximum radiation direction) (dB) with respect to the frequency of the ultrashort-wave antenna 30 in the vehicle-mounted antenna. The white circle plot is a case where the lattice-type AM antenna 50 and the ultrashort-wave antenna 30 according to the prior art are arranged with a vertical distance H = 5 mm, and the white square plot is a comb-tooth AM for this embodiment. This is a case where the antenna 10 and the ultra-high frequency antenna 30 are arranged with a vertical distance H = 5 mm. The white diamond plot, the black triangle plot, and the black diamond plot are 10 and 10 respectively. The case of 15 and 25 mm is shown. As can be seen from this figure, the performance of the ultra-short wave antenna 30 in the in-vehicle antenna of the present embodiment is improved in both the backward average gain and the F / B ratio as compared with the prior art. Thus, in the present embodiment, it can be seen that the AM antenna 10 hardly affects the performance of the ultrashort-wave antenna 30, and that each antenna has an effect of maintaining good performance.

  FIG. 7A is a cross-sectional view of the vehicle-mounted antenna showing the second embodiment. FIG. 7 a shows the arrangement of the ultrashort wave antenna 30 and the AM antenna 10 of the first embodiment upside down. The ultrashort wave antenna 30 is arranged above the AM antenna 10 with a vertical distance H. It is a thing. FIG. 7b shows a first example in which an AM antenna 10 and two types of ultra-short wave antennas 30a and 30b are arranged in a triple manner in a casing 8 which is a hollow body disposed at the rear of the vehicle 1 and through which radio waves can pass. 3 shows a third embodiment. The vertical distances of the antennas are Ha and Hb. As described above, Ha and Hb are preferably 5 mm or more when the ultra-short wave antenna 30 is a digital TV antenna, and 10 mm or more when the ultra-short wave antenna 30 is an FM antenna. In order to reduce the interference of electromagnetic fields between the antennas 30a and 30b, the distance of Ha + Hb is preferably 25 mm or more. Also in this embodiment, the AM antenna 10 hardly affects the performance of each of the ultrashort wave antennas 30a and 30b, and there is an effect that each antenna can maintain good performance.

FIGS. 8 and 9 show the fourth and fifth embodiments in which the AM antenna 10 and the two ultrahigh frequency antennas 30a and 30b arranged in the same plane are overlapped in the housing 8 at the rear of the vehicle. is there. In the arrangement of the antennas, the distance _{d 3} between the feed element 12 and the VHF element 32a VHF antenna 30a of the AM antenna 10 of FIG. 8 is preferably be kept not less than 25 mm. Also, VHF antenna 30a that are aligned vertically on the same plane as shown in FIG. 9, 30b a distance d ₅ of is preferably set to 10mm or more in order to avoid interference of the electromagnetic field of the antenna cross for VHF. It is preferable to keep the same 25mm or more other embodiments the distance d _3. The vertical distance H between the comb-tooth element 14 and the ultrahigh-frequency elements 32a and 32b of the fourth and fifth embodiments shown in FIGS. 8 and 9 is the same as in the other embodiments. Is preferably 5 mm or more in the case of a digital TV antenna, and 10 mm or more in the case where the ultrahigh frequency antennas 30a and 30b are FM antennas. Also in this embodiment, the AM antenna 10 is less likely to affect the performance of each of the ultrashort-wave antennas 30a and 30b, and the effect that each antenna can maintain good performance can be achieved.

  In the above embodiment, it has been described that a plurality of antennas are built in the hollow rear spoiler 2 disposed above the rear portion of the vehicle 1 or the hollow casing 8 through which radio waves are installed. However, the part where the antenna is built in need not be limited to the interior of the rear spoiler 2 or the housing 8 above the rear part of the vehicle, but is a hollow that can transmit radio waves such as the interior of the rear bumper 3 below the rear part of the vehicle 1 shown in FIG. As long as the metal object that can be used as a grounding body such as the vehicle 1 is present in the vicinity of the antenna, it may be incorporated in any part. Further, the present invention is applicable not only when the AM antenna 10 and the ultrashort wave antenna 30 are arranged in combination, but also when the long wave (LW) antenna having a longer wavelength and the ultrashort wave antenna 30 are arranged in combination. Can do.

It is sectional drawing of the plane of the vehicle-mounted antenna of the 1st Embodiment of this invention. It is sectional drawing of the side surface of the vehicle-mounted antenna of the 1st Embodiment of this invention. It is explanatory drawing of the antenna function of the antenna for AM of the 1st Embodiment of this invention. It is explanatory drawing which shows the flow of the electric current of each antenna element of the vehicle-mounted antenna of the 1st Embodiment of this invention. It is a figure which shows the change of the back average gain with respect to the frequency of the vehicle-mounted antenna of the 1st Embodiment of this invention. It is a figure which shows the change of F / B ratio with respect to the frequency of the vehicle-mounted antenna of the 1st Embodiment of this invention. It is sectional drawing of the side surface of the vehicle-mounted antenna of the 2nd Embodiment of this invention. It is sectional drawing of the side surface of the vehicle-mounted antenna of the 3rd Embodiment of this invention. It is sectional drawing of the plane of the vehicle-mounted antenna of the 4th Embodiment of this invention. It is sectional drawing of the plane of the vehicle-mounted antenna of the 5th Embodiment of this invention. It is sectional drawing of the plane of the vehicle-mounted antenna by a prior art. It is sectional drawing of the side surface of the vehicle-mounted antenna by a prior art. It is explanatory drawing which shows the flow of the electric current of each antenna element of the vehicle-mounted antenna by a prior art. It is a top view of the glass antenna by a prior art. It is a perspective view which shows a vehicle.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Vehicle, 2 Rear spoiler, 3 Rear bumper, 4 Rear glass, 5 Defogger line, 6 Roof, 8 Case, 10, 50 AM antenna, 12 Feeding element, 14 Comb element, 16 Feeding point, 20 GND, 30, 30a, 30b Ultra high frequency antenna, 32, 32a, 32b Ultra high frequency element, 34, 34a, 34b Feed point, 52 Long side direction element, 54 Short side direction element, 56 Feed point, 100 AM glass antenna.

Claims (2)

A vehicle-mounted antenna in which a plurality of antennas corresponding to different frequency bands are arranged in a vehicle exterior made of a hollow body,
A comb-shaped AM antenna having a linear feed element having one end connected to the vehicle body, and a plurality of comb-teeth elements arranged in parallel to the feed element;
An ultrashort wave antenna having a linear ultrashort wave element,
The ultrashort wave element and each comb element extend in an orthogonal direction,
The ultrashort wave element is disposed at a predetermined distance with respect to the feeding element and each comb element,
A vehicle-mounted antenna characterized by. The in-vehicle antenna according to claim 1,
The ultra-short wave antenna is a digital TV antenna, an analog TV antenna or an FM antenna.
A vehicle-mounted antenna characterized by.

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