JPH01184665A - Noise reducing circuit - Google Patents

Abstract

PURPOSE:To keep the continuity of a voice signal by inserting the bias-recorded- and-reproduced voice signal in the discontinuous period of a modulated wave originated in a drop out and the rotational head switching of a video tape recorder. CONSTITUTION:A frequency modulated voice signal D is added to an input terminal 1 and demodulated with a demodulator 3 through a detector 2. The demodulated signal is amplified with an amplifier 4 and added to an amplifier 7 through a switch 5. Here, when a modulated wave has a drop out, a noise is generated at a demodulating output E of the demodulator 3. However, when it has the drop out, the detector 2 works, turns off the switch 5, and moreover, turns on the switch 5. Thus, the voice signal from an input terminal 9 is amplified without transmitting the noise to the amplifier 7, and the voice signal to reduce the noise from an output terminal 8 can be always obtained as an output F from the amplifier 7.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention uses an existing helical scanning type magnetic recording/reproducing device (VH8, VTR, etc.) to record audio signals onto a recording medium using its rotating head. The present invention relates to an audio signal recording and reproducing device for reproducing.

(Conventional technology) FIG. 3 shows an example of the configuration of a conventional noise reduction circuit.

Modulated wave A reproduced from a recording medium such as a videotape
is applied to input terminal 11, passes through detector 12, and is demodulated by demodulator 13. The demodulated signal is amplified by an amplifier 14, passed through a switch 15, and applied to a hold capacitor 16 and an amplifier 17. If there is a dropout in the modulated wave, noise will occur in the demodulated output of the demodulator 13. However, if there is a dropout, the detector 12 will work,
Turn off switch 15. In this case, the noise is not transmitted to the amplifier 17, but only the voltage held by the capacitor 16 is amplified, and the output C of the amplifier 17 with reduced noise is obtained from the output terminal 18. The waveforms of each part at this time are shown in FIG.

(Problems to be Solved by the Invention) However, the above configuration has the drawback that although noise can be reduced by the hold circuit, the original continuity of the waveform cannot be obtained. .

It is an object of the present invention to eliminate the conventional drawbacks and reduce the noise in the demodulated output that occurs when there is a dropout of the modulated wave or discontinuity of the modulated wave due to switching of the rotating head of a video tape recorder. An object of the present invention is to provide a noise reduction circuit.

(Means for Solving the Problems) The noise reduction circuit of the present invention includes a first switch that controls passage of a first input signal voltage, and a second switch that controls passage of a second input signal voltage. , an amplifier for amplifying the output of the first or second switch, and a detector for detecting the occurrence of noise in the first input signal; Switch is 0FFL, 2nd
The switch is turned on.

(Function) According to the above configuration, the present invention can perform bias recording in an FM-modulated audio signal during a period when the modulated wave is discontinuous due to dropout or switching of the rotary head of a video tape recorder. By inserting the reproduced audio signal, the continuity of the audio signal can be maintained.

(Example) An example of the present invention will be described based on FIGS. 1 and 2.

FIG. 1 is a block diagram of a noise reduction circuit according to the present invention. In the figure, 1 is an input terminal for an FM-modulated audio signal;
2 is an amplitude fluctuation detector, 3 is an FM demodulator, 4 is an amplifier, 5
．． 6 is a switch, 7 is an amplifier, 8 is an output terminal, and 9
is an input terminal to which a signal from an audio signal recording and reproducing device using a bias recording method (however, blocks related to the bias recording method are not shown) is input manually.

Next, the operation will be explained.

The 1'M modulated audio signal is applied to an input terminal 1, passes through a detector 2, and is demodulated by a demodulator 3. The demodulated signal is amplified by an amplifier 4 and is applied to an amplifier 7 through a switch 5 (normally ON). If there is a dropout in the modulated wave, noise will occur in the demodulated output E of the demodulator 3. However, if there is a dropout, detector 2 is activated, turns off switch 5, and then turns off switch 6 (usually 0).
1'FL, ON). Then the noise is from amplifier 7
Instead, the audio signal from the input terminal 9 is amplified, and the original audio signal with reduced noise is always obtained from the output terminal 8 as the output F from the amplifier 7. The waveforms of each part at this time are shown in FIG.

(Effects of the Invention) According to the present invention, when reproducing an audio signal using FM modulation, the bias recording method can be used to correct the occurrence of dropouts or discontinuities in the audio signal due to switching of the rotating head. FM in a helical scanning magnetic recording/reproducing device by appropriating the
By applying the original signal to the modulation method, the noise that inevitably occurs when recording and reproducing audio signals can be reduced, and its practical effects are extremely large.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a noise reduction circuit according to an embodiment of the present invention, Fig. 2 is an operation waveform diagram of each part of the same, Fig. 3 is a block diagram of a conventional noise reduction circuit, and Fig. 4 is an operation of each part of the same. FIG. 1... FM modulated audio signal input terminal, 2...
...Amplitude fluctuation detector, 3...FM demodulator, 4.7.
...Amplifier, 5, 6...Switch, 8...Output terminal, 9...Input terminal into which the signal from the audio signal recording and reproducing device is input. Patent applicant: Matsushita Electric Industrial Co., Ltd. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] a first switch that controls passage of a first input signal voltage, a second switch that controls passage of a second input signal voltage, and an amplifier that amplifies the output of the first or second switch; a detector that detects the occurrence of noise in the first input signal, and during the period when the detector is working, the first switch is turned OFF and the second switch is turned ON. A noise reduction circuit characterized in that it is configured as follows.