JPS5816310Y2 - magnetic recording and reproducing device - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a magnetic recording and reproducing device such as a magnetic disk device that records and reproduces a color video signal on a magnetic recording medium such as a magnetic disk. The object is to provide a device that can perform recording and reproduction well.

In devices that re-record and play back color video signals,
It is necessary to correct temporal variations in color signals during recording and reproduction, and various methods have been devised as means for this purpose.

First, I will briefly explain them.

Figure 1 shows a method in which a composite color television signal is directly frequency-modulated and recorded, and a variable delay line is used to correct time axis fluctuations during playback. Electromagnetic conversion characteristics are required, moiré between the color subcarrier and the FM signal is likely to occur, and correction of time axis fluctuations in the reproduced signal also has drawbacks such as a complicated circuit and an expensive device.

Second, as a method used in simple VTRs, etc., there is a well-known method known as the so-called M method, in which the luminance signal is FM modulated, the color signal is converted to a low frequency signal, and multiplexed recording is performed with a frequency distribution as shown in Figure 1. There is a method.

However, this method has the drawbacks that beats tend to occur between the FM luminance signal and the low-frequency conversion color subcarrier, the S/M of the brown signal is poor, and color jitter is large.

The third type is the YC separated pilot recording method, which is used when a recording medium such as a one-frame or one-field refresh memory is used and multi-heads are easy to use.

This method uses, for example, a high-pass filter and a low-pass filter to separate the luminance signal and color signal, record them on separate tracks on a recording medium, and perform time axis correction of the color signal. In this method, pilot signals are multiplexed and recorded in order to achieve this goal. First, the color signal separated from the video signal is converted to a low frequency signal (for example, 1.19 MH2), and then 1/n of the converted color subcarrier frequency (for example, n= FM by multiplexing pilot signals of 397 KHz).
At the same time as modulating, the separated luminance signal is also FM modulated,
Each FM signal is recorded on a separate track of a recording medium such as a magnetic disk, and during playback, the brightness signal is directly transferred to the FM signal.
After M demodulation and FM demodulation of the color signal, the pilot signal is separated, and this pilot signal multiplied by n is added to the oscillation signal of the color subcarrier frequency, and this is combined with the FM demodulated low frequency conversion color signal. The time-axis corrected color signal is extracted by taking the difference between the two.

According to this method, even if the FM spectrum of the luminance signal is widened, a beat with the color signal does not occur, and the color signal is
On the other hand, beats between the pilot signal and color signal tend to occur, and in order to avoid this, lowering the level of the pilot signal lowers the S/N of the pilot signal itself. This method has drawbacks such as a decrease in the time axis variation, a decrease in the ability to correct time axis fluctuations, and a relatively complex circuit for generating a pilot signal and a circuit for reproducing the pilot signal.

Therefore, the purpose of the present invention is to realize a magnetic recording/reproducing device using the "rYC separated track method" with good image quality with a simple configuration that does not use pilot signals, and to improve the recording/reproducing characteristics of color signals. After converting the frequency of the color signal to a low frequency band, the color signal is FM modulated and recorded on a separate track from the luminance signal, and during playback, FM demodulation is performed to obtain a low frequency color signal, which is then reproduced using a color burst signal. In addition to correcting the time axis of the signal, when converting the color signal to low frequency, the center frequency (carrier frequency) of the low frequency conversion is set to a frequency lower than the bandwidth of the color signal, and this low frequency converted color signal is It is characterized in that the modulation index when converting the signal into FM is larger than the modulation index of the FM luminance signal.

An embodiment of the present invention will be described below with reference to FIGS. 2 and 3.

First, FIG. 2 shows the configuration of an apparatus according to an embodiment of the present invention.

Here, 1 is a video signal input terminal, from which a low-pass filter 2 extracts a luminance signal component, and a band-pass filter 6 extracts and separates a color signal component from the video signal input thereto.

The luminance signal that has passed through the filter 2 is processed by AGC in the processing circuit 33.
, clamp, white clip, etc., and performs FM modulation using the FM modulator 34.

On the other hand, the color signal is balanced modulated by a balanced modulator 7, frequency-converted to a low frequency band, and passed through a low-pass filter 8 to obtain a low-frequency converted color signal.

This low frequency converted color signal is also subjected to necessary processing such as clamping, amplitude adjustment, and white clipping in the processing circuit 9, and FM modulated in the FM modulator 10. They are amplified by recording amplifiers 5 and 11, respectively.

When recording both signals on a magnetic recording medium such as a magnetic disk, the switching positions of the switches 12 and 13 are both set to agIll, and the head 14 outputs the FM luminance signal, and the head 15 outputs the FM low-frequency conversion color signal. They are recorded separately on separate recording tracks on a magnetic recording medium.

Next, when reproducing, the switches 12 and 13 are both set to the b side, the signals recorded on the recording medium such as a magnetic disk are picked up by the heads 44 and 45, and the head amplifiers 16 and 20 are first picked up. Amplify.

The FM brightness signal amplified by the head amplifier 16 is sent to the limiter 1.
7, the signal is FM demodulated by an FM demodulator 18, and passed through a low-pass filter 19, where the original luminance signal is extracted.

On the other hand, the FM low-frequency converted color signal amplified by the head amplifier 20 passes through a limiter 21, then undergoes FM demodulation in an FM demodulator 22, and passes through a low-pass filter 23, where the low frequency signal is frequency-converted to the original low frequency. Obtain the converted color signal.

This low frequency converted color signal is subjected to time axis correction using the color burst signal as a reference in the color processing circuit 24, and balanced modulation to return the frequency to the high frequency range, and the band pass filter 24
The carrier frequency of the original video signal (3,58M
Hz) color signal is obtained.

After that, the luminance signal of the output of the filter 19 and the filter 25
A reproduced video signal is obtained by combining the output color signals of the video signal and the color signal outputted by the combining circuit 26, and outputs the reproduced video signal from the output terminal 27.

In this way, both the luminance signal and the low-frequency converted color signal are
By performing M modulation and using a color burst signal to perform time axis correction of the gray color signal during playback, it became possible to record and play back color video signals without using a pilot signal. .

Next, the color processing circuit 24 shown in FIG. 2, which performs time axis correction and balanced modulation for frequency conversion, will be explained in more detail with reference to FIG. 3.

The FM color signal subjected to FM modulation as described above is FM demodulated by the FM demodulator 22, and a low frequency converted color signal is inputted to the output terminal 30.

Here, if the low-pass conversion carrier frequency of the low-pass conversion color signal during recording is fl (for example, 767 KHz), and the frequency fluctuation due to jitter of a recording medium such as a magnetic disk is Δf, then the buffer amplifier 31 includes the sinter ( fl＋△
A color signal of frequency f) is obtained.

On the other hand, 33 is a sine wave oscillator whose oscillation frequency is the color subcarrier frequency (3, 5
8MHz), and let this be f.

32 is a balanced modulator and filter for frequency conversion; here, the color signal of (f to fl - h) and the color subcarrier of f are combined to generate a color signal with a frequency of (f8 + fl + △f). A burst gate 34 extracts only the color burst signal from this color signal.

35 is a phase comparison circuit, 36 is a voltage controlled oscillator (VCO) whose center frequency is 11, and 3γ is this VCO 36.
The phase comparator 35, the balanced modulator, and the filter 3T form an APC loop, and as a result, the output of the balanced modulator and filter 37 is a continuous wave having a frequency of (fs+11+Δf) including the frequency variation of the color signal.

Then, this and the output of the buffer amplifier 31 (fl+△f
) to the balanced modulator and filter 38 for frequency conversion, and synthesizes them so as to take the difference therein, thereby obtaining the carrier frequency fS (with frequency variation (time axis variation) removed).
-(f8+fLmf)-(f1+Δf)) can be obtained, and this can be taken out from the output terminal 39.

In this way, time axis correction can be performed using the burst signal.

Incidentally, such a correction circuit is similar to that generally used in a video tape recorder (VTR).

Now, in the present invention, the center frequency when low-frequency converting the color signal is set to a frequency lower than the bandwidth of the color signal, and the center frequency when low-frequency converting the color signal is FM modulated. It is characterized in that the S/N ratio of the color signal is improved by making the modulation index larger than that of the FM luminance signal.

For example, the low-pass conversion color subcarrier frequency is 3/3 of the color subcarrier fs = 3.579545MHz of the NTSC system.
14 times that is, 767.045 KHz, and the bandwidth is 500 KHz to 8 MHZ as a recording medium such as a magnetic disk.
When using a carrier of about z, the FM carrier frequency is 4 MH
If the frequency is set to 4.5 MHz to 4.5 MHz, it is possible to record and reproduce up to the upper and lower fifth order sideband waves.

This means that the modulation index is 2 or more, and the S/N
It is extremely advantageous for improvement.

In addition to 767.045 KHz, the low-pass conversion color subcarrier frequency is 5/26 times fs or 688.374 KH.
z can also be used, but if this frequency is used as an FM center carrier wave of 4MHz to 4.5MHz on a recording medium with the above-mentioned bandwidth.
If recorded at 767.045 KHz, an even larger modulation index is obtained than at 767.045 KHz.

When processing NTSC color signals using a narrowband reproduction method, a bandwidth of ±500 KHz is required.

Converting this bandwidth color signal to such a low gamut color subcarrier,
When frequency modulated, the spectra of the sidebands overlap, and when recorded and reproduced as they are, it is possible that some kind of coexistence occurs, but experiments have shown that the amplitude-one-phase characteristics, S/N, etc. of the reproduced signal No deterioration considered to be due to the above causes was observed.

As described above, for example, by using a low-frequency conversion color subcarrier of 767.045 KHz or lower in the M system and recording and reproducing it by FM with a large modulation index on a recording medium with a wide bandwidth, color signals can be reproduced. The S/N ratio was improved by about dB compared to the M method, the hue jitter was ±3° or less, and the level fluctuations, DG, and DP of the color signal were negligible.

In addition, in the above configuration, if the carrier frequency ft when converting the color signal to the low frequency band is set to be the same as approximately 767 KHz or 688 KHz used in M system VTR, it will be the same as a conventional VTR. "YC" using parts
It is possible to realize a "separate track system" device.

As described in detail above, the magnetic recording/reproducing apparatus of the present invention includes a circuit that separates a video signal to be recorded into a luminance signal and a chrominance signal, an FM modulation circuit that FM modulates this luminance signal, and a FM modulation circuit that modulates the chrominance signal. an FM modulation circuit that performs FM modulation on this low frequency converted color signal, and an FM modulation circuit that converts the low frequency converted color signal into a frequency range of 300 to 3000 nm. means for recording, means for picking up both FM signals from the magnetic recording medium, and means for picking up both FM signals from the magnetic recording medium;
An FM demodulation circuit that demodulates and reproduces the luminance signal, an FM demodulation circuit that demodulates the picked-up FM low-frequency conversion color signal and reproduces the low-frequency conversion color signal, and a color included in this low-frequency conversion color signal. It is equipped with a correction circuit that performs time axis correction of the reproduced color signal based on the burst, and a conversion circuit that converts this low-frequency converted color signal to the frequency of the original color signal. is set to a frequency lower than the bandwidth of the above-mentioned color signal, and the modulation index when FM modulating this low-frequency conversion color signal is set larger than the modulation index of the FM luminance signal. Since the chrominance signal can be FM modulated and recorded with a sufficiently large modulation index on a track separate from the FM luminance signal, the S/N ratio during recording and reproduction of the chrominance signal can be made extremely good.
Therefore, it is possible to perform sufficiently good time axis correction without superimposing a pilot signal, so that color video signals can be recorded and reproduced with a simple configuration that does not require a circuit for a pilot signal. However, by not using a pilot signal, there is no occurrence of beat interference between the pilot signal and the color signal, and the recording and reproducing characteristics of the color signal can be improved.

[Brief explanation of the drawing]

Fig. 1 is a spectrum diagram showing the frequency distribution in a unified type VTR, Fig. 2 is a block diagram showing the configuration of a magnetic recording/reproducing device in an embodiment of the present invention, and Fig. 3 is a time axis correction section in the same device. FIG. 2 is a block diagram showing the configuration of FIG. DESCRIPTION OF SYMBOLS 1...Input terminal, 2...Low pass filter for luminance signal separation, 3...Processing circuit, 4...
...FM modulator, 5... Recording amplifier, 6
... Bandpass filter for color signal separation, 7...
... Balanced modulator for low-pass modulation, 8 ... Low-pass filter, 9 ... Processing circuit, 10 ...
FM modulator, 11... Recording amplifier, 12, 13
・・・・・・Linked switches, 14, 15...
・Head for recording and reproduction, 16... Head amplifier, 17... Limiter, 18... FM demodulator, 19... Low pass filter, 20 ...
...Head amplifier, 21...Limiter, 22
...FM demodulator, 23...Low pass filter, 24...Color processing circuit, 25...
...High-pass filter, 26...Synthesizing circuit,
27...Output terminal, 30...Input terminal, 31...Buffer amplifier, 32...
Balanced modulators and filters for frequency conversion, 33.
... Sine wave oscillator, 34 ... Burst gate, 35 ... Phase comparison circuit, 36 ...
- Voltage controlled oscillator, 3T... Balanced modulator and filter for frequency conversion, 38... Balanced modulator and filter for frequency conversion, 39... Output terminal.

Claims (1)

[Scope of utility model registration request] A filter circuit that separates a video signal to be recorded into a luminance signal and a chrominance signal, an FM modulation circuit that FM modulates the luminance signal, a conversion circuit that converts the chrominance signal to a low frequency, and this low frequency conversion. an FM modulation circuit for FM modulating a color signal; a recording means for recording the FM-modulated FM luminance signal and the FM low-frequency conversion color signal on different recording tracks on a magnetic recording medium;
pickup means for picking up each signal;
an FM demodulation circuit that FM demodulates the picked up FM luminance signal to reproduce the luminance signal; an FM demodulation circuit that FM demodulates the picked up FM low frequency converted color signal to reproduce the low frequency converted color signal; A time axis correction circuit that performs time axis correction of the reproduced color signal based on the color burst included in the low frequency converted color signal, and a reconversion circuit that converts this low frequency converted color signal to the frequency of the original color signal. The center frequency of the low-pass conversion color signal is set to a frequency lower than the bandwidth of the color signal, and the low-pass conversion color signal is set to a frequency lower than the bandwidth of the color signal.
A magnetic recording and reproducing device in which the conversion index when performing M modulation is thicker than the modulation index of the FM luminance signal.