JPS62172828A - Stereo receiver having pseudo stereo function - Google Patents

Abstract

PURPOSE:To eliminate a sense of incongruity of a reproducing sound in case a noise is being generated, by executing a noise elimination processing of a sum signal, executing a reverberation addition processing to the sum signal which has been brought to the noise elimination processing and generating a pseudo difference signal. CONSTITUTION:In case of a normal state, a coefficient K of each multiplier 7-10 is set to '1' and the multiplier 7 and 8 are made to conduct, the multiplier 9 and 10 are cut off, and an L+R signal (sum signal) and an L-R signal (difference signal) of a converter IC 3 are led directly to a multiplexer 4. On the other hand, when a noise has been generated, the coefficient is set to '0' extending over the whole period in which the noise has been generated and the multiplier 7 and 8 are cut off, and the multiplier 9 and 10 are made to conduct, by which an L+R signal from a noise eliminating circuit 5 and a pseudo L-R signal from a reverberation adding circuit (a system of a shredder) 6 are led to the multiplexer 4, respectively. In this way, light and left output signals L, R which are separated by the multiplexer 4 become those which have a pseudo stereo reproducing sense.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a stereo receiver having a pseudo-stereo function during noise removal. The stereo receiver according to the present invention includes:
For example, it is used in a car-mounted FM stereo radio receiver, etc., and makes it possible to remove noise superimposed on reproduced sound while maintaining a natural stereo reproduction window.

[Conventional technology]

Stereo receiving devices, such as FM stereo radio receivers, generally include a noise removal circuit that removes noise such as multipath distortion noise superimposed on a reproduced audio signal. It is preferable that the noise removal process be performed separately for the left and right channels L and R, respectively. However, in this case, two noise removal circuits are required, one for the right channel and the other for the left channel, which is disadvantageous as it increases the cost. Therefore, during periods when noise is occurring, the receiver is generally switched from stereo playback mode to monaural playback mode and
Noise removal processing is performed only on the monaural signal that is the sum signal of +R.

[Problem that the invention seeks to solve]

However, in the above method, since stereo playback is switched to monaural playback during noise removal processing, the sense of spaciousness of the reproduced sound is lost. For this reason, when noise sweating occurs intermittently and frequently, the reproduced sound frequently switches between stereo sound and monaural sound, giving an audible sense of discomfort such as the sound "shaking".

[Means for solving problems]

In order to solve the above-mentioned problems, a stereo receiver having a pseudo-stereo function according to the present invention includes a sum-difference signal demodulation section that demodulates a sum signal and a difference signal of a right channel signal and a left channel signal from a received signal; a left and right channel separation unit which receives the sum signal and difference signal from the sum and difference signal demodulation unit and separates them into a right channel signal and a left channel signal;
A noise removal unit receives the sum signal of the sum-difference signal demodulation unit and performs noise removal processing on the sum signal, and a reverberation unit performs reverberation addition processing on the sum signal subjected to noise removal processing in the noise removal unit to generate a pseudo-difference signal. The addition section converts the input signal supplied to the left and right channel separation section during the noise generation period when noise occurs from the sum signal and difference signal of the sum-difference signal demodulation section to the sum signal output from the noise removal section and reverberation. A switching section is provided for switching between the pseudo difference signal outputted from the addition section and the pseudo difference signal outputted from the addition section.

The above-mentioned reverberation adding section can be constructed from a delay circuit based on Schroeder's system.

[For production]

When no noise is generated in the reproduced sound, the switching unit is switched to supply the sum signal and difference signal from the sum-difference signal demodulation unit to the left and right channel separation unit. On the other hand, when noise occurs, the output signal of the noise removal section subjected to noise removal processing is switched to be supplied as a sum signal, and the output signal of the reverberation addition section is supplied as a pseudo difference signal to the left and right channel separation sections, respectively. As a result, the stereo receiving device can create a pseudo stereo reproduction illusion even during the noise generation period, and can eliminate the unnatural feeling of the reproduced sound during the noise generation period.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing a stereo receiver having a pseudo-stereo function as an embodiment of the present invention.

In FIG. 1, l is an antenna, 2 is a tuner, and 3 is a converter I as a sum-difference signal demodulation circuit that extracts an L+R signal (sum signal) and an L-R signal (difference signal) from the detected signal.
C14 is a multiplexer as a left and right channel separation circuit that takes out both left and right channel output signals and R from the L+R signal and LR signal, 5 is a noise removal circuit, 6 is a reverberation addition circuit, and 7 to 10 are coefficient multipliers. , 11 and 12 are adders.

As the reverberation adding circuit 6, a delay circuit based on a so-called Schroeder system as shown in FIG. 2 is used, for example. This reverberation adding circuit 6 includes coefficient multipliers 61 to 64 and an adder 65.
and a delay element 67 that provides a delay of 66.72 samples (approximately 2m5), and in the figure, each multiplier 6
1 to 64 are assigned respective multiplication coefficients. In this reverberation adding circuit 6, the input signal is sent to a multiplier 6.
4, an adder 65, and a loop of a delay element 67 to circulate the signal while attenuating it, thereby generating reverberant sound. Therefore, when the L+R signal is passed through the reverberation adding circuit 6, a reverberation component is created, which can be used as a pseudo L-R signal.

To explain the operation of the receiver shown in FIG. 1, under normal conditions, the coefficient K of each multiplier 7 to 10 is set to 1, the multipliers rt7 and 8 are made conductive, the multipliers 9 and 10 are cut off, and the L of the converter IC3 is
+R signal and LR signal are led directly to multiplexer 4. On the other hand, when noise occurs, as shown in FIG. The L+R signal from the removal circuit 5 and the pseudo L-R signal from the reverberation adding circuit 6 are respectively guided to the multiplexer 4. As a result, the left and right output signals separated by the multiplexer 4, R, have a pseudo-stereo reproduction feeling.

Note that the noise removal circuit 5 can be constructed by a circuit as shown in FIG. In the figure, 51 is a variable phase shifter that can variably control the phase, 52 is a variable low-pass filter that can variably control the blocking wave number, 53 is a switching circuit, and 54 is a variable phase shifter 51 and variable low-pass filter 52. Constant control circuit that adjusts the blocking wave number according to the input signal, 55
is a noise detection circuit.

The constant control circuit 54 includes detectors 541 and 542, and a detector 54.
a deviation circuit 543 that gives a deviation δ to the detection output of 1; a difference circuit 544 that takes the difference between the detector 542 and the deviation circuit 543;
, and a hold circuit 545 that holds the output of the differential circuit 544. The noise detection circuit 55 includes a high-pass filter 551, a detector 552 that detects the output signal of the n-pass filter 551, and a comparator 553 that compares the output signal of the detector 552 with a reference voltage V (rl). 5(1) is detected, and the comparator 553 outputs a noise detection signal S (d) only in that noise section.

To explain the operation of this noise removal circuit 5, a noise detection circuit 55 detects sections in which noise is superimposed on the input signal S (11) and sections in which noise is not superimposed, and in sections where noise is superimposed, a switching circuit 53 selects an input signal S (11). The input signal S (11 is passed through the variable low-pass filter 52)
(1) Remove noise consisting of high frequency components. On the other hand, in the section where noise is not superimposed, the input signal 5(1) is taken out via the variable phase shifter 51. This variable phase shifter 5
1 is for compensating for the time delay caused by the variable low-pass filter 52. As described above, noise components are removed from the output signal. The cutoff wave number of the variable low-pass filter 52,
The phase angle of the variable phase shifter 51 is constantly adjusted by the constant control circuit 54 to an appropriate value according to the input signal, thereby improving the frequency characteristics of the signal after noise removal.

〔Effect of the invention〕

According to the present invention, one noise removal circuit can eliminate noise.

By simply removing noise from the noral signal, it is possible to remove noise from the playback sound while maintaining a pseudo-stereo playback illusion during the noise removal period. While eliminating the discomfort of
The cost of the noise removal circuit can be reduced.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a stereo receiver having a pseudo-stereo function as an embodiment of the present invention, and FIG.
A block diagram showing details of the reverberation adding circuit in the device shown in FIG.
FIG. 3 is a diagram for explaining the operation of the apparatus shown in FIG. 1, and FIG. 4 is a block diagram showing details of the noise removal circuit in the apparatus shown in FIG.

Claims (1)

[Claims] 1. A sum-difference signal demodulation unit that demodulates a sum signal and a difference signal of a right channel signal and a left channel signal from a received signal; the sum signal and difference signal from the sum-difference signal demodulation unit are input. a left and right channel separation unit that separates a right channel signal and a left channel signal from the left and right channel signals; a noise removal unit that receives the sum signal of the sum-difference signal demodulation unit and performs noise removal processing on the sum signal; a reverberation addition unit that performs reverberation addition processing on the sum signal subjected to noise removal processing to generate a pseudo difference signal, and an input signal supplied to the left and right channel separation unit during the noise generation period when noise occurs, A pseudo-stereo function, comprising a switching section that switches from the sum signal and difference signal of the sum-difference signal demodulation section to the sum signal output from the noise removal section and the pseudo-difference signal output from the reverberation addition section. Stereo receiver with. 2. The stereo receiver having a pseudo-stereo function according to claim 1, wherein the reverberation adding section is constituted by a delay circuit based on a Schroeder system.