WO1997032355A1

WO1997032355A1 - Antenna device for vehicles

Info

Publication number: WO1997032355A1
Application number: PCT/JP1997/000505
Authority: WO
Inventors: Koichi Mitarai
Original assignee: Toyota Jidosha Kabushiki Kaisha
Priority date: 1996-03-01
Filing date: 1997-02-24
Publication date: 1997-09-04
Also published as: JPH09246827A

Abstract

A TV antenna element (2) is constituted by a first belt-like antenna element (4) and a second linear antenna element (5), and is stuck in a loop onto the inner surface of a door mirror case (1). Improved characteristics are obtained owing to a combination of the capacitance feature of the first antenna element (4) and the inductance feature of the second antenna element (5). The wiring is easily routed since the antenna element is connected to the side of the car body through the second antenna element (5). The GPS antenna assembly is arranged on the rear side of the mirror.

Description

Specification

[Title of Invention]

Vehicle antenna device

[Technical field]

The present invention relates to a vehicular antenna device in which an antenna element is built in a door mirror of a vehicle.

[Background technology]

Conventionally, vehicles are equipped with radio tuners and TV tuners. In addition, those equipped with car phones and data processing terminals, and those equipped with GPS devices for navigation systems are also increasing.

In order to use such a device in a car, it is necessary to receive radio waves, which requires an antenna. Here, it is easier to secure the performance if the visibility is as wide as possible, and it is preferable to provide the antenna protruding from the vehicle body from the viewpoint of performance only. However, antennas that protrude from the vehicle body have problems in design, such as wind noise when driving, and so on.

As an antenna that does not protrude from the vehicle body, a glass antenna formed as a pattern on the rear glass is used. However, there is a problem that it is easily affected by variations in the relative permittivity of the window glass, and production management is difficult. There is also a problem that the visibility becomes worse if many antenna patterns are arranged. Such antennas may be placed inside a room mirror or a side mirror (door mirror). By arranging the antenna in such a place, the appearance problem can be completely eliminated. In view of this, Japanese Patent Application Laid-Open No. 63-170349 proposes an antenna in which an antenna is arranged inside a luma mirror or a side mirror. Here, when an antenna is arranged inside a door mirror, its size must be considerably small. In order to reduce the size of the TV antenna, It is preferable that the tenor is not a linear shape but a band shape. However, door mirrors are usually retractable, and it is considered difficult to maintain the shape of the antenna when it is stored as a strip.

Also, with the GPS antenna, it is relatively easy to miniaturize the antenna element itself, and it is considered that the antenna element can be physically (dimensionally) housed in the door mirror. However, if the antenna element is miniaturized, there is a high possibility that the receiving performance will be significantly degraded depending on the installation conditions (surrounding environment), and the production yield is expected to deteriorate. Therefore, no proposal has been made so far to house the GPS antenna in the door mirror. Also, the GPS antenna needs to be hardly affected by reflected waves from the road surface or the like.

[Disclosure of the Invention]

The present invention has been made in view of the above problems, and has as its object to provide an antenna device suitable for being incorporated in a door mirror.

In the present invention, the antenna element is arranged on the periphery of the door mirror case. Therefore, an antenna element long enough to receive TV broadcast waves can be obtained. The antenna element includes a band-shaped first antenna element and a linear second antenna element that is connected in series to the first antenna element. Further, the belt surface of the first antenna element is fixed to an inner surface of a door mirror case, and the second antenna element is arranged on a vehicle side of a door mirror.

The TV broadcast wave is received by the first antenna element. The first antenna element is band-shaped, and can suitably receive wideband TV radio waves. Also, if the first antenna element is made shorter than the center frequency of the received radio wave, the first antenna element will show capacitive but the second antenna element will show inductance and cancel out the reactance of both. Thus, a suitable antenna can be obtained. In addition, the mirror functions as a parasitic antenna element, and wideband reception can be performed effectively.

Further, since the second antenna is arranged on the vehicle mounting side, connection with the vehicle side is facilitated even if there is a rotary storage mechanism of Domira.

Further, in another embodiment of the present invention, in a device in which an antenna element is installed in a door mirror case of a vehicle, the antenna element is a GPS antenna, and the GPS antenna The antenna is placed upwards behind one side of Mira.

Since the door mirror protrudes from the vehicle, the visibility to the satellite is relatively good, and the radio wave from the satellite can be effectively received.

In addition, because the GPS antenna is located behind the mirror, reflected waves from buildings and road surfaces are less likely to enter, minimizing erroneous detection and enabling accurate position detection.

In still another embodiment, the vehicle further comprises a conductive actuator for changing an angle of the mirror, and the GPS antenna is on a front side of the mirror on the vehicle side, and is located inside the conductive actuator in a vehicle width direction. Or it is arranged on the upper side. With this arrangement, it is possible to prevent the reflected wave from being received even by the conductive actuator.

Further, by forming the GPS antenna with a microstrip antenna, the antenna can be downsized. Furthermore, by using two-point power supply, the axial ratio can be greatly improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a first embodiment.

FIG. 2 is a diagram showing a cross-sectional configuration of a second embodiment.

FIG. 3 is a diagram showing a front configuration of the same embodiment with a mirror removed.

FIG. 4 is a diagram showing a configuration of the antenna element of the embodiment.

FIG. 5 is a view showing an axial ratio characteristic of the antenna element of the embodiment.

FIG. 6 is a diagram showing a configuration of a GPS antenna assembly of the embodiment.

FIG. 7 is a circuit diagram showing a configuration of a preamplifier of the same embodiment.

FIG. 8 is a diagram showing an arrangement of a preamplifier of the embodiment.

FIG. 9 is a diagram showing a form of wire bonding of the bare chip of the embodiment.

[Preferred embodiment for carrying out the invention]

Hereinafter, preferred embodiments for implementing the present invention (hereinafter, referred to as embodiments) will be described with reference to the drawings.

"First Embodiment" FIG. 1 is a diagram showing a configuration of a vehicle antenna device according to the first embodiment. An antenna element (TV antenna element 2) is housed inside a door mirror case 1. The TV antenna element 2 is connected to a coaxial cable 3 for power supply, receives power from this, and receives TV radio waves.

The TV antenna element 2 is composed of a strip-shaped first antenna element 4 and a second antenna element 5 composed of a linear conductor, and one end of the second antenna element 5 has a coaxial cable 3. The other end is connected to one end of the first antenna element 4. The other end of the first antenna element 4 is an open end. The outer conductor of the coaxial cable 3 is electrically connected to the vehicle body and is grounded. For example, grounding may be provided near the door mirror to which the door mirror is attached, and only the inner conductor may be introduced into the door mirror case 1. In contrast, the vehicle body may be grounded via a rotatable metal shaft or the like. The mirror 6 is provided in front of the door mirror case 1.

The first antenna element 4 is made of a strip-shaped conductor, for example, a conductive tape of copper foil, and has a width of 20 to 30 mm and a length of 200 to 300 mm. . On the other hand, the second antenna element 5 is a copper wire having a diameter of about 1 mm and a length of about 5 O mm. The first and second antenna elements 4 and 5 are attached to one side of the door mirror case 1. That is, the first antenna element 4 is mounted on the upper side and right side (the side farther from the vehicle body) of the door mirror case 1, and the second antenna element ⁵ is mounted on the left side of the door mirror case 1 (closer to the vehicle body). Side). The Domira 1 case 1 is formed of a plastic material.

The TV broadcast wave is received by such a TV antenna element 2, and the TV broadcast wave is first received by the first antenna element 4. The first antenna element 4 has a band shape and has many current paths. For this reason, it is possible to receive broadband radio waves necessary for receiving TV broadcast waves.

In addition, the first antenna element 4 is shorter than the length required for receiving radio waves in the TV band. Therefore, the impedance of the first antenna element 4 , Will indicate capacitive. On the other hand, a linear second antenna element 5 is connected to the first antenna element 4. Since the second antenna element 5 has a linear shape, its impedance indicates inductance.

Thus, the TV antenna element 2 of the present embodiment is configured by connecting the capacitive first antenna element 4 and the inductance second antenna element 5. Therefore, by adjusting the capacitive and inductive reactances of both, the impedance of the two can be made to have the mutual reactance offset. Thus, the matching condition can be satisfied, and good reception power can be supplied to the TV receiver connected to the other end of the coaxial cable 3.

Further, the loop formed by the TV antenna element 2 surrounds the mirror 6. The reflection film of the mirror 6 is formed of a conductor (for example, an aluminum deposition film). Therefore, a parasitic element is loaded on the TV antenna element 2. Therefore, the frequency characteristics of the TV antenna element 2 can be further widened using this mirror. Therefore, the requirements for the accuracy of the TV antenna element 2 are not strict, the production yield is improved, and the cost is reduced.

Since the second antenna element 5 has a linear shape, it is easy to route a cable (wire harness) from the inside of the door mirror case 1 to the vehicle side, and an effect of improving assembly workability can be obtained.

In the above-described configuration, the second antenna element 5 is extended to the outside of the door mirror case 1, but the coaxial cable 3 is guided to the inside of the door mirror case 1 and is attached to the rotating shaft of the door mirror case 1. The outer conductor of the coaxial cable 3 may be grounded to a metal part (electrically conductive with the vehicle body) provided. Further, the second antenna element 5 may be arranged in a meandering manner.

"Second embodiment"

FIG. 2 shows a vehicle antenna device according to a second embodiment. In the above-described first embodiment, the TV antenna element 2 has been described, but in the second embodiment, the GPS antenna assembly 7 is provided. That is, as shown in Fig. 2, A mirror 6 is provided on the front side inside the case 1, and a GPS antenna assembly 7 is arranged behind the mirror 6. The mirror 6 is held by a mirror electric actuator 8, and the direction of the mirror 6 is changed to front, rear, left and right by the mirror electric actuator 8. In the normal case, as shown in Fig. 3, one point on the back of the mirror 16 is pivotally supported by the electric actuator 8 for the mirror 8 as a reference point 8a, and is freely movable to the side of the reference point 8a. A left-right drive shaft 8b and a front-rear movable front-rear drive shaft 8c are provided above (or below). Accordingly, the mirror 6 rotates in the horizontal plane by moving the left and right drive shaft 8b forward and backward, and the mirror 6 rotates in the elevation direction by moving the front and rear drive shaft 8c forward and backward.

A GPS antenna assembly 7 is arranged on the rear of the electric actuator 8 for mirror on the vehicle body side.

Figure 4 shows the antenna elements housed in the GPS antenna assembly 7.

FIG. 10 is a diagram showing a configuration of 10. As described above, the present antenna element 10 is configured by a microstrip antenna in which a square, thin-film antenna patch 12 smaller than the dielectric substrate is formed on the surface of the square dielectric substrate 11. In this example, one side of the dielectric substrate 11 is 25 mm, the thickness is 4 mm, and a dielectric substrate having a dielectric constant of about 21 is employed. Preferably, the dielectric constant is about 20 to 40. The antenna patch 12 is made of a printed and fired copper film having a side (L) of about 20 mm.

In the present embodiment, the power supply to the antenna patch 12 is two-point power supply. That is, as shown in FIG. 4, feed points Ρ 1 and f Ρ 2 are provided at positions that are different from each other by 90 ° when viewed from the center of the antenna patch 12 and are separated by a predetermined distance. This allows the antenna element to be reliably excited with circularly polarized waves. In other words, in the case of single-point feeding, excitation with a predetermined circular polarization is achieved by providing cuts and projections around the antenna patch 12. Therefore, the axial ratio of circularly polarized waves greatly changes depending on the frequency.

On the other hand, if two-point feeding is performed as in the present embodiment, excitation is performed with circularly polarized waves in accordance with the phase of the current fed to the two points, so that a suitable axial ratio can be secured in a wide band. The distance from the center of each feeding point fp 1 and f P 2 and the size of the antenna patch 12 By adjusting (LXL), desired characteristics can be obtained.

Figure 5 shows the relationship between the axial ratio and frequency for one-point power supply and two-point power supply. Thus, in the case of single-point feeding, a very good axial ratio is obtained at the center frequency, but the axial ratio becomes extremely poor when the frequency departs from the center frequency. On the other hand, in the case of two-point power supply, it is understood that a good axial ratio can be obtained stably over a wide area, and that excitation can be performed in a wide range and with favorable circular polarization.

In the microstrip antenna according to the present embodiment, the axial ratio must be reduced (good) over the entire reception (resonance) band (frequency range where the standing wave ratio (SWR) is 2 or less) of the antenna. Is possible. The performance of the antenna can be fully utilized.

On the other hand, in the single-point feeding method, the band with a good axial ratio is only about 20 to 30% of the antenna resonance band.

FIG. 6 shows the overall configuration of the GPS antenna assembly 7. Thus, the antenna element 10 is housed in the case 15. The inner conductor 16a of the coaxial cable 16 passes through the dielectric substrate 11 and is connected to the antenna patch 12 on the surface.

Further, the antenna element 10 is disposed on the printed circuit board 17. A circuit such as a preamplifier is arranged on the back side of the printed circuit board 17. FIG. 7 is a diagram showing a preamplifier circuit. In this figure, the antenna element 10 fed from two feeding points having phases different from each other by 90 ° is represented as two antennas: antennas 10Q and 101. The two antennas 10Q and 10I are connected to the hybrid circuit 20 via connectors CNI-I and CN-Q. The hybrid circuit 20 distributes the power supply current to the two antennas 10Q and 101 with a 90 ° phase difference.

The hybrid circuit 20 is connected to the amplifier IC 21. This amplifier IC 21 performs the first-stage amplification of the received signal. The amplifier IC 21 is connected to the amplifier IC 24 via a bandpass filter 23. The amplifier IC 24 amplifies a signal of which a predetermined frequency is selected by the band-pass filter 23. The output of the amplifier IC 24 is connected to the inner conductor〗 6 a of the coaxial cable 16 via the capacitor C 6. The outer conductor 16b of the coaxial cable 16 is connected to the ground of the printed circuit board. A DC of about 5 V is superimposed on the inner conductor 16 a of the coaxial cable 16, and the length is 1 of the wavelength of the center frequency, and the relatively narrow characteristic impedance is about 100 Ω. DC is extracted through microstrip line 25 and supplied to amplifier ICs 21 and 24 as power. The capacitors C1 to C5 and C7 are for noise removal.

With such a preamplifier, the current excited by the circularly polarized wave and flowing through the antenna patch 12 is amplified and transmitted to the coaxial cable 16. The printed circuit board 17 is formed of a resin having a dielectric constant of about 10, and the wiring on the printed circuit board 17 is a microstrip line (characterized as MSL 50) having a characteristic impedance of 50 Ω. ).

FIG. 8 is an overall layout diagram of a printed circuit board 17 on which a preamplifier is mounted. In this way, a connector (for signal output) CNOUT is provided at one end (upper left) to connect with the vehicle body side, the power supply line goes down, and the signal processing line turns right and goes to the center. Has reached. The signal input terminals C N−1 and C N−Q connected to the hybrid circuit 20 are located just below the feed point f p] and ί p 2. This allows connection to the antenna patch 12 with relatively short pins.

Further, it is preferable that the amplifiers IC 21 and 24 are formed of bare chips and connected to the microstrip line by wire bonding. FIG. 9 shows the state of wire bonding of the amplifiers IC 21 and 24. In the figure, thick lines with a symbol at both ends indicate wire bonding. This makes it possible to reduce the size of the circuit as a whole and obtain sufficient characteristics.

By combining such a preamplifier with the above-described antenna element, the GPS antenna assembly 7 can be reduced in size and stabilized, and can be incorporated in the door mirror case 1.

According to such a PS antenna, the radio wave from the GPS satellite is received by the antenna patch 12 and supplied to the GPS receiver via the preamplifier and the coaxial cable 16. And the GPS antenna assembly 7 is behind the mirror 6 Are located in Therefore, there is a low possibility that the reflection reflected on the building or the road surface is received by the antenna patch 12, so that erroneous detection can be prevented, and the positioning accuracy can be improved. In addition, outside the GPS antenna assembly, there is an electric mirror for Mira. Therefore, this also blocks the radio waves and prevents erroneous detection due to reflected waves.

Also, since the antenna element was placed on the preamplifier substrate 17 and housed in a case, it was only necessary to connect it to the GPS receiver with a coaxial cable. In other words, the antenna is adjusted at the time of manufacture so that a predetermined function can be exhibited. Therefore, at the time of installation, fine adjustment of the antenna element is not required, and the assembling work becomes very simple.

Here, this antenna element was used only for GPS reception, but with the same configuration, it is also used for other radio waves, such as reception of radio waves from traffic information and road beacons for toll collection on toll roads can do.

Furthermore, diversity reception can be easily achieved by incorporating this antenna into the two door mirrors.

Also, since both the TV antenna and the GPS antenna are built in the door mirror, there is no appearance problem.

In the above description, only the antenna with a built-in antenna in the door mirror case has been described. However, a fender mirror or the like may be used as long as it has the same shape as the door mirror.

Claims

The scope of the claims

1. In the case of a car with an antenna element installed on the door mirror case of the vehicle,

An antenna device for a vehicle in which an antenna element is provided inside a door mirror case and near a mirror peripheral portion.

2. The apparatus according to claim 1,

The antenna device for a vehicle, wherein the antenna element includes a band-shaped first antenna element and a linear second antenna element coupled in series to the first antenna element.

3. The apparatus according to claim 2,

A vehicle antenna device in which the belt surface of the first antenna element is fixed to the upper surface of a door mirror case and the second antenna element is disposed on a vehicle mounting side in the door mirror case.

4. The apparatus according to claim 3,

An antenna device for a vehicle, wherein a connection line to a receiver inside the vehicle is connected to the second antenna element.

5. The apparatus according to any one of claims 1 to 4,

The mirror reflector is a vehicle antenna device formed of a conductor.

6. A vehicular antenna device in which the antenna element is installed in a door mirror case of a vehicle and the antenna element is a GPS antenna, and the GPS antenna is arranged upward behind a mirror surface.

7. The apparatus according to claim 6, wherein

A conductive actuator for changing the angle of the mirror is provided inside the door mirror case.

1 ϋ A vehicle antenna device provided.

8. The apparatus according to claim 7, wherein

The antenna apparatus for a vehicle, wherein the GPS antenna is disposed on the front side of the mirror on the front side of the vehicle and inside or above the conductive actuator in the vehicle width direction.

9. The apparatus according to any one of claims 6 to 8, wherein

The GPS antenna is a vehicular antenna device formed of a microstrip antenna including a thin-film antenna patch, and feeding the antenna patch at two points.

10. In a device in which an antenna element is installed in a door mirror case of a vehicle, a first antenna element for receiving a television broadcast wave is provided inside the door mirror case and near a mirror periphery,

A second antenna element for GPS arranged upwards behind one side of the mirror inside the domira case,

A vehicle antenna device having: