JPS5849072B2 - Carrier color signal processing circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION When recording a luminance signal (monochrome video signal) on a magnetic tape or the like, the following method can significantly increase the recording amount.

That is, as shown in FIG. 1, the rotating magnetic hesode IA,
The IBs are spaced 1800 angularly apart from each other and
The magnetic tape 2 is rotated at a speed of approximately 180 degrees, and the magnetic tape 2 is run obliquely along the tape guide drum 3 over an angular range of approximately 180 degrees.

In this case, as shown in FIG. 2, the operating gap ga. The width direction of gb, that is, the azimuth angle is different from each other.

Then, the luminance signal is converted to an FM signal that occupies the Takagi side of the recordable band, and this FM luminance signal is transferred to the Hesodo IA,
Supply to IB.

Therefore, according to such a recording method, as shown in FIG. 3, one field of the luminance signal is recorded obliquely on the tape 2 as one magnetic track 4. Since the corners are different from each other,
Correspondingly, the azimuth angles of the trunks 4A and 4B are different from each other.

Let us now consider the case where such a recording pattern is reproduced by heads IA and 1B.

Then, trunks 4A and 4B are connected to trunks IA and IB.
The FM brightness signal is reproduced from head 1, but in this case, head 1
The azimuth angle is different between the person and the track 4B, and the azimuth angle is also different between the head 1B and the track 4A.
Since the FM luminance signal is recorded on the Takagi side, there is no crosstalk between tracks due to azimuth loss.
M luminance signal can be reproduced.

In this way, there is no inter-track crosstalk in the reproduced FM luminance signal, so when recording, the third
As shown in the figure, there is no guard band between adjacent trucks 4A, 4B, or adjacent trunks 4A.
The FM luminance signal can be recorded so that 4B partially overlaps, and therefore the amount of recording can be greatly increased.

By the way, in order to magnetically record a PAL color video signal, generally the luminance signal is converted to an FM luminance signal, the carrier color signal is frequency-converted to the low frequency side of the FM luminance signal, and the frequency-converted carrier color signal and , and the FM luminance signal are magnetically recorded.

Therefore, when recording a PAL color video signal using the recording method shown in FIGS. 1 to 3, it is conceivable to frequency-convert the carrier color signal to a low frequency band, add it to the FM luminance signal, and record the signal simultaneously.

However, simply recording in this way will not cause inter-track crosstalk for the luminance signal due to the azimuth loss of the reproducing head during playback, but since the carrier color signal occupies a low frequency band, the carrier color of the adjacent magnetic track will not occur. The azimuth loss of the reproducing head is small with respect to the signal, so inter-trunk crosstalk occurs in the carrier color signal.

Taking these points into consideration, the present invention significantly increases the recording amount of PAL color video signals, and also prevents inter-track crosstalk from occurring in the carrier color signal during playback.
Furthermore, it is an attempt to solve the problems that arise with this high-density recording.

Therefore, in the present invention, at the time of recording, the luminance signal is converted to an FM signal so as to occupy the Takagi side of the recordable band,
Further, the carrier color signal is frequency-converted to the lower frequency side of the FM luminance signal, and a multiplexed signal of the carrier color signal subjected to the lower frequency conversion and the FM luminance signal is recorded, and in this case, the carrier color signal is The frequencies of the tracks 4A and 4B are set so that the carrier color signals are interleaved.

That is, as shown in the frequency spectrum of the recording signal in FIG.
Figure A), an FM luminance signal S and a carrier color signal S with carrier frequency fa.

The multiplexed signal Sa is sent to track 4A by one head.
while the remaining every other field period T
b (FIG. 4B), an FM luminance signal S, and a carrier color signal S having a carrier frequency fb.

The multiplexed signal sb is sent to track 4 by head 1B.
In this case, it is recorded as B.

Further, in this case, in the present invention, an AFC circuit is provided,
As a result, during recording, an alternating signal for converting the carrier frequency of the carrier color signal Sc to fa is formed, and the carrier frequency of the carrier color signal Sc is changed by this alternating signal and another alternating signal from the AFC circuit. It forms an alternating signal for conversion to fb.

Let's explain one example below.

In FIG. 5, the PAL color video signal is input to input terminal 1.
1 to a low-pass filter 2 where a luminance signal is extracted, this luminance signal is supplied to an FM modulation circuit 13 to form an FM luminance signal Sy, and this signal Sy is supplied to an adder circuit 14.

Further, an AFC circuit 20 is provided, and in this example, an alternating signal having a frequency of 44fh and an alternating signal having a frequency fh are formed in synchronization with the horizontal synchronizing pulse.

That is, an oscillation signal So having a free running frequency of 44fh is generated in the variable frequency oscillation circuit 21, and this signal So is supplied to the frequency dividing circuit 22 to generate a rectangular wave signal sh having a frequency fh.
This signal sh is supplied to the phase comparison circuit 23, and the color video signal from the terminal 11 is supplied to the synchronization separation circuit 24 to extract the horizontal synchronization pulse. Supplied.

In this manner, the comparator circuit 23 compares the phases of the signal sh and the horizontal synchronizing pulse, extracts a DC signal with a level corresponding to their phase difference, and supplies this DC signal to the variable frequency oscillation circuit 21 as its control signal.

Therefore, in a steady state, the signal St and the horizontal synchronization Hals are in a synchronized state, so the signal sh from the frequency divider circuit 22 has the frequency fh of the horizontal synchronization pulse, and is synchronized with this signal. The signal So, which is the signal before sh is frequency-divided, has a frequency of 44fh and is synchronized with the horizontal synchronizing pulse.

In this way, the AFC circuit 20 outputs a signal So with a frequency of 44fh and a signal sh with a frequency fh in synchronization with the horizontal synchronizing pulse.

Furthermore, based on these signals So and Sh, the carrier color signal Sc is
The carrier frequency of is frequency-converted to fa or f.

That is, a fixed oscillation circuit 31 is provided, and from this the frequency is (f, +7fh) (f5: carrier frequency of the carrier color signal, 4).

43MHz) is supplied to the frequency converter 32, and the signal S from the variable frequency oscillation circuit 21 is supplied to the frequency converter 32.
o is supplied to the converter 32 and made into a signal Sf with a frequency of It is supplied to the other input contact of the switch circuit 33.

Further, a switching signal forming circuit 100 (details will be described later) is provided, and as shown in FIG. Sw is formed, and this signal Sw is supplied to the switch circuit 33 as its control signal. For example, when the signal Sw is rising, the switch circuit 33 is switched to the state shown in the figure, and when the signal Sw is falling, the switch circuit 33 is switched to the state shown in the figure. , the state is switched to the opposite state as shown in the figure.

Therefore, if the output signal of the switch circuit 33 is Ss, the switch circuit 33 is switched to the state shown in the figure during the field period Ta, so the signal Ss is equal to the output signal Sf of the converter 32, and therefore, as shown in FIG. As shown in , during the field period Ta, the frequency of the signal Ss is (f8+
fa).

On the other hand, during the field period Tb, the signal Sf and the signal Sf are alternately taken out from the switch port path 33 every two horizontal periods, but this is because, as shown in FIG. A square wave signal Sr that inverts between +1 and -1
This is equivalent to balanced modulation of the signal Sf, and therefore, during the field period Tb, the output signal Ss of the switch circuit 33
is a balanced modulated signal by signal Sr.

And if we think about this signal, this signal is the signal S
Since it is a signal obtained by balanced modulation of f with signal Sr, its frequency spectrum is as shown in FIG.
(2) +fa) is the carrier frequency, and from this, there are sideband components at frequency positions that are odd multiples of 7fh.

However, in this case, It can be expressed as

However, in this case, as will be described later, the m base O sideband components of the modulated signal Ss have no meaning, so these sideband components are ignored.

Therefore, during the field period Tb, as shown in FIG. 8H, the frequency of the signal Ss is (f8+fb).

In this way, from the switch circuit 33, the field period Ta
, the frequency is (f8+fa) and the field period T
A signal Ss having a frequency (f5+fb) is taken out at b.

Then, this signal Ss is supplied to the frequency converter 1, and the color video signal from the terminal 11 is supplied to the high-pass filter 16 to extract the carrier color signal Sc (carrier frequency is f8). is supplied to the converter 7 and frequency-converted by the signal Ss, and as shown in FIG. 8, the carrier frequency is f during the field period Ta, and the carrier frequency is f during the field period Tb.
It is assumed that the carrier color signal ba is the carrier color signal Sc.

In this case, during the field period Tb, the signal Ss includes a signal component with a frequency of (f5+f5) as well as a signal component with a frequency of (f5+f5).
Since it also includes the signal component sb of ff ±m-fh) (m to O), the carrier color signal Sc is also low-frequency converted by this signal component of m to 0, and the low-frequency conversion The converted carrier color signal is added to the original carrier color signal Sc which has been low-pass converted.

However, in this case, the signal components m to O are sideband components balanced modulated by the harmonics of the signal Sr,
Since the level of the harmonics of the signal Sr is low, the level of the signal components m to O is also low.

Furthermore, since the carrier color signal Sc that has not been low-band-converted is distributed for each frequency fh with that frequency as the center, the carrier color signal that has been low-band-converted by the signal components from m to 0 has its original low frequency. This will exactly overlap the carrier color signal Sc that has been subjected to area conversion.

Therefore, for these reasons, the signal component m to 0 of the signal Ss can be ignored, and it can be considered that the frequency of the signal Ss is (fs+fb) during the field period Tb.

In this way, the carrier color signal Sc with the carrier frequency fa or f5 is taken out from the converter 7, and this carrier color signal Sc is supplied to the adder circuit 14, and the field period Ta
As shown in FIG. 4A, the carrier color signal Sc with the carrier frequency fa and the FM luminance signal Sy are multiplexed as a signal Sa, and during the field period Tb, as shown in FIG. 4B, A carrier color signal Sc with a frequency fb and an FM luminance signal Sy
A multiplexed signal sb is obtained.

This signal Sa or sb is then sent to the head LA through the recording amplifier 15. 1B, the signal Sa is recorded on the tape 2 as track 4A, as shown in FIG.
Signal sb is recorded as trunk 4B.

In this case, a pulse generating means 41 is provided in the portion 5 that rotates together with the hemsodes IA and IB, such as the rotating shaft of the hesodes IA and IB, so that a pulse of 30 Hz is extracted every rotation of the heads IA and IB. This pulse is supplied to the servo circuit 42 and the hesode IA. The rotational phase of IB is controlled to have a constant relationship with respect to the signals Sa and Sb, resulting in the magnetization pattern shown in FIG.

Further, in this case, the switching signal forming circuit 100 is configured as shown in FIG. 6, for example.

That is, as shown in FIG. 8A from the servo circuit 42,
Field period Ta. A rectangular wave signal Sg that is inverted slightly before Tb is taken out, and this signal Sg is sent to the NAND circuit 10.
At the same time, the color video signal from the terminal 11 is also supplied to the synchronization separation circuit 102, and as shown in FIG. 8B, the vertical synchronization pulse Pv is taken out.
is supplied to the NAND circuit 101, and from the NAND circuit 101, a pulse Pa is taken out for each pulse Pv in the field period Ta, as shown in FIG. The signal is supplied to a NAND circuit 111 constituting an S flipflop circuit 110.

Further, the signal Sg from the servo circuit 42 is transmitted to the inverter 10.
4 to the NAND circuit 103, and the pulse Pv from the synchronous separation circuit 102 is also supplied to the NAND circuit 103, and from the NAND circuit 103, as shown in FIG. ,
Pulse pb is taken out, and this pulse Pb is supplied to a NAND circuit 112 constituting a Frisopflosop circuit 110.

Therefore, from the flip-flop circuit 110, for example, the eighth
As shown in FIG. E, a rectangular wave signal Sv that falls during the field period Ta and rises during the field period Tb is extracted.

Further, transistors 121 and 122 constitute an unstable multi-by-break 120 that oscillates at a substantially horizontal frequency fh.

Then, the signal sh from the AFC circuit 20 or the differentiating circuit 10
The oscillation frequency of the multi-by break 120 is made equal to the frequency fh of the signal sh, and the horizontal synchronizing pulse from the sync separation circuit 24 is supplied to the multi-by break 120 through the transistor 123. The phase of the oscillating signal is locked to the horizontal sync pulse.

In this way, an oscillation signal of the same frequency fh is extracted from the multi-by-break 120 in synchronization with the horizontal synchronizing pulse.

This oscillation signal is supplied to the NAND circuits 131 and 132 forming the Frithop flop circuit 130 through the differentiating circuit 106 and the inverter 10γ, and the signal Sv from the Frithop flop circuit 110 is supplied to the NAND circuit 13
1, and from the NAND circuit 131, as shown in FIG. 8F, it rises during the field period Ta,
In the field period Tb, a signal Sx that is inverted every 100 periods is taken out.

This signal Sx is supplied to NAND circuits 141 and 142 constituting the Frithop flop circuit 140, and the signal Sv from the Frithop flop circuit 110 is supplied to the NAND circuit 141.
As shown in FIG. G, a switching signal Sw is taken out which is high during the field period Ta and inverted every 2,000 periods during the field period Tb.

Then, this signal Sw is applied to the switch circuit 3 as described above.
3 as a control signal to switch the switch circuit 33.

In this way, a PAL color video signal is recorded on tape 2, but when track 4 recorded in this way is played back with heads IA and IB, as mentioned above, FM
Since the luminance signal sy occupies a high frequency band, it can be extracted without causing inter-track crosstalk due to azimuth loss.

However, since the carrier color signal Sc occupies a low frequency band, it cannot be expected to reduce inter-track crosstalk due to azimuth loss like the FM luminance signal Sy. Therefore, during the field period Ta, as shown in FIG. , trunk 4
At the same time that the carrier color signal Sc of the carrier frequency fa is reproduced from the track A, the carrier color signal of the carrier frequency fb (shown by the dotted line) is reproduced from the adjacent track 4B as a crosstalk component Sk, and in the field period Tb, As shown in FIG. 11B, at the same time that the carrier color signal Sc of the carrier frequency fb is reproduced from the track 4B, the carrier color signal (shown by the dotted line) of the carrier frequency fa from the adjacent track 4A is reproduced as a crosstalk component Sk. It will be played.

However, in this case, between adjacent tracks 4A and 4B,
The carrier frequencies of the carrier color signal Sc are fa and fb, and the carrier color signals Sc are interleaved with each other, so the crosstalk component Sk from the adjacent track is interleaved with respect to the original carrier color signal Sc. .

If the crosstalk component Sk is interleaved, the crosstalk component Sk can be removed by supplying the carrier color signal Sc to a C-shaped comb filter, thereby obtaining a carrier color signal Sc free of inter-trunk crosstalk. be able to.

In the reproduction system, the color video signal is reproduced by paying attention to such points, and in this case, an AFC circuit is also provided.

Let's explain one example below.

In FIG.
Tracking servo is performed for track 4 of heads IA and IB so that the relationship between fB and tracks 4A and 4B is the same as during recording, and during the field period Ta, one head performs multiplexed signal Sa and crosstalk. Component S
During the field period Tb, the head 1B reproduces the multiplexed signal sb and the crosstalk Sk.

Then, the reproduction signals from the hesodes IA and IB are supplied to the high-pass filter 52 through the reproduction amplifier 51 and F
The M luminance signal Sy is taken out, and this signal Sy is supplied to the demodulation circuit 54 through the limiter 53 to demodulate the luminance signal, and this luminance signal is supplied to the addition circuit 55.

Further, the luminance signal from the demodulation circuit 54 is transmitted to the sync separation circuit 61.
A horizontal synchronizing pulse is extracted from the horizontal synchronizing pulse, and this synchronizing pulse is supplied to the AFC circuit 62.

This AFC circuit 62 has the same configuration as the AFC circuit 20 in FIG. An alternating signal So is extracted.

From these signals Sh and So, an alternating signal S is formed for converting the carrier frequencies fa and fb of the carrier color signal Sc to the original carrier frequency f5.

That is, a signal So from the AFC circuit 62 is supplied to the frequency converter 63, and an oscillation signal of frequency (r8-7 rh) is supplied to the converter 6 from a variable frequency oscillation circuit 84 of the APC circuit 80, which will be described later.
3, an alternating signal Sf with a frequency 1 of {44fh+(f8-ifh)}=(r8+ra) is taken out from the converter 63, and this signal Sf is supplied to one input contact of the Swissochi circuit 64. At the same time, the inverter 65 inverts the phase of the signal Sf, which is then supplied to the other input contact of the switch circuit 64.

Further, a switching signal forming circuit 200 similar to the switching signal forming circuit 100 in FIG.
A signal sh is supplied from 2, a signal Sg is supplied from a servo circuit 71, and a luminance signal from a demodulation circuit 54 is supplied to a synchronization separation circuit 72 to generate a vertical synchronization pulse P.
v is extracted and this pulse Pv is supplied to the forming circuit 200.

In this way, in the forming circuit 200, a switching signal Sw is formed as in the case of recording, and this symbol Sw is supplied to the switching circuit 64 as its control signal.

Therefore, as in the case of recording, the switch circuit 64 outputs a frequency fa during the field period Ta, as shown in FIG. 8H.
Therefore, during the field period Tb, the alternating signal S becomes fb.
s is retrieved.

The carrier color signal Sc is frequency-converted to the original carrier frequency by this signal Ss.

That is, the signal from the amplifier 51 is supplied to the low-pass filter 57, and as shown in FIG. In the field period Tb, a carrier color signal Sc with a carrier frequency of fb and a crosstalk component S with a carrier frequency of fa are extracted.
k is taken out.

Then, a carrier color signal S having this crosstalk component Sk
c is supplied to the frequency converter 58, and at the same time, a signal Ss is supplied to the converter 58 from the switch circuit 64.

Therefore, in the converter 58, as shown in FIG. 8K, the carrier frequency of the carrier color signal Sc is set to the original frequency f5 in any field period, and the carrier frequency of the crosstalk component 5k is set to the original frequency f5 in the field period Ta. is set to 1 (f8-Hfh), and the field period 1 Tb is set to (f5+Zfh).

And the crosstalk component Sk from this converter 58
The carrier color signal Sc having the following values is supplied to a C-comb filter 59.

In this case, this filter 59 is constituted by a delay circuit that delays the input signal by two horizontal periods, and a subtraction circuit that performs subtraction between the output signal of this delay circuit and the input signal.

At this time, while the carrier frequency of the carrier color signal Sc is f8, the carrier frequency of the crosstalk component Sk1 is (f8-Hfh) or (f8+■-zfh), and the crosstalk component Sk is the carrier frequency of the carrier color signal S
Since it is interleaved with respect to c, filter 5
9, the crosstalk component Sk is removed and only the carrier color signal Sc is extracted.

Then, this extracted carrier color signal Sc is added to the adder circuit 55.
and is added to the luminance signal from the demodulation circuit 54,
Therefore, the original PAL color video signal is taken out at the terminal 56.

In this case, the APC circuit 80 is provided to output the card conveyance color signal S.
The reference phase of c is stabilized.

That is, a fixed oscillation circuit 81 is provided, from which an oscillation signal with a frequency f is supplied to a phase comparator circuit 82, and a carrier color signal Sc from a filter 59 is supplied to a burst gate circuit 83 to generate a burst signal. is taken out, this burst signal is supplied to a comparison circuit 82, where it is phase-compared with the oscillation signal from the oscillation circuit 81, and the comparison output is supplied to the variable frequency oscillation circuit 84 as its control signal.

In this way, the reference phase of the carrier color signal Sc is stabilized.

Thus, according to the present invention, as shown in FIG. 3, for example,
Even if color video signals are recorded so that there is no guard band between adjacent tracks 4A and 4B, or so that they partially overlap, crosstalk between trunks will not occur, so record in this way. This allows the recording amount to be significantly increased.

Further, since all the carrier color signals Sc are recorded and reproduced, the S/N of the reproduced carrier color signals Sc is good, and a clear color image can be reproduced.

Furthermore, during recording, two oscillation circuits are generally required to convert the carrier frequency of the carrier color signal Sc to fa or fb, which results in a complicated configuration and problems such as interference between the two oscillation circuits. However, in the present invention, only one oscillation circuit is required, so the configuration does not become complicated and signal interference does not occur.

Similarly, in the reproduction system, the carrier frequency of the carrier color signal Sc is set to f.
One oscillation circuit is sufficient for converting the signal to 8, and from this point of view, there is no need for complexity or signal interference.

Further, in the present invention, during recording, the signal Sw is obtained in the forming circuit 100 by the signal sh from the AFC circuit 20, and even if noise is included in the horizontal synchronizing pulse, the noise is removed from the signal by the flywheel effect of the AFC circuit 20. sh
Therefore, the correct signal Sw can always be obtained, and therefore the carrier frequency of the carrier color signal Sc can be reliably converted to fb during the field period Tb.

The same holds true during reproduction, and the forming circuit 200 uses the signal sh from the AFC circuit 62 to generate the carrier color signal S during the field period Tb.
The carrier frequency of c can also be reliably converted to f.

Further, since the signal Sg from the servo circuit 42.71 is used to ensure that the signal Sw always rises during the field period Ta, this operation is reliable.

Note that in the above description, the carrier frequency of the carrier color signal Sc is f
When converting from 8 to fa or fb and from fa or f5 to f5 V'f, the frequency of the conversion signal Ss is changed between field periods Ta and Tb by a switch circuit 33.64 and an inverter 34.65. ,
(f8+fa) and (f8+fb), but if the frequency of this signal Ss is (f5+fa), the carrier color signal S
While converting the frequency of c, the carrier color signal Sc is
Similar frequency conversion can be performed by switching and extracting the signal Ss using the switch circuits 33, 64, inverters 34, 65, and the signal Sw.

For example, when recording or reproducing an NTSC color video signal, the signal Sw may be inverted every horizontal period in the field period Tb.

Furthermore, the present invention can be applied to the case where a color video signal is recorded on a magnetic sheet or the like.

[Brief explanation of the drawing]

Figures 1 to 4 are diagrams for explaining the present invention, Figure 5 is a system diagram of an example of the present invention, Figure 6 is a system diagram of a part of the system, and Figure 7 is an example of a regeneration system. The system diagrams of FIGS. 8 to 11 are diagrams for explaining them. 13 is an FM modulation circuit, 17, 32, 58, and 63 are frequency converters, 20 and 62 are AFC circuits, 59 is a comb filter, 80 is an APC circuit, and 100 and 200 are switching signal forming circuits.

Claims (1)

[Claims] 1. Provided in a recording device that converts the frequency of a carrier color signal and records it, supplies a horizontal synchronizing pulse obtained from a luminance signal to an AFC circuit, and from this AFAFC circuit transmits mutually different frequencies synchronized with the horizontal synchronizing pulse. Different first and second signals are obtained, a conversion signal for frequency converting the carrier color signal is formed based on the first signal, and a phase control circuit is provided in the signal system of the conversion signal to perform frequency conversion. The carrier color signal processing circuit is configured to control the phase control circuit based on the second signal so that the carrier color signals obtained by the color signals are frequency interleaved in adjacent trunks.