JPS58156283A - Chroma signal recorder - Google Patents

Abstract

PURPOSE:To minimize the power consumption required for a 1/(3N) divided period, by setting the frequency of 4 times as high as the frequency of a chroma signal to be recorded on a tape at a 3N-fold level of a horizontal synchronizing frequency (N: product of prime numbers of a digit). CONSTITUTION:The oscillating frequency of a voltage control oscillator (VCO) 2 is set at 189fH=3XNfH, where N=63=(3X3X7). The output of the VCO 2 is applied to a filter 5 via a 1/4 frequency divider 3 and the 1st frequency converter 4, and the signal of a sum frequency is sampled. At the same time, a chroma signal 1 is applied to an LPF 8 via the 2nd frequency converter 7. A 1/189 frequency divider 9 contains 1/3 frequency dividers 30-32 and a 1/7 frequency divider 33. Then the difference of phase between the output of the divider 9 and a horizontal synchronizing signal 17 is detected by a phase comparator 13. Then the VCO 2 is driven. Furthermore the difference of phase is detected by a phase comparator 15 between the output of a VCO 14 and the output of a burst gate circuit 16. Then the VCO 14 is driven. As a result, the frequency emerging at an output terminal 19 is set at (47+1/4)fH.

Description

[Detailed Description of the Invention] The present invention converts a luminance signal into an IPMq signal, converts a chroma signal into a low frequency signal, and records both signals on a tape using two heads with different azimuth angles. Regarding cross-azimuth helical type video tape recorders, especially N
The present invention relates to a TSC type chroma signal recording/reproducing circuit.

There is a β method as a chroma signal recording method used in an NTSC cross-azimuth type helical-skipping video tape recorder.

The problems with this method are (1) it requires a large number of flip-flops (hereinafter referred to as FF) that operate at high speed, making it difficult to integrate into ICs, (2) it is difficult to secure a band for chroma signals, especially for pilot signals for track king control. There is a problem when multiplexing 51N TSC and PAL systems, which makes the ROMA signal IC extremely complicated.
There was a problem in that the 41 chroma signal recording circuit and the pilot signal generation circuit could not be used together.

The conventional problems will be explained in detail below using the drawings.

FIG. 1 is a block diagram showing the main parts of a chroma signal recording circuit of a β-system video tape recorder.

First, a method of recording an NTSC chroma signal in a β-scheme video tape recorder will be explained. 5.5Bk in β method
The chroma signal of Hz is converted to the frequency of 11g (in is the horizontal synchronization frequency), and the frequency-converted chroma signal is recorded as it is on the first track, and the frequency is recorded on the second track. By inverting the phase of the converted chroma signal every horizontal period, the chroma frequency is converted to (a a a + 2) f' and recorded. As described above, the necessary and sufficient number of recording chroma signal station waves is established.

Next, the above operation will be explained using FIG.

1 is the input electron of the chroma signal, 2 is the voltage that oscillates at a frequency of 175fH? 11 rise oscillator (hereinafter referred to as VCO), 5 is a frequency divider, 4 is a first frequency converter, 5 is a filter that extracts the sum frequency signal from the output of 4. 6 does nothing on the first track, In the second track, a circuit performs phase inversion every horizontal period, 40 is an input electron for a signal indicating the track, 7 is a second frequency converter, and 8 is a low-pass comparator that extracts a difference frequency signal from the output of 7. The phase difference between the output signal of the frequency divider 9 and the horizontal synchronizing signal applied to the syringe 17 is detected and the VCO 2 is driven. 14
is 5.5BkHz X'tat VC'0, and the phase comparator 15 outputs the output signal of 14 and the burst gate circuit Ii! 1
The phase difference between the output signals of No. 6 and 6 is detected.

Therefore, a carrier 75 whose frequency matches that of the chroma signal applied to the single element 1 is obtained at the output of the FCC 14. The output of filter 5 is ←-fI-Hss)M
A Hz signal is taken out and sent to the output 175 of the 1 phase inversion circuit 6.
1 In the second track ((-+-)fI+5.sa)h
utz2 signals are obtained respectively. Therefore, a pair is outputted to the first track to the low frequency converted chroma signal output 19, and a chroma signal converted to the frequency of (T±1)fl is outputted to the second track.

Next, the above-mentioned (11) problem points will be explained.

In FIG. 1, a □ frequency divider 9 is required, and in order to design the frequency divider 9 to have the minimum chip size and minimum power consumption, it is necessary to use a hundred frequency divider 10. N, -
Divided into frequency divider 12, especially divider 10 is +75 pi
(2.75 MHz) is composed of high-speed flip-flops (hereinafter referred to as FF) so as to be able to separate channels.

FIG. 2 is a circuit diagram showing a specific example of the branching unit 10 of the first section. To divide frequencies over 2MHz, a synchronous counter shown in Fig. 2 is required, and all of FF22゜25, '4 are 1.
It is necessary to operate at 75fH (=2.75MHz). An FF that operates at 2 MHz or higher has a required chip size and power consumption approximately 10 times larger than an FF that operates at 500 kHz or lower, and the key point is how to reduce the number of high-speed FFs. The branching unit 9 of the system shown in FIG. 1 requires 15 high-speed FFs, resulting in an increase in chip size and power consumption.

Next, the problems of (21) mentioned above will be explained.

FIG. 5 shows a recording signal spectrum 26 and a high lot signal spectrum 27 in the chroma signal band. Frequency characteristics 25 of the tape head system are shown respectively. As can be seen from the figure, the lower wave of the chroma signal is at the cutoff m wave number K of the tape head system, and in order to secure a sufficient bandwidth of the chroma signal, the lower conversion frequency must be further increased from 68BKHz to 700kHz.
It is necessary to raise the frequency above Hz.

Furthermore, when multiplexing the tracking control pilot signal 27, it is necessary to further increase the recording frequency of the chroma signal. The most excellent method for pilot signals is the one developed by Philips, and the pilot frequency is 65 fl (1021 HI) f 7.5 fl I 9
．． 5fl I 10.5N (1651H1).

When the chroma frequency is set to 8 BkHz, the frequencies are too close to each other, and there is a problem that interference caused by the pilot signal cannot be sufficiently removed.

Next, the problems of (51) mentioned above will be explained.

The PAL chroma signal of the β system video tape recorder is the first
C44-1) fle on the second track (4)
4+8) fHK frequency is selected. Therefore, if NTSC and PAL are shared in the configuration shown in Figure 1, VCO2
is 175fl for NTSC and 551fl for PAL.
, 55SfH. Furthermore, the frequency divider 3 is set to 1 for NTSC and 1 for PAL, and the frequency divider 9 is set to 1 for NTSC and 1 for PAL.
SC time -, P, 4L time 18
175 switching is +75=5X5
X7, +55:5X5X5XI5,555=555(
(prime number), and as mentioned above, the frequency divider cannot be divided, and all the FFs that make up the hundredth frequency divider must operate at high speed.In the end, it is impossible to use the frequency divider 9 in common with NTSC, P, and 4L. It becomes possible.

Next, the above-mentioned problem (41) will be explained. FIG. 4 shows the chroma signal circuit of FIG.
8 is added, and 29 is the output terminal of the pilot signal. Since a signal of +75fl is applied to the input of the frequency divider 2B, the frequency division s28 is applied to each troy) The signal output terminal 29 button is fl = 179 = t o, 29f'& 175
175f2 =-7fl =
9.21fl #f5=-72-,7'#: 7.
29fl, fa==fi:6,7,9. IQ. This is determined by the fact that it is less susceptible to harmonic interference from flyback pulses from televisions, and the pilot signal is less likely to interfere with chroma and luminance signals.

Furthermore, the condition for stabilizing tracking control is 4=1(
fl -12>-CfS-14)1 and B= l (fl
-f5) -Cf2-fa)1 is as close to zero as possible.

In Figure 4, the frequency deviates considerably from the ideal, and
The problem is that A==0.05fIv B=α04fH, which are quite large.

The purpose of the present invention is to solve all of the four problems mentioned above.
To provide a circuit for recording a TSC type chroma signal on a video tape.@The present invention has a frequency of 5 fir (lx
I (horizontal synchronization frequency) N times (N1 integer), and N
By selecting a number represented by the product of −-digit prime numbers, the chip size and power consumption required for the −N splitter are minimized, and by selecting the chroma frequency to be 70 kHz or higher, the bandwidth can be secured and the pilot signal Improve coexistence.

An embodiment of the present invention will be described below with reference to FIGS. 5 to 11.

FIG. 5 is a block diagram showing the main parts of a chroma signal recording circuit according to an embodiment of the present invention. The characteristic of Fig. 5 is that the oscillation frequency of VCO2 is '8N' = 5XNfx,
#=65=5X5X7 is selected. Therefore, the difference between FIG. 5 and FIG. 1 is the oscillation frequency of the VCO 2 and the configuration of the frequency divider 9, and as a result, the frequency of the recording O signal appearing at the output terminal 19 is (47+-).
It is composed of a frequency generator 55, which is called fl. The input frequency of the i-divider B50 is 189fl=2.97MHz, which requires high-speed operation. Therefore, as mentioned above, a synchronous counter is preferable, and the FF configuration shown in FIG. 6 can be considered.

As is clear from FIG. 6, only two KFFs are required, and the chip size and power consumption required for the branching unit 9 can be minimized. On the other hand, the frequency of the low-frequency converted chroma signal is (47+7
) fI is 745kHz, and the spectrum 59 of this chroma signal and the frequency characteristic 2 of the tape head system shown in Fig. 7
As you can see from the relationship 5, the band is 745±500&Hz! Ensure that the frequency is just right.

Also, when multiplexing the pilot signal 27, the difference between the pilot signal frequency of 102 to 165 kHz and the T1 frequency of the chroma signal of 245 kHz is approximately 80 kHz.
z can be taken, resulting in an appropriate frequency arrangement to prevent mutual interference.

FIG. 8 is a block diagram showing the main parts of a chroma signal recording circuit according to another embodiment of the present invention. The difference between Fig. 8 and Fig. 1g5 is that in Fig. 8, the divider 5 of Fig. 5 is divided by i@a+
, and that it was divided into 42 parts.

This is because a waveform shaper 45 is added and the type of the 1-phase inversion circuit 6 is changed.

The reason for dividing the frequency divider 5 into the i frequency divider a1 and 42 is to supply the 189 waveform shaper a 5K-T-fl signal and to obtain the 189fH signal which has a phase difference of about 186 from each other. It is. (The Q and Q outputs of the FF can be used as they are.) Phase and rotation @6 in FIG. A signal is input, and switching is performed so that the input signal on one side is output as is in the first track, and the two input signals are alternately output in each horizontal period in the second track.

The waveform shaper #1I45 has the function of adjusting the rising timing of the output signal of the phase inversion circuit 6.

An example of the waveform shaping circuit 45 is shown in FIG.
By applying the output signal of the frequency-divided WjI 41 to the T input electron 45 and the output signal of the phase inversion circuit 6 to the D input 1 element 46, a signal with a well-timed rise timing can be obtained at the output terminal 47.

FIG. 10 is a block diagram showing a main part of an embodiment of the present invention when used in an NTSC system chroma symbol continuous recording PAL system Oma signal recording circuit.

In Figure 10, NTSC is (4) in the first track.
7+ -) Select the chroma signal frequency for f'.

In the second track, the recording method is to perform phase inversion so that (47+7±->)fl, and in PAL, the first track is (47-100)fH, and the second track is (47B+7)fH. In order to achieve this, a phase shift is performed in which the phase advances by +90'' every horizontal period.

The difference between Fig. 10 and Fig. 8 is that four signals, o, +9o', -zso', and +27o°, whose phases differ by 90'' from each other, are output as the /44 frequency divider 3 output.1 In place of the phase inversion circuit 60, the first track of NTSC and PAL does not perform phase inversion or phase shift, and for the second track, N75C performs phase inversion and PAL performs +96 phase shift.5 phase selection circuit 46 The NT5C has the same frequency as the input chroma signal (IJPC=5.57
9545MH2) to Jll's converter 4, and P
, 4L, the frequency of the input chroma signal (fzc ==
A switch 50 for inputting the carrier g+ converter 4 with a frequency 5 fil lower than 4455618 mHz),
A control signal input terminal 49 for switching between TSC and PAL is provided, and a pilot signal generation circuit 52. This is because the pilot signal output 1 child 55 was thrown.

The pilot signal generation circuit 52 has f1=189 f,
=8 89 1(150f' e f2 = -f'F = 9.4
It is possible to output four signals: 51', fs = 7.560 fH, fa = 652 fl, which is the ideal value of the pilot frequency.

(n+-)fil<f' + f2 + f5- fa
<(9+, >f' is satisfied. Also, A=
+(71-f2)-(15-fa)l=αo1fl
,B=)(fl-fs)-(f2-fa)l=αo
1fx, ensuring necessary and sufficient characteristics as a pilot signal.

FIG. 11 is a block diagram showing another embodiment of the NTSC and PAL chroma signal recording circuit described in FIG. 10.

The difference between Fig. 11 and Fig. 10 is that the oscillation frequency of VCO2 is (a y 10a)%Bfl == in NTSC.
578fl, (47-100)X8f in PAL
#=575fl 1 Frequency divider 9 is 9 in NTSC
In order to minimize the chip size and power consumption when converting into an IC, the τ frequency divider 51 is switched to 100 for NTSC and PAL, and the frequency divider 56 is switched to 100 for NTSC and IJL. The frequency divider 57 is switched to - for NTSC and 100 for PAL.

Also, by newly installing the %i frequency divider 54, the output of the 1 frequency divider 54 will be 1 atpfi in NTSC and (t 8
7 +7)fi'. Therefore, the switch 50°X'tat onrator 51 provided in FIG.

According to the present invention 14, the number of free-lag flops that require high-speed operation can be minimized, and when integrated into an IC, the chip size and power consumption can be reduced to 1/11. In addition, the chroma signal recording circuits of the NTSC system and the P, iL system can be made similar, and the chroma signal recording circuit of the NTSC, P-4L system can be made similar.
Dual-purpose ICs can be designed extremely easily. Furthermore, the chroma signal recording circuit of the present invention can be extremely easily used in combination with a pilot signal generation circuit, and the obtained pilot signal frequency can be set to an optimum value.

[Brief explanation of drawings]

Figure 1 is a block diagram showing the main parts of the NTSC chroma signal recording circuit of a β-method video tape recorder, the 1m2 diagram is a circuit diagram showing an example of a hundredth frequency divider, and Figure 5 is a block diagram showing the main parts of the NTSC chroma signal recording circuit of a β-method video tape recorder. A characteristic diagram showing the signal spectrum and the frequency characteristics of the tape head system. FIG. 4 is a block diagram showing an example of generating a pilot signal from the chroma circuit shown in FIG. 1. FIG. Figure aI6 is a circuit diagram showing an example of a hundredth frequency divider. Figure 7 is a characteristic diagram showing an example of the chroma signal spectrum of the present invention and the frequency characteristics of the tape head system. is a block diagram showing the main parts of another embodiment of the present invention. 1gl is a circuit diagram showing an example of a waveform shaping circuit, and FIG. 10 is an example of a case where the optical signal recording circuit of the present invention is used for PAL.
! FIG. 11 is an implementation of the No. 2011 recording circuit that can be used for both the NTSC system chroma signal symbol circuit of the present invention and the P, 4L system chroma signal symbol circuit that is compatible with this circuit. FIG. 2 is a block diagram showing main parts of an example. Explanation of symbols> 1... Chroma signal input terminal 4... First frequency converter 6... Phase inversion circuit 7... Frequency converter 2 of building 2... Voltage controlled oscillator 9 ...Frequency divider 27...Pilot signal 30...1 Frequency divider 43...Waveform shaping circuit 1) 1 m;+-3 flash 5 ;+4 膓O 5 no 2 6 O Δ Prisoner 71! 1 Dark Tears Cooking 80 O/θl O r+ m Death with the corrector Kou Patent applicant aPfT 〒log 5-1 Marunouchi-chome, Chiyoda-ku, Tokyo Company name ζ 4510) Japan Co., Ltd.
26-3-1) Osamu Katsu Shigeyo Address Address: 5-1 Marunouchi-chome, Chiyoda-ku, Tokyo, Hitachi, Ltd., 1 (3) Tel: 435-422
1. Subject of amendment Contents of amendment in the column of detailed explanation of the invention in the specification 1.) ≦, Nittomo 1゜+1) lUMIIE page 12, line 9 r+9o°" wo [90aJK Correction. Ru. (3) Page 12, line 12 “+90°, +180
°, +270'J are corrected to "90°, 180°, 270°". (4) On page 12, line 17, “+90°” is changed to “90°”.
°”. Above 47

Claims (1)

[Claims] In a two-head helical scan video tape recorder, the frequency four times the frequency of the chroma signal recorded on the tape is 5Nfx (N 1% number, fHI horizontal sync frequency), and y is equal to writing a converted chroma signal formed by a first head having a first azimuth angle; A chroma signal recording device characterized in that a converted chroma signal formed by a second head having a second azimuth angle is phase-inverted substantially every horizontal period and then written on a tape.