JPS628696A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording and reproducing device in which a burst signal is little deteriorated even in several dubbings by expanding the passing band of a chrominance component only in the burst period of the chrominance component. CONSTITUTION:A compound video signal inputted from an input terminal 1, the luminance signal of which is taken out at a luminance signal process circuit 2 and is FM-modulated, and is mixed with a low-pass conversion chrominance component ingredient at a mixer 7 and is recorded on a magnetic tape by a magnetic head 9. The chrominance component ingredient in the video signal is taken out at a BPF3 or a BPF32 and through a switch 33 and an ACC4, it is converted to a low-pass frequency by a frequency converter 5, and is band- limited at an LPF6 or an LPF38, and is inputted to the mixer 7 through a switch 39. By a burst gate pulse from a burst gate generating circuit 31, the switches 33 and 39 are controlled so as to select the BPF32 and the LPF38 of wide band in the burst period.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetic recording and reproducing apparatus such as a video tape recorder for recording and reproducing color video signals including carrier color signals.

Conventional technology Home video tape recorder (hereinafter abbreviated as VTR)
Conventionally, the color signal (carrier frequency fc!;s, saMl-1z) included in a composite video signal is converted to a low frequency/s
(for example, fs=s29KHz) and records, a so-called color under one-way system is used.

Figure 4 (2L), (b) is the - column;
L) is a main block diagram of the recording system, and ('b) is a main block diagram of the reproducing system. First, during recording, the color signal component (fc''=3.58MHz) included in the composite video signal is extracted by a band-pass filter (hereinafter abbreviated as B, P, and F) 3, and then A, C
, C (Automatic Chroma 1 level
Control ) 4 automatically adjusts the color signal level to a predetermined value.

Next, this is converted to a low frequency fS (for example, /s Milo 29Kl!Z) by a frequency converter 5, and after band-limiting by a low-pass filter (hereinafter abbreviated as P and F) 6, the luminance is It is mixed with the FM luminance signal component which is the output of the signal processing circuit 2 in a mixer 7. The mixed FM luminance signal component and low frequency color signal component are sent to a recording amplifier 8. The information is recorded on the magnetic tape via the magnetic head 9.

During reproduction, as shown in FIG. 4(b), the regenerative amplifier 1
From the reproduced signal amplified in step 1, low-range color signal components are extracted at L, P, and F13, and after automatically adjusted to a predetermined color signal level at A, C, and C4, frequency converter 15 extracts the low-range color signal components. IC
″=3, frequency converted to a color signal of 58 Mtlz.

At this time, the playback frequency fluctuation Δf is removed by using a signal multiplied from the horizontal synchronization signal (output signal of the horizontal synchronization separation circuit 20) of the playback luminance signal to remove the frequency change Δf due to changes in playback tape speed and jitter. (Reliba, edited by the Television Society, "Introduction to Home VTR" pp. 164-1)
71). AF for removing the above reproduction frequency fluctuation
G (Automatic Frequency Con
(trol) system, as well as APC (Automatic
The phase control system is represented as the chroma AFC, APC system 21 in FIG. 4('b).

By further passing the reproduced color signal from which the frequency change Δf has been removed by the frequency conversion system 15 to a crosstalk removal circuit consisting of a 1H delay line 16 and a mixer 17, and B, P, and F 18, Unnecessary components in the output of the reproduction frequency converter are removed and mixed with the demodulated luminance signal component in a mixer 19. The mixed demodulated signal is amplified by an output amplifier 22 and outputted as a composite video signal from an output terminal 23.

As mentioned above, in the color under one-type color signal recording method, the color signal is recorded at a frequency f lower than the 7M band of the luminance signal.
It is possible to effectively utilize the limited recording band by converting the luminance signal into s and recording it by superimposing it on the low carrier FM signal of the luminance signal. In addition, when converting the frequency of the low-range color signal during playback, it is possible to eliminate jitter by eliminating playback frequency fluctuations using the APC and AFC methods. This technology has been established as a
, PP, 28-36).

Problems to be Solved by the Invention However, in the above-mentioned color under type, in order to record the color signal by superimposing it on the luminance FM signal, the band of the color signal component is centered around 3.58MH7. I
It is necessary to limit the number of pixels to approximately 1z, which has the problem of deteriorating the burst signal during color signal reproduction.

In other words, when superimposing the luminance FM signal and the low-range color signal,
In order to prevent the lower side band components of the luminance FM signal from being mixed with the upper side band components of the low frequency chrominance signal,
) A low-pass filter (L, P, F) 6 and
The cutoff frequency of 13 is 1.2~ at the -3dB attenuation point.
1.5 MHz is selected. Usually, the bandpass filters 3 and 18 are also selected to have a center frequency of 3.58 MHz, iC-, +: 500 to 600 KllZ.

This band limitation of the chrominance signal causes deterioration of the high-frequency sideband components of the burst signal (the rising and falling edges of the envelope of the burst signal), resulting in an increase in noise when reproducing the chrominance signal.
c. It is having an adverse effect on the operation of the FC. The above-mentioned deterioration of the burst signal is noticeable during dubbing, and the envelope of the burst signal is rounded, resulting in color unevenness during playback.

SUMMARY OF THE INVENTION It is an object of the present invention to overcome the above-mentioned problems and to provide a magnetic recording/reproducing apparatus in which the passband width is widened only when a burst signal is used, and the burst signal does not deteriorate even after dubbing several times.

Means for Solving the Problems In order to solve the above-mentioned problems, the magnetic recording and reproducing apparatus of the present invention is a magnetic recording and reproducing apparatus that frequency-separates a carrier color signal, converts it into low frequency signals, and records the signals. A first LPF conventionally used to separate the gamut color signal component and the frequency modulated luminance component, a second LPF having a wider band than the first LPF, and the first LPF and the second LPF. A switch circuit that switches between the two LPFs and a second LPF during the burst period.
and a control circuit that controls the switch circuit so as to select the PF and select the first LPF during periods other than the burst period.

Effect of the Invention With the above-described configuration, the present invention widens the color signal pass band only during the burst period of the color signal, and even if dubbing is performed several times, there is little deterioration of the burst signal due to band limitation.
The color signal processing system PC9AFC operates stably, and reproduced color signals with less color unevenness than before can be obtained.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A magnetic recording and reproducing apparatus according to one embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a recording system according to an embodiment of the present invention.

In FIG. 1, 1 is an input terminal, 2 is a luminance signal processing circuit,
7 is a mixer for mixing the luminance signal component and the color signal component. As is well known, from the composite image (ψ signal) inputted from the input terminal 1, only the luminance signal is extracted by the luminance signal processing circuit 2, and then the AGO.

After luminance signal processing such as color:y 7'',
recorded on magnetic tape.

On the other hand, the color signal components in the composite video signal are the first B, P,
F3 or second B, P, and F32, and the outputs thereof can be switched by a switch 33. Here, the first B, P, and F3 are the same as the B, P, and F3 of the conventional example described above,
IC-3, ±500 to 600 around 58Ml-Iz
It has a KHz band. Also, the second B, P, F
32 is /c=3. ±700 K around ssMHz
Hz to IMI (wideband B, P, F having a band of z, which are switched and used by the switch 33 during the burst period (the operation of the switches 33 and 39 will be described later).The first B-P, F 3° or second B, P
, F32, the color signal components extracted at switch 33
, A, and C0C4, and is converted into a low frequency fs by the frequency converter 15 and the local oscillator 29. The low-pass converted low-pass color signal is the first glue, P, Fe, or
The signal is band-limited by the second signal P, 738, and mixed with the luminance FM signal by the mixer 7 via the switch 39. Here, the cutoff frequency of the first glue, P, and F6 is 1.2 to 1 at the -3 dB attenuation point, as described above.
In contrast, the cutoff frequency of the second glue, P, 738 is selected to be approximately 1.7 to 2.5 MHz, which is a wide band.

Switches 33, 39 are in the lower position during the burst period, i.e.
Broadband second B, P, F32 and second glue, P, F
During the burst period, the band of the color signal processing system is set to a wide band, and the burst signal is recorded with little deterioration.

Further, the switches 33 and 39 are controlled by the burst gate pulse which is the output of the burst gate generation circuit 31 [Fig.
C)], and switches 33 and 39 are connected to the lower side (broadband side) during the burst period [period ta in Figure 3 (C)], and to the upper side (normal band side) at other times. . Note that the burst gate pulse is a horizontal synchronizing pulse [FIG. 3(b)] which is the output of the horizontal period separation circuit 2o in FIG.
] Created by.

FIG. 2 is a block diagram of a reproduction system of PIJ, which is an embodiment of the present invention. In FIG. 2, 9 is a magnetic head, 11 is a regenerative amplifier,
12 is a luminance signal processing circuit, and 19 is a mixer for mixing the luminance signal component and the color signal component. A reproduction signal reproduced by the magnetic head 9 is amplified by a reproduction amplifier 11 and inputted to a luminance signal processing circuit 12. Luminance signal processing circuit 1
2, as is well known, after filtering the high frequency component from the reproduced signal and extracting the FM luminance signal component, it is subjected to luminance signal processing such as demodulation, de-emphasis, and noise cancellation, and then sent to the mixer 19. The video signal is mixed with the color signal component at the output amplifier 22 and output as a composite video signal.

On the other hand, the low-frequency color signal component in the reproduced signal (fs=
s2sKIIz) is the third glue, P, F 13, or
taken out by the fourth glue, P, F41, through the switch 421, G, G4, the first frequency converter 1
5, carrier frequency fc=3. The frequency is converted into a saMIIz color signal. The frequency-converted color signal is 1
Unnecessary components are removed by a crosstalk removal circuit (<C type filter) composed of an H delay line 16 and a mixer 17, and a third B, P, 718, and mixed with the luminance signal by a mixer 19 through a switch 51. .

Also, like the recording system described above, L, P, F and B, P,
F is a normal band filter (third glue, P, Fl 3
and the third B, P, F1a) and the broadband filter (the fourth glue, P, F41 and the fourth B, P, F2O) are switched by switches 42 and 51, and during the burst generation period, the color signal is The configuration is such that the playback system has a wide band. That is, referring to FIG. 4, during the burst generation period [period tB in FIG. 3 (0)], the burst gate pulse [FIG. 3 (C)] is output from the burst gate generation circuit 31, and as a result, Switches 42 and 51 are switched to the lower side (broadband side), and the fourth glue, P, F41, and the fourth
B, P, and Fe0 are selected. The fourth glue, P, F41 is the second glue used in Figure 1, P, F.
Use the same one as 3a (cutoff frequency is 1.7 to 2.5 Mll at 13 dB attenuation point, ! Nori, P, F) or a slightly narrower band Nori, P, F, and usually The third glue used during playback (periods other than the burst generation period), P, F 13 (Cutoff frequency is 1.0 to 1.6 M at -3 dB attenuation point) Broadband compared to -17 glue, P, F) The mold paste is P and F. Also, the fourth B, P
, F2O similarly, the second B, P, F32 used in FIG.
Same as (117 to ±700 centered on 3,58MHz)
~1M1] B, PJ) having a band of B having a band of 1-Iz from ±500 to 600,
B, P, F are broadband types compared to B, P, F).

Also, in the color signal reproduction system, a multiplier circuit 44 and a phase shift circuit 45 are provided.
The system consisting of the voltage controlled oscillator 46, phase comparator 48, burst removal circuit 49, and second frequency converter 43 is similar to the chroma AFC and APC system 2 in FIG. 4(b).
As already known, this system corresponds to No. 1, and performs processes such as removal of reproduction frequency fluctuation Δf (jitter component) and phase shift.

In this embodiment, as can be seen from FIGS. 3(a) and (C), only the burst period ta is broadband type B, P, F, and P
, F, and the luminance signal level during that period is the pedestal level (PJ in Fig. 3 (a)).
Yes, the lower [+11 band component in the luminance FM component is wide to the low frequency range. Therefore, even if the pass band of the low-frequency color signal is widened by this period, there is almost no mixing of the luminance FM component. However, if the cutoff frequencies of the second L 2 , P 2 , F 6 and the fourth L 2 , P 2 , F 41 are made too wide, noise components will increase, so care must be taken to this point.

In addition, in FIGS. 1 and 2 of this embodiment, the second B, P, F 32 of the recording system and the fourth B, P, F 60 of the reproduction system
Although they are presented as separate things, cost reduction,
In order to reduce weight, it is also possible to use it for both recording and playback. Similarly, the second L-P, F 38 and the fourth glue, P
, F41 can also be used. Furthermore, if the bands of the first B, P, F 3 and the third B, P, F 18 are sufficiently wide, the second B, P, F 32 and,
It can also be used as a substitute for the fourth B, PJ 50.

In addition, in FIG. 2, the fourth B, P, F 60 and the first
However, when there is a large amount of crosstalk from adjacent tracks, such as during long-term recording, the crosstalk removal circuit (1H delay line 1
6 and a mixer 17), and the output of the mixer 17, which is the output thereof, may be guided to the fourth B, p, y6o.

Effects of the Invention As described above, according to the present invention, by widening the pass band during the burst period, deterioration of the burst signal can be minimized, and the operation of the color signal processing system becomes stable. Therefore, excellent effects such as color reproduction with less color unevenness can be obtained even during dubbing.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the main part of the recording system of a magnetic recording and reproducing apparatus according to an embodiment of the present invention, FIG. 2 is a block diagram of the main part of the reproducing system of the same embodiment, and FIG. Signal waveform diagrams for explaining the operation of one embodiment, Fig. 4(a), (
b) is a professional diagram of the main parts of a conventional recording system and reproduction system. 3...First BPF, 32...Second BP
F. 33... Switch circuit, 6... First LPF
, 38... Second LPF 139... Switch circuit, 31... Burst gate generation circuit.

Claims (3)

[Claims] (1) A magnetic recording and reproducing device that frequency-separates a carrier color signal from a composite video signal using a frequency separation means, performs low-frequency conversion, and records and reproduces the signal. a first low-pass filter for limiting;
a second low-pass filter having a wider band than the first low-pass filter; a switch circuit for switching between the first low-pass filter and the second low-pass filter; and a burst period. and a control circuit that controls the switch circuit to select the second low-pass filter and select the first low-pass filter during periods other than the burst period. magnetic recording and reproducing device. (2) A magnetic recording and reproducing device that frequency-separates a carrier color signal from a composite video signal using a frequency separation means and then performs low-frequency conversion to record and reproduce the signal, and when recording, the band of the low-frequency color signal component is a first low-pass filter for limiting, a second low-pass filter having a wider band than the first low-pass filter, and a first low-pass filter and a second low-pass filter; a first switch circuit that selects the second low-pass filter during a burst period and selects the first low-pass filter during a period other than the burst period; a recording system comprising a first control circuit for controlling the first switch circuit; and a third low-pass filter for separating a low-pass color signal component and a frequency-modulated luminance component during playback. and a fourth low-pass filter having a wider band than the third low-pass filter, and a second switch for switching between the third low-pass filter and the fourth low-pass filter. circuit and
a second control circuit that controls the second switch circuit to select the fourth low-pass filter during the burst period and select the third low-pass filter during periods other than the burst period; 1. A magnetic recording and reproducing device comprising a reproducing system comprising: (3) A magnetic recording and reproducing device that frequency-separates a carrier color signal from a composite video signal using a frequency separation means and then performs low frequency conversion to record and reproduce the signal, and when recording, the color signal component is extracted from the composite video signal. a first band-pass filter for extracting the signal; a second band-pass filter having a wider band than the first band-pass filter; and the first band-pass filter and the second band-pass filter. The first to switch between
a first low-pass filter for limiting the band of the low-pass color signal component; a second low-pass filter having a wider band than the first low-pass filter; a second switch circuit that switches between the first low-pass filter and the second low-pass filter; and a second switch circuit that switches between the first low-pass filter and the second low-pass filter; the first one except for the burst period.
a recording system comprising a control circuit for controlling the first switch circuit and the second switch circuit so as to select a band-pass filter and a first low-pass filter; a third low-pass filter for separating a signal component and a frequency-modulated luminance component; a fourth low-pass filter having a wider band than the third low-pass filter; a third switch circuit for switching between a band pass filter and a fourth low pass filter; a third band pass filter for limiting the band of a color signal component; and the third band pass filter. a fourth band-pass filter having a wider band than the second band-pass filter; a fourth switch circuit for switching between the third band-pass filter and the fourth band-pass filter; the second switch circuit and the fourth band-pass filter, and select the third low-pass filter and the third band-pass filter during periods other than the burst period. 1. A magnetic recording and reproducing device comprising a reproducing system including a control circuit for controlling a switch circuit.