JPS61129906A - Antenna system for automobile - Google Patents

Abstract

PURPOSE:To reduce multi-path noise by arranging two high frequency pickups to a circumferential ridge of a ceiling plate of a car body at a prescribed pitch and selecting a better pickup in the reception state so as to improve the directivity of the antenna. CONSTITUTION:The two high frequency pickups 38, 138 are provided respectively in the vicinity of the circumferential ridge of a rear glass side of the ceiling plate 32 of the car body and in the vicinity of the circumferential ridge of a front glass side to constitute a diversity reception antenna. Either of the reception waves by the pickups 38, 138 is inutted selectively to a high frequency amplifier circuit 78 via a switch circuit 74. Then the signal is fed to a detection circuit 84 via an intermediate frequency amplifier circuit 82 and a sound signal is extracted. A comparator 92 compares an output of the circuit 82 with a reference level and when the signal level is lowered below the reference level, a switch circuit 74 is controlled to switch the connected pickups.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention relates to a vehicle antenna device using a high frequency pickup as an antenna.

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

A conventional general antenna device is known as a ball antenna, and although the antenna protruding from the car body shows favorable performance in terms of reception characteristics, it has the fate of always 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 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 a V windshield has been put into practical use.

As another conventional solution, there is also an antenna device in which a high frequency pickup is disposed close to the periphery of the vehicle body, thereby detecting high frequency surface current of a predetermined frequency or higher, and generally detects the vehicle body current. Since antennas are unable to obtain good reception characteristics because the wavelength of the target broadcast wave is too large, this conventional device focuses on frequency dependence and transmits the target broadcast wave to the normal FM frequency band or above. In this case, by setting the frequency to 50 MHz or higher, it is possible to receive signals from the vehicle body current extremely effectively.

In addition, considering that the high-frequency car body current has a distribution characteristic that is significantly different in the current value in each part of the car body, high-frequency pickups are installed in areas where it is difficult to pick up noise and where the density of current induced by broadcast waves is high. Therefore, the vicinity of the periphery of the vehicle body is particularly selected as the installation location that satisfies these conditions.

Furthermore, this conventional example is characterized in that, in order to reliably detect the high-frequency current having the above-mentioned frequency characteristics, the high-frequency pickup is arranged along the edge of the vehicle body within 12 x 10 cm/f, (m). As a pickup, the magnetic flux generated by the vehicle body current is NF! The antenna is of an electrode type or a sliding core coil type that can electrostatically detect a high frequency signal by forming an electrostatic capacitance a between the loop antenna and the trunk hinge for i-directional detection.

[Problems to be Solved by the Invention] 11 Arashi Kou February 1 In the conventional vehicle antenna device in which one high-frequency pickup for picking up the current induced in the vehicle body as described above is arranged at the periphery of the heavy body, The directional characteristics of the high-frequency pickup used as an antenna are poor, and when receiving FM broadcasts at high frequencies in the IF band, there is strong straightness. There was a problem in that path noise was likely to occur.

Purpose of the Invention The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to provide a high-frequency pickup that picks up high-frequency surface currents induced by the vehicle body and concentrated around the periphery of the ceiling plate of a heavy object. The purpose is to provide a diversity receiving system by arranging two antennas at a required interval in the antenna, thereby improving the directivity of the antenna and reducing multipath noise.

[Means and Effects for Solving the Problems 1] In order to achieve the above-mentioned object, the present invention provides a system that is arranged close to a heavy ceiling plate along its longitudinal direction and that is induced into the vehicle body by broadcast waves and concentrated on the periphery of the ceiling plate. Two high-frequency pickups that efficiently pick up the high-frequency surface current that flows are placed at the required interval around the periphery of the ceiling panel. It is characterized in that it can be switched to.

According to such a vehicle antenna device, the directivity characteristics of the antenna are improved and multipath noise is reduced.

[Embodiment 1] Hereinafter, a preferred embodiment of the automotive antenna device according to the present invention will be described based on the drawings.

11 to 16 explain the steps for determining the most efficient antenna device position by examining the distribution characteristics of high frequency current.

FIG. Of these radio waves, only the frequency bands used for FM waves of 508H2 or higher, television waves, etc. belonging to relatively high frequency bands are targeted.

Then, in such a specific high frequency band, the induced current distribution of the vehicle body is measured, and a high frequency pickup is installed in a part where the surface layer R density is high and there is little noise.To know the surface current distribution, a total of r5 A probe based on the same principle as the high-frequency pickup installed on the desired vehicle body part described later is used, and this probe is spread over the entire surface of the heavy body. The surface current was measured by moving it over the entire area while changing the direction at each point.

FIG. 12 shows a schematic configuration of a probe P created based on a principle similar to that of a high-frequency pickup described later, in which a case 10 made of a conductive material is used to avoid mixing of radio waves from the outside. 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 through this opening 10a, and the exposed part of the loop coil 12 is placed close to the surface of the vehicle body B. The loop coil 12 detects the magnetic flux generated from the vehicle 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 si! Connected to 2'O. Further, a capacitor 22 is provided in a part of the loop coil 12, so that the frequency of the loop coil 12 can resonate 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. 12, 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 2G. This output voltage is read by the meter indication value of the measuring device 26, and the voltage corresponding to this meter indication value is
The sensor 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.

FIG. 13 shows the deviation angle θ between the high-frequency surface current ■ and the loop coil 12 of the pickup. ■Let's generate the first
As shown in Figure 4, the maximum voltage is obtained when θ is O, that is, the surface current ■ is parallel to the loop coil 12 of the pickup, and the maximum voltage is obtained when the probe P is rotated at each measurement point and the maximum voltage is 4q. The direction of current I can be known.

Figures 15 and 16 show the magnitude and direction of high-frequency surface currents generated in various parts of the vehicle body at a frequency of 80H1lz, which were determined from both the measurement results with the probe P and computer simulations. As is clear from the above, the magnitude of the surface current exhibits a distribution in which the density is high in the portion along the edge of the flat portion of the vehicle body, and the density is extremely low in the central portion of the flat portion.

Furthermore, as shown in the current direction in FIG. 16, 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.

Therefore, from FIG. 15, it is understood that broadcast waves can be picked up with good sensitivity near the periphery of each part of the vehicle body.

In this embodiment, the high-frequency pickups are installed on the ceiling panel, and furthermore, in this embodiment, the pair of high-frequency pickups as diversity antennas are installed near the periphery of each ceiling panel. For example, a loop antenna is placed along the length of the antenna, but in order to obtain extremely good sensitivity in practice, the pickup installation range from the edge may be set to a range that depends on the carrier frequency of the broadcast wave. suitable.

1 to 4 show a state in which one of the high-frequency pickups constituting the diversity antenna is disposed near the periphery of the ceiling plate on the rear glass side in this embodiment.

In FIG. 1, a ceiling plate 32 is shown exposed, and this metal ceiling plate 32 is connected to a rear glass 36 via a rear window frame 34. In this embodiment, the position near the periphery of the ceiling plate 32 is 4.5 cm inward from the edge of the rear window frame 34.
A high frequency pickup 38 is provided in an area within n+.

As shown in detail in FIG. 2, it includes a metal case 40 that seals the magnetic flux from the high-frequency pickup 38, and includes a loop antenna 42 therein.
It forms a fla-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 the 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 dam 48 are airtightly attached using an adhesive 50. 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. 13, the case 40 is provided with an opening 40a through which the longitudinal blade 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 electromagnetic waves from the outside are reliably shielded by the case 40, it becomes possible to detect the current induced in the heavy object with high sensitivity using the high frequency pickup 38.

In order to securely position and fix the case 4o 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 or the like.
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 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.

The loop antenna 42 is a single-turn antenna, and the coil is insulated 7111. m and is pressed against the rear window frame 34, and the magnetic flux generated from the surface current can be more strongly linked to the loop antenna 42.

As described above, after the high frequency pickup 38 is assembled into the rear window frame 34 on the exposed ceiling panel 32VI, the roof garnish 64 is fixed to the ceiling panel, and the ends of the roof garnish 64 and the rear window frame 34 are fixed. Edgemol 66 is fixed to the.

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.
．． placed within 5 cm, thereby providing 80 HIf
The broadcast wave of the FM broadcast frequency z can be reliably detected from the car body surface current flowing at the periphery of the rear window frame 34, and the direction of the car body surface current at this time is as shown in 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.

Further, as shown in FIGS. 5 and 6, the high frequency pickup 138 as the other antenna constituting the diversity antenna is provided near the front edge of the ceiling plate 32. Header inner panel 64 provided at the front end of 32
The service hole 64a is located within the service hole 64a.

As is clear from FIG. 6, the roof panel 44 of the ceiling board
A windshield 68 is fixed through a dam 66, and a molding 7 is secured through a stopper 70 as is well known.
2 connects between the roof panel 44 and the windshield 68.

This high frequency pickup 138 has a structure similar to that of the high frequency pickup 38, and has a structure similar to that of the high frequency pickup 38.
The reference numeral 100 is added to each member of 8 to indicate the corresponding member. As is clear from FIG. 6, the loop antenna 142 extends 4.5 C
This makes it possible to reliably detect the vehicle body surface current of the header inner panel 64, which is concentrated at a high density.

Furthermore, the mountain high frequency pickup 38, 138 has a wavelength of 4I.
The two antennas are separated by a distance of -1 which satisfies the condition that the antenna spacing is λ/2 or less in an FM band diversity reception system, which is about 1.5 m, and in the embodiment, the distance is 18 to 1.5 m square.

A diversity reception antenna is configured by the aforementioned mountain high-frequency pickups 38 and 138, and then the one with better reception sensitivity is automatically selected between the mountain high-frequency pickups 38 and 138 to receive the C broadcast wave. The circuit configuration will be explained with reference to FIG.

In the figure, the coaxial cables 60 and 160 drawn out from the high frequency pickup 38 installed near the rear glass side periphery of the ceiling plate 32 of the vehicle body and the high frequency pickup 138 installed near the front side periphery are connected to switch circuits. 7
When the switch circuit 74 is switched by the output from the T-type flip 70 tube 76 which will be described later, either the received wave of the high frequency pickup 38 or the high frequency pickup 138 is selectively input to the high frequency amplifier circuit 78. The received wave passes through an intermediate frequency amplification circuit 82 connected to a local oscillation circuit 8o, and a detection circuit 84 extracts only the audio signal.

Thereafter, this audio signal is divided into a right output and a left output via a multiple filter 86 and a left and right layer width divider 88L.

The signals are sent to Subi 901 and 90R via 88R, respectively.

By the way, the output signal from the intermediate frequency amplifier 82 is
2, the level values of the signals are compared, and the comparator 92 includes high frequency pickups 38 and 13, respectively.
A level value of a signal outputted from the intermediate frequency amplification circuit 82 when the reception sensitivity by 8 falls below a predetermined value is set, and the comparator 92 uses this level value and either the high frequency pickup 38 or the high frequency pickup 138. The signal output from the intermediate frequency amplifier 82 is compared with the signal output from the intermediate frequency amplifier 82 when the broadcast wave is being received by the T-type flip-flop 96. The output of flop 96 is inverted.

This output reversal causes the switch circuit 74 to switch, and the high frequency pickup that receives the broadcast wave is switched to the one with the better reception condition.

In this way, the high frequency pickup 38 provided near the periphery of the rear 77 lath side of the ceiling plate 32 and the high frequency pickup 138 provided near the periphery of the windshield side of the ceiling plate 32 constitute a diversity receiving antenna. , it is designed to automatically switch to the high frequency pickup with better reception sensitivity, and by mutually complementing the parts of weak reception sensitivity in each directional characteristic of the mountain high frequency pickup 38.138 shown in Figure 8. Directional characteristics of a high frequency pickup as an antenna are improved.

At the same time, multipath noise is reduced by the diversity reception method using the high-frequency pickups 38 and 138.

Further, the arrangement of a pair of high-frequency pickups for performing diversity reception is not limited to the above-mentioned embodiment, but as shown in FIG. Mountain high frequency pickup 238
．． 338 is placed and there is C, and there is also a mountain high frequency pickup 2
38, 338 is an F with a wavelength λ of about 4 m, which sets the condition that the antenna spacing is λ/2 or less in a diversity receiving system.
The distance is within the M band, for example, about 1 to 1.2 m.

Even in this embodiment, as shown in the directional characteristics of FIG. 10, the mountain high-frequency pickups 238 and 338 each compensate for the weak receiving sensitivity, and the directional characteristics of the antenna are improved as in the previous embodiment. At the same time, multipath noise is reduced.

[Effects of the Invention] As explained above, according to the present invention, the diversity receiving anti-dog is configured by a pair of high-frequency pickups that detect the high-frequency surface current induced in the vehicle body ceiling plate and concentrated at the periphery of the ceiling plate. This has the effect of improving the directional characteristics of the antenna and reducing multipath noise.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a state in which one of the high-frequency pickups constituting the diversity antenna of the vehicle antenna device of the present invention is attached to the rear window frame of the ceiling plate of a vehicle. FIG. 2 is a perspective view of the high-frequency pickup in FIG. 1. 3 is a sectional view of the main part in Fig. 1, Fig. 4 is a sectional view of the main part in Fig. 1 from another direction, and Fig. 5 is a plan view showing the structure of the diversity antenna in detail. A schematic perspective view that does not show the state in which other high-frequency pickups are installed on the inner panel of the heater on the ceiling, Figure 6 is a sectional view of the main parts showing the installed state of the high-frequency pickup shown in Figure 5, and Figure 7 is for vehicles. An explanatory diagram showing one embodiment of the antenna device, FIG. 8 is a directional characteristic diagram of the mountain high frequency pickup in the above embodiment, FIG. 9 is an explanatory diagram showing another embodiment of the antenna device for a vehicle, and FIG. Figure 9 shows the directivity characteristics of the mountain high-frequency pickup, and Figure 11 shows the surface current f generated on the vehicle body B by the external wave W.
Figure 12 is an explanatory diagram of a probe and its processing circuit for determining the distribution of car body surface current using a probe similar to the high frequency pickup used in the present invention, and Figure 13 is an explanatory diagram of the surface current I. FIG. 14 is an explanatory diagram showing the directional characteristics of the loop antenna in FIG. 13. FIG. 15 is an explanatory diagram showing the distribution characteristics of surface current intensity. is an explanatory diagram showing the direction of surface current. 32... Ceiling plate 38.138,238,338... High frequency pickup 36... Rear glass 68... Windshield

Claims (3)

[Claims] (1) They are placed close to each other along the longitudinal direction of each periphery at predetermined intervals at different positions near the periphery of the car body ceiling plate, and efficiently reduce the high-frequency surface current that is induced in the car body by broadcast waves and flows concentrated around the periphery of the ceiling plate. What is claimed is: 1. A vehicle antenna device comprising a pair of high frequency pickups that pick up signals in a consistent manner, and automatically selecting the high frequency pickup with a better reception condition among the pair of high frequency pickups. (2) The antenna device for a vehicle according to claim 1, wherein the pair of high-frequency pickups are arranged at a predetermined interval near a peripheral edge of a ceiling plate on the rear glass side. (3) In the antenna device according to claim 1, one of the pair of high-frequency pickups is arranged near the periphery of the ceiling plate on the rear glass side, and the other one is arranged near the periphery of the ceiling plate on the windshield side. A vehicle antenna device characterized by: