JPS61128608A - Antenna device for automobile - Google Patents

Abstract

PURPOSE:To attain improvement of the directivity of an antenna and reduction of multi-path nose by arranging two high frequency pickups to a car body connecting part at a required interval and selecting automatically a pickup with a good reception state. CONSTITUTION:A couple of the high frequency pickups 32, 132 forming a diversity reception antenna are incorporated in both front pillars 34, 134 supporting a ceiling plate. The front pillars 34, 134 have a high density of current induced to the car body by a broadcast wave. A pickup with good reception sensitivity of both the pickups 32, 132 is selected automatically to receive the broadcast wave. Then the weak reception sensitivity is compensated together to improve the directivity of the antenna. Further, the multi-path noise is reduced by the diversity reception system.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an antenna device for an automobile that uses 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, and telephone broadcast communication waves.
This type of antenna device is also extremely important for transmitting and receiving citizen band radio waves, for example, for communication between cars and other stations, and plays a major role in the standard communication functions of modern 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 in terms of car body design. had.

In addition, such ball antennas are susceptible to breakage, bending, and other damage even in actual use, and are subject to mischief or theft. Furthermore, they can cause various problems such as generating unpleasant wind noise at 11 o'clock when running at high speed. has,
In the past, there have been many requests to somehow remove this.

In particular, as the frequency bands of broadcast waves or communication waves received inside automobiles have expanded in recent years, it has become necessary to install multiple antennas for each frequency band, which has made it difficult to improve the aesthetic concept of the automobile's exterior. There is a problem in that the receiving performance of these antennas is significantly degraded due to mutual electrical interference between these various antennas.

In the past, several efforts have been made to remove or hide the above-mentioned ball antenna so that it cannot be seen from the outside, and for example, pasting a thin antenna wire on the rear windshield has been put into practical use.

As another conventional solution, 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. By setting the frequency to 50 Hllz or more, it is possible to receive signals from the vehicle body current extremely effectively.

In addition, we focused on the fact that high-frequency car body current has a distribution characteristic that varies significantly in the current value in each part of the car body, so high-frequency pickups are installed in areas where noise is difficult to pick up and where the current density induced by broadcast waves is high. The vicinity of the periphery of the vehicle body is particularly selected as the location where the U is installed to satisfy 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 placed along the edge of the vehicle body within 12×10-3 c, #(m). The pickup is a loop antenna for electromagnetically detecting the magnetic flux generated by the vehicle body current, and an electrode type or slide core that can electrostatically detect high frequency signals by forming capacitance between it and the trunk hinge. It is a coil type.

[Problems to be Solved by the Invention] Problems of the Prior Art In the conventional vehicle antenna device in which one high-frequency pickup for picking up the current induced in the vehicle body is disposed on the periphery of the vehicle body, it cannot be used as an antenna. The directivity characteristics of high-frequency pickups are poor, and when receiving high-frequency FM broadcasts in the Vl-I F band, there is a strong straightness in the reception of FM broadcasts. One problem was that path noise was likely to occur.

OBJECTS OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art.The object of the present invention is to install a high-frequency pickup that picks up high-frequency surface currents induced in the vehicle body and flowing concentratedly at the vehicle body joints, at a required distance from the vehicle body joints. The aim is to install two antennas in a row to form a diversity reception system, improving the directivity of the antenna and reducing multipath noise.

[Means and effects for solving the problems] In order to achieve the above object, the present invention provides a high-frequency pickup that efficiently picks up high-frequency surface currents induced by broadcast waves and concentrated in the vehicle body connection parts. The present invention is characterized in that two high-frequency pickups are disposed at a required interval in the connecting portion, and the high-frequency pickup of the pair is automatically switched to the one with a better reception condition.

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

[Embodiments] Hereinafter, preferred embodiments of the automotive antenna device according to the present invention will be described with reference to 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. 11 shows that when an external radio wave W such as a broadcast wave passes through a car body B made of a metal conductor, a surface current (■) corresponding to the strength of the electromagnetic wave is induced in each part of the car body. Of these radio waves, only the frequency bands used for FM waves of 50 HIIz 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 high frequency pickups are installed in areas where the surface current density is high and there is little noise.A computer simulation is performed to understand the surface current distribution. Then, the actual current intensity is measured at each point. A probe based on the same principle as a high-frequency pickup installed on a desired part of the car body, which will be described later, is used, and this probe is applied at each point over the entire surface of the car body. The surface current was measured by moving it over the entire area while changing the direction.

Fig. 12 shows an outline of a probe P created based on almost the same principle as the high frequency pickup described later.
A loop coil 12 is fixed inside a case 10 made of a conductor to avoid mixing of radio waves from the outside, and a part of the case 10 has an opening 10a.
is provided, and a part of the loop coil 12 is connected to this frontage 10a.
The loop coil 12 is exposed to the outside, and the exposed portion of the loop coil 12 is brought close to the surface of the vehicle body B, so that 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 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 and rotating the 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 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
Signals indicating each position on the vehicle body are manually generated from the sensor, 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 I and the loop coil 12 of the pickup. Generate voltage ■, and
As shown in Figure 4, the maximum voltage is 14 when θ is O, that is, the surface current I and the loop coil 12 of the pickup are parallel, and the surface current I when the probe P is rotated at each measurement point and the maximum voltage is 17. You can know the direction of

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 using the probe P and computer simulations. As is clear from the above, the magnitude of the surface current exhibits a distribution in which the density is high in the parts along the edges of the flat part of the vehicle body, and the density is extremely low in the central part of the flat part.

Further, 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 vehicle body connection portion of each plane portion.

Therefore, from FIG. 15, it is understood that broadcast waves can be picked up with good sensitivity at the connecting portion of the vehicle body.

In particular, such a current density distribution indicates that the surface current is concentrated at a high density in a part of the pillar that supports the ceiling board, and this example is characterized by focusing on such a part of the pillar. As is clear from the special figure, in the FM frequency band d3, a high-density surface current that is equal to or higher than other parts flows through the pillar, and this tendency becomes more pronounced as the frequency increases; The band shows that it is possible to detect current from the pillar, which was previously only possible by increasing the antenna output.

FIG. 1 shows a schematic structure of an automotive antenna device according to the present invention, in which a pair of high-frequency pickups 32132 constituting a diversity receiving antenna are built into both front pillars 34, 134 that support the ceiling plate. In the embodiment, these high-frequency pickups 32 and 132 are of an electromagnetic pickup type including a loop antenna.

Next, one front pillar 34 is constructed based on FIGS. 2 to 4.
The structure of the high-frequency pickup 32 installed in the following will be explained.

As is clear from the cross-sectional view of FIG. 3, it includes a pillar 34 and a pillar leg plate 36 formed into a hollow rectangular prism serving as its main pillar. A windshield molding 38 is fixed to the outer surface of the vehicle body of the pillar leg plate 36, and a windshield 40 is held on this molding 38.

Further, a weather strip rubber 42 is fixed to the rear side of the vehicle body of the pillar leg plate 36, and the rubber 42 ensures watertightness between the pillar leg plate 36 and the side glass 44.

Further, a front pillar garnish 46 is attached to the pillar leg plate 36 on the side of the single room, which hides the surface of the pillar leg plate 36 and maintains an aesthetic appearance.

In this embodiment, a high frequency pickup is disposed on the front pillar 34 along the longitudinal direction of the front pillar, and an electromagnetic coupling type high frequency pickup 32 is inserted into the hollow interior of the pillar leg plate 36.

As is clear from FIGS. 3 and 4, the high frequency pickup 32 has a structure in which a loop antenna 50 is provided within a case 48 made of a conductor.The case 48 shields electromagnetic fields from the outside, but Frontage 48 on the side
a, and from this opening A8a the loop antenna 50
Pillar where is exposed and high frequency surface current flows concentratedly,
In particular, it is arranged close to the pillar leg plate 36.

In the embodiment, in order to insert the high frequency pickup 32 into the hollow prism of the pillar leg plate 36, an opening 36affi is provided in a part of the pillar leg plate 36, and the high frequency pickup 32 is inserted into the hollow prism of the pillar leg plate 36 before the front pillar garnish 46 is fixed. is inserted inside the pillar.

In order to fix the case 48 of the high frequency pickup 32 to the pillar leg plate 36, brackets 52 and 54 are fixed to both ends of the case 48 by spot welding. It is firmly fixed to the leg plate 36 with screws.

Therefore, in this fixed upper plate, the loop anchor 50 is disposed at a position 1η close to the opposite side of the opening 36a of the pillar leg plate 36, so that the magnetic flux caused by the high-frequency surface current flowing intensively in the pillar leg plate 36 is effectively Loop anti :)
It will be linked to 50.

A circuit section 56 including a preamplifier and the like is built into the case 48 on the back side of the loop antenna 50 described above, and power and signals for controlling the circuit are supplied to this circuit section 56 from a cable 58. Further, the high frequency detection signal taken out by the loop antenna 50 is taken out from the coaxial cable 60 and processed by the same circuit as used in the surface current distribution described above.

In the embodiment, the loop antenna 50 is made of a single-turn antenna, and the coil is coated with an insulating coating so that it is placed in close contact with the pillar leg plate 36 in an electrically insulated state. A structure in which it is pressed against the edge is preferable, and the magnetic flux generated by the high-frequency surface current that flows intensively in the pillar can be efficiently interlinked with the loop antenna 50.

After the high-frequency pickup 32 is mounted in the front pillar 34 in the manner described above, the front pillar garnish 46 is attached to the pillar 34, and a structure that is no different in appearance from a normal pillar structure can be obtained.

As described above, according to 32, the pair of high-frequency pickups constituting the diversity receiving antenna pick up the high-frequency surface current that flows intensively in the front pillar of the automobile with the loop antenna arranged in the longitudinal direction of the pillar. The high frequency pickup 32 is not exposed to the outside at all.

Further, the high frequency pickup 132 used to constitute the diversity receiving antenna is an electromagnetic coupling type pickup having a structure similar to that of the high frequency pick-up 32, and is mounted in the front pillar 134 on the opposite side (inside the front pillar 134 on the opposite side). (see Figure 1), so the explanation will be omitted.

And both front pillars 34°1311 shown in Figure 1
The interval is approximately 18 for the wavelength 4III of the FM broadcast wave band.
~15, so the mountain high frequency pickups 32 and 13 installed in both front pillars 34 and 134, respectively.
If antenna 2 is used as a diversity receiving antenna, the spatial diversity effect will be great.

A diversity reception antenna is configured with the aforementioned mountain high-frequency pickups 38.138, and then the one with better reception sensitivity is automatically selected among the mountain high-frequency pickups 38.138 to receive the broadcast wave. The circuit configuration will be explained with reference to FIG.

In the figure, coaxial cables 60 and 160 drawn out from high frequency pickups 32 and 132 provided on both front pillars 34 and 134 of the vehicle body are connected to a switch circuit 64,
Since the switch circuit 64 is switched by the output from the T-type flip-front processor 6, which will be described later, either the received wave of the high-frequency pickup 32 or the high-frequency pickup 132 is selectively input to the high-frequency amplifier circuit 68, and the received wave is locally Intermediate frequency amplification circuit 72 connected to oscillation circuit 70
After that, the audio signal is extracted by the detection circuit 14.

Then, this audio signal is divided into a right output and a left output via a multi-channel scanner 76, and left and right amplification B78. .

78 and are sent to speeds 80L and 80R, respectively.

By the way, the output signal from the intermediate frequency amplifier 72 is sent to the comparator 8.
2, the level values of the signals are compared, and the comparator 92 includes respective high frequency pickups 32 and 13.
The level value of the signal output from the intermediate frequency amplification circuit 72 when the reception sensitivity by 2 falls below a predetermined value is set, and the comparator 82 uses this level value and either the high frequency pickup 32 or the high frequency pickup 132. When the signal output from the intermediate frequency amplifier 72 is compared with the signal output from the intermediate frequency amplifier 72 while receiving broadcast waves at the
The output of the T-type flip-flop 66 is inverted.

This output reversal causes the switch circuit 64 to switch, and the high frequency pickup that receives the broadcast wave is switched to the one with better reception status.

In this way, the high frequency pickups 32 and 132 provided on both front pillars 34 and 134 constitute a diversity reception antenna, and the high frequency pickup with better reception sensitivity is always automatically switched. The directivity characteristics of the mountain high-frequency pickups 32 and 132 shown in Figure 6 are also symmetrical with the front and back direction as the central axis between the left and right high-frequency pickups 32 and 132, and the antenna is As a high frequency pickup, the directional characteristics are multiplied several times.

At the same time, multipath noise is reduced by the diversity reception method using the mountain high frequency pickup 32.132.

Furthermore, the arrangement of a pair of high frequency pickups for performing diversity reception is not limited to the above embodiment, but as shown in FIG. It is also possible to deploy high-frequency pickups 232, 332.

A second embodiment in which seven high-frequency picks serving as diversity receiving antennas are disposed on both trunk hinges will be described below with reference to FIGS. 7 and 8.

FIG. 7 shows two high-frequency pickups constituting a diversity receiving antenna fixed to trunk hinges on both sides, and FIG. 8 shows the detailed structure of one high-frequency pickup. Incidentally, since the high frequency pickups 232 and 332 have the same configuration, only one of the high frequency pickups 232 will be explained.

The high frequency pickup 232 in this embodiment is 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.

One end of the trunk hinge 86 is pivotally supported by the main body, and the other end is fixed to the trunk lid 88.
8 rotational shaft supports.

Further, a torsion bar 90 is provided on the pivot side of the trunk hinge 86, and performs a positioning and moderating action when the trunk lid 88 is opened. As is well known, there is a watertight strip 92 between the trunk lid 88 and the vehicle body.
is provided to prevent rainwater from entering through the rear glass 94.

In the embodiment, the high-frequency pickup 86 is fixed to the outside along the longitudinal direction of the trunk hinge 86, that is, to the trunk room side, and the longitudinal direction of the loop antenna 96 provided inside coincides with the longitudinal direction of the trunk hinge 86. In this embodiment, the surface current flowing through the trunk hinge 86 can be reliably captured by the loop antenna 96 with high efficiency.

The high frequency pickup 86 includes a case 98 made of a conductive material, and the above-mentioned loop antenna 96 is disposed inside the case 98.
A circuit section 100 including a preamplifier and the like is built in, and its open side faces toward the trunk hinge 86. At both ends of the opening of the case 98, L fittings 102,
104 is fixed, and one end of both metal fittings 102, 104 is firmly fixed to the trunk hinge 86 by screwing. Therefore, it is understood that only the magnetic flux induced from the high frequency surface current flowing through the trunk hinge 86 is captured inside the case 98, and the magnetic flux from the outside is reliably shielded by the case 98.

The loop antenna 96 is preferably provided along the trunk hinge 86 and has a shape that matches the curvature of the hinge 86.

Power and signals for controlling the circuit are supplied to the circuit section 100 described above from a cable 106.

Further, the high frequency detection signal taken out by the loop antenna 96 is taken out from the coaxial cable 108 and processed by a circuit similar to that used in the surface current distribution described above.

111. The loop antenna 96 is a single-wound antenna, and the coil is coated with an insulating coating so that it is electrically insulated from the trunk hinge 86 and arranged tightly.
It has a structure in which this is pressed against the hinge 86, and the magnetic flux generated from the surface current can be efficiently linked to the loop antenna.

This high frequency pickup 232 and another high frequency pickup 332 having the same configuration constitute a diversity receiving antenna, and a circuit configuration that automatically selects the one with a better reception condition among these high frequency pickups 232 and 332 is as follows. Since this is the same as the previous embodiment, the explanation will be omitted.

In this embodiment as well, both trunk hinges are 86°186°.
The spacing is about 1.5 m compared to the FM broadcast wave band of about 4 m.
Since it is about 1.8m, the mountain high frequency pickup 232.
332 increases the effect of spatial diversity and reduces multipath noise.

Further, since the mountain high frequency pickups 232 and 332 are symmetrical with respect to the longitudinal direction of the vehicle body as shown in FIG. 10, the directivity can be improved, that is, interpolation in the dip direction can be performed.

[Effect of the Invention 1] As explained above, according to the present invention, a pair of high-frequency pickups that are induced in the vehicle body and flow concentrated in the vehicle body connection portion are provided to perform spatial diversity reception,
This has the effect of improving the directivity characteristics of the antenna and reducing multipath noise while driving.

[Brief explanation of drawings]

i1'! 1 to 6 show an embodiment of the automotive antenna device of the present invention, FIG. 1 is a strategic perspective view showing the installation 1 of the high frequency pickup provided on both front pillars, and FIG. An explanatory diagram showing the general arrangement of the front pillars on which the high frequency pickups are arranged, FIG. 3 is a cross-sectional view showing the front pillars shown in FIG. Figure 5 is a circuit diagram of the automatic heavy-duty antenna device, Figure 6 is a directional characteristic diagram of the high-frequency pickup installed on both front pillars, and Figures 7 to 10 are the automotive antenna device. 7 is a schematic perspective view of a pair of high frequency pickups constituting a diversity receiving antenna, not showing the state in which they are fixed to both trunk hinges, and FIG. 8 is a schematic perspective view of one of the high frequency pickups shown in FIG. 7. Fig. 9 is a circuit diagram of the automobile antenna device, Fig. 10 is a directional characteristic diagram of the high frequency pickup installed on the trunk hinge, Fig. 11 is a diagram of the main parts of the trunk hinge side, Surface current generated1
FIG. 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. FIG. 13 is an explanatory diagram of the surface current ■ and the pickup. An explanatory diagram showing the electromagnetic coupling state with the loop antenna, Fig. 14 is an explanatory diagram showing the directivity characteristics of the loop antenna in Fig. 13, Fig. 15 is an explanatory diagram showing the distribution characteristics of the surface current intensity, and Fig. 16 is an explanatory diagram showing the distribution characteristics of the loop antenna in Fig. 13. FIG. 3 is an explanatory diagram showing the direction of surface current. 32.132,232,332... High frequency pickup 34.134... Front pillar 64...
Switch circuit 86.186... Trunk hinge.

Claims (3)

[Claims] (1) A pair of high-frequency pickups configured to constitute a spatial diversity receiving antenna by efficiently picking up high-frequency surface currents induced in the vehicle body connection portion by broadcast waves and flowing through the vehicle body connection portion, and a receiving antenna of the pair of high frequency pickups is provided. An antenna device for an automobile, characterized in that a high frequency pickup in good condition is automatically selected. (2) An antenna device for an automobile according to claim 1, wherein the pair of high-frequency pickups are provided in both front pillars of the connecting portion. (3) The antenna device for an automobile according to claim 1, wherein the pair of high-frequency pickups are provided on both trunk hinges of the connecting portion.