JPH09196990A - Testing device for am stereophonic receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a testing device for AM stereophonic receiver, whose circuit scale is small, whose adjustment is not required and which can output a good- accuracy test signal by using an adder, a divider, a computing unit, a phase modulator, a multiplier and the like. SOLUTION: A matrix circuit 1 generates a signal (L+R) and a signal (L-R) on the basis of signal data L and signal data R. An adder 2 adds the signal (L+R) to amplitude data '1' on carrier waves so as to output a signal (1+L+R). An adder 3 adds the signal (L-R) to pilot signal data S so as to output a signal (S+L-R). A divider 5 divides the signal by the signal (1+L+R). A computing unit 6 computes tan<-1> (S+L-R)/(1+L+R), and a phase modulator 7 phase-modulates the carrier waves. A multiplier 8 multiplies the output of the phase modulator 7 by the output of the adder 2, and a D/A converter 9 converts the output of the multiplier 8 into an analog signal so as to be given to a device (DUT) 10 to be tested. Then, whether the device (DUT) 10 is a normal circuit or not is tested.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AM stereo receiver test apparatus for testing an AM stereo receiver, which has a small circuit scale, requires no adjustment, and can output an accurate test signal. The present invention relates to a receiver test device.

[0002]

2. Description of the Related Art Currently, AM stereo broadcasting is based on C-QUA.
The M (Compatible Quadrature Amplitude Modulation) method is the standard. When testing an AM stereo receiver according to this standard, for example, the Institute of Television Engineers, Vol. 43, no. 7 (1989), pp. 68
The test signal was generated through the modulators described in JP-A Nos. 4-691 and JP-B-60-34299. In such a modulation device, the amplitude component of the quadrature modulation wave synthesized from the balanced modulator is removed by a limiter, and the carrier wave containing only this phase modulation component is amplitude-modulated by the (L + R) signal to generate an AM stereo wave. I am synthesizing.

However, since the limiter process is required, the time constant must be adjusted, and the precision of the modulated wave is not good. A
When testing the M stereo receiver, if the test signal from this modulator is input to the device under test (receiver), the accuracy of the test signal is not good, so that the receiver is non-defective It might have been judged as a good product. There is also a problem in that a test signal including a carrier wave may be output, and the 90-degree phase shifter has to deal with this, so that the circuit scale becomes large.

[0004]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to realize an AM stereo receiver test apparatus which has a small circuit scale, requires no adjustment, and can output an accurate test signal. is there.

[0005]

SUMMARY OF THE INVENTION The present invention is a test apparatus for an AM stereo receiver, which modulates a carrier wave with (L + R) signal data and (LR) signal data and supplies the carrier wave to an AM stereo receiver for testing. And the (L + R) signal data and the amplitude data of the carrier are added to obtain (1 + L +
A first adder for outputting (R) signal data;
R) signal data and pilot signal data (S) are added to output a (S + LR) signal data; and (1) is added to the (S + LR) signal data.
+ L + R) Divide by the signal data and the signal data from this divider are input and tan ^-1 ((S + L-R) /
An arithmetic unit for calculating (1 + L + R)), a phase modulator for inputting signal data from this arithmetic unit and phase modulating the carrier wave with this signal data, data from this phase modulator and the (1 + L + R) signal A multiplier for multiplying the data and a D / A converter for converting the digital data from the multiplier into an analog signal and giving the analog signal to the AM stereo receiver;
It is characterized by having.

In the present invention as described above, the first adder is
The (L + R) signal and the amplitude data of the carrier are added, and (1
+ L + R) signal is output. The second adder is (L-
R) signal and pilot signal data (S) are added,
The (S + LR) signal is output. And the divider is
The (S + L-R) signal data is divided by the (1 + L + R) signal data. The arithmetic unit inputs the signal data from the divider, and tan ^-1 ((S + LR) / (1 + L +
R)) is calculated. The phase modulator to which the signal data from this arithmetic unit is input performs the phase modulation of the carrier wave with the input signal data and outputs it. Then, the multiplier multiplies the data from the phase modulator by the (1 + L + R) signal data,
Output to D / A converter. The D / A converter converts the digital data from the multiplier into an analog signal and gives it to the AM stereo receiver.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing one embodiment of the present invention. In the figure, reference numeral 1 denotes a matrix circuit which inputs L signal data and R signal data, and (L + R) signal data and (L-).
R) signal data and output. 2 is the first adder,
The (L + R) signal data and the amplitude data “1” of the carrier wave are added, and the (1 + L + R) signal data is output. A second adder 3 adds (LR) signal data and pilot signal data (S) from the DDS (direct digital synthesizer) 4 and outputs (S + LR) signal data. A divider 5 divides (S + LR) signal data by (1 + L + R) signal data. 6 is an arithmetic unit, which inputs the signal data from the divider 5, and tan ^-1
((S + L-R) / (1 + L + R)) is calculated. Reference numeral 7 is a phase modulator which inputs the signal data from the arithmetic unit 6 and phase-modulates the carrier wave with this signal data. 8 is a multiplier,
The data from the phase modulator 7 is multiplied by the (1 + L + R) signal data. Reference numeral 9 is a D / A converter, which converts the digital data from the multiplier 8 into an analog signal and supplies it to the DUT 10 which is an AM stereo receiver.

The operation of such a device will be described below. The matrix circuit 1 inputs the L signal data and the R signal data generated by DDS or the like (not shown), and outputs (L
The + R) signal and the (LR) signal are output. The first adder 2 adds the (L + R) signal and the amplitude data “1” of the carrier wave and outputs a (1 + L + R) signal. The second adder 3 adds the (LR) signal and the pilot signal data (S signal) from the DDS 4 and outputs the (S + L + R) signal. Then, the divider 5 divides the (S + L + R) signal data by (1 + L + R) signal data.
The arithmetic unit 6 inputs the signal data from the divider 5,
^-1 ((S + LR) / (1 + L + R)) is calculated. Phase modulator 7 to which the signal data from the calculator 6 is input
Modulates the carrier wave with this signal data. here,
The carrier wave is generated by the phase modulator 7, and the frequency of the carrier wave is changed according to an instruction from a control unit (not shown). Then, the multiplier 8 multiplies the data from the phase modulator 7 by the data from the first adder 2, and outputs the result to the D / A converter 9. The D / A converter 9 converts the digital data from the multiplier 8 into an analog signal and supplies it to the DUT 10. And
The signal output from the DUT 10 is used to test whether the DUT 10 is a normal circuit.

As described above, since the limiter circuit is unnecessary,
No adjustment is required, and a highly accurate test signal can be output. This allows for accurate testing of AM stereo receivers. Further, since a 90-degree phase-shifted signal is not required, a 90-degree phase shifter is not required, so that the circuit scale is small and the configuration is simple.
Note that the present invention is not limited to this, and the amplitude data of the carrier wave is set to "1", but it is needless to say that the amplitude value is merely an amplitude value and varies depending on the carrier wave. Further, the AM stereo receiver includes not only the entire concept of the AM stereo receiver but also a simple AM stereo demodulator.

[0010]

According to the present invention, since a limiter circuit is unnecessary, adjustment is unnecessary and a highly accurate test signal can be output. This allows for accurate testing of AM stereo receivers. Further, since a 90-degree phase-shifted signal is not required, a 90-degree phase shifter is not required, so that the circuit scale is small and the configuration is simple.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention.

[Explanation of symbols]

 2, 3 Adder 5 Divider 6 Operator 7 Phase modulator 8 Multiplier 9 D / A converter 10 DUT

Claims (1)

[Claims] 1. A test apparatus for an AM stereo receiver, which modulates a carrier wave with (L + R) signal data and (LR) signal data and supplies the modulated carrier wave to an AM stereo receiver, wherein (L + R) A first adder that adds the signal data and the amplitude data of the carrier wave and outputs (1 + L + R) signal data, and the (LR) signal data and the pilot signal data (S) are added, and (S + L) A second adder that outputs -R) signal data; and (1 + L) for the (S + LR) signal data.
+ R) Divide by the signal data and the signal data from this divider are input, and tan ^-1 ((S +
(L-R) / (1 + L + R)), a phase modulator for inputting signal data from this calculator and phase-modulating the carrier wave with this signal data, and data from this phase modulator A multiplier for multiplying the (1 + L + R) signal data, and digital data from the multiplier into an analog signal,
A D / A converter provided to the AM stereo receiver, and a test apparatus for the AM stereo receiver.