JPS623505A - Tv antenna system for automobile - Google Patents

Abstract

PURPOSE:To improve remarkably the antenna directivity without making the external appearance of the car body poor by constituting the diversity reception antenna with high frequency pickups detecting a high frequency surface current flowing concentrately onto the circumferential ridge of an engine hood and a trunk lid. CONSTITUTION:The high frequency pickups 44a, 44b, 46a, 46b are arranged respectively to both right/left edges of the engine hood 40 and the trunk lid 42 at both sides of the car body and the four high frequency pickups 44a, 44b, 46a and 46b constitute the space diversity antenna. Thus, the direction with low sensitivity is compensated together to attain the best TV reception. Further, since the high frequency surface current is detected by the high frequency pickups from the inside of the trunk lid, the reception at a high frequency band is ensured without exposing the antenna system externally.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is a TV antenna device for an automobile, in particular, detects surface current induced by broadcast waves received on the body of an automobile using a plurality of high-frequency pickups, and performs diversity reception. This invention relates to a full-width TV antenna device.

[Prior Art] In recent years, automobiles are increasingly equipped with television (TV) receivers, and in such automobiles, T.
The importance of a TV antenna device for a personal vehicle that effectively receives V broadcast waves is increasing.

By the way, VHFLO band like TV broadcast waves <90~
108HIIZ), V HF Hr band (170-22
0H1lz).

High-frequency radio waves such as those in the U I-IF band (440-7708 IIZ) have strong straight propagation properties, and if distortion occurs due to interference between direct waves and counter-waves reflected from buildings or mountains, or if you stop your car and watch the TV. When receiving signals, if another vehicle passes by and disrupts the radio waves, multipath noise may occur, causing the sound to be momentarily interrupted. An antenna device cannot reduce such multipath noise that occurs when receiving TV broadcast waves.

Furthermore, while a car is moving, with a general ball antenna, the reception condition changes every time the car changes direction with respect to the direction of arrival of broadcast waves due to its directional characteristics. Even when listening to audio only,
It is difficult to receive stable TV broadcast waves.

Therefore, conventionally, two or more antennas are placed on the vehicle body at a required interval, and the antenna with the best reception condition is automatically selected from among these multiple antennas to improve the directivity characteristics of the antenna and to avoid multi-purpose antennas. 2. Description of the Related Art An automotive TV antenna device using a diversity reception method that reduces path noise is known.

However, the conventional general antenna is a ball antenna, and although an antenna protruding from the car body may be preferable in terms of reception characteristics, it has the fate of always being treated as an evil N person in terms of car body design. Was.

In particular, as mentioned above, when performing diversity reception using the car's TV antenna B installation, it is necessary to install multiple new antennas, and if a general ball antenna is used, the aesthetic concept for the appearance of the car is lost. In addition, mutual electrical interference between these various antennas may significantly degrade their reception performance.

Therefore, in the past, it has been proposed as an antenna device for a vehicle to detect the surface current induced in the vehicle body itself by broadcast waves.

[Problems to be solved by the invention] Problems with the prior art However, at first glance, using the current flowing through the car body seems to be the most reliable and efficient method, but conventional experiments have not been conducted in this way. It continued to show results that completely betrayed expectations.

The first problem in not being able to use the surface current generated by general car body broadcast waves is that the surface current value is not as large as expected, and conventional surface current mainly targets the car body ceiling panel. However, even with this, it was not possible to obtain a detection output of a level 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 such noise is mainly generated from the engine's ignition system and battery charging regulator system, and when the engine is not active. As long as it was installed, these noises leaked into the vehicle body, making it impossible to receive clear broadcast wave reception that could be used on the side of the vehicle.

Purpose of the Invention The present invention has been made in view of the above-mentioned conventional problems.
The purpose is to provide a TV antenna device for a vehicle that can effectively perform diversity reception without damaging the appearance of the vehicle body.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides an antenna that receives TVtli transmission radio waves with a high-frequency pickup that efficiently picks up high-frequency current induced in the vehicle body by the broadcast waves. It is formed from

The present invention is characterized in that the high frequency pickups are disposed close to at least the left and right side edges of the engine hood and trunk lid of the vehicle body along the longitudinal direction thereof, and a diversity reception system is configured by these high frequency pickups.

[Function] As is clear from the configuration described above, according to the automotive TV antenna device according to the present invention, since the antenna constituting the spatial diversity reception system is formed from a high frequency pickup, There is no need to provide a ball antenna or the like on the antenna, and there is no risk of damaging the appearance.

Here, conventional antenna devices were mainly intended to receive AM waves due to the background of the times, but for this reason, the antenna that detects the car body current has a problem that the wavelength of the target broadcast wave is too large. The results showed that good reception characteristics could not be obtained.

The present inventors focused on this frequency dependence, and in the present invention, the broadcast waves to be received are TV broadcast waves, that is, 9
By using high-frequency broadcast waves of 0.8112 or higher, it has become possible to receive signals from vehicle body current extremely effectively, which was previously considered impossible.

Furthermore, 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 high-frequency pickups are provided in areas where it is difficult to pick up noise and where the density of broadcast waves is high. Therefore, in the present invention, the side edges of the engine hood and trunk lid of the vehicle body are selected as installation locations that satisfy such conditions.

Therefore, according to the automotive TV antenna system d according to the present invention, a high-frequency pickup with good reception sensitivity is always selected, and the antenna characteristics of each high-frequency pickup complement each other to a great extent, so the combination of these can be effective. Omnidirectional spatial diversity reception becomes possible.

In addition, in a normal car, there is a distance of about 1.5 m between the engine hood and the trunk lid on both sides, a distance of about 2 m or more between the engine hood and the trunk lid, and there is a gap between each high frequency pickup for the broadcast waves of the TV band. The antino spacing 2 is a necessary condition to obtain the spatial diversity effect.
Since a distance of 74 to 272 or more (λ=wavelength) can be set, the effect as a spatial diversity reception system is extremely large.

[Example] Hereinafter, examples related to the present invention will be described. A preferred embodiment of a TV antenna device for a VL car will be described based on the drawings.

゛Pip ara no! 10 to 15 show the steps for determining the most efficient installation position of the high-frequency big-up by examining the distribution characteristics of high-frequency current in the vehicle body.

Figure 10 shows that when an external radio wave W such as a TV broadcast wave passes through a car body B made of gold B conductor, a surface current ■ corresponding to the strength of the electromagnetic wave is induced in each part of the car body. In the present invention, only TV waves of 90HIIZ or higher belonging to a relatively high frequency band among these radio waves are targeted.

The present invention measures the induced current distribution of the vehicle body in such a specific high frequency band, and installs a high frequency pickup in an area where the surface current density is high and there is little noise. The computer simulation and actual current intensity were measured at each point.

That is, surface current was measured by using a probe based on the same principle as a high-frequency pickup installed in a desired part of the vehicle body, which will be described later, and by moving the probe across the entire surface of the vehicle body while changing direction at each point.

Fig. 11 shows the schematic configuration of a probe P created based on almost the same principle as the high frequency pickup described later, and is made of a conductor to avoid mixing of radio waves from the outside. A loop coil 12 is fixed inside the case 10. An opening 10a is provided in a part of the case 10, and a part of the loop coil 12 is exposed to the outside from 010a during this time, and the exposed part of the loop coil 12 is brought close to the surface of the vehicle body. It consists of a configuration in which a loop coil 12 detects the magnetic flux generated from the 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 coaxial cable 1.
8 core wires 20. Also, the loop coil 12
A capacitor 22 is provided in a part of the loop coil 12 to resonate the frequency of the loop coil 12 to a desired frequency to be measured, thereby increasing pickup efficiency.

As described above, by moving the probe P along the surface of the vehicle body 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. 11, the output of the probe P is amplified by a high frequency voltage amplifier 24, and the output voltage is measured by a high frequency voltage measuring device 26. This coil output voltage is read by the meter indication value of the measuring device 26, and the voltage corresponding to this meter indication value is recorded by the XY recorder 28 as a surface current distribution in each part of the vehicle body. The XY recorder 28 has a potentiometer 30
A signal indicating each position of the vehicle body is input from the sensor, making it possible to know the high-frequency surface current at each position.

FIG. 12 shows the deviation angle θ between the high-frequency surface current ■ and the loop coil 12 of the pickup, and as shown in the figure, the magnetic flux φ due to the current ■ is output to the loop coil 12 by interlinking with the loop coil 12. Generate voltage ■, and
As shown in Figure 3, the maximum voltage is obtained when θ is 0, that is, the surface current ■ is parallel to the loop coil 12 of the pickup, and the surface current I when the probe P is rotated at each measurement point to obtain the maximum voltage. You can know the direction of

Figures 14 and 15 show the magnitude and direction of the high-frequency surface current generated in each part of the vehicle body at a frequency of 90 HIlz, which was determined from both the measurement results using the probe P and the simulation using the δ1 calculator. As is clear from the figure, the magnitude of the surface current exhibits a distribution in which the density is high along the edges of the flat plate portion of the vehicle body, and the density is extremely low in the central portion of the flat plate portion.

Furthermore, as shown in the current direction in FIG. 15, it is understood that each current is concentrated in a direction parallel to the edge of the vehicle body or along a connecting portion of each plane portion.

In Fig. 14, if we examine in detail the current distribution induced in the metal parts of the car body along the chain line that traverses the car body, we find that
Distribution characteristics as shown in FIGS. 16 and 17 are obtained.

FIG. 16 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 the current flows from both ends toward the center of the trunk lid. It does not show any distribution characteristics where the value decreases.

Therefore, as shown in FIG. 16, if a high frequency pickup is placed near the periphery of the trunk lid, it becomes possible to detect the current flowing intensively near the periphery. Similarly, Fig. 17 shows the C-
The current distribution along D is shown, and as you can see from the figure,
It is understood that the largest current flows at both ends of the engine hood, 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.

Furthermore, in the present invention, the high-frequency pickup is installed close to the peripheral edge of each lid body along the peripheral edge, for example, in the longitudinal direction of the loop anti-dog, which has very good sensitivity for practical use. In order to obtain this, it is preferable to set the pickup installation range from the edge of the lid body to a range that depends on the carrier frequency of the broadcast wave.

The distribution characteristics in Figures 16 and 17 are for 908IIZ TV.
This is the current of the car body in response to broadcast waves, and as mentioned above, the surface current value decreases according to the distance from the edge of the metal lid of the car body, and the current decreases below 6 db where good sensitivity can actually be obtained. Considering the range, it is understood that for each characteristic, extremely good sensitivity can be obtained if the CI is 4.0 CI or less from the edge.

Therefore, in the present invention, the high frequency pickup for the carrier frequency of 90 Hflz is carried out from the edge of the metal lid of the vehicle body by 4.
By arranging it below Ocn+, a practically sufficient antenna device can be obtained.

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, since the practical separation distance is 4.0 crnl at the carrier frequency of 908H2 mentioned above and is inversely proportional to the frequency, in the present invention, the installation position of the high frequency pickup from the edge of the metal lid of the vehicle body is set at 12 x 10-3 crnl.
/f (m) or less, a good reception effect can be obtained depending on each carrier frequency. (In the above equation, C = speed of light, f =
As described above, according to the present invention, the high frequency pickup is provided close to the periphery of each metal lid, and preferably within the above-mentioned distance from the rim. A good receiving effect can be obtained.

In the present invention, the separation distance actually depends on the frequency, so for example, at a carrier frequency of 1008H2,
It is sufficient to install the high-frequency pickup within 3.6 cm from the edge of the lid, 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 of the lid. becomes.

FIGS. 18 and 19 show the measurement results of the noise current distribution characteristics.

FIG. 18 shows the noise current distribution on the cross section 1ilE-F in FIG. 14, and as is clear from the figure, the noise current value decreases at both end positions and at the center. Therefore, from FIG. 18, it is possible to detect the high frequency surface current with less noise by arranging the high frequency pickups on both side edges or the center of the engine hood.

In addition, FIG. 19 also shows the vertical line C-- in FIG. 14.
The noise current distribution along the engine hood of D is shown, and as is clear from the figure, the noise current value becomes minimum at both end positions.

The present invention has been made based on the above findings, and is particularly applicable to the left and right edges of the engine hood and trunk lid, where surface current is concentrated at a high density and noise current is extremely low. High-frequency pickups are placed closely along the line.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of an antenna device according to the present invention.

A feature of this embodiment is that high-frequency pickups 44a, 44b, 46a having the same structure as the probes described above are installed on the left and right edges of the engine hood 40 and trunk lid 42 on both sides of the vehicle body, respectively.

46b, and these four high frequency pickups 44a
, 44b, 46a, and 46b constitute a spatial diversity antenna.

Typically, the antenna pair of a spatial diversity receiving system is
It is well known that a spacing of 274 to 272 or more (λ=wavelength) can provide a practically sufficient spatial diversity effect. Here, each of the high frequency pickups 44 and 46 for the TV band horse antenna has a distance of about 1.5 m between the left and right edges of the hood 40 and the lid 42, and
There is a spacing of approximately 2m between each other, and the wavelength of TVV transmission is 3.5m.
From the following points, it is understood that the effect as a spatial diversity antenna in the TVV transmission frequency band is great.

Hereinafter, based on FIG. 1, each high frequency pickup 44a, 4
A circuit configuration for automatically selecting a high frequency pickup with good reception sensitivity among 4b, 46a, and 46b for TV reception will be described.

In the figure, the received signals of high frequency pickups 44, 46 are transmitted through coaxial cables 48a, 48b, 48c,
48d is input to the switching circuit 100.

The switching circuit 100 includes high frequency pickups 44a, 44b, 46a, 4 used for receiving TVV transmission radio waves.
6b, selects one received signal from each of these high frequency pickups 44 and 46, and outputs it to the buyuna 102.

This tuner 102 performs tuning of the received signal, and is constituted by a well-known circuit including a high frequency amplifier 1042, a local oscillator 106, and a mixer 108.

The reception signal tuned by the tuner 102 is amplified by the video intermediate frequency amplifier 110 and sent to the image display circuit 1.
12 and audio output circuit 114, respectively.

Here, the image display circuit 112 includes the video detection circuit 11
6. Video amplification abuse 118. A synchronous deflection circuit 122 connected to the deflection circuit of the cathode ray tube 120 through vertical and horizontal deflection circuit sections. It is constructed with a well-known circuit consisting of a chromaticity circuit 124 connected to a grid of Bla-Kung tubes 120.

The video signal is detected by the video detection circuit 116, and the video signal is amplified by the video signal amplifier 118.
0, the image of the video signal is displayed.

Furthermore, in this embodiment, the audio output circuit 114 is connected to the audio separation circuit 120. ? 11 Volume wave amplifier 128. It consists of a well-known configuration of an audio detection circuit 130 and an audio amplifier 132, and separates an audio signal from the signal output from the video intermediate frequency amplifier 110, detects it, and outputs it to a speaker 134.
Outputs audio signals from.

In this way, the vehicle TV of this embodiment separates the video signal and the audio signal from the received signal, and sends the video signal to the f-time tube 12.
Displays the image on 0 and sends audio No. 13 to the speaker.
Output from 134.

Furthermore, in this embodiment, a drive state determination circuit 136 that determines whether the vehicle is stopped or running, and a video detection circuit 11
6 and the video amplifier 118, and includes a switch 138 that turns on/off the detection signal, and when the drive state determination circuit 136 detects a vehicle stopped state, switch
38 is turned on, and when the vehicle running state is detected, the switch 138 is turned off.

FIG. 2 shows the circuit configuration of the drive state determination circuit 136, and the illustrated example circuit is in a vehicle stopped state when both the parking switch and the handbrake are activated and the vehicle speed is below a certain reference speed. , and outputs a high level signal from the AND gate to turn on the switch 138. Otherwise, it determines that the vehicle is in a running state and outputs a low level signal from the AND gate. death,
Turn switch 138 off.

Here, the vehicle speed is detected by inputting a vehicle speed detection pulse to a comparator via a bypass filter, and comparing the pulse with a predetermined reference value.

Therefore, in the illustrated example, when the vehicle is stopped, the switch 138 is turned on, so the cathode ray tube 1
An image is displayed on 20-hi, and audio is output from the speaker 134. Further, when the vehicle is running, the switch 138 is turned off, so that no image is displayed on the cathode ray tube 120, and only audio is output from the speaker 134.

In this way, the device according to the present embodiment outputs only audio from the speaker 134 when the vehicle is running, and displays an image on the brake tube 120 only when the vehicle is stopped, thereby reducing the driver's attentiveness. It is prevented.

In such a car TV device, the reception condition of TV broadcast radio waves changes while the vehicle is running, so in order to obtain good images and sounds, the high frequency pickup 44a used for reception is adjusted according to the change in the radio wave reception condition. .

A diversity reception system is adopted that switches between 4.4b, 4Ga, and 46b to the optimal one.

The switching circuit 10 that switches the high frequency pickup
0, the antenna switching circuit 140 generates a switching signal 5140 when the output of the video detection circuit 116 falls below a specific level to switch to the high frequency pickup with the best reception condition.

Note that the pickup can also be switched using the output of the audio detection circuit.

In addition, the antenna switching timing is I direct Tomoshintan 5122
It is possible to synchronize with , and perform switching in the retrace section of the scanning line.

Figure 3 (Δ) and (B) show J31J in the TV broadcasting frequency band.
Figure 3 (A>
indicates the directional characteristic when the high-frequency pickup is installed at the right end of the rear edge of the right engine hood, and <8) indicates the 7-ndena directivity characteristic when the high-frequency pickup is installed at the right end of the rear edge of the trunk lid.

In other words, the antenna directivity characteristic of the high-frequency pickup 44a attached to the right end of the rear edge of the engine hood is approximately a figure 8 pattern with good sensitivity toward the front, as is clear from the characteristic curve (Δ) in the figure. Indicates the characteristics of a type. In addition, according to the high frequency pickup 46a attached to the right end of the front edge of the silane lid, as shown in the characteristic curve of FIG. characteristics are obtained.

Furthermore, the directional characteristics of the high-frequency pickups installed at symmetrical positions on the left and right sides are not completely the same. Therefore, by installing the high-frequency pickups on the left and right edges of the engine hood and trunk lid, the sensitivity characteristics of each other can be improved. It becomes possible to supplement.

As described above, according to this embodiment, by performing diversity reception using four high-frequency pickups installed on the left and right side edges of the heavy engine hood and trunk lid, the direction of decrease in sensitivity can be reduced. This allows for the best TV reception.

1. Next, the mounting structure of the high frequency pickup to the engine hood and the rear lid will be explained based on Fig. 4 and Fig. 9.

FIG. 4 shows the detailed structure of the high frequency pickup fixed to the trunk lid in this embodiment.

In the figure, a watertight tape lip 50 is provided between the trunk lid 42 and the rear tray panel 49 to prevent rainwater from entering through the rear glass 52.

There is a dam 5 between the rear glass 52 and the rear tray panel 49.
4 to prevent intrusion of rainwater, noise, etc., and a molding 56 is provided at the lower end of the rear glass 52 on the outside side as is well known.

A feature of this installation example is that the high frequency pickup 46 is fixed to the edge of the rear panel 48 of the trunk lid 42, and the high frequency pickup 46 is an electromagnetic coupling type pickup, as described above. It has a similar structure to the probe containing a loop coil used to determine the surface current distribution of a car body.

As is clear from the figure, the loop coil 58 provided inside the high frequency pickup 4G is arranged so that its longitudinal direction coincides with the longitudinal direction of the trunk lid 42.

Here, the loop coil 58 is connected to the i of the trunk lid 42.
From part i 12X 10-3c/f (m) V'CJ
4 to receive TV broadcast waves of '590H1lz
．． In the present invention, the loop coil 58 reliably and highly efficiently captures the surface current flowing concentrated around the periphery of the trunk lid 42.
' can be done.

In addition, the direction of the car body surface current is clearly shown in FIG. - Arranged along the periphery of the rank lid 42.

The high frequency pickup 46 in the J3 installation example has a case 60 made of a conductor, and the circuit section 6 including the loop coil 58 and preamplifier described above is installed in the case 60.
2, and its opening 60a faces toward the trunk lid 42.

Therefore, only the magnetic flux induced from the high-frequency surface current flowing around the periphery of the trunk lid 42 is captured inside the case 60, and the magnetic flux from the outside is reliably shielded by the case 60.

Here, the loop coil 58 is a single-turn coil installed along the bent portion of the periphery of the trunk shoes 142, and the loop coil 58 is arranged so as to be installed in close contact with the trunk lid 42 while being electrically insulated from the trunk lid 42. It has an insulating coating and is pushed onto the trunk lid 42 so that the magnetic flux generated from the surface current can be efficiently transmitted to the loop coil 58.

Further, power and signals for controlling the circuit are supplied to the circuit section 62 through the cable 64hu, and a high frequency detection signal taken out by the loop filter 58 is taken out from the sympathy cable 48, and the above-mentioned surface current It is processed using a circuit 1 similar to that used in the molecule li.

As described above, according to Example d, the high-frequency surface current is detected from inside the trunk lid using the high-frequency pickup, so reception in the high-frequency band is possible without exposing the antenna device to the outside. This can be done reliably.

FIG. 5 shows the mounting structure of the high frequency pickup 46 to the run grids 1 to 42 according to the installation example, and the same parts as in FIG.

In the figure, mounting brackets 66 are provided with bolts or the like on both sides of a case 60 of the high frequency pickup 4G, and by fixing the mounting brackets 66 and the inner plate of the trunk lid 42 with screws 68, the high frequency pickup 46 can be installed in the trunk. It is securely installed inside the lid 42.

Therefore, it is preferable that the high frequency pickup 46 be constructed as shown in FIG.

FIGS. 7 to 9 show an installation example in which the high frequency pickup is located close to the periphery of the engine hood according to the present invention.

In FIG. 7, the - side of the engine hood 40 is rotatably supported by the main body, and the inner surface of the peripheral edge on the windshield 70 side faces the front outer panel 72 in the closed state. The interior side of the front outer panel 72 is connected to the front inner panel 74 and is connected to the windshield 70.
is supported by a stopper 76 on the front outer panel 72, and the windshield 70 and front mill inner panel 7
A dam 78 is installed between the 4 and 4 to prevent rainwater from entering.

Further, as is well known, a trolley 80 is provided at the lower end of the windshield 70.

The high frequency pickup 44 in this installation example also has a similar configuration to the high frequency pickup used in the above installation example on the trunk lid, and includes a case 82) a loop coil 84 and a circuit section 86.

A characteristic feature of this installation example is that the high frequency pickup 44 is connected to the front outer panel 12 of the engine hood 40.
It is fixed within a distance of 4.0 cm inward from the periphery of the engine hood, especially the edge, thereby reliably detecting the high frequency current flowing in the periphery of the engine hood, which is concentrated in high density. be able to.

FIG. 8 shows the mounting structure of the high frequency pickup 44 to the engine hood 40 according to this installation example, and FIG. 9 shows an external view of the high frequency pickup for mounting on the engine hood. The details are almost the same as the above installation example on the trunk lid, and the high frequency pickup 44 is attached to the engine hood with the mounting bracket 88 and screws 90, and the power supply and signal for circuit control are
The high frequency detection signal is supplied from the cable 92 and taken out by the coaxial cable 48.

In this installation example, the high frequency pickup needs to be installed at a position that does not interfere with the storage of the wiper blade.

In the above embodiments, an electromagnetic coupling type pickup is used as the high frequency pickup, but the present invention is an antenna device that detects the surface current of the engine hood and trunk lid and receives external waves. As the high frequency pickup, not only the above-mentioned electromagnetic coupling type but also an electrostatic coupling type pickup can be used.

In the case of a capacitively coupled pickup, J31 is shown in each of the above figures.
A detection electrode is arranged along the longitudinal direction of the engine hood or trunk lid through an air layer or an insulating layer,
A high frequency surface current is extracted to the detection electrode side through each electrostatic pair formed between the surface of the hood or lid and the detection 1π pole, thereby making it possible to extract a high frequency signal of 831 in a desired band. .

[Effect of the invention 1 d1 As explained above, according to the present invention, the diversity receiving antenna is configured with a high-frequency pickup that detects the high-frequency surface current that flows concentratedly at the periphery of the engine hood and trunk lid. It is possible to improve antenna directivity characteristics without damaging the appearance of the vehicle body.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the schematic configuration of the automotive TV antenna device according to the present invention, Fig. 2 is a detailed explanatory diagram of the drive state discrimination circuit in Fig. 1, and Fig. 3 shows the antenna directivity characteristics of each high frequency pickup. Figures 4 to 6 are explanatory diagrams showing the state in which the high frequency pickup is attached to the trunk lid in the present invention, and Figures 7 to 9 are explanatory diagrams showing the state in which the high frequency pickup is attached to the engine hood in the present invention. 10 is an explanatory diagram showing the surface current I generated on the vehicle body B by the external TV broadcast wave W. FIG. 11 is an explanatory diagram showing the surface current I generated on the vehicle body B by the external TV broadcast wave W. FIG. An explanatory diagram of a probe and its processing circuit to know the distribution of FIG. 14 is an explanatory diagram showing the distribution characteristics of surface current intensity in the vehicle body. FIG. 15 is an explanatory diagram showing the direction of surface current in the vehicle body.
17 are explanatory diagrams showing the current distribution on the surface of the vehicle body along the longitudinal section of the vehicle body in FIG. 14, and FIG. 18 is a characteristic diagram showing the noise current distribution on the transverse line E-F in FIG. 14. , FIG. 19 is a characteristic diagram showing the noise current distribution on the vertical line CD in FIG. 14. 40... Engine hood 42... Trunk lid 44, 46... High frequency pickup. Applicant G] Yu Jidosha Co., Ltd. Agent Patent attorney Kenji Yoshida [7-54] (1 other person) No. 2 Figure 1, Figure 4, 42゛F rank 9)°゛46: Men's shoulders C7ri1 . 49゛(Attack to Noah Tray) 52: Rear sword 5th figure 6th figure 9th concave 10th figure 11th figure 10'0 12th figure 13th figure ゑ 14th figure 16th figure 17th figure

Claims (2)

[Claims] (1) In a TV antenna device for a car that receives TV broadcast waves using multiple antennas installed on the car body and outputs the reception signal of the antenna in the optimal reception state, the antenna receives high-frequency current induced in the car body by the broadcast waves. and a high-frequency pickup that efficiently picks up a TV antenna device. (2) In the device according to claim (1), the high frequency pickup is carried out from the edge of the engine hood and the trunk lid at 12×10^-^3c/f (m) (c = speed of light,
1. A TV antenna device for an automobile, characterized in that the TV antenna device is provided within a range of f=carrier frequency of broadcast waves).