JPS61129907A - Antenna system for automobile - Google Patents

Abstract

PURPOSE:To decrease variance of an output by forming an antenna assembly with a high frequency pickup detecting a high frequency surface current having a prescribed frequency or over, a bracket and a car body connecting piece and fixing the assembly to the car body so as to uniform a fitting work. CONSTITUTION:The car body connecting piece 34 is clippsed between folding parts 31b, 32b and the connecting piece 34 is fixed incorporatedly to brackets 31, 32 by a bolt 31a and a nut 35b. Then the high frequency pickup 38 is supported between hooks 31a, 32a of the brackets 31, 32 and the follded parts 31b, 32b and the upper/lower face of a magnetic core 48 is clipped closely by the brackets 31, 32 at the same time. Further, a loop antenna 42 and a ridge 34a of the connecting piece 34 are fixed while being opposed to each other. Through the constitution above, since the magnetic flux due to the current flowing to the ridge of the car body connecting piece 34 is concentrated effectively to a closed magnetic flux circuit comprising the brackets 31, 32 and the magnetic core 48, the magnetic flux interlinking the loop antenna 42 is increased and an output voltage extracted by the high frequency pickup 38 is increased by the share to form the antenna system with high sensitivity.

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 transmitting and receiving citizen band radio waves, for example, to communicate with other stations, and will play a major role in the standard communication functions of future JL cars.

Conventional general antenna devices are known as ball antennas, and although antennas that protrude from the car body show favorable performance in terms of reception characteristics, they are always seen as a nuisance when it comes to car body design. He had a destiny.

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 bands of broadcast waves or communication waves received inside automobiles have expanded in recent years, it has become necessary to install multiple antennas for each frequency band, which has made it difficult to improve the aesthetic concept of the automobile'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 method, it was not possible to obtain 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 electrical insulator is formed in a current concentration area of the vehicle body, and the current across the insulator is directly detected by a sensor. 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 automobiles produced in ε.

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.

[Problems to be Solved by the Invention] Problems of the Prior Art As described above, antenna devices for detecting current induced in a vehicle body by broadcast waves have not necessarily been successful in the past.

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 the vehicle body by broadcast waves and transmit it to a receiver mounted on the vehicle. Another object of the present invention is to provide an antenna device for a small automobile in which the installation work of a high-frequency pickup is made more uniform and the output sensitivity is improved.

[Means for Solving the Problems] In order to achieve the above object, the present invention disposes a high frequency pickup close to the circumferential R portion of the vehicle body, thereby detecting high frequency surface current of a predetermined frequency or higher. The high frequency pickup has a loop antenna and a magnetic core inside the loop of the loop antenna, and the high frequency pickup is sandwiched from both sides, and one end of the high frequency pickup is attached to the vehicle body. a bracket that is fastened and fixed to the peripheral edge of the vehicle; and a vehicle body connection piece that is separated from the vehicle body and is configured to clamp and fix the high-frequency pickup with the loop antenna of the high-frequency pickup facing the vehicle body peripheral edge. An antenna assembly is configured. The antenna assembly is characterized in that both sides of the magnetic core are held between brackets, and the antenna assembly is integrated into the vehicle body by fixing the vehicle body connection piece to the vehicle body.

Conventional antenna devices were mainly intended for receiving AM waves due to the background of the times, but for this reason,
It has been found that antennas that detect vehicle body current cannot obtain good reception characteristics because the wavelength of the target broadcast wave is too long. In the invention, the broadcast wave to be received is F.
By setting it to 508H2 or higher in the normal case of the M frequency band or higher, it has become possible to extremely effectively receive signals 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 vicinity of the peripheral edge of the vehicle body is particularly selected as the installation location that satisfies such conditions.

Furthermore, in the present invention, in order to reliably detect the high-frequency current having the frequency characteristics described above, the high-frequency pickup is installed at a distance of 12x1 (13c#(m) (c = speed of light, f = carrier frequency of broadcast wave) from the edge of the vehicle body. The pickup includes a loop antenna for electromagnetically detecting the magnetic flux generated by the car body current, and a
- An electrode type or sliding core coil type is used that can electrostatically detect high frequency signals by forming an electrostatic capacitor between it and the rank hinge, and by these, an efficient detection effect is obtained.

[Embodiments] Hereinafter, preferred embodiments of the automotive antenna device according to the present invention will be described with reference to the drawings.

4 to 12 explain the steps for determining the most efficient antenna installation position by examining the distribution characteristics of high-frequency current.

FIG. 4 shows that when an external radio wave W such as a broadcast wave passes through a car body B made of a metal conductor, a surface current (■) corresponding to the strength of the electromagnetic wave is induced in each part of the car body. Of these radio waves, only the frequency bands used for FM waves, television waves, etc. of 50 Hflz or higher, which belong to relatively high frequency bands, are targeted.

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 performed at each point.In the present invention, a probe based on the same principle as the high frequency pickup provided at a desired vehicle body part, which will be described later, is used. The surface current was measured by moving the probe across the entire surface of the car body, changing direction at each point.

Figure 5 shows the schematic configuration of a probe P created based on almost the same principle as the high frequency pickup described later. Loop coil 12 inside case 10
is fixed, an opening 10a is provided in a part of the case 1o, 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 short circuit wire 14 in case 1.
0, and the output end 16 is connected to the 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.

In the above manner, by moving the probe P along the surface of the vehicle body B and rotating its angle at each measurement point, it becomes possible to accurately determine the surface current distribution and its direction on the vehicle body surface. In FIG. 5, 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 output voltage is measured by a high frequency voltage measuring device 26. The voltage corresponding to the meter reading is recorded by the XY recorder 28 as a surface current distribution in each part of the car body.The XY recorder 28 receives signals indicating each position of the car body from the potentiometer 30, and the high-frequency surface at each position is input to the XY recorder 28. It becomes possible to know the current.

FIG. 6 shows the deviation angle θ between the high-frequency surface current I and the loop coil 12 of the pickup. As shown in Fig. 7, the maximum voltage is obtained when θ is 0, that is, the surface current I and the loop coil 12 of the pickup are parallel, 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 8 and 9 show the magnitude and direction of high-frequency surface currents generated in various parts of the vehicle body at a frequency of 80 MHz, which were determined from both the measurement results using the probe P and computer simulations. As is clear from the above, the magnitude of the surface current exhibits a distribution in which the intensity is high along the edge of the flat portion of the vehicle body, and the density is extremely low in the center of the flat portion of the vehicle body.

Furthermore, as shown in the direction of the current in FIG. 9, it is understood that each current is concentrated in a direction parallel to the edge portion of the vehicle body or along a connection portion of each plane portion.

In Fig. 8, if we examine in detail the current distribution induced in the aforementioned metal parts of the car body along the chain line that traverses the car body, we find that
The distribution characteristics shown in FIGS. 10 to 12 are shown in FIG.

Figure 10 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 toward the center of the lid. The current value decreases as the current value decreases.

Therefore, as shown in FIG. 10, 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. 11 shows the current distribution along the ceiling plate of the car body, and Fig. 12 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 vehicle body, and along the peripheral edge, for example, a loop antenna is arranged in the longitudinal direction. , 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 10 to 12 are the car body current for the FM broadcast frequency of 80HIIz, and as mentioned above, the surface current value decreases as the distance from each car body end or edge increases, indicating that the sensitivity is actually good. 6dB that can be obtained
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 MHz, the high frequency pickup is placed 4 to 5 cm from the periphery of the vehicle body.
A practically sufficient antenna device can be obtained by arranging the antenna device within the range.

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

Therefore, in the present invention, the installation range of the high frequency pickup from the flat edge of the vehicle body is set to 12X 1, since the practical separation distance al114.5 cm at the carrier frequency of 80 HIIz is inversely proportional to the frequency.
If it is provided within O-3c# (m), a good reception effect will be obtained depending on each carrier frequency (in the above equation, C - speed of light, f =
carrier frequency).

As described above, according to the present invention, the high frequency pickup is provided close to the edge of each metal car body, and preferably within the above-mentioned distance from the edge, thereby obtaining a good reception effect. It will be done.

In the present invention, the separation distance actually depends on the frequency, so for example, at a carrier frequency of 100H11z,
It is sufficient to install the high frequency pickup within 3.6 cm from the edge of the vehicle body, and as the carrier frequency f increases, the installation position of the high frequency pickup is limited to a narrow area extremely close to the edge.

FIG. 1 shows a sectional view of an antenna assembly including a high frequency pickup according to the present invention, and FIG. 2 shows an exploded perspective view thereof.

The antenna assembly 70 includes a high frequency pickup 38, a pair of brackets 31 and 32 that sandwich this from both sides,
The antenna assembly 70 consists of a vehicle body connecting piece 34 that is separated from the vehicle body and to which the brackets 31 and 32 are fixed.The structure of this antenna assembly 70 will be described below.

The high frequency pickup 38 includes a metal case 40 that shields electromagnetic waves from the outside, and has a loop antenna 42 inside the case 40 and a magnetic core 48 disposed within the loop of the loop antenna 42 to achieve electromagnetic coupling. It forms a type pickup and has a configuration similar to the probe including a loop coil used to determine the surface current distribution of the vehicle body described above.

The F41 core 48 is made of a ferromagnetic material such as iron, and is fitted into a through hole 50 bored through the upper and lower surfaces of the case 40 at a height slightly protruding from the case 40.

Further, the case 40 is provided with an opening 40a through which the longitudinal side of the loop antenna 42 is exposed, and in this way, a portion of the loop antenna 42 exposed from the case 4° made of a conductor is exposed as described below. It is disposed so as to face the end face of the vehicle body connection piece 34.

Further, a circuit section 58 connected to the loop antenna 42 described above is built in the case 40 of the high frequency pickup 38, and a signal detected by a preamplifier etc. provided in the circuit section 58 is processed by IU. . 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.

The loop antenna 42 is a single-turn antenna, and the coil is coated with an insulating coating so as to be placed in close contact with the vehicle body connection piece 34 while being electrically insulated. It has a pressing structure, and the magnetic flux generated from the surface current can be more strongly linked to the loop antenna 42.

Such a high frequency pickup 38 is held between both sides by a pair of brackets 31 and 32, one end of which is fastened and fixed to the peripheral edge of the small body. This bracket 31.3
Reference numeral 2 is made of a metal plate, and is provided with bent portions 31b and 32b which are arranged opposite to each other and have hook portions 31a and 32a on one side and have attachment holes 31c and 32c on the other side. A vehicle body connecting piece 34 is sandwiched between the bent portions 31b and 32b, and the vehicle body connecting piece 34 is integrally fixed to the brackets 31 and 32 by bolts 35a and nuts 35b.

The high frequency pickup 38 is mounted on the bracket 3
1.32 hook parts 31a, 32a and bent parts 31b, 32b
At the same time, the magnetic core 48 is tightly sandwiched between the brackets 31 and 32 on its upper and lower surfaces.

Further, the loop antenna 42 and the edge 34a of the vehicle body connection piece 34 are fixed in a state where they are opposed to each other.

According to this embodiment, the vehicle body connection piece 3 extending the vehicle body peripheral portion
Magnetic flux due to current flowing through the edge of 4 & yo, bracket 31
．． 32 and the magnetic core 48, the magnetic flux passing through the loop antenna 42 increases, and the output voltage extracted from the high frequency pickup 38 increases by the increased amount, making it possible to create a highly sensitive antenna device. It is formed. Note that the magnetic core 48 is attached to one bracket 32, for example.
These pair of brackets 31.
When the high frequency pickup 38 is held between the high frequency pickup 38 and the magnetic core 48
The workability will be further improved by inserting it.

High frequency pickup 38. Bracket 31
．． 32 and the vehicle body connecting piece 34 form an antenna assembly 70, and by fastening and fixing the vehicle body connecting piece 34 to the vehicle body, the antenna assembly 70 is integrally assembled to the vehicle body. As mentioned above, the vehicle body connection piece 34 is a member that is separated by cutting out a part of the vehicle body ceiling plate to which the antenna assembly 70 is attached, and is attached to the original position with an appropriate fixing means. pickup 38
can be installed in a narrow space easily and uniformly.

FIG. 3 is a sectional view of a main part of such an antenna assembly 70 attached to a vehicle ceiling plate.

That is, the ceiling plate is made up of an outer plate 44 and an inner plate 46, and the antenna assembly 70 is fastened and fixed to the inner plate 46 by the vehicle body connecting piece 34 with bolts 36a and nuts 36b. At this time, the bolt 36a is connected to the inner plate 46 and the vehicle body connection piece 3.
Since it is necessary to ensure continuity with 4, it is better to use a ground bolt. The mounting accuracy of the antenna assembly 70 described above can be arbitrarily adjusted using the bolt 36a and nut 36b. By doing this, errors and variations during installation can be minimized and the installation work can be made more uniform.

As described above, it is possible to reliably detect the broadcast waves of the FM broadcasting frequency from the car body surface current flowing around the car body periphery, and the direction of the car body surface current at this time is as it is clear from Fig. 9 that the car body surface current flows along the car body periphery. Therefore, in this embodiment, the loop antenna 46 is arranged so that its longitudinal direction runs along the peripheral edge of the vehicle body connection piece 34.

In this way, the surface current flowing in the periphery of the vehicle body, especially the periphery of the ceiling plate, is electromagnetically detected using a high frequency pickup, and reception in the high frequency band is ensured without exposing the antenna device to the outside. This makes it extremely useful as an automotive antenna.

[Effects of the Invention] As explained above, according to the present invention, high-frequency surface currents generated in specific parts of the vehicle body, particularly at the periphery of the vehicle body, in response to broadcast waves in a relatively high-frequency band, for example, the FM frequency band or higher, are reduced to high-frequency waves. By detecting with a pickup and forming an antenna assembly with the high frequency pickup, the bracket, and the vehicle body connection piece, it is possible to equalize the installation work of the high frequency pickup and reduce variations in output.

In addition, by arranging the magnetic core within the loop of the loop antenna, the magnetic flux due to the high-frequency surface current generated at the periphery of the vehicle body is concentrated on this magnetic core, and as a result, the magnetic flux passing through the loop antenna increases, making the antenna highly sensitive. You can get the equipment.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of the antenna assembly of the automotive antenna device according to the present invention, Fig. 2 is an exploded perspective view thereof, and Fig. 3 is a cross-sectional view of the main part showing the state in which the antenna assembly is attached to the vehicle ceiling plate. Figure 4 is an explanatory diagram showing the surface current I generated on the vehicle body B by the external wave W. Figure 5 is a probe for determining the distribution of the vehicle body surface current using a probe similar to the high frequency pickup used in the present invention. and an explanatory diagram of its processing circuit; FIG. 6 is an explanatory diagram showing the electromagnetic coupling state between the surface current 1 and the big 7′ tube loop antenna; FIG. 7 is an explanatory diagram showing the directivity characteristics of the loop antenna in FIG. 6; Fig. 8 is an explanatory diagram showing the distribution characteristics of surface current intensity, Fig. 9 is an explanatory diagram showing the direction of surface current, and Figs. FIG. 3 is a characteristic diagram showing current distribution. 38, ... high frequency pickup, 31.32
... Bracket 34 ... Vehicle body connection piece, 42 ... Loop antenna 48 ... Magnetic core 70 ... Antenna assembly.

Claims (1)

[Claims] (1) A high-frequency pickup that has a loop antenna disposed close to the peripheral edge of the vehicle body along its longitudinal direction and detects high-frequency surface current that is induced in the vehicle body by broadcast waves and flows concentrated in the peripheral edge of the vehicle body; A pair of brackets that sandwich the high frequency pickup from both sides and have one end fastened and fixed to the peripheral edge of the vehicle body, and the pair of brackets are separated from the vehicle body and the loop antenna of the high frequency pickup is opposed to the peripheral edge of the vehicle body. a vehicle body connection piece that clamps and fixes the high frequency pickup; the high frequency pickup has a magnetic core disposed within the loop of the loop antenna and held on both sides by the bracket; the high frequency pickup, the bracket and the vehicle body; An antenna device for an automobile, characterized in that an antenna assembly is constituted by a connection piece, and the antenna assembly is integrated into the car body by fixing the car body connection piece to the car body.