JP2001352266A - Received electric field intensity detector circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a received electric field intensity detector circuit capable of accurately detecting the received electric field intensity. SOLUTION: The received electric field intensity detector circuit in a tuner with an AGC circuit comprises a received electric field intensity table memory circuit 121 having a previously stored table of received electric field intensity information based on an S-meter voltage for detecting the electric field intensity detected in an intermediate frequency amplifier circuit 5 and an AGC voltage outputted from an AGC detector circuit 7. It retrieves the received electric field intensity information in the table memory circuit 121 with reference to the detected S-meter voltage and the AGC voltage to thereby take the retrieved received electric field intensity information as a received electric field intensity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a reception electric field strength detection circuit in a tuner, and more particularly, to a reception electric field strength detection circuit in a tuner provided with an AGC (automatic gain control) circuit.

[0002]

2. Description of the Related Art A conventional tuner provided with an AGC circuit, for example, an FM tuner, detects a received electric field strength by detecting an output from an antenna as shown in FIG. The signal is supplied to the mixer 4 for amplification, supplied to the mixer 4 and mixed in frequency with the local oscillation output to be converted into an intermediate frequency signal. The intermediate frequency signal is supplied to the intermediate frequency amplifier circuit 5 for amplification. An output of the intermediate frequency amplifier circuit 5 is used as an S meter circuit 6 for detecting a received electric field strength.
And the received electric field intensity is detected by the S-meter voltage output from the S-meter circuit 6.

On the other hand, an input signal of the mixer 4 and an output signal from the intermediate frequency amplification circuit 5 are supplied to an AGC detection circuit 7 for detection, and an AGC detection output is supplied to control circuits 8 and 9 so that the control circuit 8 AGC for controlling the high frequency tuning and the gain of the amplifier circuit based on the output is performed to prevent the desired signal and the interference signal from becoming excessive, and the attenuation of the antenna attenuation circuit 1 is controlled based on the output of the control circuit 9. AGC for control is performed to prevent excessive input to the FM tuner.

Using the S-meter voltage output from the S-meter circuit 6 as described above, various controls such as mute control, tuning control, stereo blend amount control, and high frequency cut are performed.

[0005]

However, in the conventional reception electric field strength detection circuit as described above, AGC control is performed by the control circuits 8 and 9 so that the signal level input to the mixer 4 becomes constant. For this reason, when the control electric field strength is equal to or higher than the operation of the control circuits 8 and 9, the S-meter voltage becomes constant, and after the S-meter voltage is saturated, the normal reception electric field strength cannot be grasped. was there.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a reception electric field strength detection circuit capable of accurately detecting a reception electric field strength.

[0007]

A receiving electric field strength detecting circuit according to the present invention is a receiving electric field strength detecting circuit in a tuner provided with an AGC circuit, and is used for detecting an electric field strength detected from an intermediate frequency stage. A receiving electric field intensity information storage means for preliminarily storing receiving electric field intensity information based on the meter voltage and the AGC voltage;
The received electric field strength information is retrieved from the received electric field strength information storage means with reference to the voltage, and the retrieved received electric field strength information is used as the received electric field strength.

According to the reception electric field intensity detection circuit of the present invention, the reception electric field intensity is detected based on the AGC voltage and the S-meter voltage, so that the reception can be accurately performed even after the S-meter voltage is saturated. The electric field strength can be detected. As a result, based on the detected received electric field strength, AG
A feedback can be given to C, and AGC can be performed without interference. Furthermore, the conventional S
More detailed control can be performed on the portion controlled by the meter voltage.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A reception field strength detection circuit according to the present invention will be described below with reference to an embodiment.

FIG. 1 is a block diagram showing a configuration of a reception electric field strength detection circuit 20 according to an embodiment of the present invention.

In the reception electric field strength detection circuit 20 according to the embodiment of the present invention, the same components as those in FIG. 3 are denoted by the same reference numerals, and the description thereof will be omitted to avoid duplication. Omitted.

A reception electric field strength detection circuit 20 converts an AGC voltage output from the AGC detection circuit 7 into an A / D converter 10.
A / D conversion is performed, and the S-meter voltage output from the S-meter circuit 6 is supplied to the A / D converter 11 to perform A / D conversion.
Converts the output of the A / D converter 10 and the A / D converter 1
1 is supplied to the electric field intensity analysis circuit 12 to analyze the received electric field intensity, and the electric field intensity analyzed by the electric field intensity analysis circuit 12 and the S meter voltage are supplied to the control circuit 14 to generate signals for various controls. .

The electric field intensity analysis circuit 12 includes a reception electric field intensity table storage circuit 121 in which a table of reception electric field intensity information for the AGC voltage output from the AGC detection circuit 7 and the S meter voltage output from the S meter circuit 6 is stored. And the AG output from the AGC detection circuit 7
With reference to the C voltage and the S-meter voltage output from the S-meter circuit 6, the received electric field strength information is searched from the received electric field strength table, and the searched received electric field strength information is read, and the electric field strength analysis is performed. Output from the circuit 12.

Here, the reception electric field strength table storage circuit 1
21 is an AGC table.
It has a reception field strength table corresponding to each of the voltage and the S-meter voltage, and uses each table based on the relationship between the AGC voltage and the S-meter voltage. For example,
AGC voltage 6.0V, 5.5V, 5.0 in 0.5V increments
V,..., 1.0 V, the electric field strength in steps of 10 dBμ is 100 dBμ, 90 dBμ, 80 dBμ,.
0 dBμ, and stored so that the received electric field strength based on the S-meter voltage is obtained when the AGC voltage is 1.0 V or less.

The control circuit 14 receives the signal based on the received electric field strength information output from the electric field strength analysis circuit 12 and the S meter voltage output from the S meter circuit 6, and receives a signal based on the received electric field strength information and an S signal. An output based on the meter voltage is sent. The control circuits 8 and 9 are controlled by the output sent from the control circuit 14 to change the sensitivity of AGC, forcibly stop AGC, control the amount of stereo blending, control the high frequency cut, and control the noise canceller.

By performing such control, feedback can be applied to the AGC, and the AGC can be performed so that sensitivity suppression and intermodulation do not occur. Further, it is possible to perform more detailed control on a portion which is conventionally controlled by the S-meter voltage output from the S-meter circuit 6.

Specifically, the AGC voltage (RF band) and S
By monitoring the meter voltage (IF band),
The state in which self-sensitivity is suppressed by a station other than the receiving station can be canceled by turning off the AGC. Further, it is possible to grasp that the S-meter voltage is saturated, and it is possible to maintain the stereo state for a long time by reducing the control sensitivity of the stereo blend amount. Further, since the received electric field strength can be accurately detected, the entire receiving band can be checked by searching for the receiving station, and thus, it can be used substantially as a simple spectrum analyzer.

In the above-described reception electric field strength detection circuit 20, when the electric field intensity analysis circuit 12 is provided with a table of reception electric field intensity information, the table of the reception electric field intensity information is searched to obtain a signal based on the electric field intensity. However, in the reception electric field intensity detection circuit 20, the A / D converters 10 and 11, the electric field intensity analysis circuit 12, the control circuit 14
Alternatively, a configuration as shown in FIG. 2 may be used.

In the configuration shown in FIG. 2, an AGC voltage output from the AGC detection circuit 7 is input, an inverting amplifier 70 for inverting the output phase, an output of the inverting amplifier 70 as an input, and different threshold voltages VthA , V
, VthC are input separately, and the threshold voltages Vt which are different from each other are input with the output voltages from the S meter circuit 6 and the comparators 71, 72,.
, 63 to which h1, Vth2,..., Vth3 are separately input, and outputs the outputs of the comparators 71, 72,. Circuit 1
5, the received electric field strength is determined based on the input, and the control circuits 8 and 9 are controlled by the output of the interface circuit 15 to change the sensitivity of AGC, forcibly stop AGC, control the amount of stereo blending, High frequency cut control,
Controls the noise canceller.

Here, the threshold voltages VthA, Vt
.., VthC are 100 dBμ, 90 dBμ,..., 6 based on the values of the received field strength table of the AGC voltage.
0 dBμ, and the threshold voltage Vth1,
Vth2,..., Vth3 are set based on the values of the received electric field strength table of the S meter voltage.

In the configuration shown in FIG. 2, the comparators 71 and 7 whose outputs become high potential based on the AGC voltage.
, 73 are determined, and the comparators 61, 62,..., 63 whose outputs have a high potential based on the S meter voltage are determined, and the comparators 71, 72,.
3 and comparators 61, 62,...
3, the received electric field strength is substantially detected by the interface circuit 15, and the sensitivity of the AGC is changed based on the output from the interface circuit 15.
Forcibly stopping, controlling the amount of stereo blending, high-frequency cut control, and controlling the noise canceller.

As is clear from the above, the comparators 71, 72,...
, 63 are functionally the same as the A / D conversion means, and the comparators 71, 72, ..., 73, 61, 6
, 63, and the interface circuit 15 can be said to be substantially the same in function as the electric field intensity analysis circuit 12 provided with the reception electric field intensity information table 121 and the control circuit 14.

[0023]

As described above, according to the reception electric field strength detection circuit according to the present invention, the reception electric field strength is detected based on the AGC voltage and the S meter voltage.
The effect is obtained that the received electric field strength can be accurately detected even after the S-meter voltage is saturated.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a reception electric field strength detection circuit according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of a modification example of the reception electric field strength detection circuit according to one embodiment of the present invention;

FIG. 3 is a block diagram showing a configuration of a conventional reception electric field strength detection circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Antenna attenuation circuit 2 Antenna tuning circuit 3 High frequency tuning and amplifying circuit 4 Mixer 5 Intermediate frequency amplifying circuit 6 S meter circuit 7 AGC detection circuit 8 and 9 Control circuit 10 and 11 A / D converter 12 Electric field strength analysis circuit 20 Received electric field Intensity detection circuit 121 Received electric field intensity table storage circuit

Claims (2)

[Claims] 1. A receiving electric field intensity detecting circuit in a tuner provided with an AGC circuit, wherein received electric field intensity information based on an S-meter voltage and an AGC voltage for detecting electric field intensity detected from an intermediate frequency stage is stored in advance. Receiving electric field intensity information storage means, and searching for received electric field intensity information from the received electric field intensity information storing means with reference to the detected S-meter voltage and AGC voltage, and retrieving the retrieved received electric field intensity information. A reception electric field strength detection circuit characterized by the following. 2. The reception electric field strength detection circuit according to claim 1, wherein the S meter voltage and the AGC voltage are digital data obtained by A / D conversion.