JPS61102896A - Color signal processoring circuit - Google Patents

Abstract

PURPOSE:To remove the jitter of the signals by recording pilot signals in a frequency band between those of the FM illuminance signals and the low-band conversion color signals, and using the jitter information of the pilot signals during reproducing to control the VCO of the color signal processing system. CONSTITUTION:A pilot signal oscillator 40 exists in a record circuit and its output is added to a mixer 6. The recording current spectrum is formed of FM illuminance signal 41, low-band conversion chrominance signal 42, and the pilot signal, 43 that is between the bands of these two signals. The pilot signal 43 is taken out the output of a pre-amplifier by a BPF. The circuit consists a PLL with a phase comparator, an LPF, and a VCO by using an f1 as a reference signal. The pilot PLL system has only one lock point because the pilot signal fp is a continuous wave, accordingly, the gain of the PLL is increased therefore, the jitter removal effect of the color signal processoring system is improved in large magnitude.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a color signal recording and reproducing circuit for a magnetic recording and reproducing device, and particularly to a video tape recorder (hereinafter referred to as V
The present invention relates to a color signal recording/reproducing circuit suitable for use in a color signal recording/reproducing circuit (abbreviated as TR).

[Background of the invention]

Conventionally, the video signal recording and reproducing method used in home VTRs (for example, VH8 system) has been to perform FM modulation on a luminance signal, and then frequency-multiplex it with a color signal converted to a low frequency to record and reproduce the signal. . In a color signal recording/reproducing method, as a means of correcting so-called jitter such as frequency fluctuations and phase fluctuations of color subcarriers during reproduction, a continuous signal synchronized with the reproduced color synchronization signal (color burst) is generated, and this continuous A method is used in which the signal is used to perform frequency conversion with the reproduced color signal, and jitter is canceled by 51G. FIG. 4 shows a conventional recording circuit for luminance signals and color signals.

In the case of the NTSC system, a composite video signal V in which a luminance signal and a color signal are frequency-multiplexed is input. In the case of the VH8 system, after the luminance signal and color signal are separated, they are processed separately, and then frequency-multiplexed and recorded using the same magnetic head.

Specifically, after a luminance signal α is separated by a low-pass filter (hereinafter abbreviated as LPF) IK, an FM luminance signal k is obtained by a PMfv4 circuit C (Modl) 2). Next, I will show you the color Shin MK. The color signal fs is separated by a bandpass filter (abbreviated as lower BPF) 5.

fs represents the frequency of the color signal. The color signal f8 is converted to a low frequency by the main converter 4, and after removing unnecessary frequency components by the LPF 5, the color signal f8 is sent to the mixing circuit 6.
The mixed signal is mixed with the FM luminance signal by the recording amplifier 7 and the magnetic head 8 and recorded on the tape. Next, a method of generating a conversion signal d input to the main converter 4 for converting a color signal into a low frequency signal will be described.

From the horizontal synchronization signal, a frequency control circuit (hereinafter abbreviated as AFC) 14 and a voltage controlled oscillator circuit (hereinafter referred to as vco)
) 15, a signal e with a frequency of 160 fH is obtained, and the frequency division and phase shift circuit ('/4P in the figure)
8. 161CJ: A signal with a frequency of 4ofH? is obtained. A signal t at a frequency of 5.58 MHz synchronized with the burst signal is obtained from the burst gate circuit 10, phase comparison circuit 11, LPF 12, and VC015vc. signal? The sub-converter 9 converts the frequency of the signal d to obtain a converted signal d.

Next, the reproducing circuit will be explained. FIG. 5 shows a specific example of the reproducing circuit. A bypass filter (hereinafter H
The reproduced FM luminance signal is separated by a demodulation circuit (hereinafter abbreviated as DEMO) 19 into a reproduced luminance signal t. On the other hand, the reproduced low frequency conversion color signal f, f to L+ containing jitter separated by the LPF 21 is converted into a reproduced color signal by the conversion signal χ in the main converter 22, and unnecessary frequency components are further removed by the K B P P 25. Next, a method of generating a conversion signal difference will be described. Burst gate circuit 25, crystal oscillation circuit 24
, a control signal μ for the VCO 29 is obtained by the phase comparison circuit 26 and the LPF 51. The control signal U also includes a component corresponding to jitter, and the oscillation frequency of the VCO 29 includes a jitter component of the reproduced color signal. Further, the VCO 29 is controlled by the discriminator 28 and the reproduced horizontal synchronizing signal fH so that the oscillation frequency error does not become extremely large. From the signal J obtained by VC029, frequency division and shift circuit 50, sub-converter 27 and oscillation circuit 2
4, the converted signal χ is obtained. The converted signal l is fs
+fsL+Δf, and this button contains a frequency or phase fluctuation component Δf that is compatible with jitter, and the jitter is corrected by performing frequency conversion with the reproduced low-frequency conversion color signal in the main converter 22. In this method, since the reproduced color burst signal is an intermittent signal, the range for correcting the variation is restricted in the process of creating a continuous signal for frequency conversion from the reproduced color burst signal, and it is not possible to sufficiently compensate for the variation. It had some drawbacks.

In order to compensate for this drawback, for example, as shown in Japanese Patent Publication No. 55-45656, a signal that is an integer fraction of the color synchronization signal is used as a pilot signal instead of the above-mentioned synchronization signal, and when recording the video signal as shown in FIG. A known method is to correct jitter by inserting the pilot signal at a position lower than the lower limit of the signal, multiplying this pilot signal during reproduction, returning the frequency to the original color synchronization signal frequency, and converting the frequency with the reproduced color signal. However, in this method, since the lower limit of the band recorded on the tape is used in the process of recording and reproducing the pilot signal, the ψ ratio of the reproduced pyro-node signal is poor and sufficient jitter correction cannot be performed. It had a In addition, the special public
As shown in Publication No. 9-2410, there is a method of recording and reproducing the pilot signal by providing a band for inserting the pilot signal at a frequency higher than the lower limit of the band that can be recorded and reproduced on tape, but the band of the recorded video signal is However, it has disadvantages such as being limited.

[Purpose of the invention]

An object of the present invention is to eliminate the above-mentioned drawbacks of the conventional method, record and reproduce the pilot signal by multiplexing it to a frequency that does not cause isobaric interference to the recorded video signal, and use this pilot signal to properly correct jitter. S of reproduced color signal
The object of the present invention is to provide a circuit that greatly improves the

[Summary of the invention]

The present invention records a pilot signal in the frequency band between the FM luminance signal and the low-frequency conversion color signal, and uses the jitter information of this pilot signal during playback to control the color signal processing system.
0 and removes jitter from the color signal.

, [Examples of the Invention] The present invention will be described in detail below based on specific examples. 1st
The figure shows an embodiment of the invention. FIG. 2 shows the recording circuit according to the present invention, and the conventional circuit No. 4.
The difference from the diagram is that there is a pilot signal oscillation 54o,
The way it comes out is that it is added to the mixing circuit 6. The recording current spectrum at this time, as shown in FIG. 5, consists of an FM luminance signal 41, a low frequency conversion color signal 42, and a pilot signal 45 located therebetween.

For example, the pilot signal frequency is 1.5MHz.
etc. are possible. This is particularly true when applying the present invention to a VH8 system FM audio multiplexing VTRK using a dedicated audio head, where the FM carrier is 1.5, 1.7 MH! and 1.
5 MHz is advantageous in that it lies just in between.

FIG. 1 shows a color signal reproducing system using the above-mentioned pilot signal f, and the differences from the conventional example shown in FIG. 5 will be mainly described. BPF50 from the output of preamplifier 17
The pilot signal f.

Take out. This signal has a frequency fluctuation of Δf due to jitter in the reproduction system, and the overall frequency is f, -=b+Δf. f, as a reference signal and a phase ratio of 1
An iR device 51, an LPF 52, a VCO 51CJ, and a PLL are configured. VCO55 is jp+Δ in the locked state.
It oscillates at a frequency of f. The output voltage of LPF52 is Vo
+Δυ′, and Δν′ corresponds to jitter Δf.

On the other hand, the low frequency conversion color signal extracted by the LPF 21 is f to fBL+, and Δf is the frequency fluctuation due to jitter. Here, since fax and jp are affected by the same jitter, the following relationship holds true.

In the conventional color circuit, the intermittent burst signal from the color signal f8 is extracted by the burst gate 25, and this is used to configure the APC from the intermittent PLLK. In this case, since the burst signal is an intermittent signal every 1H, the PLL
There are many points every h, and it is unstable.

On the other hand, in the pylon) PLL system, the pilot signal f
Since , is a continuous wave, the lock point can be set to one, and the PLL system can have a large gain and be extremely stable.

In the color system shown in Figure 1, 160 fHV C029
is fsp (= 629KHz = 40 fH)
f) Since the oscillation frequency is four times higher, in order to cancel out the fluctuation Δf of f3L due to jitter in the main converter 22, 160fHvCO29 needs to have a fluctuation of 4Δf. Output Δ of LPF52 of pilot system PLL
ν′ is set to ΔV by the variable amplifier 54. In this case, the gain G of the variable amplifier is as follows.

The gain G of the variable amplifier 54 is controlled by the output of the LPF 51 of the conventional intermittent PLL system, and Δν is 160 fHVCO2.
9 is given a frequency fluctuation of 4Δf. At this time LP
The cutoff frequency of F51 is set sufficiently low to completely eliminate the ripples generated from intermittent control.

With the configuration of the present invention shown in FIG. 1, the jigter removal effect of the color signal processing system can be greatly improved.

Since the pilot signal f has a single frequency, even if the recording level is reduced, a pilot signal with a sufficiently good S/N can be obtained by extracting it with a narrow band filter during reproduction. Therefore, in FIG. 5, even if the in-band pressure of the FM luminance signal 41 enters, the setting can be made within a range without interference.

〔Effect of the invention〕

As described above, according to the present invention, by recording and reproducing a pilot signal and using jitter information obtained from this pilot signal, APC control of the color signal processing system is performed, and color PMS is greatly improved. be able to.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a reproduction system of a color signal processing circuit according to an embodiment of the present invention, FIG. 2 is a block diagram of a recording system of a color signal processing circuit of the present invention, and FIG. 5 is a block diagram of a pilot signal multiplex signal according to the present invention. Figure 4 is a block diagram of the recording system of a conventional color signal processing circuit, Figure 5 is a block diagram of the reproduction system of a conventional color signal processing circuit, and Figure 6 is a block diagram of the reproduction system of a conventional color signal processing circuit.
The figure is a spectrum diagram of a conventional pilot signal multiplex signal. 45... Pilot signal, 51... Phase comparator, 52... LPF. 55...■C01 54...Variable amplifier. Figure 1 Figure 2 Figure 5 r- Pilot Iro No. + Figure 5

Claims (1)

[Claims] In a magnetic recording and reproducing device that multiplexes a pilot signal into an FM luminance signal and a low-frequency conversion color signal for recording and reproducing, the reproduced pilot signal is FM demodulated, the demodulated voltage is level-adjusted through a variable amplifier, and the level-adjusted voltage is used to record and reproduce the color signal. Controls the voltage controlled oscillator in the APC system, and controls the color AP
A color signal processing circuit comprising a phase comparator for a reference signal and a color burst signal in a C system, and a control voltage obtained by passing the output through an LPF to control the amplification degree of the variable amplifier.