JPH04280188A - Magnetic reproducing device - Google Patents

Abstract

PURPOSE:To obtain a reproduced picture with high quality by decreasing a distortion component appeared due to nonlinear odd number order distortion of a magnetic recording and reproducing system through the application of amplitude modulation to the reproduction signal. CONSTITUTION:A phase modulation component is reduced by an equalizer 5 and most of distortion energy is converted into an amplitude modulation component and the result is inputted to an amplitude modulator 104, modulated at an opposite phase, the distortion component is cancelled, A color signal separated by a low pass filter 9 in a modulation signal inputted to the amplitude modulator 104 is converted into a signal with a double frequency at a frequency converter 101 and attenuated to a proper amplitude by an attenuator 102. The amplitude is set to have modulation coincident with the amplitude modulation of the modulated signal being an output of the equalizer 5. The output of an attenuator 102 is inputted to a phase shifter 103 and the phase is decided so that the phase of the amplitude modulation of the modulated signal is inverted. Thus, the reproduction signal in which the amplitude modulation is less and distortion component is less is realized.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is applied to video tape recorders (hereinafter referred to as VTRs), etc., and is a magnetic reproducing device adapted to reproduce frequency multiplexed signals from a recording medium such as a magnetic tape. It is related to.

0002

[Prior Art] Figure 3 shows, for example, "Introduction to Home VTR"
(Published by Corona Co., Ltd.) is a block diagram showing the configuration of a signal processing circuit of a conventional home VTR disclosed on page 151. In the figure, 1 is a magnetic tape which is an example of a recording medium; A magnetic head picks up magnetic flux from the magnetic tape 1. 3 is a head amplifier, 4 is a high-pass filter that removes color signals, 5 is an equalizer, 6
The limiter cuts the high frequency components of the FM luminance signal. 7 is an FM demodulator that demodulates the FM luminance signal. 8 is a luminance signal processing circuit which processes and outputs the demodulated luminance signal.

9 removes the FM luminance signal from the luminance signal. 10 is a color signal processing circuit which processes and restores the color signal and outputs it. Reference numeral 11 denotes an adder which adds the luminance signal and color signal and outputs a video signal to a terminal 12.

[0004] Next, the operation of the above configuration will be explained. The magnetic flux picked up from the magnetic tape 1 by the magnetic head 2 is converted into an electrical signal and sent to the head amplifier 3. As a signal at this time, the FM luminance signal and the low frequency conversion color signal should be added to obtain a spectrum as shown in FIG. 4(a). In FIG. 4, 13 is a subcarrier for a low frequency color signal, and 14 is a carrier for an FM luminance signal.

By the way, due to the nonlinear odd-order distortion in the magnetic recording and reproducing system, distortion components 15 and 16 as shown in FIG.
appears. These distortion components 15 and 16 are passed through the high-pass filter 4
, equalizer 5, limiter 6, it does not disappear, F
It remains even after demodulation by the M demodulator 7, and even after being converted into a final video signal by the luminance signal processing circuit 8, and appears as a beat on the screen. On the other hand, the FM luminance signal of the color signal is removed by a low-pass filter 9, then restored by a color signal processing circuit 10, and then added to the luminance signal by an adder 11 to form a complete video signal, which is output to a terminal 12. .

[0006]

[Problem to be Solved by the Invention] Since the conventional magnetic reproducing device is configured as described above, the above-mentioned distortion components 15 and 16 occur in the reproduced video signal, degrading the quality of the reproduced image. There was a problem.

The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a magnetic reproducing device that can reduce distortion components and obtain high-quality reproduced images.

[0008]

[Means for Solving the Problems] A magnetic reproducing device according to the present invention converts the frequency of one signal out of at least two types of signals reproduced from a frequency-multiplexed magnetically recorded medium to double the frequency. , the amplitude of another signal is modulated by the frequency-converted signal.

[0009]

[Operation] According to the present invention, by converting the frequency of one signal to twice the frequency and modulating the amplitude of another signal with the frequency-converted signal, distortion components generated during magnetic recording can be obtained. It can be decreased when playing.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a household V according to an embodiment of the present invention.
3 is a block diagram showing the configuration of a signal processing circuit of a TR. In the same figure, 1 to 12 are the same as the conventional example shown in FIG. do.

In FIG. 1, 101 is a frequency converter;
Converts the frequency of the color signal to twice the frequency. An attenuator 102 attenuates the amplitude of the color signal converted to twice the frequency to an appropriate amplitude. 103 is a phase shifter, and the above-mentioned attenuator 10
The phase of the modulated signal output from the equalizer 5 is made opposite to the phase of the amplitude modulation of the modulated signal output from the equalizer 5. 104
is an amplitude modulator that modulates the amplitude of the modulated signal using the frequency-converted modulation signal.

Next, the operation of the above configuration will be explained. First, the principle of generation of the above-mentioned distortion components 15 and 16 will be explained with reference to FIG. 5. The signal obtained by adding the low frequency conversion color signal and the FM luminance signal carrier with the waveform shown in FIG. 5(a) has an amplitude limit shown in B in FIG. 5(b) corresponding to the nonlinear distortion of magnetic recording and reproduction. receive. Basically, this signal is reproduced, but if the low-range color signal shown in FIG. 5(c) is removed, an FM luminance signal carrier as shown in FIG. 5(d) is obtained. As is clear from the waveform in the same figure, it can be seen that the signal is amplitude modulated at twice the frequency of the low-range color signal. In reality, the recording levels of the low-range color signal and the FM luminance signal carrier are different, and the strength of the magnetic field generated from the magnetic head 2 is different, as shown in FIG. 5(e).
) is out of phase. In this way, the signal itself obtained from the magnetic head 2 is completely amplitude modulated, but due to the characteristics of the circuits such as the head amplifier 3 and the high-pass filter 4, a phase modulation component is also generated, which removes the amplitude fluctuation component. This component remains even after passing through the limiter 6.

According to the embodiment based on the above considerations, after the above-mentioned phase modulation component is reduced by the equalizer 5 and most of the distortion energy is converted into an amplitude modulation component,
By inputting the signal to the amplitude modulator 104 and modulating it with an opposite phase, the distortion component can be canceled. The modulated signal inputted to the amplitude modulator 104 is a color signal separated by the low-pass filter 9, and the frequency converter 101 converts the color signal into two.
After being converted to double the frequency, it is attenuated to an appropriate amplitude by an attenuator 102. Its amplitude is determined by the amplitude modulator 1
The amplitude modulator 104 is set so that the modulation degree matches the amplitude modulation degree of the modulated signal which is the output of the equalizer 5 inputted to the equalizer 5.

Next, the output of the attenuator 102 is input to a phase shifter 103, where the phase is determined to be opposite to the phase of the amplitude modulation of the modulated signal. That is, the signal is determined to cancel the amplitude modulation of the modulated signal and is input to the amplitude modulator 104. With the above operation, the amplitude modulation is small and the distortion component 1 in FIG. 4(b) is
A high-quality reproduced signal with fewer numbers of 5 and 16 can be obtained.

In the above embodiment, the equalizer 5 plays the role of making the distortion components 15 and 16 mainly amplitude modulation components, but the role of the equalizer 5 shown in FIG. It was intended to prevent errors from occurring and to improve the frequency characteristics and S/N of reproduced images. Therefore, as shown in FIG.
A more realistic configuration can be achieved by adding the equalizer 201 at the latter stage to play the role of the equalizer 5 of the conventional example. Further, in the above embodiment, two types of signals have been described, but even in the case of three or more types of signals, the same configuration as in the above embodiment may be adopted between any two of the signals. A similar effect can be achieved.

[0016]

As described above, according to the present invention, by applying amplitude modulation to the reproduced signal, it is possible to reduce the distortion components that appear due to nonlinear odd-order distortion in the magnetic recording and reproducing system, thereby achieving high quality. A reproduced image can be obtained.

[Brief explanation of the drawing]

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

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

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

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

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

[Explanation of symbols]

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)

[Claims] 1. A magnetic reproducing device configured to reproduce signals from a magnetically recorded medium by multiplexing the frequencies of at least two types of signals, wherein the frequency of one of the at least two types of signals is multiplexed. What is claimed is: 1. A magnetic reproducing device comprising: a frequency converter that converts a frequency to double the frequency; and an amplitude modulator that modulates the amplitude of another signal using the frequency-converted signal.