JP2006080602A - Booster amplifier for radio receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide "a booster amplifier for a radio receiver" which can utilize information from a radio receiver for control of the AGC circuit of a booster amplifier without providing a special signal line. <P>SOLUTION: The booster amplifier 200 for a radio receiver connected on a prestage of the radio receiver 300 is provided with a voltage-controlled attenuator 210 capable of attenuating a high-frequency signal from an antenna 10, an RF amplifier 220 for amplifying a high-frequency signal from the attenuator 210, an impedance detector 230 for detecting change in impedance on the output signal line of the RF amplifier 220 to be connected to the input section of the radio receiver, and a voltage control unit 240 for controlling an operation of the attenuator 210 in response to the detection result of the impedance detecting means 230. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a booster amplifier for a radio receiver, and more particularly to gain control of a booster amplifier connected to an in-vehicle radio receiver.

  In general, an in-vehicle radio receiver system includes a booster amplifier connected to an antenna and a radio receiver connected to a subsequent stage of the booster amplifier. The booster amplifier amplifies the RF signal in order to prevent loss of the RF (high frequency) signal received from the antenna, and outputs this to the radio receiver side.

  FIG. 6 is a diagram illustrating a configuration example of a conventional in-vehicle radio receiver system. As shown in the figure, the antenna 10 is connected to a booster amplifier 20 via a connection port 12. The booster amplifier 20 includes an attenuator 22 that receives an RF signal from the antenna 10, an RF amplifier 24 connected to the output stage of the attenuator 22, and an AGC circuit 26 that controls the operation of the attenuator 22. . The AGC circuit 26 detects the output level of the RF amplifier 24 and supplies a control voltage corresponding to the detected level to the attenuator 22 to prevent an excessive RF signal from being input from the antenna 10. Yes.

  The RF signal output from the booster amplifier 20 is input via the connection port 32 of the radio receiver 30. The radio receiver 30 selects a desired frequency signal from the input RF signal, converts the selected signal into an IF (intermediate frequency) signal, performs detection, etc., and then outputs the radio broadcast of the desired station from the speaker. I am letting.

  The booster amplifier 20 shown in FIG. 6 itself has an AGC function, but besides this, an output signal from an AGC circuit provided on the radio receiver 30 side is used as an attenuator 22 or an RF of the booster amplifier 20. It can also be used to control the amplifier 24.

  For example, Patent Document 1 relates to an in-vehicle FM receiving system apparatus, and outputs of an RF-AGC output circuit that detects electric field strength in a relatively wide band and an IF-AGC output circuit that detects electric field strength in a relatively narrow band. A technique for outputting an optimum voltage from the level to the intermodulation and intermodulation characteristics to the attenuator and the RF amplifier in the antenna amplifier is disclosed.

  Patent Document 2 discloses a technique for outputting an optimum voltage for intermodulation and intermodulation characteristics to an RF amplifier inside an antenna amplifier by the same method as Patent Document 1.

JP-A-5-22174 JP-A-5-22175

  However, in the radio receiver booster amplifier 20 as shown in FIG. 6, since the AGC circuit 26 operates for the entire band of the reception signal of the antenna 10, the reception intensity of the desired broadcast station is weak, and the undesired broadcast station is close. If it exists and its reception intensity is high, the reception level of the antenna 10 becomes high, and the AGC circuit 26 attenuates the reception signal by the attenuator 22 in response to this. Due to this attenuation, there is a problem that the signal of the desired station is attenuated and the output level of the audio signal of the desired station is lowered. Further, since the detection level of the AGC circuit 26 depends on the gain of the RF amplifier 24, there is a problem that an arbitrary operation level cannot be selected. On the other hand, the inventions disclosed in Patent Documents 1 and 2 are not capable of solving the above-described problems, and the configuration is complicated because it is necessary to provide a control circuit for controlling the operation of the booster amplifier in the radio receiver. And cost reduction is difficult.

  The present invention solves the above-described conventional problems, and the booster for a radio receiver that can be used for gain control of an AGC circuit of a booster amplifier without providing a special signal line with information from a radio receiver arranged in a subsequent stage. The purpose is to provide an amplifier.

  A booster amplifier for a radio receiver according to the present invention is connected to a front stage of a radio receiver and can attenuate a high-frequency signal from an antenna, amplifies the high-frequency signal from the attenuator, and outputs the amplified signal An amplifier for supplying to the signal line; impedance detecting means for detecting an impedance change on the output signal line connected to an input unit of the radio receiver; and an operation of the attenuator in response to a detection result of the impedance detecting means. Control means for controlling.

  According to the booster amplifier for a radio receiver according to the present invention, since the AGC circuit of the booster amplifier is controlled based on information on the radio receiver side connected to the subsequent stage, the operation condition is optimal for the radio receiver. It is possible to control the AGC circuit of the booster amplifier. Furthermore, since the impedance change of the signal line of the input part of the radio receiver to which the booster amplifier is connected is detected, the original control line for controlling the AGC circuit of the booster amplifier is not required, and the radio reception is performed. No dedicated control circuit is required on the machine side. Therefore, the booster amplifier according to the present invention can be used in combination with various radio receivers, and an inexpensive and high-performance radio reception system can be provided by giving the booster amplifier versatility. .

  Further, since the AGC circuit on the radio receiver side is operated by a band-limited frequency signal, for example, an intermediate (IF) frequency signal, the AGC circuit of the booster amplifier is operated in an optimum state for the radio receiver, and the reception intensity is weak. Even the signal of the desired station is not overwhelmed by the received signal of the non-desired station, and an audio output can be obtained with high sensitivity.

  The best mode for carrying out the present invention will be described below in detail with reference to the drawings.

  FIG. 1 is a diagram showing a configuration of an in-vehicle FM radio receiver system according to a first embodiment of the present invention. The radio receiver system 100 includes a booster amplifier 200 connected to the antenna 10 and a radio receiver 300 connected to the subsequent stage of the booster amplifier 200.

  The booster amplifier 200 includes a voltage-controlled attenuator 210 that receives the RF signal from the antenna 10, an RF amplifier 220 that amplifies the output signal from the attenuator 210, and an impedance change on the output signal line of the RF amplifier 220. Impedance detector 230, and a voltage control unit 240 that controls the operation of the attenuator 210 based on the detection result of the impedance detector 230.

  The voltage control unit 240 includes a threshold detector 242 and an integrator 244. The threshold detector 242 is preferably set with a plurality of thresholds, and a predetermined threshold is selected from the plurality of thresholds based on the detection value of the impedance detector 230, and is selected. A voltage corresponding to the threshold value is output. The plurality of threshold values of the threshold detector 242 may be variable and set by the user.

  The integrator 244 receives the voltage signal from the threshold detector 242, shapes the waveform thereof, and outputs it as the control voltage S 1 to the attenuator 210. The attenuator 210 attenuates the input RF signal according to the control voltage S1 within a predetermined range.

  The antenna 10 and the booster amplifier 200 are connected via the connection port 250. The booster amplifier 200 and the radio receiver 300 are connected via the connection port 260. The connection port 260 is connected to the output signal line of the RF amplifier 220 of the booster amplifier 200 and is connected to the input unit of the radio receiver 300. The radio receiver system 100 can be connected or disconnected via connection ports 250 and 260.

  FIG. 2 is a block diagram showing a general internal configuration of the radio receiver 300. As shown in the figure, the radio receiver 300 receives the RF signal from the booster amplifier 200 via the connection port 260 and amplifies the RF signal, and selects the frequency signal of the desired station from the amplified RF signal. Tuned circuit 320, mixer 340 for mixing the frequency signal and RF signal from local oscillator 330 to generate an intermediate frequency (IF) signal, detector 350 for detecting the audio signal from the IF signal, and audio signal A multiplexer (MPX) demodulator 360 that separates the left and right channels, an audio amplifier 370 that amplifies the demodulated audio signal and outputs an audio signal from the speaker, an RF signal from the tuning circuit 320 and / or an IF from the mixer 340 And an AGC circuit 390 for controlling the operation of the attenuator 380 based on the signal. The AGC circuit 390 can also control the operation of the RF amplifier 310.

  FIG. 3 is a circuit example of the attenuator 380 shown in FIG. The input line connected to the connection port 260 is connected to the RF amplifier 310 including the FETMOS via the capacitors C1 and C2. Further, the input line is grounded via a PIN diode D2, and is grounded via a PIN diode D1, a resistor R1, and a capacitor C3 in parallel therewith. The ACG circuit 390 connects the control voltage S2 to a node between the resistor R1 and the capacitor C3 according to the level of the RF signal or IF signal. The PIN diodes D1 and D2 are turned on by a predetermined resistance in accordance with the control voltage S2, and the RF signal from the input line is sent to the GND side, so that the RF signal is attenuated.

Next, the operation of the booster amplifier according to this embodiment will be described.
The booster amplifier 200 connected to the front stage of the radio receiver 300 as shown in FIG. 2 detects the impedance change of the signal line connected to the connection port 260 by the impedance detector 230. That is,
When a signal with high reception intensity is input to the booster amplifier 200 via the antenna 10, this signal is amplified by the RF amplifier 220 and supplied to the connection port 260 of the radio receiver 300. Then, the AGC circuit 390 of the radio receiver 300 is activated, the input line is short-circuited to GND via the PIN diodes D1 and D2 of the attenuator 380, and an operation for limiting the input signal level is started. This operation reduces the impedance of the input signal line of the connection port 260 from about 75Ω to several Ω.

  The impedance detector 230 connected to the connection port 260 detects a change in impedance on the input signal line, and the voltage control unit 240 supplies the control voltage S1 corresponding to the impedance change to the attenuator 210. To control the operation. On the other hand, in the input region where the AGC circuit 390 of the radio receiver 300 does not operate, impedance change does not occur, and the AGC of the booster amplifier 200 does not operate and operates as a normal amplifier.

  According to the present embodiment, the booster amplifier 200 can control the gain of the reception level from the antenna using the optimum operation information of the AGC circuit 390 in the radio receiver 300. Therefore, even when the reception intensity of the desired station is lower than the reception intensity of the non-desired station, an audio output with good reception sensitivity can be obtained without the reception intensity of the desired station being crushed. In addition, while the AGC circuit 390 is in operation, the radio receiver operates so that the input impedance is constant, so that the Q of the input stage and the tuning circuit is reduced and the selectivity can be maintained. Furthermore, since the booster amplifier 200 has a configuration that does not require a dedicated control circuit, a new signal line, or the like on the radio receiver side, it can be used in combination with various radio receivers.

  Next, the configuration of the impedance detector 230 according to the present embodiment will be described. The impedance detector 230 can detect a change in impedance from the VSWR (Voltage Standing Wave Ratio) of the signal line. The impedance at the antenna 10 is 75Ω (nominal), and when the impedance at the connection port 260 (input signal line) decreases from 75Ω to several Ω, impedance mismatching (mismatch) occurs, and the transmission line termination (here, connection) A reflected wave is generated from the port 260), and a VSWR is generated on the transmission line. The impedance detector 230 uses a directional coupler, for example, to connect the output signal line of the RF amplifier 210 and the connection port 260, and can detect an impedance change from the reflected power due to the generation of the VSRW. As the directional coupler, for example, a quadrature hybrid type may be used.

  Next, another configuration example of the impedance detector 230 will be described. When the impedance of the input signal line of the radio receiver 300 decreases, the load on the booster amplifier 200 increases, and the distortion of the output waveform increases. Since this increases the harmonics of the output signal component, the attenuator 210 may be controlled using a high-pass filter (HPF) having a predetermined cutoff characteristic. For example, as shown in FIG. 4, a high-pass filter 232 is connected to the output signal line of the amplifier 210. The high-pass filter 232 has a frequency characteristic of the cutoff frequency f1 as shown in FIG. 5, and detects a harmonic superimposed on the RF output signal of the cutoff frequency f1 or higher. The threshold value corresponding to the detected result is selected by the threshold detector 242, and the selected threshold voltage is supplied to the attenuator 210 via the integrator 244.

  The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific embodiments, and various modifications can be made within the scope of the gist of the present invention described in the claims. Deformation / change is possible.

  In the above embodiment, the in-vehicle FM radio receiver system is exemplified, but the present invention can also be applied as a booster amplifier for an AM radio receiver.

  The booster amplifier for a radio receiver according to the present invention can be used as an antenna amplifier mounted on a moving body such as an automobile.

It is a figure which shows the structure of the radio receiver system which concerns on 1st Example of this invention. It is a part which shows the internal structure of a radio receiver. It is an example of a circuit of the attenuator of a radio receiver. It is a figure which shows the example of the other impedance detector of a booster amplifier. It is a figure which shows the frequency characteristic of a high-pass filter. It is a figure which shows the structure of the conventional radio receiver system.

Explanation of symbols

10: Antenna 100: Radio receiver system 200: Booster amplifier 210: Attenuator 220: RF amplifier 230: Impedance detector 232: High-pass filter 240: Voltage controller 242: Threshold detector 244: Integrator 250 260: Connection port 300: Radio receiver 310: RF amplifier 320: Tuning circuit 330: Transmitter 340: Mixer 350: Detector 360: MPX multiplexer 370: AF amplifier 380: Attenuator 390: AGC circuit S1, S2: Control voltage

Claims (8)

A radio receiver booster amplifier connected to the front stage of the radio receiver,
An attenuator capable of attenuating a high-frequency signal from the antenna;
An amplifier that amplifies the high-frequency signal from the attenuator and supplies the amplified signal to the output signal line;
Impedance detection means for detecting an impedance change on the output signal line connected to an input unit of a radio receiver;
Control means for controlling the operation of the attenuator in response to the detection result of the impedance detection means;
A booster amplifier for radio receivers. 2. The booster amplifier for a radio receiver according to claim 1, wherein the impedance detection means detects an impedance change on the output signal line connected to the input unit where the AGC circuit on the radio receiver side is operated. The booster amplifier for a radio receiver according to claim 2, wherein the impedance detection means includes a directional coupler on the output signal line, and detects a change in reflected power in the directional coupler. The impedance detection means includes a high-pass filter (high-pass filter) connected to the output signal line, and detects a harmonic component on the output signal line by the high-pass filter. The booster amplifier for radio receivers described in 1. The control means includes threshold value setting means for setting a plurality of threshold values, and the control means includes a plurality of threshold values set by the threshold value setting means and a detection result by the impedance detection means. The booster amplifier for a radio receiver according to any one of claims 1 to 4, wherein the booster amplifier compares and supplies a control voltage corresponding to a selected threshold value to an attenuator. The booster amplifier for a radio receiver according to claim 5, wherein the control means includes an integration circuit, and supplies the control voltage to the attenuator via the integration circuit. The booster amplifier for a radio receiver according to any one of claims 1 to 6, wherein the output signal line of the booster amplifier is detachable with respect to an input unit of the radio receiver. A booster amplifier according to any one of claims 1 to 7,
A radio receiver connected to a booster amplifier;
The radio receiver system includes an attenuator connected to the input, and the attenuator is controlled by an AGC circuit that operates based on a high frequency signal or an intermediate frequency signal.

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