JPH01174007A - Antenna attenuator - Google Patents

Abstract

PURPOSE:To obtain an excellent reception characteristic even at a strong electric field district by connecting an attenuation circuit close to a conductor part of a nearly cylindrical antenna receptacle and controlling the attenuation of the attenuation circuit by an AGC loop of a receiver. CONSTITUTION:An attenuation circuit 5 is mounted to a circuit board 4 and fitted directly to the rear part in an outer conductor 1. The attenuation circuit 5 is connected to an inner conductor 2 via a signal input terminal 5a and connected to an antenna input terminal of a receiver via a signal output terminal 5b, and connected to an AGC loop of the receiver via a connection control voltage input terminal 5c. When a strong electric field signal is given via the inner conductor 2 and the signal input terminal 5a and a control voltage by the AGC loop from the receiver via a control voltage input terminal 50 are inputted, the strong electric field signal is attenuated in response to the control voltage and outputted to the receiver via the signal output terminal 5b.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an antenna attenuator for receiving FM broadcasts etc. well in strong electric field areas where intermodulation and cross modulation are likely to occur.

BACKGROUND ART The antenna attenuator of a conventional FM receiver is composed of a PIN diode, etc., and is built into the front end stage of the FM receiver or mounted on a printed circuit board within the FM receiver to input to the antenna. It is configured to attenuate strong electric field signals.

Problems to be Solved by the Invention However, the above-mentioned conventional antenna attenuators are built into the front-end stage of the FM receiver or mounted on the printed circuit board of the FM receiver, so there is a problem with the antenna. There is a problem in that the amount of attenuation is not constant due to the spatial distance between the FM receivers and the influence of adjacent high impedance parts within the FM receiver, and the reception characteristics vary.

SUMMARY OF THE INVENTION In view of the problems of the prior art described above, it is an object of the present invention to provide an antenna attenuator having good reception characteristics in areas with strong electric fields.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention connects an attenuation circuit close to the conductor portion of a substantially cylindrical antenna socket, and calculates the amount of attenuation of this attenuation circuit into a receiving device. It is designed to be controlled by an AGC loop.

Effect of the Invention With the above configuration, the attenuation circuit is placed close to the antenna and further away from the high impedance portion of the receiving device, so that good reception characteristics can be obtained in strong electric field areas.

EXAMPLES Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1(a) is a schematic configuration diagram showing one embodiment of the antenna attenuator according to the present invention, FIG. 1(b) is an explanatory diagram of JASO (Japan Automobile Manufacturers Association) standard D501, and FIG. FIG. 2 is a circuit diagram showing an attenuation circuit of the antenna attenuator of FIG. 1;

In Fig. 1, 1 is a cylindrical outer conductor at ground potential, 2 is an inner conductor disposed within the outer conductor 1, and 3 is an insulating layer that supports the inner conductor 2 within the outer conductor. The diameter A of the outer conductor 1, the distance B from the tip of the outer conductor 1 to the insulating support part 2, and the diameter C of the inner conductor 2 are J ASO (Japan Automobile Industry Co., Ltd.) as shown in FIG. It is formed to comply with the Society) Standard D501.

4 is a circuit board on which an attenuation circuit 5 is mounted and is directly attached to the rear part of the outer conductor 1, and the attenuation circuit 5 is connected to the inner conductor 2 through a signal input terminal 5af, and a signal output terminal 5.
It is connected to the antenna input terminal of the receiving device (not shown) through the connection control voltage input terminal 5C and the AGO (Automatic Galn Co.
ntrol ) connected to the loop.

In FIG. 2, C] has one end as the control voltage input terminal 5c.
A grounding capacitor C2 is connected to the anode of the PIN diode D1 for attenuation, and the other end is grounded. A DC blocking capacitor connected to the anode of the PIN diode D2 and one end of the DC blocking capacitor C3, C3 is a DC blocking capacitor whose other end is connected to the signal output terminal 5b, and D2 is an attenuator whose cand is grounded. This is a PIN diode for

In the above configuration, the attenuation circuit 5 receives a strong electric field signal through the inner conductor 2 and the signal input terminal 5a, and receives a control voltage from the AGC loop from the receiver through the control voltage input terminal 5c.
When input via i, the strong electric field signal is attenuated according to the control voltage and output to the receiving device via the signal output terminal 5b.

Therefore, according to the above embodiment, compared to the conventional example, the attenuation circuit 5 is arranged closer to the antenna, further away from the high impedance part of the receiving device, and is shielded within the antenna sockets 1 to 3. Therefore, it is not induced into other circuits, and therefore good reception characteristics can be obtained in strong electric field areas.

FIG. 3 shows another attenuation circuit, in which one end of the DC blocking capacitor C5 is connected to the signal input terminal 5a, and the other end is one end of the high resistance resistor R1 for supplying the control voltage, which determines the amount of attenuation. It is connected to one end of the current resistance ratio 2 and the anode of the PIW diode Dll for attenuation.

The other end of the resistor R1 is connected to the control voltage input terminal 5C and one end of the grounding capacitor C4, and the other end of the grounding capacitor C4 is grounded.

The other end of the resistor FLz and the cathode of the PIN diode Dll are connected to one end of the DC blocking capacitor C6 and the attenuation PIN.
It is connected to the anode of the diode D12, and the other end of the DC blocking capacitor C6 is connected to the signal output terminal 5b. The cand of the PIN diode D12 is connected to one end of a resistor R3 that determines the amount of attenuation, and the other end of the resistor R3 is grounded.

The above diodes Dll and D12 respectively correspond to the diodes D1 and D2 shown in FIG.
4. C5 and C06 correspond to capacitors cl, C2 and C3 shown in FIG. 2, respectively. In this circuit, resistor 2
A desired amount of attenuation can be obtained by changing the values of resistors 2 and FL.
By selecting 3f, good reception characteristics can be obtained even in other receiving devices.

FIG. 4 is a schematic configuration diagram showing another embodiment, where 10 is a cylindrical antenna socket similar to the antenna sockets 1 to 3 shown in FIG. An inner conductor 12 mounted coaxially and projecting outwardly,
This is a box-shaped shield portion made of sheet metal, and a substrate 4 on which the above-described attenuation circuit 5 is mounted is attached inside this shield portion 12 .

In this embodiment, since the attenuation circuit 5 is shielded from the outside by the shield section 2, the input signal is not guided to other circuits, and the input signal can be efficiently attenuated.

DETAILED DESCRIPTION OF THE INVENTION As described in detail, the present invention provides an arrangement in which an attenuation circuit is connected in close proximity to a conductor portion of a substantially cylindrical antenna socket, and the amount of attenuation of this attenuation circuit is controlled by an AGO loop of a receiving device. Therefore, good reception characteristics can be obtained in strong electric field areas.

[Brief explanation of the drawing]

FIG. 1(a) is a schematic configuration diagram showing one embodiment of the antenna attenuator according to the present invention, FIG. 1(o) is an explanatory diagram of JASO (Japan Automobile Manufacturers Association) standard D501, and FIG. , 1st
FIG. 3 is a circuit diagram showing another attenuation circuit, and FIG. 4 is a schematic configuration diagram showing another embodiment. 1-3.10... Antenna socket, 2.11... Internal conductor, 5... Attenuation circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person M
l Figure l~3
Ryoji Te 102 Yen Fraud/Minato S Shinsei Hyakurei (I)
2 4 (mouth second mouth

Claims (4)

[Claims] (1) An attenuation circuit is connected close to the conductor part of the approximately cylindrical antenna socket, and the attenuation amount of this attenuation circuit is measured by the AG of the receiving device.
An antenna attenuator characterized by being controlled by a C loop. (2) The antenna attenuator according to claim 1, wherein the attenuation circuit is installed within the antenna socket. (3) The conductor part of the antenna socket is attached coaxially with the antenna socket and protrudes to the outside, shields the attenuation circuit, and is connected in close proximity to the protruding conductor part. An antenna attenuator according to claim 1. (4) The antenna socket is Japan Automobile Manufacturers Association standard D5
The antenna attenuator according to any one of claims 1 to 3, characterized in that the antenna attenuator is formed in accordance with the Patent No. 01.