JPH09102933A - Playback signal processing device - Google Patents

Abstract

(57) Abstract: When reproducing from a recording medium in which a plurality of RF modulation signals are superposed and recorded, the amplitude of the reproduction RF modulation signal can be optimized, and stable demodulation reproduction can be realized. it can. SOLUTION: A reproduction RF modulation signal is read from a recording tape by rotary heads 1a and 1b and supplied to a bandpass filter 3 and a variable gain amplifier 5 which are AFM systems via a preamplifier 2. The bandpass filter 3 extracts the component of the AFM signal, and the detection circuit 4 controls the gain of the variable gain amplifier 5. The reproduction RF modulated signal from which the gain is optimized from the variable gain amplifier 5 is supplied to the demodulation system including the bandpass filters 6 and 7, the FM demodulator and the noise reduction circuits 8 and 9. Then, via the matrix decoding circuit 10,
The output terminal 11 takes out the left channel output, and the output terminal 12 takes out the right channel output.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
(Video tape recorder), LD (Laser disc)
The present invention relates to a reproduction signal processing device used in a reproduction device for reproducing a recording medium such as.

[0002]

2. Description of the Related Art A conventional reproducing apparatus, for example, a rotary head type V
In TR, a signal reproduced from a recording medium is frequency-multiplexed with an FM-modulated luminance signal, a color signal converted into a low-frequency carrier frequency, an FM-modulated audio signal, a servo signal for ATF (track following), and the like. Signal (referred to as a superposed wave). In the superimposed wave demodulation system, the reproduction gain is fixed or the reproduction gain control is performed by the amplitude detection output of the entire superimposed wave. Then, in the reproduction gain control by the amplitude detection output of the entire superimposed wave, the reproduction RF modulation signal (FM modulation luminance signal in the VTR), which is the main component, can be optimized.

[0003]

However, the above-described fixed gain may not be able to follow the unstable amplitude of the reproduced RF modulation signal in some cases. Further, in the reproduction gain control by the amplitude detection output of the entire superimposed wave, the modulation signal of the recording level close to the main component or the modulation signal of the frequency component different from the main component (8 mmV
In TR and βVTR, the audio signal, the servo signal, etc.) could not be set as the optimum amplitude of the reproduction RF modulation signal. Therefore, reproduction was still performed while being unstable.

Therefore, an object of the present invention is to optimize the amplitude of a reproduced RF modulation signal when reproducing from a recording medium in which a plurality of RF modulation signals are superposed and recorded.
It is an object of the present invention to provide a reproduction signal processing device capable of realizing stable demodulation reproduction.

[0005]

SUMMARY OF THE INVENTION The present invention provides a plurality of RFs.
In the reproduction signal processing device to which the reproduction RF modulation signal is supplied from the recording medium in which the modulation signal is superimposed and recorded, the reproduction R
Filter means for extracting some modulation signals from the F modulation signal, detection means for detecting the amplitude of the modulation signal extracted by the filter means, and RF for controlling the gain corresponding to the output of the detection means. It is a reproduced signal processing device characterized by having an amplifier means.

A reproduction RF modulation signal is read from the recording tape, and the reproduction RF modulation signal is supplied to the filter means band pass filter and also to the RF amplifier means, for example, a voltage control amplifier. The filter means extracts a component of a predetermined modulation signal, and the detecting means converts it into a DC voltage. The converted voltage controls the gain of the RF amplifier means.
Then, the reproduced RF modulated signal whose gain is controlled from the RF amplifier means is supplied to the demodulation system.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below. FIG. 1 shows a reproduced signal processing apparatus according to an embodiment of the present invention. One example of this is an 8 mm VTR AFM.
This is the case when applied to voice, and the playback RF of this AFM voice
It is intended to optimize demodulation of a modulated signal.

Here, the 8 mm VTR AFM sound is
L (left channel), R (right channel) L + R, L
The matrix processing is performed on -R, the carrier signals of 1.5 MHz and 1.7 MHz are FM-modulated by L + R and L-R, respectively, and the obtained 1.5 MHz is obtained.
FM of ± 100 KHz and 1.7 MHz ± 50 KHz
The modulated signal is superposed and recorded on the recording medium. The recording level is
As an example, the recording level of the modulated luminance signal is −27 dB and the recording level of the modulated color signal is −13 dB. Since the recording level is set in this way, the reproduced RF modulation signal is mainly composed of the modulated luminance signal. The center frequency of this modulated luminance signal is 3 to 6 MHz, and the frequency characteristics of recording and reproduction are completely different from those of the modulated signal on the low frequency side.

In FIG. 1, 1a and 1b are 8 mm
It is a pair of rotary heads arranged on the rotary drum of the VTR. A reproduction RF modulation signal is read from the recording tape by the rotary heads 1a and 1b. The reproduction RF modulation signal is amplified by the preamplifier 2, and the gain here is adapted to the video system (luminance signal, color signal). The reproduction RF modulation signal amplified by the preamplifier 2 is supplied to the video circuit system and the servo circuit system, and
The signal is supplied to the bandpass filter 3 and the variable gain amplifier 5 which have an FM system with a center frequency of 1.5 MHz.

Then, by the bandpass filter 3,
A component of the AFM signal is extracted from the reproduction RF modulation signal on which the four modulation signals of the luminance signal, the color signal, the servo signal, and the AFM signal are superimposed. Here, the 1.7 MHz component is also A
Although it is an FM signal, in the monaural mode, only the L + R component of 1.5 MHz is present, so this 1.5 MHz component is extracted.

AF extracted by the bandpass filter 3
The component of the M signal is converted by the detection circuit 4 into a DC voltage for controlling the variable gain amplifier 5. The gain of the variable gain amplifier 5 is changed by this converted voltage, and when the component of the AFM signal included in the output of the preamplifier 2 is small, the gain of the variable gain amplifier 5 is increased,
When the component of the AFM signal is large, control is performed to reduce the gain of the variable gain amplifier 5. By this operation, the amplitude of the AFM signal can be optimized.

The reproduced RF modulated signal with the optimized gain from the variable gain amplifier 5 is supplied to the FM demodulator and the noise reduction circuit 8 via the bandpass filter 6 having a center frequency of 1.5 MHz which is a demodulation system. It is also supplied to the FM demodulator and noise reduction circuit 9 via the band pass filter 7 having a center frequency of 1.7 MHz. The L + R signal from the FM demodulator and noise reduction circuit 8 is transferred to the matrix decoding circuit 10
Supplied to Further, the matrix decoding circuit 10 is supplied with the LR signal from the FM demodulator and the noise reduction circuit 9. By passing through the matrix decoding circuit 10, the left channel output is taken out to the output terminal 11 and the right channel output is taken out to the output terminal 12. In this way, the amplitude of the AFM signal in the reproduced RF modulated signal can be kept constant and a stable demodulated audio output can be obtained.

The circuit portion of the variable gain amplifier 5 is
If there is an amplitude margin (margin for slight amplitude fluctuation) in the input of the AFM signal to the band pass filter 6 to the FM demodulator and the noise reduction circuit 9 that is the demodulation system, as in a specific example shown in FIG. An RF amplifier having a gain changeover switch may be configured.

FIG. 2 shows a more specific circuit configuration of the bandpass filter 3, the detection circuit 4, and the variable gain amplifier 5 in one embodiment of the present invention. In FIG. 2, 30 is
It is a power supply terminal. The bandpass filter 3 corresponds to the transistors 24, 25 and 26 and resistors and capacitors connected to these transistors.
The detection circuit 4 corresponds to the transistor 27,
28 and a comparator 29 connected to these transistors, a resistor and a capacitor, and the like.

Further, here, as the variable gain amplifier 5, not the VCA but an RF amplifier having a gain changeover switch is used. That is, the transistor 2
1, 22, 23 and resistors and capacitors connected to these transistors.

The amplified reproduced RF modulation signal from the preamplifier 2 shown in FIG. 1 is input to the input terminal 20. A bandpass filter 3 including transistors 24, 25, and 26 is provided from the reproduced RF modulation signal input to the input terminal 20.
Thus, the component of the AFM signal is extracted. When the component of the extracted AFM signal is large, the output of the detection circuit 4 including the transistors 21 and 23, which are RF amplifiers, becomes large, and the output of the comparator 29 becomes low level. As a result, the transistor 22 is turned off,
The gain of the RF amplifier including the transistors 21 and 23 is reduced.

When the component of the extracted AFM signal is small, the transistor 22 is turned on and the gain of the RF amplifier including the transistors 21 and 23 is increased. In this way, the gain of the RF amplifier is switched according to the level of the 1.5 MHz AFM signal,
The amplitude of the AFM signal is made substantially constant.

From the output terminal 31, a reproduced RF modulation signal whose gain is controlled is taken out. Then, the reproduced RF modulated signal is supplied to the band pass filters 6 and 7 of the demodulation system shown in FIG.

If the amplitude control according to the present invention is not performed, the amplitude of the AFM signal in the reproduction RF modulation signal is small, so that the circuit of the demodulation system performs a mute (output stop) operation or a monaural / stereo signal. There is a problem that the operation is wrong. However, according to the present invention, such a problem can be avoided and a stable demodulated audio output can be obtained.

In the embodiment of the present invention, 8 mmV
Although the TR AFM signal is shown, similar servo signal systems to which the present invention can be applied include an 8 mm VTR servo signal system, a βVTR AFM signal, and a laser disk F.
It can also be used for M-modulated audio signals.

[0021]

According to the present invention, the amplitude of a modulation signal having a low recording level and a frequency component different from that of the main modulation wave can be optimized, and this modulation signal can be stably demodulated and reproduced.

[Brief description of the drawings]

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

FIG. 2 is a connection diagram showing an example of a specific configuration of a main part in one embodiment of the present invention.

[Explanation of symbols]

 1a, 1b Rotating head 3 Bandpass filter 4 Detection circuit 5 Variable gain amplifier

Claims (1)

[Claims] 1. A reproduction signal processing apparatus, to which reproduction RF modulation signals from a recording medium in which a plurality of RF modulation signals are superimposed and recorded are supplied, for extracting some modulation signals from the reproduction RF modulation signals. And a detection means for detecting the amplitude of the modulated signal extracted by the filter means, and an RF amplifier means for controlling the gain corresponding to the output of the detection means. Processing equipment.