JP2655759B2 - Magnetic playback device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to a video tape recorder (hereinafter referred to as "VTR") and the like, and reproduces a frequency multiplexed signal from a recording medium such as a magnetic tape. It is about.

[0002]

2. Description of the Related Art FIG.
FIG. 1 is a block diagram showing a configuration of a signal processing circuit of a conventional home VTR disclosed on page 151 of Corona Co., Ltd., where 1 is a magnetic tape as an example of a recording medium, Is a magnetic head for picking up magnetic flux from the magnetic tape 1. 3 is a head amplifier, 4 is a high-pass filter for removing a color signal, 5 is an equalizer, 6
Cuts the amplitude fluctuation component of the FM luminance signal by the limiter. An FM demodulator 7 demodulates an FM luminance signal. Reference numeral 8 denotes a luminance signal processing circuit that processes and outputs a luminance signal after demodulation.

[0003] Reference numeral 9 denotes a low-pass filter for converting a luminance signal into an FM signal.
Remove the luminance signal. A color signal processing circuit 10 processes, restores, and outputs color signals. An adder 11 adds the luminance signal and the chrominance signal and outputs a video signal to a terminal 12.

Next, the operation of the above configuration will be described. The magnetic flux picked up from the magnetic tape 1 by the magnetic head 2 is converted into an electric signal and sent to the head amplifier 3. As the signal at this time, the spectrum as shown in FIG. 4A should be obtained by adding the FM luminance signal and the low-frequency conversion color signal. In FIG. 4, reference numeral 13 denotes a subcarrier of a low-frequency color signal, and 14 denotes a carrier of an FM luminance signal.

Incidentally, due to nonlinear odd-order distortion of the magnetic recording / reproducing system, distortion components 15 and 16 as shown in FIG.
Appears. The distortion components 15 and 16 are not lost even after passing through the high-pass filter 4, the equalizer 5, and the limiter 6,
The signal remains after demodulation by the FM demodulator 7 and remains even when the luminance signal processing circuit 8 becomes a final video signal, and appears as a beat on the screen. On the other hand, the FM signal is removed from the chrominance signal by the low-pass filter 9 and then restored by the chrominance signal processing circuit 10. .

[0006]

Since the conventional magnetic reproducing apparatus is configured as described above, the above-mentioned distortion components 15 and 16 are generated in the reproduced video signal, and the quality of the reproduced image is degraded. There was a problem.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has as its object to provide a magnetic reproducing apparatus capable of reducing distortion components and obtaining a high-quality reproduced image.

[0008]

SUMMARY OF THE INVENTION A magnetic reproducing apparatus according to the present invention multiplexes at least two kinds of signal frequencies to produce a magnetic signal.
Playback of the signal from the recorded medium
A magnetic reproducing apparatus, wherein the at least two types of signals are
A frequency that converts the frequency of one of the signals to twice the frequency
Number conversion means, and the frequency-converted signal is referred to as a modulation signal.
Amplitude to modulate the remaining signal by inputting
Modulating means .

[0009]

According to the present invention, the distortion component generated at the time of magnetic recording is converted by converting the frequency of one signal to a double frequency and modulating the amplitude of another signal by the frequency-converted signal. Can be reduced during playback.

[0010]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a home V according to an embodiment of the present invention.
FIG. 4 is a block diagram showing a configuration of a signal processing circuit of the TR. In the same figure, reference numerals 1 to 12 denote the same parts as in the conventional example shown in FIG. I do.

In FIG. 1, reference numeral 101 denotes a frequency converter.
The frequency of the color signal is converted to a double frequency. Reference numeral 102 denotes an attenuator that attenuates the amplitude of the color signal converted into a double frequency into an appropriate amplitude. Reference numeral 103 denotes a phase shifter.
The phase of the modulated signal, which is the output of 2, is made opposite to the phase of the amplitude modulation of the modulated signal output from the equalizer 5. 104
Is an amplitude modulator which modulates the amplitude of the modulated signal by the frequency-converted modulated signal.

Next, the operation of the above configuration will be described. First, the principle of generating the above-described distortion components 15 and 16 will be described with reference to FIG. The signal obtained by adding the low-frequency converted chrominance signal having the waveform shown in FIG. 5A and the FM luminance signal carrier corresponds to the amplitude limitation shown in B of FIG. Receive. Basically,
This signal is reproduced. When the low-frequency color signal shown in FIG. 5C is removed, an FM luminance signal carrier as shown in FIG. 5D is obtained. As is apparent from the waveforms shown in the figure, it is understood that amplitude modulation is performed at twice the frequency of the low-frequency color signal. Actually, the recording levels of the low-frequency chrominance signal and the FM luminance signal carrier are different, the strength of the magnetic field generated from the magnetic head 2 is different, and as shown in FIG. Out of phase. As described above, although the signal itself obtained from the magnetic head 2 is completely amplitude-modulated, a phase modulation component is also generated due to the characteristics of the circuits such as the head amplifier 3 and the high-pass filter 4, which removes the amplitude fluctuation component. Remains even after passing through the limiter 6 for this purpose.

According to the embodiment based on the above considerations, the FM luminance signal carrier is input to the equalizer 5 , the above-mentioned phase modulation component is reduced, most of the distortion energy is converted into an amplitude modulation component, and then the modulated This FM shine as a signal
The signal carrier is input to the amplitude modulator 104 and the
By modulating with the low-pass color signal , the FM luminance signal
The distortion component of the carrier can be canceled. The modulated signal input to the amplitude modulator 104 is obtained by converting the color signal separated by the low-pass filter 9 into a double frequency by the frequency converter 101 and then attenuating the signal to an appropriate amplitude by the attenuator 102. It is. That is, the attenuator 10
Amplitude of the low frequency chrominance signal by 2, b to the amplitude modulator 104
The modulation degree is set to match the amplitude modulation degree of the modulated signal input from the equalizer 5 .

[0014] Then, the output of the attenuator 102 is input to the phase shifter 103, where the modulated signal phase is determined Me such that the phase and opposite amplitude modulation of the modulated signal.
In other words, the modulation signal phase so as to cancel the phase modulation amount of the modulated signal is determined, an amplitude modulator 104
Is input to By the above operation, the amplitude modulator 104
From the FM luminance signal output from the
A) The amplitude fluctuation component is removed from the
By demodulation, the distortion component 1 in FIG.
Good reproduction signals of less than 5 and 16 are obtained.

In the above embodiment, the equalizer 5 plays the role of mainly converting the distortion components 15 and 16 into amplitude modulation components. However, the role of the equalizer 5 shown in FIG. This is to prevent an error from occurring and to improve the frequency characteristics and S / N of a reproduced image. Therefore, as shown in FIG.
By adding the equalizer 201 to the stage subsequent to the step 4 and having the role of the conventional equalizer 5, a more realistic configuration can be achieved. In the above-described embodiment, two types of signals have been described. However, even in the case of three or more types of signals, a configuration similar to the above-described embodiment may be employed between any two of the signals. Thus, a similar effect is achieved.

[0016]

As described above, according to the present invention, for example,
For example, by applying amplitude modulation to the FM luminance signal carrier,
Therefore, non-linear
Distortion components due to odd-order distortion can be reduced, and a high-quality reproduced image can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a magnetic reproducing apparatus according to one embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a magnetic reproducing apparatus according to another embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of a conventional magnetic reproducing apparatus.

FIG. 4 is a spectrum diagram of a reproduction signal.

FIG. 5 is a waveform diagram of a reproduction signal.

[Explanation of symbols]

 Reference Signs List 1 magnetic tape 8 luminance signal processing circuit 10 color signal processing circuit 15, 16 distortion component 101 frequency converter 102 attenuator 103 phase shifter 104 amplitude modulator

Claims (1)

(57) [Claims] 1. A magnetic reproducing apparatus which reproduces a signal from a magnetically recorded medium by multiplexing frequencies of at least two types of signals, wherein the frequency of one of the at least two types of signals is Frequency conversion means for converting the frequency into a double frequency, and modulating the frequency-converted signal
A magnetic reproducing apparatus, comprising: amplitude modulation means for amplitude-modulating the remaining signal by inputting the signal as a signal .