JPS61114604A - Antenna system for automobile - Google Patents

Abstract

PURPOSE:To obtain a small-sized antenna system having a wide band characteristic by detecting effectively a current induced in a car body due to a broadcast wave and transmitting the result of detection to an on-vehicle receiver. CONSTITUTION:A high frequency pickup 38 is provided to a special position of a rear window frame 34. A loop antenna 42 is included in the inside of the pickup 38 and a magnetic flux induced from a high frequency surface current flowing in the inside of a metallic case 40 and at the edge of the frame 34 is measured by the antenna 42. A circuit section 58 connected to the antenna 42 is incorporated in the case 40. A varactor diode 70 is is provided in the circuit section 58 and adjusts the resonance frequency of the pickup optionally, the capacitance of said diode 70 is selected by using the tuning frequency of the on-vehicle receiver to control that the tuning frequency of the receiver and the resonance frequency of the pickup 38 are made coincident. The mounting position of the pickup 38 is selected at a position where the largest car body current induced by a ratio wave is given.

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 ball antennas, and although antennas protruding from the car body exhibit favorable performance in terms of reception characteristics, they are always treated as a nuisance when it comes to car body design. It had

In addition, such pole antennas are susceptible to breakage, bending, and other damage even in actual use, are subject to tampering 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, in recent years, as the frequency bands of radio waves or communication waves received inside automobiles have expanded, it has become necessary to install multiple antennas for each frequency band, and the aesthetic concept for the exterior of automobiles has become more and more difficult. Moreover, mutual electrical interference between these various antennas significantly deteriorates their reception performance.

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 it was not possible to use the surface current generated by general car body broadcast waves 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 it to cars manufactured by Nissan.

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 a heavy 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] 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.

In addition, in conventional devices, the resonant frequency of the antenna itself is fixed, so there is a drawback that multiple antenna devices are required when receiving in a wide frequency band. An antenna device for automobiles was requested.

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. An object of the present invention is to provide an antenna device for a small automobile with wideband characteristics.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides an antenna for detecting high frequency surface currents having a predetermined frequency or higher by disposing a high frequency pickup close to the peripheral edge of the vehicle body. The apparatus is further characterized in that a variable capacitance 6-diode controlled by a receiver is connected to the high frequency pickup, and the antenna resonance frequency is matched to a tuning frequency selected by the receiver.

Conventional antenna devices were mainly intended to receive AM waves due to the background of the times, but for this reason, antennas that detect vehicle body current have difficulty receiving good reception because the wavelength of the target broadcast wave is too large. As a result, the characteristics were not obtained.The present inventors focused on this frequency dependence, and in the present invention, the broadcast waves to be received are
By setting the M frequency band or higher to 50 MHz or higher in the normal case, 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 such high-frequency vehicle body current has a distribution characteristic in which the current value is significantly different in each part of the vehicle body, and we have developed a system that is difficult to pick up noise and has a high density of current induced by broadcast waves. 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 arbitrarily adjust the resonant frequency of the antenna according to the tuning frequency required by the receiver, a variable capacitance diode is provided in the high frequency pickup, and the resonant frequency of the antenna can be adjusted according to the tuning frequency of the receiver. A feature is that desired frequency characteristics are obtained by selecting the capacitance of the capacitive diode.

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

FIG. 9 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 I 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 of 50 MHz or higher belonging to relatively high frequency bands used for FM waves, television waves, etc. 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, and 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. The surface current was measured by moving this bulb over the entire surface of the vehicle body while changing direction at each point.

FIG. 10 shows a schematic configuration of a probe P created based on a principle similar to that of a high-frequency pickup described later.A case 10 made of a conductive material is shown in FIG. Loop coil 1 inside
2 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. The 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 the output end 16 is connected to the coaxial cable 1.
8 core wire 2o. 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 the pickup efficiency.

As described above, by moving the probe P along the surface of the vehicle body B 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. 10, 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. The voltage corresponding to the meter indication is XY
The recorder 28 records the surface current distribution in each part of the vehicle body. The XY recorder 28 has a potentiometer 3
A signal indicating each position of the vehicle body is input from 0 to 0, making it possible to know the high frequency surface current at each position.

1 to 4 show a first embodiment of the present invention in which a high frequency pickup is disposed close to the rear peripheral edge of a ceiling plate.

In FIG. 2, a ceiling panel 32 is shown exposed or painted, and this metallic ceiling panel 32 is connected to a rear glass 36 with a rear window frame 34 as its peripheral edge. In this embodiment, from the outer peripheral edge of the body of the rear window frame 34, Q =
It is characterized in that a high frequency pickup 38 is provided in a region within 12X 13-3λ(III)λ-wavelength (++) of the telegraph frequency.

As shown in detail in FIG. 1, the high frequency pickup 38 includes a metal case 40 that shields magnetic flux from the outside, and includes a loop antenna 42 therein.
It forms an electromagnetic coupling 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.

FIG. 3 shows a cross-sectional view in which the high frequency pickup 38 is fixed to the ceiling plate 32, and the ceiling plate 32 includes a roof panel 44, and the above-mentioned rear window frame 34.
is fixed to one end of this roof panel 44, and the rear glass 36 is fixed to the roof panel 44 via a fastener 46 and a dam 48, and the fastener 46 and dam 48 are airtightly attached with an adhesive 50. ing.

Further, a molding 52 is fixed between the roof panel 44 and the rear glass 36.

In this embodiment, in order to dispose the loop antenna 42 of the high frequency pickup 38 facing the peripheral edge of the rear window frame 34, the rear window frame 34 is provided with an opening 34a in a part thereof, and the high frequency pickup 38 is provided in this opening 34a. case 40 is inserted and arranged.

As shown in detail in FIG. 3, the case 40 is provided with an opening 408 through which the longitudinal side of the loop antenna 42 is exposed.
A portion of the loop antenna 42 exposed from the rear window frame 34 is disposed close to and facing the opening edge of the rear window frame 34. Therefore, inside the case 40, the magnetic flux induced from the high frequency surface current flowing around the periphery of the rear window frame 34 is reliably captured by the loop antenna 42.
Further, since magnetic flux from the outside is reliably shielded by the case 40, the current induced in the vehicle body can be detected with high sensitivity by the high frequency pickup 38.

In order to securely position and fix the case 40 of the high frequency pickup 38 to the rear window frame 34,
As shown in FIG. 4, L-shaped brackets 54 and 56 are connected to both ends of the case 40 with bolts, etc., and these brackets 54 and 54 are attached to the rear window frame 34.
It is fixed with a screw.

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 matching circuit provided in the circuit section 58,
A signal detected by a preamplifier or the like is processed. Furthermore, the high frequency detection signal obtained in this way is transmitted to the coaxial cable 6.
0 to the outside and transmitted to various receivers installed in the car, such as radios and televisions. The circuit section 58 is connected to the cable 6 for power and signals for circuit control.
It is supplied from 2.

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.

After the high-frequency pickup 38 is installed in the exposed or painted ceiling board 32, especially the rear window frame 34, as described above, the roof garnish 64 is fixed to the ceiling board, and the roof garnish 64 and the rear window frame 34 are fixed to each other. Edge mole 66 is fixed to the end.

In this embodiment, the side of the loop antenna 42 exposed from the case 40 is Q from the edge of the rear window frame 34.
=12 Since the surface current flows along the periphery of the rear window frame 34, in this embodiment, the loop antenna 46 is arranged so that its longitudinal direction runs along the periphery of the rear window frame 34.

As described above, according to the first embodiment of the present invention, the surface current flowing in the peripheral portion of the vehicle body, particularly the peripheral portion of the ceiling plate, is electromagnetically detected by the high frequency pickup, and the antenna device is not exposed to the outside at all. This makes it possible to reliably receive reception in a high frequency band, making it extremely useful as an automotive antenna.

A further feature of the present invention is that the circuit section 5 described above is
8 is provided with a variable capacitance diode 70, and by this variable capacitance diode 70, the resonance frequency of the high frequency pickup including the loop antenna 42 can be arbitrarily adjusted. The capacitance value of the variable capacitance diode 70 is selected according to the tuning frequency of the on-vehicle receiver, and the tuning frequency of the receiver is controlled to match the resonance frequency of the high frequency pickup 38.

In FIG. 5, the variable capacitance diode 70 and the preamplifier described above are connected to the loop antenna 42 of the electromagnetically coupled high frequency pickup 38 in the embodiment shown in FIGS. 1 to 4, and the variable capacitance diode 70 and the receiver A circuit diagram showing the connection relationship with is shown.

In the figure, the loop antenna 42 has a contact
The capacitor C1, the variable capacitance diode 70, and the capacitor C2 are connected in series, and have a resonant frequency determined by the series capacitance value. High frequency pickup 38
The output of capacitor C1 and variable capacitance diode 7
Desired impedance conversion and high frequency amplification are performed by the preamplifier taken out from the anode end of the pickup 38 and provided as the circuit section 58 as described above in the vicinity of the pickup 38. As shown in the figure, the preamplifier includes a bandpass filter BPF, which selects a desired frequency band and removes other noise signals and the like. Then, the band-amplified high-frequency detection signal is impedance-converted by an impedance conversion circuit consisting of a resistor and a capacitor, and after being further high-frequency amplified, it is output from the coaxial cable 60 toward the receiver. A power supply voltage for controlling the circuit is supplied to these preamplifiers from a cable 62.

Therefore, the detection signal in the preamplifier reaches its maximum value at the resonant frequency of the high frequency pickup 38, and in order to match this resonant frequency with the desired reception frequency, the capacitance value of the variable capacitance diode 70 is changed, and the resonant frequency of the high frequency pickup 38 is changed. By tuning the antenna to the desired reception frequency, it is possible to perform extremely sensitive reception even though it is a small antenna. It also has the function of protecting the elements.

In order to change the capacitance value of the variable capacitance diode 70 described above, a predetermined control voltage is applied to the cathode side of the variable capacitance diode 70, and in the present invention, this applied voltage is controlled in conjunction with the tuning frequency of the receiver. has been done.

A portion of the receiver 72 is shown in FIG.
The other end of the coaxial cable 60 described above is connected to an antenna terminal 74 of a receiver 72 and is connected to a capacitor 78 from a tuning circuit 76.
It is connected to the next stage receiving circuit via. Tuning circuit 7
6, the tuning frequency is arbitrarily selected by changing the inductance of the coil or the capacitance of the capacitor. In the embodiment, the frequency selected in this manner is controlled and selected by the tuning frequency control circuit 79, and the currently selected frequency is digitally displayed in the vehicle interior on the display section 80.

A characteristic feature of this embodiment is that the tuning frequency control voltage from the tuning frequency control circuit 79 of the first receiver 72 is supplied to the cathode side of the variable capacitance diode 70 via the variable resistor 84 and the resistor 86. As a result, the variable capacitance diode 70 is supplied with a control voltage corresponding to the tuning frequency selected by the tuning circuit 76.

Therefore, according to the present invention, when a desired reception frequency is selected by the receiver 72, the high frequency pickup 38 changes its resonance frequency to match the previous tuning frequency, thereby achieving reception with good sensitivity even with a small antenna. Kudzu that can perform the action.

As described above, according to this embodiment, it is possible to effectively detect the vehicle body surface current using the electromagnetic coupling type high frequency pickup, and furthermore, it is possible to pick up the high frequency current at a resonant frequency tuned only to the necessary receiving frequency. This makes it possible to obtain high-quality detection signals with extremely good sensitivity.

In the present invention, the high frequency pickup can detect the surface current not only with the above-mentioned single-coil loop antenna, but also with a high frequency pickup with an antenna coil wound around a ferrite core. A high frequency pickup 138 having a pickup coil 90 wound thereon is shown at 88, and this ferrite core type high frequency pickup 138 is arranged along the peripheral edge of the vehicle body to detect a desired vehicle surface current.

In the embodiment shown in FIG. 6 as well, a variable diode 70 is connected to the coil 90, and a receiving
The control voltage of the variable capacitance diode 70 is changed by the tuning signal, whereby the tuning frequency selected by the receiver 72 and the resonance frequency of the high frequency pickup 138 are controlled to match.

Furthermore, the present invention can be used not only for the electromagnetic coupling type described above but also for capacitive coupling type high frequency pickups, and as shown in FIG. A high frequency pickup 238 is shown, and this electrostatic pickup can also effectively detect the surface current of the vehicle body. Also in the embodiment shown in FIG. 7, the variable capacitance diode 70 is connected to the detection electrode 9.
By providing a tuning circuit connected to the receiver 2 and controlling it with the tuning frequency of the receiver □, the resonance frequency of the capacitively coupled pickup can be arbitrarily adjusted.

FIG. 8 shows another embodiment of the capacitively coupled pickup, in which two detection electrodes 94.
96 are provided, and by providing these detection voltages 1494 and 96 in predetermined peripheral areas of the vehicle body, surface current can be detected. In this embodiment as well, the variable capacitance diode 70 allows the resonance frequency of the high frequency pickup to be controlled to match the tuning frequency of the receiver.

[Effects of the Invention] As explained above, according to the present invention, 1. A broadcast wave receiving antenna is formed using high-frequency surface current generated in specific parts of the car body, especially around the periphery of the car body, and its resonant frequency is controlled to match the tuning frequency of the receiver using a variable manufacturer's diode. To obtain a compact and high-performance automobile antenna device that can perform a high-quality detection action on waves with high density and low noise, and does not require a conventional externally exposed pole antenna or the like. becomes possible.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing in detail the fixed state of the high-frequency pickup in FIG. FIG. 3 is a sectional view of the main parts of the first embodiment, and FIG. 4 is another perspective view showing the mounting state of the high frequency pickup in the first embodiment. Main part sectional view from the direction, 5th
The figure is a circuit diagram showing a preferred circuit configuration of the electromagnetically coupled high-frequency pickup shown in Fig. 2, together with a part of the receiver, and Fig. 6 is a circuit diagram of the present invention in an electromagnetically coupled pickup using a ferrite core. Figure 7 is a circuit diagram showing the main part of a capacitively coupled pickup with a variable capacitance diode connected to it, Figure 8 is a capacitively coupled high frequency pickup using two detection electrodes. 9 is an explanatory diagram that does not show the surface current I generated on the vehicle body B by the external wave W, and FIG. 10 is a probe similar to the high frequency pickup used in the present invention. FIG. 2 is an explanatory diagram of a probe and its processing circuit for determining the distribution of vehicle body surface current using the probe. 38.138,238... High frequency pickup 34... Rear window frame 42... Loop antenna 70... Variable capacitance diode 72... Receiver.

Claims (1)

[Claims] (1) A high-frequency pickup is placed close to the periphery of the car body along its longitudinal direction to detect the high-frequency surface current that is induced in the car body by broadcast waves and flows concentrated at the periphery of the car body. An antenna device for an automobile, characterized in that a variable capacitance diode controlled by the receiver is connected, and the antenna resonance frequency is matched with a tuning frequency selected by the receiver.