JPH0621837A - Receiver - Google Patents

Abstract

PURPOSE:To provide the receiver implementing the gain adjustment by the AGC function corresponding to the fluctuation of an incoming radio wave signal. CONSTITUTION:The receiver is constituted of a reception means 10 attenuating/ amplifying a reception signal obtained through the reception of an incoming radio wave signal and outputting the attenuated/-amplified signal, a gain adjustment means 20 converting the received signal into a 1st AGC detection output signal with AGC detection with a large time constant and sending a gain control signal adjusting the gain of the reception means 10 in response to the 1st AGC detection output signal, a gain fixing means 30 sending a gain fixing signal used to set the gain of the reception means 10 to a constant value, a fluctuation discrimination means 40 converting the reception signal into a 2nd AGC detection output signal with AGC detection with a small time constant, comparing and detecting whether or not the 2nd AGC detection output signal is resident in a reference level range and sending a discrimination signal representing the result, and a changeover means 60 selecting the gain control signal or the gain fixing signal in response to the discrimination and giving the selected signal to the reception means 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiver having an AGC function for receiving radio waves such as television broadcasts.

[0002]

2. Description of the Related Art A conventional receiver having an AGC function will be described with reference to FIG.

The conventional receiving apparatus comprises a receiving means 10 and a gain adjusting means 20. The receiving means 10 includes a receiving antenna 11, a tuner section 12, a video intermediate frequency amplifier circuit 13, a video detection circuit 14, and a video amplifier circuit 15. The gain adjusting means 20 is composed of a noise removal circuit 21, an AGC detection circuit 22, an AGC amplification circuit 23, and an AGC-RF amplification circuit 24.

Next, the operation of the conventional receiving apparatus configured as described above will be described.

The receiving antenna 11 for receiving the radio wave signal coming from the transmitting station supplies the received signal to the tuner section 12. The tuner unit 12 selects the received signal, amplifies it at a high frequency, and supplies it to the video intermediate frequency amplifier circuit 13. The video intermediate frequency amplifier circuit 13 converts the received signal into an intermediate frequency signal (for example, 58,75 MHz in the case of a video signal) and supplies it to the video detection circuit 14. The video detection circuit 14 detects the received signal and supplies it to the video amplification circuit 15. The video amplifier circuit 15 amplifies the received signal, outputs it to the next stage, and supplies it to the noise removal circuit 21.

The noise removing circuit 21 removes noise in the received signal and supplies the received signal to the AGC detection circuit 22. The AGC detection circuit 22 detects the received signal, converts the received signal into a first AGC detection output signal, and supplies the first AGC detection output signal to the AGC amplifier circuit 23.

The AGC amplifier circuit 23 amplifies the first AGC detection output signal and supplies it to the video intermediate frequency amplifier circuit 13 as a gain control signal. As a result, the video intermediate frequency amplifier circuit 13 amplifies or attenuates the received signal according to the gain control signal.

Further, the AGC amplifier circuit 23 includes a first AGC
The detection output signal is supplied to the AGC-RF amplifier circuit 24.
The AGC-RF amplifier circuit 24 also amplifies the first AGC detection output signal and supplies it to the tuner unit 12 as a gain control signal, similarly to the AGC amplifier circuit 23. As a result, the tuner unit 12 amplifies or attenuates the received signal at a high frequency according to the gain control signal.

According to the conventional receiver configured as described above, a good received signal can be amplified or attenuated and output by adjusting the gain of the incoming radio wave signal.

[0010]

However, when the above conventional receiving device is used in a vehicle-mounted television device, the radio signal received during traveling is different from the fixed home radio signal. Since the incoming radio signal fluctuates greatly due to reflection from buildings, fading, etc., there is a problem that the gain adjustment by the AGC function cannot be fully tracked, and a flutter phenomenon occurs in which the image becomes dark or thin. there were.

The present invention has been made in view of the above problems, and an object thereof is to provide a receiving apparatus capable of performing gain adjustment by an AGC function in response to fluctuations of an incoming radio wave signal. To do.

[0012]

In order to achieve the above object, the present invention provides a receiving means for attenuating or amplifying a received signal obtained by receiving an incoming radio wave signal, and outputting the received signal with a time constant. 1st AGC by large AGC detection
Gain adjusting means for converting into a detection output signal and transmitting a gain control signal for adjusting the gain of the receiving means according to the first AGC detection output signal, and a fixed gain signal for setting the gain of the receiving means to a constant value. A gain fixing means for sending the received signal and a second AG for the received signal by AGC detection with a small time constant.
C-detection output signal, comparing and detecting whether or not the second AGC detection output signal is within a reference level width, and sending a determination signal, and a variable value determination means, and the gain control according to the determination signal. And a switching means for selecting a signal or the fixed gain signal and giving it to the receiving means.

[0013]

With this configuration, the fluctuation value discriminating means supplies the discrimination signal to the switching means, and when it is discriminated that the fluctuation of the radio wave signal is small, the conventional gain control signal is given to the receiving means to change the fluctuation of the radio wave signal. If it is determined that is large, the receiver is provided with a fixed gain signal that fixes the gain to a constant gain regardless of the fluctuation of the received signal without adjusting the gain, and it is possible to sufficiently cope with the fluctuation of the radio wave signal arriving during traveling. You can

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A receiving apparatus of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the outline of the receiving apparatus of the present invention.

The receiver of the present invention comprises a receiving means 10 for attenuating or amplifying a received signal obtained by receiving an incoming radio wave signal and outputting the received signal, and an AG having a large time constant for the received signal.
Gain adjusting means 20 for converting into a first AGC detection output signal by C detection and sending out a gain control signal for adjusting the gain of the receiving means 10 according to the first AGC detection output signal.
A gain fixing means 30 for sending a gain fixed signal for setting the gain of the receiving means 10 to a constant value; and a conversion of the received signal into a second AGC detection output signal by AGC detection with a small time constant, and the second AGC detection. The variation value discriminating means 40 for comparing and detecting whether or not the output signal is within the reference level width and transmitting the discrimination signal, and the gain control signal or the gain fixed signal according to the discrimination signal to select the gain control signal or the gain fixed signal. It is composed of a switching means 60 which is provided to the receiving means 10.

FIG. 2 is a diagram showing a concrete example of FIG. The same reference numerals are given to those described in the prior art, and the description of the operation thereof will be omitted.

Further, the receiving means 10 in FIG.
In FIG. 3, the receiving antenna 11, the tuner unit 12, the video intermediate frequency amplifier circuit 13, the video detection circuit 14, and the video amplifier circuit 15 are included, and similarly, the gain adjusting means 20.
Is a noise removal circuit 21, an AGC detection circuit 22, and an AGC.
It is composed of an amplifier circuit 23 and an AGC-RF amplifier circuit 24. Further, the fluctuation value determination circuit 40 uses the AGC having a charge / discharge time constant smaller than the charge / discharge time constant of the AGC detection circuit 22.
From the detection circuit 41, the AGC amplification circuit 42, the sampling circuit 43, the control circuit 44, the holding circuit 45, the subtraction circuit 46, the reset signal transmission circuit 47, the absolute value voltage holding circuit 48, the reference voltage circuit 49, and the comparison detection circuit 50. It is configured.

The noise removal circuit 21 supplies the received signal from which the noise component has been removed to the AGC detection circuits 22 and 41.

In the signal change receiving means 40, the AGC
The detection circuit 41 converts the received signal into a second AGC detection output signal and supplies it to the AGC amplification circuit 42. The AGC amplifier circuit 42 amplifies the second AGC detection output signal and supplies it to the sampling circuit 43. The sampling circuit 43 samples the second AGC detection output signal by the control signal from the control circuit 44, holds it in the holding circuit 45, and supplies the second AGC detection output signal at the next timing to the subtraction circuit 46. Further, the holding circuit 45 holds the held second AGC.
The detection output signal is supplied to the subtraction circuit 46. The reset signal sending circuit 47 has the second AGC held by the holding circuit 45.
A reset signal is generated to clear the detection output signal as needed.

The subtraction circuit 46 receives the second AGC detection output signal held by the holding circuit 45 and the second AGC detection output signal at the next timing.
The absolute value of the difference voltage is held in the absolute value holding circuit 48 by subtracting it from the AGC detection output signal. Further, the absolute value voltage holding circuit 48 supplies the absolute value to one input of the comparison and detection circuit 50. Further, the reference voltage circuit 49 supplies the reference voltage to the other input of the comparison detection circuit 50.

The absolute value represents the level fluctuation value of the received signal, and the reference voltage represents the limit level fluctuation value that can be followed by the gain adjustment by the conventional AGC function.

The comparison and detection circuit 50 compares and detects the absolute value and the reference voltage and supplies a determination signal to the changeover switch which is the changeover means 60.

As a result, when the level fluctuation value of the radio signal is smaller than the level fluctuation value corresponding to the reference voltage, AGC-
The tuner unit 1 receives the gain control signal from the RF amplifier circuit 24.
The changeover switch 60 is provided with a discrimination signal to be supplied to No. 2. The tuner unit 12 amplifies or attenuates the received signal according to the gain control signal.

When the level fluctuation value of the radio signal is larger than the level fluctuation value corresponding to the reference voltage, the changeover switch 60 is provided with a determination signal for supplying the gain fixed signal to the tuner section 12. The tuner unit 12 amplifies or attenuates the received signal with a constant gain according to the fixed gain signal.

According to the receiving apparatus of the present invention configured as described above, when the level fluctuation value is smaller than the level fluctuation value corresponding to the reference voltage, the gain adjustment by the conventional method is performed and the level fluctuation value is reduced. If the level fluctuation value is larger than the reference voltage, the gain is not adjusted and fixed to a fixed gain regardless of the fluctuation of the received signal, so that the fluctuation of the radio signal coming during traveling can be sufficiently dealt with. it can.

[0026]

As described above, the receiving apparatus of the present invention includes receiving means for attenuating or amplifying a received signal obtained by receiving an incoming radio wave signal and outputting the received signal, and AGC detection of the received signal having a large time constant. And a gain adjusting means for converting the first AGC detection output signal to a first AGC detection output signal and transmitting a gain control signal for adjusting the gain of the receiving means according to the first AGC detection output signal, and a gain for setting the gain of the receiving means to a constant value. A gain fixing means for transmitting a fixed signal and the received signal are converted into a second AGC detection output signal by AGC detection with a small time constant, and the second AGC detection output signal is compared and detected whether it is within a reference level width. And a switching means for selecting the gain control signal or the fixed gain signal according to the discrimination signal and giving it to the receiving means. It has been made.

Therefore, when the level fluctuation value is smaller than the level fluctuation value corresponding to the reference voltage in response to the fluctuation of the radio wave signal arriving during traveling, the gain adjustment is performed by the conventional method, and the level fluctuation value is the standard value. If it is larger than the level fluctuation value corresponding to the voltage, the gain is not adjusted and fixed to a constant gain regardless of the fluctuation of the received signal, so that the incoming radio signal fluctuates greatly due to reflection from the building, fading, etc. Thus, it is possible to prevent the flutter phenomenon in which the gain adjustment by the AGC function cannot be fully followed and the image becomes dark or light.

[Brief description of drawings]

FIG. 1 is a block diagram showing an outline of a receiving apparatus of the present invention.

FIG. 2 is a block diagram showing a specific embodiment of the receiving apparatus of the present invention.

FIG. 3 is a block diagram showing an outline of a conventional receiving device.

[Explanation of symbols]

 10 receiving means 20 gain adjusting means 30 gain fixing means 40 fluctuation value determining means 60 switching means

Claims (1)

[Claims] 1. A receiving means for attenuating or amplifying a received signal obtained by receiving an incoming radio wave signal and outputting the received signal, the first received signal being subjected to AGC detection with a large time constant.
Gain adjusting means for converting into an AGC detection output signal and transmitting a gain control signal for adjusting the gain of the receiving means according to the first AGC detection output signal; and gain fixing for setting the gain of the receiving means to a constant value. A gain fixing unit for transmitting a signal, and a second unit for detecting the received signal by AGC detection with a small time constant.
A variable value discriminating means for converting into an AGC detection output signal, comparing and detecting whether or not the second AGC detection output signal is within a reference level width, and transmitting a discrimination signal, and the gain control according to the discrimination signal. A receiving device comprising a switching means for selecting a signal or the fixed gain signal and giving it to the receiving means.