JPH0652849B2 - Pickup of car antenna - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention effectively picks up a broadcast wave received by an automobile antenna pickup, particularly a vehicle body of an automobile, and supplies a detection signal to various receivers mounted on the vehicle. The present invention relates to an improved automobile antenna pickup.

[Prior Art] An antenna device is indispensable for a vehicle in order to reliably receive various broadcast waves, for example, broadcast communication waves of radio, television, telephone, etc., by a receiver provided in the vehicle. This kind of antenna device is extremely important for transmitting and receiving citizen's band radio waves that communicate with other stations,
It plays a major role in the standard equipped communication functions of the upcoming automobiles.

The conventional general antenna device is known as a pole antenna, and the antenna protruding from the vehicle body shows preferable performance in terms of its reception characteristics, but it has the fate that it is always treated as an obstacle in terms of vehicle body design. Was.

Further, such a pole antenna has various problems such as breaking, bending, etc. even in actual use, being a target of mischief or theft, and generating an unpleasant wind noise at high speed. In the past, however, there have been many requests to somehow remove this.

In particular, as the frequency band of broadcast waves or communication waves received inside a car expands, as in recent years, it is necessary to install multiple antennas according to each frequency band, and the aesthetic concept of the car's appearance is neglected. There is a problem that they are destroyed and their reception performance is significantly deteriorated due to electrical mutual interference between these various antennas.

In the past, some efforts have been made to remove the above-mentioned pole antenna or conceal it so that it cannot be seen from the outside. For example, attaching an antenna thin wire to a rear windshield has been put into practical use.

As another conventional solution, it has been proposed to detect the surface current induced in the vehicle body itself by broadcast waves. The use of such a current flowing through the vehicle body is considered to be the most reliable and efficient method at first glance, but conventional experiments have continued to show results that completely violate such expectations.

The first reason that the surface current induced by a general broadcast wave on the vehicle body cannot be used is that the surface current value is not as large as expected, and conventional surface current is mainly applied to the ceiling plate of the vehicle body. Although it was the target, even with this, it was not possible to obtain a detection output of a level sufficient for sufficient use.

The second conventional problem is that noise is mixed into the surface current at an extremely large rate. Such noise is mainly generated from the ignition system of the engine and the regulator system for charging the battery, and the engine is operating. As long as these noises leaked to the car body, it was impossible to perform a clear broadcast wave reception action that could be practically used.

Even under such disadvantageous conditions, some proposals have been made in the past. As a conventional antenna device that utilizes the current induced in the vehicle body by broadcast waves, Japanese Patent Publication No. 53-22
418 is known, and an electrical insulating portion is formed in a current concentrating portion of a vehicle body, and a current between both ends of the insulating portion is directly detected by a sensor. Certainly, it was suggested that this conventional device can obtain a practical detection signal with an SN ratio induced, but the pickup structure requires a notch in a part of the vehicle body. It was impossible to apply this to mass-produced automobiles.

Japanese Utility Model Publication No. 53-34826 is known as another conventional device, and an antenna has been proposed in which a pickup coil detects a current flowing through a pillar of a vehicle. This conventional device was useful for indicating the development direction of incorporating the antenna in the vehicle body, but in practice, it is not practical to provide a pickup coil orthogonal to the longitudinal direction in the vicinity of the pillar, In addition, such a pickup arrangement could not obtain a practical antenna output, and was considered to be a mere idea.

[Problems to be Solved by the Invention] Problems of Prior Art As described above, conventionally, the antenna device for detecting the current induced in the vehicle body by the broadcast wave has not always been successful.

Particularly, in the related art, a pickup structure and a practicable S for effectively detecting the current induced by the broadcast wave flowing in the vehicle body, which is the above-mentioned major problem of the related art.
The arrangement of the pickup for obtaining the N ratio has not been properly solved, and rather various experimental results have pointed out that the antenna device utilizing the vehicle body current could not be used in principle.

OBJECT OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is an improvement that can detect a current induced in a vehicle body by a broadcast wave with high sensitivity and transmit it to a vehicle-mounted receiver. The present invention is to provide a pickup of an antenna for a small car.

[Means for Solving the Problems] In order to achieve the above object, in a pickup of an automobile antenna according to the present invention, a core of the pickup has a rectangular parallelepiped shape and has a groove parallel to the longest side of the rectangular parallelepiped. In addition, the loop antenna wound around the core is wound a plurality of times through the groove, and is covered with an insulating coating. Furthermore, the opening edge of the vehicle body peripheral edge is covered over the entire length of the groove. It is characterized in that the opening edge and the loop antenna are sandwiched and are arranged in parallel with each other and are in close contact with each other.

The antenna device in the past was mainly intended to receive the AM wave from the background of the times, but for this reason, the antenna that detects the vehicle body current receives a good reception because the wavelength of the target broadcast wave is too long. The result is that the characteristics cannot be obtained, and the inventors of the present invention pay attention to this frequency dependence and set the broadcast wave to be received in the present invention to FM.
By setting the frequency to 50MHz or higher in the normal case of the frequency band or higher, it has become possible to effectively receive from the vehicle body current, which was previously impossible.

Further, in the present invention, attention is paid to the fact that the current value of such a high-frequency vehicle body current also has a distribution characteristic that is remarkably different in each part of the vehicle body. The present invention is characterized in that a high-frequency pickup is provided, and in the present invention, the vicinity of the peripheral portion of the vehicle body is particularly selected as the installation location that satisfies such conditions.

Further, in the present invention, in order to reliably detect the high-frequency current having the above-mentioned frequency characteristic, the high-frequency pickup is placed at 12 × 10 ⁻³ c / f (m) (c = luminance, f = broadcast wave Carrier frequency), and the pickup is a loop antenna for electromagnetically detecting the magnetic flux generated by the vehicle body current.
An efficient detection action is obtained.

[Embodiment] A preferred embodiment of an automobile antenna device according to the present invention will be described below with reference to the drawings.

5 to 13 explain the steps for investigating the distribution characteristics of the high-frequency current and obtaining the most efficient antenna installation position.

FIG. 5 shows a surface current I depending on the intensity of an electromagnetic wave when an external radio wave W such as a broadcast wave passes through a vehicle body B made of a metal conductor.
Is induced in each part of the vehicle body, and in the present invention, only the frequency band used for FM waves of 50 MHz or more, television waves, etc. belonging to a relatively high frequency band among these radio waves is 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 noise is small.

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 a high-frequency pickup provided in a desired vehicle body part described later is used. This probe was used, and the surface current was measured by moving the probe over the entire surface of the vehicle body while changing the direction at each point.

FIG. 6 shows a schematic structure of a probe P produced on the basis of a principle similar to that of a high-frequency pickup to be described later, and a case 10 made of a conductor is provided in order to avoid mixing of radio waves from the outside. 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 through the opening 10a, and an exposed portion of the loop coil 12 is brought close to the surface of the vehicle body B. The magnetic flux generated from the vehicle body surface current is detected by the loop coil 12. A part of the loop coil 12 is connected to the case 10 by a short-circuit wire 14, and the output end 16 has a core wire 20 of a coaxial cable 18.
It is connected to the. 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 measured frequency and the pickup efficiency can be increased.

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

FIG. 7 shows the deviation angle θ between the high frequency surface current I and the loop coil 12 of the pickup. As shown in the figure, the magnetic flux φ due to the current I is linked to the loop coil 12 so that the detected voltage is applied to the loop coil 12. As shown in FIG. 8, the maximum voltage is obtained when V is generated, that is, when the surface current I and the loop coil 12 of the pickup are parallel, and the probe P is rotated at each measurement point to obtain the maximum voltage. It is possible to know the direction of the surface current I when being applied.

FIGS. 9 and 10 show the magnitude and direction of the high frequency surface current generated in each part of the vehicle body at 80 MHz and the frequency obtained from both the measurement result by the probe P and the simulation by the computer. As is apparent from the figure, the magnitude of the surface current shows a high density in the portion along the edge of the plane portion of the vehicle body and an extremely low density in the central portion of the flat plate portion.

Further, it is understood that each current is concentrated in the direction parallel to the edge portion of the vehicle body or in the direction along the connecting portion of each flat surface portion as shown in the direction of the current in FIG.

Referring to FIG. 9, a detailed study of the current distribution induced in the metal part of the vehicle body along the chain line that longitudinally extends through the vehicle body
The distribution characteristics as shown in FIGS. 11 to 13 are obtained.

FIG. 11 shows the surface current distribution along the trunk lid from the vertical cut lines A to B. As is clear from the figure, the largest current flows at both ends, and from both ends toward the center of the lid. Shows the distribution characteristic that the current value decreases.

Therefore, from FIG. 11, regarding the trunk lid, if a high frequency pickup is arranged in the vicinity of the peripheral portion thereof, it becomes possible to detect the intensively flowing current in the vicinity of the peripheral portion.

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

Therefore, in the present invention, it is understood that the broadcast wave can be picked up with good sensitivity in the vicinity of the peripheral edge 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 plates, but is similarly applicable to pillars and fenders.

Further, in the present invention, the high-frequency pickup is installed in the vicinity of the peripheral portion of each vehicle body along the peripheral portion, for example, in the longitudinal direction of the loop antenna. It is preferable to set the pickup installation range from the edge to a range depending on the carrier frequency of the broadcast wave.

The distribution characteristics of Figs. 11 to 13 are the currents of the car body with respect to the FM broadcasting frequency of 80MHz, and the surface current value decreases as described above according to the distance from the end or edge of each car body, and the sensitivity is actually good. Considering the current drop range of 6 dB or less that can obtain
It is understood that extremely good sensitivity is obtained within cm.

Therefore, in the present invention, if the high frequency pickup is arranged within 4.5 cm from the peripheral portion of the vehicle body with respect to the carrier frequency of 80 MHz, a practically sufficient antenna device can be obtained.

Then, it was clarified that this practical separation distance depends on the carrier frequency by computer simulation results and various experimental results, and it was confirmed that the practical separation distance decreases as the frequency increases.

Therefore, since the practical separation distance of 4.5 cm at the carrier frequency of 80 MHz is inversely proportional to the frequency, in the present invention, the installation range of the high frequency pickup from the metal flat edge of the vehicle body is 12 × 10 ^-3 c. If it is set within / f (m), a good receiving action can be obtained according to each carrier frequency (in the above equation, c = light velocity, f =
Carrier frequency).

As described above, the high-frequency pickup is provided close to the edge of each metal vehicle body, and preferably is provided within the above-mentioned distance from the edge, whereby a good receiving action can be obtained.

In addition, since the separation distance actually depends on the frequency, for example, at a carrier frequency of 100 MHz, 3.6 c from the edge of the vehicle body
It is only necessary to provide the high-frequency pickup within m, 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. 3 shows a mounting example in which the high-frequency pickup according to the present invention is arranged near the rear peripheral edge of the ceiling plate.

In the figure, the ceiling plate 32 is shown exposed.
This metal ceiling plate 32 is connected to a rear glass 36 with a rear window frame 34 as its peripheral edge. In the present embodiment, the rear window frame 3
A high-frequency pickup 38 is provided in an area within 4.5 cm from the edge of No. 4.

FIG. 1 shows an appearance of a high frequency pickup of the present invention. The high frequency pickup 38 includes a metal case 40 that shields electromagnetic waves from the outside, and a core 44 around which a loop antenna 42 is wound. And forming an electromagnetic coupling type pickup, and having a configuration similar to that of the probe including the loop coil used to know the surface current distribution of the vehicle body.

The core 44 is made of a high magnetic permeability material such as ferrite and has a rectangular parallelepiped shape. Then, a groove parallel to the long side is formed on the side surface including the longest side of the rectangular parallelepiped,
Further, a groove 46 is provided around the core 44 including this groove, and the loop antenna 42 is wound around the groove. That is, in the embodiment, a groove 46 is formed around the core 44 as shown in FIG. 2, and the loop antenna 42 described above is wound a plurality of times around the groove 46.

The groove 46 serves as a guide when the loop antenna 42 is wound as described above, and as shown in FIG. 4, the high frequency pickup 38 with the peripheral portion of the vehicle body sandwiched therebetween.
Is attached, the mounting position accuracy between the loop antenna 42 and the vehicle body peripheral portion is enhanced, and a closed magnetic flux circuit is formed between the vehicle body peripheral portion and the core 44 to reduce the leakage of the magnetic flux induced by the high frequency surface current. Is prevented. Therefore, the magnetic flux is reliably captured by the loop antenna 42, and the magnetic flux from the outside is reliably shielded by the case 40, so that the current induced in the vehicle body can be detected by the high frequency pickup 38 with high sensitivity. .

In order to surely 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 provided at both ends of the case 40, and the brackets 54 and 56 are the rear brackets. It is fixed to the wind frame 34 with screws.

Further, the case 40 of the high-frequency pickup 32 has a built-in circuit section 58 connected to the loop antenna 42 described above, and a signal detected by a preamplifier or the like provided in the circuit section 58 is processed. Further, 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 above-mentioned surface current distribution measurement. The circuit section 58 is supplied with power and signals for controlling the circuit from a cable 62.

The loop antenna 42 is composed of a plurality of antennas. An insulating coating is applied to the coil so that the loop antenna 42 is placed in an electrically insulated state and in close contact with the opening edge of the rear window frame 34, and the magnetic flux generated from the surface current is generated. The loop antenna 42 can be more strongly interlinked.

In the present embodiment, the loop antenna 42 is arranged within 4.5 cm from the edge of the rear window frame 34, so that the broadcast wave of the FM broadcasting frequency of 80 MHz can be reliably generated from the vehicle body surface current flowing in the peripheral portion of the rear window frame 34. Since the direction of the vehicle body surface current at this time is flowing along the peripheral edge portion as apparent from FIG. 10, in the present embodiment, the loop antenna 4
The longitudinal direction of 6 is arranged along the peripheral edge of the rear window frame 34.

Thus, according to the embodiment of the present invention, the peripheral portion of the vehicle body,
In particular, the surface current flowing in the peripheral portion of the ceiling plate is electromagnetically detected by the high frequency pickup, and at this time, the core 44 sandwiches the peripheral portion of the vehicle body to prevent leakage of magnetic flux and reliably perform reception in the high frequency band. Therefore, it is extremely useful as a pickup for an automobile antenna.

[Effects of the Invention] As described above, according to the present invention, a high frequency surface current generated in a specific portion of a vehicle body, particularly in a peripheral portion of the vehicle body, is detected for a broadcast wave in a relatively high frequency band, for example, an FM frequency band or higher. A high-frequency pickup that is arranged on the peripheral portion of the vehicle body, and this high-frequency pickup includes a core formed so as to sandwich the peripheral portion of the vehicle body. It can be carried out.

[Brief description of drawings]

FIG. 1 is an external view of a pickup for an automobile antenna according to the present invention, FIG. 2 is a sectional view taken along line II-II of FIG. 1, and FIG. 3 is a view showing a state in which a high-frequency pickup is attached to a ceiling plate. FIG. 4 is a cross-sectional view of an essential part of FIG. 3, FIG. 5 is an explanatory view showing a surface current I generated in a vehicle body B by an external wave W, and FIG. 6 uses a probe similar to the high frequency pickup used in the present invention. Explanatory drawing of the probe and its processing circuit for knowing the distribution of the vehicle body surface current, FIG. 7 is an explanatory view showing the electromagnetic coupling state of the surface current I and the pickup loop antenna, and FIG. 8 is the loop antenna of FIG. FIG. 9 is an explanatory view showing the directivity characteristic, FIG. 9 is an explanatory view showing the distribution characteristic of the surface current intensity, FIG. 10 is an explanatory view showing the direction of the surface current, and FIGS. 11, 12, and 13 are respectively the vehicle body in FIG. Along the vertical line It is a characteristic diagram showing the vehicle body surface current distribution. 38: high frequency pickup 34: rear wind frame, 42: loop antenna, 44: core, 46: groove.

Claims (1)

[Claims] 1. A pickup for an automobile antenna for detecting a high frequency surface current induced in a vehicle body by broadcast waves from a core made of a high magnetic permeability material around which a loop antenna is wound, wherein the core has a rectangular parallelepiped shape. And has a groove parallel to the longest side of the rectangular parallelepiped, the loop antenna is wound a plurality of times through the groove, is further covered with an insulating coating, and the vehicle body peripheral portion along the entire length of the groove portion. A pickup for an automobile antenna, wherein the opening edge is sandwiched, and the opening edge and the loop antenna are arranged in parallel and are in close contact with each other.