JPH04326819A - Radio receiver - Google Patents

Abstract

PURPOSE:To prevent jamming or the like by switching sensitivity to a reception signal when a specified broadcasting station is selected. CONSTITUTION:A tuner is equipped with a traffic information switch for selecting traffic information broadcasted at 1620kHz. When this traffic information switch is selected, a tuning control circuit 28 controls an RF circuit 14, matches a tuning frequency to the frequency of the traffic information and outputs a sensitivity switching signal 100 to an AGC circuit 26. When this sensitivity switching signal 100 is inputted, the AGC circuit 26 increases AGC sensitivity, and the attenuation, etc., of the reception signal from an antenna 10 is executed by controlling an antenna circuit 12 so as to prevent distortion caused by the over input of an FET for high frequency amplification provided on the RF circuit 14. On the other hand, by providing a position information output equipment, a specified frequency is selected and only when a vehicle is traveled in a specified area, reception sensitivity can be switched.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio receiver that is attached to a moving vehicle to receive AM broadcasts and FM broadcasts.

0002

2. Description of the Related Art Conventionally, vehicles are usually equipped with radio receivers. Through this radio receiver, the driver can enjoy music from general broadcast stations or obtain useful information such as traffic information.

[0003] Such radio receivers are generally provided with a so-called AGC circuit (auto gain control circuit). That is, the receiving sensitivity is adjusted in response to changes in the strength of the received signal. Specifically, this AGC circuit adjusts the reception sensitivity by setting the gain in high frequency amplification, attenuating the received signal, etc. based on the RF signal after high frequency amplification or the IF (intermediate frequency) signal.

0004

[Problems to be Solved by the Invention] However, in the above-mentioned conventional AGC circuit, the AGC level is uniquely set. When receiving relatively weak radio waves from broadcasting stations, there is a problem in that clear reception cannot be achieved due to interference.

A specific example will be explained. In Japan, traffic information is broadcast at 1620 KHz in some areas. On the other hand, FEN broadcast station is broadcasting at 810KHz. Therefore, if you try to receive the traffic information in the area near that FEN broadcast station, the traffic information will be FEN.
There were cases where EN broadcasting caused interference. That is, F
The high frequency amplifier consisting of ET etc. is the above-mentioned AGC.
The degree of amplification is controlled by the circuit, but if the level of the AGC circuit is set high, the received signal of FEN broadcasting will be over-input, resulting in distortion, and within that distortion, harmonics due to second-order distortion will be generated. was received along with the traffic information signal, causing interference.

[0006] On the other hand, it is possible to set the level of the AGC circuit low, but this will result in a reduction in the level of the received signal in areas other than the above-mentioned areas. There is a need for a means for appropriately controlling the AGC circuit to prevent the interference when reception of one of the broadcast stations in a frequency relationship is selected.

[0007] The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to provide a radio reception system that allows optimal reception sensitivity to be set when a specific broadcasting station (frequency) is selected. The aim is to provide the opportunity.

[0008]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a radio receiver which is attached to a moving body and is equipped with a tuning means for selecting a broadcasting station, in which the tuning means selects a broadcasting station in advance. The present invention is characterized in that a control circuit is provided that switches the receiving sensitivity for the received signal when a specific set broadcasting station is selected.

[0009] Furthermore, the present invention is provided with a position information output device that measures the geographical position of the mobile object and outputs the position information, and the control circuit is configured to perform a specific The present invention is characterized in that when a broadcasting station is selected and the position information indicates a predetermined specific area, the reception sensitivity for the received signal is switched.

0010

[Operation] According to the above configuration, when a specific preset broadcasting station is selected by the channel selection means, the control circuit
Since the receiving sensitivity can be switched, the above-mentioned interference can be effectively prevented. That is, when a specific frequency is selected, by lowering the receiving sensitivity etc., it is possible to extract the desired received signal while preventing the above-mentioned distortion in the high frequency amplifier.

[0011] Furthermore, by providing a position information output device, the receiving sensitivity can be switched only when a specific frequency is selected and the vehicle is traveling in a specific area, so that interference does not occur. When a vehicle is driving in an area, reception sensitivity switching by selecting that specific frequency is avoided.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the overall configuration of a radio receiver according to the present invention.

The received signal received by the antenna 10 is
The signal is sent to the antenna circuit 12. This antenna circuit 1
2 performs matching with the antenna and attenuation of the received signal. The received signal output from the antenna circuit 12 is sent to the RF circuit 24. This RF circuit 14 performs high frequency amplification and tuning.

[0014] The received signal output from the RF circuit 14 is
The mixer 16 mixes the signal with the predetermined signal transmitted by the oscillator 18 and converts it to an intermediate frequency, and then the IF circuit 20
The signal is sent to , where it is amplified. The received signal is detected by a detection circuit 22 and then sent to a speaker 24 via an amplifier.

On the other hand, the antenna circuit 12 and the RF circuit 14
An AGC circuit 26 is connected to. The AGC circuit 26 operates according to the output signal on the output side of the RF circuit 14 as shown in the figure or the IF signal after detection (not shown).
Controlling the attenuation of the received signal in the antenna circuit 12,
This is to set the high frequency amplification degree in the RF circuit 14. These antenna circuit 12, RF circuit 14, and AGC circuit 26 will be described in detail later.

A channel selection control circuit 28 is connected to the RF circuit 14. The tuning control circuit 28 receives a selection signal from a tuning device 30 composed of a dial or a plurality of keys, and controls the tuning circuit in the RF circuit 14 based on the signal.

In this embodiment, the channel selector 30 has 16
A traffic information switch is provided for selecting traffic information broadcast at 20KHz. When this traffic information switch is selected, the tuning control circuit 28 controls the RF circuit 14 to match the frequency of the traffic information, as described above, and sends a circuit switching signal 100 to the AGC circuit 26. Output.

FIG. 2 shows a specific circuit configuration of the block indicated by a dashed line 200 in FIG. Here, a received signal from the antenna 10 is input to the gate terminal of an FET 32 that performs high frequency amplification. and,
The drain of the FET 32 is connected to the emitter of a transistor 34 that sets the AGC level. The collector of this transistor 34 is connected to a tuning circuit 36, and power is supplied to the tuning circuit 36 via a small resistor 38.

The input of the AGC circuit 26 is connected between the small resistor 38 and the tuning circuit 36. in particular,
This AGC circuit 26 is composed of an amplifier section 26a and a control section 26b. The sensitivity switching signal 100 from the above-described channel selection control circuit 28 is supplied to the amplifier section 26a.

The output of the AGC circuit 26 is connected to the transistor 3
4 and an attenuator 42 via a driver 40. This attenuator 42 forms a part of the antenna circuit 12 described above, and attenuates the received signal according to the output signal of the transistor 40.

Therefore, the AGC circuit 26 can set the sensitivity to the received signal by controlling this transistor 44 and the transistor 34 according to the tuned output signal.

In this embodiment, when the sensitivity switching signal 100 is not output from the tuning control circuit 28, the gain of the amplifier section 26a is G1, and the gain of the tuning circuit 36 and the resistor 38 is
The RF signal obtained at the connection point is amplified by a factor of G1 and applied to the control section 26b. Therefore, A.G.
The C sensitivity becomes the first value, and RF gain control is performed as in the conventional case.

On the other hand, when the sensitivity switching signal 100 is output from the tuning control circuit 28, the gain of the amplifier section 26a is switched to G2, which is larger than the gain G1, and the connection point between the tuning circuit 36 and the resistor 38 is switched. The RF signal obtained in G2
The signal is amplified twice and applied to the control section 26b. Therefore, the AGC sensitivity has a second value higher than the first value, and the received signal is attenuated to a greater extent. That is, when the sensitivity switching signal 100 is generated, the AGC sensitivity increases, the reception sensitivity decreases, and the reception signal is attenuated more by the transistor 44.

That is, due to such attenuation, the FET
Excessive input to the gate at FET 32 is prevented, and this FET3
It becomes possible to avoid distortions caused by 2.

Therefore, according to this embodiment, when a driver or the like turns on the traffic information switch in the channel selector 30 in order to receive traffic information (1620 KHz), the message shown in FIG.
The attenuation caused by the transistor 44 shown in FIG.
As a result, it is possible to avoid distortion caused by the received signal of the FEN broadcast station broadcast at 810 KHz, that is, distortion caused by excessive input in the FET 32. Therefore,
It becomes possible to effectively eliminate interference when traffic information is received.

By the way, if the vehicle is traveling in an area other than the vicinity of a high-output broadcasting station, it may be preferable not to perform the above-described switching of reception sensitivity.

A configuration for realizing such a request is shown in FIG. 3 as a second embodiment.

Here, the tuning frequency controlled by the tuning control circuit 28 is sent to the receiver controller 46 as frequency information 102. A position information output device 48 constituted by a well-known navigation system or the like is connected to this receiver controller 46. That is, this position information output device 48 measures the geographical position of the vehicle and outputs position information 104 as the result.

The receiver controller 46 outputs a sensitivity switching signal 106 to the AGC circuit 26 when the input frequency condition and position condition match the preset setting conditions. Then, this sensitivity switching signal 10
6, the AGC circuit 26 turns on the transistor 44 shown in FIG. 2 to attenuate the received signal to prevent excessive input to the FET 32, as described above.

Therefore, the configuration shown in FIG. 3 has the advantage that the sensitivity can be switched only when receiving traffic information and when driving in an area near a FEN broadcasting station. Here, the definition of the neighborhood can be determined by a geographic table provided in the receiver controller 46.

That is, according to such a configuration, it is possible to realize appropriate reception sensitivity switching according to the frequency and reception position.

[0032]

[Effects of the Invention] As explained above, according to the present invention,
When a specific broadcasting station is selected, reception sensitivity can be switched to effectively avoid interference.

Furthermore, by providing a position information output device, it becomes possible to switch the sensitivity only when a specific frequency is selected and the vehicle is located in a specific area. Therefore, appropriate reception according to the geographical situation is ensured.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a radio receiver according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing a specific circuit configuration of a block 200 indicated by a dashed line in FIG. 1;

FIG. 3 is a block diagram showing the configuration of a radio receiver according to a second embodiment of the present invention.

[Explanation of symbols]

12 Antenna circuit 14 RF circuit 26 AGC circuit 28 Tuning control circuit 30 Tuning device

Claims (2)

[Claims] Claims: 1. A radio receiver that is attached to a mobile body and includes a tuning means for selecting a broadcasting station, in which when a specific broadcasting station set in advance is selected by the tuning means, A radio receiver characterized by being provided with a control circuit that switches reception sensitivity. 2. The radio receiver according to claim 1, further comprising a position information output device that measures the geographical position of the mobile object and outputs the position information, and the control circuit is configured to control the channel selection means. A specific broadcast station set in advance is selected,
The radio receiver is further characterized in that when the position information indicates a predetermined specific area, the reception sensitivity for the received signal is switched.