JPS60169204A - On-vehicle antenna system - Google Patents

Abstract

PURPOSE:To obtain an antenna with high sensitivity without causing fluctuation in the reception characteristic independently of the mobile direction of an automobile by using a cabin itself as a part of an antenna and synthesizing outputs of a couple of pickup coils. CONSTITUTION:A magnetic shield box 30 is fixed to the cabin 10, a couple of open slots 30a, 30b orthogonal respectively to an opposite face of the magnetic shield box 30 to the cabin 10 are provided, a current induced on the surface of the cabin 10 is led into the magnetic shield box 30 via the orthogonal open slots 30a, 30b, a signal is detected by a couple of the orthogonal pickup coils 20, 22, the synthesis with added phase difference is performed by a phase difference adding device 50 and a synthesis circuit 48 so as to obtain a stable reception wave with high output independently of the mobile direction of the cabin.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an antenna device for a vehicle, and in particular, to an antenna device for a vehicle, which has a simple structure by using the vehicle body as a part of the antenna and picking up the current induced on the surface of the vehicle body by broadcast waves. The present invention relates to an improved vehicle antenna device that can efficiently receive broadcast waves.

[Prior Art] Broadcast waves from FM broadcasts, television broadcasts, personal radios, telephones, etc. are used as communication systems for vehicles, and in order to reliably receive these broadcast waves, vehicles are equipped with antenna devices. Therefore, a pole antenna is usually used as a conventional vehicle antenna device.

However, with such a pole antenna, a large number of different antennas must be installed for different types of broadcast waves, and such a large number of antennas must be installed. With the pole antenna, there was a problem of performance deterioration due to phase U interference between each antenna, for example, loss of gain due to impedance change, deterioration of directivity, and other deterioration of reception performance.

In addition, this type of conventional pole antenna imposes restrictions on the design of the vehicle itself, and the antenna that protrudes outside the vehicle body generates wind noise when the vehicle is running, and furthermore, the ball antenna may be damaged due to mischief, theft, dust, etc. It is necessary to take measures to prevent sliding parts from sticking due to intrusion or freezing, and there are also problems with operability, such as the need to store or remove the extended ball antenna when washing the car or parking it in the garage. Ta.

Purpose of the Invention The present invention has been made in view of the above-mentioned problems in the prior art.The purpose of the present invention is to eliminate the drawbacks of the prior art, always ensure the best reception performance, and in particular, to make the structure of the antenna itself small and simple, and to be suitable for vehicles. It is an object of the present invention to provide a highly sensitive vehicle antenna device whose reception characteristics do not vary depending on the direction of movement.

[Means and operations for solving the problem] In order to achieve the above object, the present invention provides a magnetic shielding box on the vehicle body, particularly on the passenger compartment side, and the magnetic shielding box has a magnetic shielding box that is substantially perpendicular to the surface facing the vehicle body. A pair of opening grooves are provided, and a pair of pickup coils are disposed within the magnetic shield box, and the pickup coils are arranged substantially perpendicularly to the opening so as to face each other, and thereby,
By using the heavy body itself as a part of the antenna and combining the electrical output signals obtained from the pair of pickup coils according to a predetermined calculation method, a highly sensitive antenna device that is independent of the direction of movement of the vehicle is obtained. It is characterized by

[Example] Preferred embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows a state in which a current ■ is induced on the outer surface of the vehicle body by the arriving broadcast wave Ei, and in the present invention,
As shown in FIG. 2, this induced current I is caused by
It is characterized by being picked up by 0.

In the basic principle shown in Figure 2, the line current I flowing on the surface of the car body is
The magnetic field H generated by is electrically picked up by the pickup coil 20 as an open end voltage . However, in the present invention, the pickup coil 20 is placed in a magnetically shielded box, and the opening groove provided in the magnetically shielded box makes it possible to pick up only the line current flowing in a predetermined direction.

FIG. 3 shows the arrangement of a pair of pickup coils according to the present invention, and FIG. 4 shows the combination structure of each pickup coil and a magnetic shield box.

In the figure, the magnetic shielding box 30 is fixed to the vehicle body 10, particularly to the passenger compartment side thereof, and is preferably placed, for example, near the ceiling of the vehicle body. A pair of openings 130a and 30b are provided on the surface of the magnetic shielding box 30 facing the vehicle body, and the current induced on the surface of the vehicle body 10 is transmitted through the orthogonal opening grooves 308 and 30.
Magnetic shielding box 30 as a current in the direction along b
Guided within.

A pair of pickup coils 20 and 22 are disposed inside this magnetically shielded box 30, and both pickup coils 20 and 22 are provided substantially perpendicular to each other, and the pickup sides thereof are connected to the pair of openings F530a and 22, respectively.
30b.

Therefore, as will be described later, the pair of pickup coils 20.22 that are perpendicular to each other allows both coils 20.22 to be used even if the direction of the broadcast wave changes while the vehicle is running.
By combining the detection signals from 22, the desired stable and highly sensitive output can be achieved.

As shown in FIG.
The detection signal from 0.22 is transmitted from the connector 32.34 fixed to the magnetically shielded box 30 to the coaxial cable 36.
38 and extracted as a desired electrical signal.

In addition, in the illustrated embodiment, shorters 4.0 and 42 are fixed to both big fat coils 20 and 22,
Furthermore, tuning trimmer capacitors 44 and 46 are inserted into each coil. The shorteners 40 and 42 described above connect each of the coils 20 and 22 to the magnetic shield box 30, and by adjusting their positions, the input impedance can be adjusted to 50Ω to increase the sensitivity of the antenna, and each of the capacitors 44 By adjusting the capacitance value of .46, the Q (frequency sharpness) of each loop can be increased.

Further, in the present invention, the electrical output signals obtained from the pair of pickup coils 20122 are supplied to the combining circuit 48 from the coaxial cable 36, 38,
A desired combining effect is applied and the stabilized signal output is supplied to the receiver.

In the embodiment of FIG. 3.4, the combining effect is shown as a phase difference addition combination, in which a phase difference addition device 50 is provided on the coaxial cable 36 on the side of the pickup coil 20, whereby it is possible to A constant output voltage can be obtained. It is preferable that the phase difference adding device @50 is, for example, a λ/4 line.

The synthetic action in the present invention will be explained in detail below.

FIG. 5 shows a state in which the direction of the current () induced in the vehicle body with respect to a single pickup coil 20 does not match and has an angle θ, and due to this deflection angle θ, the open end voltage V of the pickup coil 20 is The intensity changes as shown in FIG. 6, and it is clear from FIG. 5.6 that in the installation of a single pickup coil 20, the open end voltage intensity is highly dependent on the direction of movement of the vehicle. In Fig. 6, the characteristics of the open circuit voltage intensity show approximately the characteristics of COSθ, and as a result, the induced current direction 0 is 90° or 27”.
In this direction, reception is theoretically impossible.

In the present invention, the disadvantages of the single pickup coil described above are eliminated by arranging a pair of pickup coils 20, 22 that are substantially perpendicular to each other.

FIG. 7 shows the relationship between the pair of orthogonal pickup coils 20, 22 and the induced current (2) in the present invention, and FIG. 8 shows the characteristics of the output voltage intensity with respect to the deflection angle θ. In the figure, the pickup coil 22 has a phase difference of 90° with the pickup coil 20, and as a result,
As is clear from FIG. 6, the output from the pickup coil 20 has the characteristic of COS θ shown by the broken line in FIG. 8, and the output from the pickup coil 22 has the characteristic of sin θ shown by the dashed line in FIG. becomes. Therefore,
In the present invention, a desired stable output waveform can be achieved by subjecting both of these outputs to a predetermined combining operation.

In the present invention, the synthesis operations are generally divided into three types: sum of both outputs, switching, and phase difference addition synthesis, and each synthesis operation will be explained.

This can be obtained by simply combining the first summation or both outputs in FIG. 8, and the characteristic shown by the solid line in the figure shows the summation output.

Here, if k is a constant, the composite output vx is lVx l
=l kI (cosθ+sinθ) 1”=2”
ki' 5in (θ+45m) Therefore, according to summation, it is possible to double the output gain. However, even in this case, the deflection angle θ becomes zero in the 1356 or 3156 direction, but there is an advantage that extremely good high-sensitivity reception is possible in a predetermined designated direction.

The second synthesis is a switching synthesis, and as shown in FIG. 9, the synthesis circuit 48 includes a level comparator and an input switch;
As shown in the characteristics of Figure 10, the outputs of both coils detected from the coaxial cable 36 and 38 are taken out, whichever is larger, and thereby a rectified output can be obtained. This greatly contributes to stable reception characteristics.

The third synthesis is phase difference additive synthesis, which is described in 3.4 above.
As shown in the figure, the output obtained from one pickup coil 20 is corrected for a 90° phase shift by the phase difference adding device, and as a result, the output of the additional circuit 50 to which the phase difference is added is ej90° x kl sinθ, and as a result, the composite output is IVX l=l kl (cosθ+jsinθ)l=
As shown in FIG. 11, it is possible to obtain a constant voltage regardless of the current direction.

As described above, the present invention has the advantage that an extremely stable combined output can be supplied to a receiver, and that a desired output can be obtained by arbitrarily selecting the combining characteristics.

[Effects of the Invention] As explained above, according to the present invention, a pair of pickup coils that are substantially perpendicular to each other is provided, and by combining the outputs from these two coils, stable operation independent of the moving direction of the vehicle can be achieved. It is now possible to obtain high-output received 43 waves without using a conventional ball antenna, etc., and there is no protrusion on the surface of the heavy body. Become.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the flow induced state of the vehicle body by incoming broadcast waves, Fig. 2 is a principle explanatory diagram showing the relationship between the line current flowing in the car body and the pickup coil, and Fig. 3 is a vehicle according to the present invention. 4 is a partially cutaway perspective view showing the structure of the pickup coil and magnetic shield box in FIG. 3, and FIG. FIG. 6 is a characteristic diagram of the output voltage with respect to the declination angle θ of FIG. 5. FIG. 7 is an explanatory diagram showing the declination angle between the pair of pickup coils and the line current according to the present invention. , Fig. 8 is a characteristic diagram showing the relationship between the declination angle θ and the output voltage in Fig. 7 and the output voltage by summation, and Fig. 9 shows a preferred embodiment of a combining circuit that switches the output from both pickup coils. The explanatory diagram, FIG. 10, is a characteristic diagram of the declination angle and output voltage in FIG. 9, and FIG. 11 is a characteristic diagram of the declination angle and output voltage when performing phase difference addition synthesis. 10...Vehicle body 20.22...Pickup coil 30...
Magnetic shielding boxes 30a, 30b... Opening groove 48... Composite circuit. Agent Patent Attorney Kenji Yoshida Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 WE Figure 10 Figure 11

Claims (1)

[Claims] (1) A magnetic shielding box is fixed to the vehicle body by forming a pair of opening grooves that are substantially orthogonal to each other on a surface facing the vehicle body, and a pair of opening grooves that are substantially orthogonal to each other are formed in the magnetic shielding box in opposing proximity to the opening grooves, respectively. The circuit includes a pair of pickup coils disposed in the same direction, and a synthesis path for synthesizing the electrical outputs obtained from the pair of pickup coils. An antenna device for a vehicle that is characterized by receiving signals with high sensitivity.