JPS61127204A - Antenna system for automobile - Google Patents

Abstract

PURPOSE:To obtain an antenna system with excellent vibration-proof by arranging a loop antenna supported fixedly in a case with a packing member closely to the peripheral of the car body of an automobile along its lengthwise direction so as to detect effectively a current induced in the car body due to a broadcast wave. CONSTITUTION:An opening 40a from which a lengthwise side of a loop antenna 42 is exposed is provided to the case 40 and a part of the loop antenna 42 exposed from the case 40 made of a conductor is arranged closely and oppositely to the car body peripheral. Thus, the magnetic flux induced from a high frequency surface current flowing to the peripheral of the car body is acquired surely by the loop antenna 42 in the case 40 and an external electromagnetic wave is shielded surely by the case 40, then the current induced on the car body is detected by a high frequency pickup 38 with high sensitivity. Further, a low dielectric constant dielectric substance such as polyester, epoxy resin or silicone resin is impregnated or formed by a forming method into the air gap between the case 40 and the loop antenna 42 to support incorporatedly the loop antenna 42.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is an antenna device for an automobile, particularly an antenna device for effectively detecting broadcast waves received on the body of an automobile and supplying a detection signal to various receivers mounted on the automobile. The present invention relates to an improved antenna device for automobiles.

[Prior Art] An antenna device is indispensable for a car in order to ensure that a receiver installed in the car receives various broadcast waves such as radio, television, telephone broadcast communication waves, etc. This type of antenna device is extremely important for communicating with other stations, such as transmitting and receiving citizen band radio waves.
It will play a major role in the standard communication functions of future vehicles.

Conventional general antenna devices are known as pole antennas, and although antennas that protrude from heavy bodies exhibit favorable performance in terms of reception characteristics, they always have the fate of being treated as a nuisance when it comes to car body design. Was.

In addition, such ball antennas are susceptible to breakage, bending, and other damage even in actual use, are subject to mischief or theft, and have various problems such as generating unpleasant wind noise when driving at high speeds. Conventionally, there have been many requests to somehow remove this problem.

In particular, as the frequency band of broadcast waves or communication waves received inside a car has expanded in recent years, it has become necessary to install multiple antennas for each frequency band, which has ruined the aesthetic concept of the car's exterior. There is a problem in that the receiving performance of these antennas is significantly degraded due to mutual electrical interference between these various antennas.

In the past, several efforts have been made to remove or hide the above-mentioned ball antenna so that it cannot be seen from the outside, and for example, pasting a thin antenna wire on the rear windshield has been put into practical use.

As another conventional solution, it has been proposed to detect surface current induced in the vehicle body itself by broadcast waves. At first glance, utilizing the current flowing through the car body seems to be the most reliable and efficient method, but previous experiments have continued to show results that completely contradict these expectations.

The first reason why the surface current induced by broadcast waves on a general car body could not be used is that the surface current value was not as large as expected. However, even with this, it was not possible to achieve a level of detection output sufficient for full use.

The second problem with the conventional method is that a very large proportion of noise mixes into the surface current, and this noise mainly comes from the engine's ignition system and battery charging regulator system, and when the engine is active. As a result, these noises leaked into the vehicle body, making it impossible to receive clear broadcast waves that could be used for practical purposes.

Even under such disadvantageous conditions, several proposals have been made in the past. Japanese Patent Publication No. 53-22 as a conventional antenna device that utilizes the current induced in the car body by broadcast waves.
418 is known, in which an electrically insulating part is formed at a current concentration part of the vehicle body, and the current between both ends of this insulating part is directly detected by a sensor 2. It is certainly suggested that this conventional device can obtain a practically usable detection signal with an excellent S/N ratio, but its pickup structure requires a cutout in a part of the vehicle body, etc. It was impossible to apply this method to mass-produced automobiles.

Another conventional device is known from Japanese Utility Model Publication No. 53-34826, which proposes an antenna that uses a pickup coil to detect the current flowing through the pillar of a vehicle. Although this conventional device was useful in showing the direction of development in which the antenna is built into the vehicle body, it is actually impractical to provide a pickup coil near the pillar and perpendicular to the longitudinal direction of the pillar. Furthermore, it was not possible to obtain a practical antenna output with such a pickup arrangement, and it was considered to be nothing more than an idea.

[Problem to be solved by the invention] -- of.

As described above, conventional antenna devices for detecting current induced in a vehicle body by broadcast waves have not always been successful.

In particular, in the past, a pickup structure and a practical S
The pickup arrangement for obtaining the N ratio has not been properly resolved, and rather, various experimental results point to the fact that antenna devices that utilize vehicle body current may not be usable in principle.

Purpose of the Invention The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to effectively detect the current induced in a heavy body by broadcast waves and transmit it to a receiver mounted on a vehicle. An object of the present invention is to provide an antenna device for a small automobile that has excellent vibration resistance.

[Means for Solving the Problems] In order to achieve the above object, the present invention disposes a high frequency pickup close to the peripheral edge of the vehicle body, thereby detecting high frequency surface current of a predetermined frequency or higher. , the loop antenna of the high frequency pickup is fixedly held within the case with a filling material.

Conventional antenna devices were mainly intended to receive AM waves due to the prohibitions of the times, but for this reason, antennas for detecting car body currents have a long wavelength of target broadcast waves, so they are not suitable for receiving AM waves. As a result, the present inventors focused on this frequency dependence, and in the present invention, the broadcast waves to be received are changed to FM.
By setting the frequency band to 50M1-1z or higher in the normal case, it has become possible to extremely effectively receive reception from the vehicle body current, which was previously considered impossible.

In addition, in the present invention, we have focused on the fact that the current value of such high-frequency car body current has a distribution characteristic that is significantly different in each part of the car body, and we have focused on the fact that the current value of such high-frequency car body current has a distribution characteristic that is significantly different in each part of the car body. The present invention is characterized by the provision of a high frequency pickup, and in the present invention, the area near the peripheral edge of the vehicle body is particularly selected as the feeding area that satisfies these conditions.

Furthermore, in the present invention, in order to reliably detect the high frequency waves with the above-mentioned frequency characteristics, the high frequency pickup is mounted from the edge of the vehicle body at a speed of 12
= carrier frequency of broadcast waves), and the pickup is a loop antenna for N magnetically detecting the magnetic flux generated by the car body current, and these provide an efficient detection action. It has been obtained.

"Embodiments" Hereinafter, preferred embodiments of the automotive antenna device according to the present invention will be described based on the drawings.

5 to 13 explain the steps for determining the most efficient antenna installation position by examining the characteristics of the high-frequency current.

Figure 5 shows that when an external radio wave W such as a broadcast wave passes through a car body B made of gold pA conductor, a surface current I corresponding to the strength of the N13 wave is induced in each part of the car body. In the present invention, only the frequency bands used for FM waves, pre-waves, etc. of 50 MHz or higher, which belong to relatively high frequency bands, are targeted in the present invention.

The present invention is characterized in that the induced current distribution of the vehicle body is measured in such a specific high frequency band, and the pickup is installed in a portion where the surface current density is high and there is little noise.

In order to know the surface current distribution, computer simulations and actual current intensity measurements are carried out at each point.In the present invention, a probe based on the same principle as a high frequency pickup installed at a desired vehicle body part, which will be described later, is used. was used, and the surface current was measured by moving the probe across the entire surface of the car body, changing direction at each point.

FIG. 6 shows a schematic configuration of a probe P created based on a principle similar to that of a high frequency pickup described later. Loop coil 12 inside
is fixed, an opening 10a is provided in a part of the case 10, a part of the loop coil 12 is exposed to the outside from this opening 10a, and the exposed part of the loop coil 12 is brought close to the surface of the vehicle body B. It consists of a configuration in which a loop coil 12 detects the magnetic flux generated from the vehicle body surface current.

A part of the loop coil 12 is connected to the case 1 by the shorting wire 14.
0, and output m16 is connected to coaxial cable 1
8 core wires 20. Also, the loop coil 12
A capacitor 22 is provided in a part of the loop coil 12 to resonate the frequency of the loop coil 12 to a desired frequency to be measured, thereby increasing pickup efficiency.

As described above, by moving the probe P along the surface of the vehicle body and rotating its angle at each measurement point, it is possible to accurately determine the surface current distribution and its direction on the vehicle body surface. In FIG. 6, the output of the probe P is amplified by a high frequency voltage amplifier 24, and the output voltage is measured by a high frequency voltage measuring device 26. This coil output voltage is read by the meter indication value of the measuring device 26, and the voltage corresponding to this meter indication value is recorded by the XY recorder 28 as a surface current distribution in each part of the vehicle body. A signal indicating each position of the vehicle body is inputted to the XY recorder 28 from the potentiometer 30, and it is possible to know the high frequency surface current at each position.

FIG. 7 shows the deviation angle θ between the high-frequency surface current and the loop coil 12 of the pickup. As shown in Figure 8, the maximum voltage is obtained when θ is 0, that is, the surface current ■ is parallel to the loop coil 12 of the pickup, and the maximum voltage is obtained by rotating the probe P at each measurement point. It is possible to know the direction of the surface current I when the surface current I is applied.

Figures 9 and 10 show the magnitude and direction of the high-frequency surface current generated in each part of the vehicle body at a frequency of 80 MHz, which was determined from both the measurement results using the probe P and the computer simulation.
As is clear from the figure, the magnitude of the surface current exhibits a distribution in which the density is high along the edges of the flat plate portion of the vehicle body, and the density is extremely low in the central portion of the flat plate portion.

Furthermore, as shown in the direction of the current in FIG. 10, it is understood that each current is concentrated in a direction parallel to the edge of the vehicle body or in a direction along the connecting portion of each plane portion.

In Fig. 9, if we examine in detail the current distribution induced in the metal parts of the car body along the chain line that traverses the car body, we find that
Distribution characteristics as shown in FIGS. 11 to 13 are obtained.

Figure 11 shows the surface current distribution along the trunk lid from longitudinal line A to B. As is clear from the figure, the largest current flows at both ends, and from these ends towards the center of the lid. This shows a distribution characteristic in which the electric tl value decreases.

Therefore, as shown in FIG. 11, if a high frequency pickup is placed near the periphery of the trunk lid, it becomes possible to detect the concentrated current flowing near the periphery.

Similarly, Fig. 12 shows the current distribution along the ceiling plate of the car body, and Fig. 13 shows the current distribution along the engine cover of the car body. It is understood that the largest current flows at both ends, and the current value decreases toward the center.

Therefore, it is understood that in the present invention, it is possible to pick up broadcast waves with good sensitivity near the periphery of each part of the vehicle body.

Of course, in the present invention, the installation position of the high frequency pickup is not limited to the above-mentioned lids or ceiling panels, but can be similarly applied to pillars and fenders.

Furthermore, in the present invention, the high-frequency pickup is installed close to the peripheral edge of each mid-stop, and along the peripheral edge, for example, in the longitudinal direction of the loop antenna. In addition, it is preferable to set the pickup installation range from the edge to a range that depends on the carrier frequency of the broadcast wave.

The distribution characteristics shown in Figures 11 to 13 are the car body current for the FM broadcast frequency of 80 MHz. As mentioned above, the surface current value decreases as the distance from each car body end or edge increases. 6dB that can obtain sensitivity
Considering the following current reduction range, it is understood that extremely good sensitivity can be obtained within 4.5 cm from the edge in each characteristic.

Therefore, in the present invention, for a carrier frequency of 80 M)lz, a high frequency pickup is carried out from the peripheral part of the vehicle body by 4.
If placed within 5ctiX, a practically sufficient antenna device can be obtained.

It has become clear from computer simulations and hard experimental results that this practical separation distance depends on the carrier frequency, and it has been recognized that the practical AT separation distance decreases as the frequency increases.

Therefore, since the above-mentioned practical separation distance #t is 4.5 cm at the carrier frequency of 80 MHz and is inversely proportional to the frequency, in the present invention, the installation range of the high frequency pickup from the flat metal edge of the vehicle body is set to 12xlO- 3
If it is provided within c/r (Ill), a good reception effect can be obtained depending on each carrier frequency (in the above equation, C=speed of light and f=carrier frequency).

As described above, the high frequency pickup is provided close to the edge of each metal car body, and preferably within the above-mentioned separation distance from the edge, thereby providing a good reception effect.

Note that, in practice, the separation distance depends on the frequency, so for example, at a carrier frequency of 100 MHz, it is sufficient to provide the high frequency pickup within 3.6 cm from the edge of the vehicle body, and as the carrier frequency f increases, The installation of the high frequency pickup will be limited to a narrow area very close to the edge.

FIG. 1 is an external view of a high frequency pickup according to the present invention, and FIG. 2 is a longitudinal sectional view thereof. This high-frequency pickup 38 includes a metal case 40 that shields electromagnetic waves from the outside, and includes a loop antenna 42 and a circuit section 58 therein, forming an electromagnetic coupling type pickup and detecting the above-mentioned surface current distribution of the vehicle body. It consists of a similar structure to the probe including the loop coil used for this purpose.

The case 40 is provided with an opening 40affi through which the longitudinal side of the loop antenna 42 is exposed, and a portion of the loop antenna 42 exposed from the case 40 made of a conductor is placed close to and facing the peripheral edge of the vehicle body. It will be done. Therefore, inside the case 40, the magnetic flux induced from the high-frequency surface current flowing around the periphery of the vehicle body is reliably captured by the loop antenna 42, and the case 40
Since electromagnetic waves from the outside are reliably shielded by this, the current induced in the vehicle body can be detected with high sensitivity by the high frequency pickup 38.

Further, a circuit section 58 connected to the loop antenna 42 described above is built in the case 46 of the high frequency pickup 32, and a signal detected by a preamplifier or the like provided in the circuit section 58 is processed. Furthermore, the high frequency detection signal thus obtained is taken out from the coaxial cable 60 and processed by the same circuit as used in the surface current distribution measurement described above. The circuit section 58 is supplied with power and signals for circuit control from a cable 62.

Here, the characteristic feature of the present invention is that the loop antenna 4
2 is that it is fixedly held within the case 40 by a filler 44. That is, in the embodiment, a low permittivity dielectric material such as polyester, epoxy resin, silicone resin, etc. is molded by injection or molding into the gap between the case 40 and the loop antenna 42, as shown by the shaded area in FIG. , the loop antenna 42 is integrally and fixedly held. Such a filler 44 has a frequency of 70 to 1,000 as described above.
It is preferable that the material has a dielectric constant of 2 to 4 at MHz and a small dielectric loss tangent in order to efficiently extract output.

In addition, in the embodiment, lips 48-1, 48-2. ... is installed on the printed board 46.
This prevents tilting and deformation.

According to the embodiment described above, the loop antenna 42 is securely held fixed, and even if the pickup 38 vibrates as the vehicle body is photographed, the loose antenna 42 will not cause joint photography or output failure. There is no. Also, printed board 4
6 and the loop antenna 42 will not cause poor contact. Furthermore, the loop antenna 42 is made of filler material 4.
Since the loop antenna 42 is covered with a loop antenna 42, dew condensation does not occur on the loop antenna 42 even in winter.

FIG. 3 shows another embodiment, in which the loose antenna 42 is provided at an angle with respect to the printed board 46.

Therefore, it has the advantage that the loop surface can be large and the output can be large.

FIG. 4 shows an installation example in which the high frequency pickup is disposed close to the rear peripheral edge of the heavy ceiling plate according to the present invention.

In the figure, the ceiling board 32 is shown in an exposed state,
This metal ceiling plate 32 is connected to the rear glass 36 with the rear window frame 34 as its peripheral edge. 4 inwards from the edge of the rear window frame 34.
．． A high frequency pickup 38 is provided in an area within 5 cm.

In this case, in order to arrange the loop antenna 42 of the high frequency pickup 38 to face the peripheral edge of the rear window frame 34, an opening 34a is provided in a part of the rear window frame 34, and this opening 348:
A case 40 of the i-frequency pickup 38 is inserted and arranged.

In order to securely position and fix the case 40 of the high frequency pickup 38 to the rear window frame 34,
L-shaped brackets 54 and 56 are connected to both ends of the case 40 with bolts and the like, and these brackets 54 and 54 are fixed to the rear window frame 34 with screws.

The loop antenna 42 consists of a single-turn antenna, and has a structure in which the coil is coated with an insulating coating so that it is placed in close contact with the rear window frame 34 while being electrically insulated, and the coil is pressed against the rear window frame 34. Therefore, the magnetic flux generated from the surface current can be more strongly linked to the loop antenna 42.

In the present embodiment, the side of the loop antenna 42 exposed from the case 40 is 44 mm from the edge of the rear window frame 34.
．． 5cll1, thereby making the 80M
Broadcast waves at the FM broadcast frequency of Hz can be reliably detected from the vehicle body surface current flowing around the periphery of the rear window frame 34, and as is clear from FIG. Therefore, in this embodiment, the loop antenna 46 is arranged so that its longitudinal direction runs along the peripheral edge of the rear window frame 34.

As described above, according to the present invention, the surface current flowing in the periphery of the vehicle body, especially the periphery of the ceiling plate, is electromagnetically detected by a high-frequency pickup, and the antenna device is not exposed to the outside at all, and it is possible to detect This enables reliable reception and is extremely useful as an automotive antenna.

[Effect of the Invention 1] As explained above, according to the present invention, high-frequency surface currents generated in specific parts of the vehicle body, particularly in the peripheral portion of the vehicle body, are used for broadcast waves in a relatively high frequency band, for example, the FM frequency band or higher. Since the antenna for receiving broadcast waves is formed using the antenna, and the loop antenna of the current detection pickup is fixedly held by the filling material, the vibration resistance is improved and the output voltage can be stabilized.

[Brief explanation of drawings]

Fig. 1 is an external view of the high frequency pickup of the automotive antenna system U according to the present invention, Fig. 2 is a 1'' sectional view of Fig. 1, and Fig. 3 is a longitudinal sectional view of the high frequency pickup showing another embodiment. Figure 4 shows the high-frequency pickup installed on the ceiling panel of the car body, Figure 5 is an explanatory diagram showing the surface current generated on the car body by the external wave W, and Figure 6 shows the high-frequency pickup used in the present invention. An explanatory diagram of a probe and its processing circuit for determining the distribution of car body surface current using a similar probe. Figure 7 is an explanatory diagram showing the electromagnetic coupling state between the surface current T and the pickup loop antenna. Figure 8 is an explanatory diagram of the probe and its processing circuit. Fig. 7 is an explanatory diagram showing the directivity characteristics of the loop antenna; Fig. 9 is an explanatory diagram showing the distribution characteristics of surface current intensity;
The figure is an explanatory diagram showing the direction of surface current, No. 11.12.13
Each figure is a characteristic diagram showing the vehicle body surface current distribution along the longitudinal section of the vehicle body in FIG. 9. 38...High frequency pickup 34...Rear window frame 40...Case 44...Filling material 42...Loop antenna 58...Circuit part Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 4 S2 Figure 5 Figure 6 Defense Figure 7

Claims (2)

[Claims] (1) A loop antenna and a circuit section are provided in the case, and the loop antenna is arranged close to the periphery of the car body along its longitudinal direction, and the air is induced in the car body by broadcast waves and flows concentrated at the periphery of the car body. What is claimed is: 1. An antenna device for an automobile, which detects a high-frequency surface current, and wherein the loop antenna is fixedly held within a case with a filling material. (2) An antenna device for an automobile according to claim (1), wherein the filler is a low dielectric constant dielectric.