JPS5850077B2 - SECAM video signal recording/playback device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording and reproducing apparatus for SECAM video signals.

In a magnetic recording and reproducing device for SECAM video signals (hereinafter referred to as "SECAM signals"), as an effective means for compressing the band of recorded signals and improving recording density,
There is a method in which the frequency of the carrier color signal is lowered during recording and frequency multiplied during reproduction.

The present invention is characterized by a means for frequency multiplication of the reproduction carrier color signal during reproduction in the above-mentioned system, and the above-mentioned recording and reproduction system will be briefly explained below.

FIG. 1 is a block diagram showing the recording system of this system, and FIG. 2 is a block diagram showing the reproducing system.

In Fig. 1, G is the input terminal of the SECAM signal to be recorded, 2 is the low-band p-wave generator, 3 is the FM modulator, 5 is the band-pass filter, 6 is the frequency down-converter, and 4 is the synthesizer. , 7 is a magnetic head, 8
is a magnetic recording medium.

The video signal applied to the input terminal 1 is applied to the low frequency transducer 2 and the low frequency transducer 5.

The luminance component is extracted by the low frequency filter 2, and the FM modulator 3 extracts the luminance component.
The signal is M-modulated and applied to the synthesizer 4.

On the other hand, the carrier color signal component extracted by the band filter 5 is frequency-downgraded by a frequency downgrader 6 and then applied to a synthesizer 4.

Both signals are combined by a combiner 4 and recorded on a magnetic recording medium 8 via a magnetic head 7.

FIG. 2 shows the reproduction system, in which 9 is a magnetic recording medium, 10 is a magnetic head, 11 is a high-frequency waver, 12 is an FM demodulator, 1
4 is a low frequency wave transducer, 15 is a frequency multiplier, 13 is a synthesizer,
16 is an output terminal.

Information on the magnetic recording medium 9 is added to the high frequency transducer 11 and the low frequency transducer 14 via the magnetic head 10, and the information is added to the high frequency transducer 11 and the low frequency transducer 14.
1, the luminance signal component is extracted, and the FM demodulator 12 extracts the luminance signal component.
It is demodulated and applied to the synthesizer 13.

On the other hand, the carrier color signal component extracted by the low-pass p-wave filter 14 is frequency-multiplied by the original frequency 1 by the frequency multiplier 15 and then added to the synthesizer 13.

The synthesizer 13 combines both signals and appears at the output terminal 16 as a reproduced SECAM signal.

Incidentally, the frequency spectrum diagram in FIGS. 1 and 2 is shown in FIG. 3.

Figure 3A shows the spectrum of the SFCAM signal applied to the input terminal 1, where 18 is the luminance component, 19 is the carrier part of the carrier color signal component, 20 is the sideband part, and the end is the spectrum of the output signal of the synthesizer 4. 24 is a signal FM modulated with a luminance component, 22 is a carrier portion of a frequency-downgraded carrier color signal, and 23 is a sideband portion.

Note that the horizontal axis indicates frequency, and the vertical axis indicates level. As is clear from FIG. 3, the carrier shift width of the carrier color signal is reduced and the band is compressed and recorded.

In such a system, the frequency of the carrier color signal must be multiplied and inversely converted to a predetermined band during reproduction.

Therefore, a commonly considered method is to distort the reproduced carrier color signal and depict its harmonics using a filter.

Figure 4 shows the spectrum in this case.

In FIG. 4, 25 is the fundamental wave component of the reproduced carrier color signal, 2
6 is a harmonic component caused by distortion, and 27 is a frequency characteristic of the bandpass filter.

That is, frequency multiplication is performed by distorting the carrier color signal and extracting only its harmonics.

However, in such a method, the level of the fundamental wave component is low, and this component inevitably remains, and on the other hand, the efficiency is not good.

Moreover, various unnecessary components may be generated depending on the linearity of the recycled yarn.

SUMMARY OF THE INVENTION Therefore, the present invention provides a frequency multiplier that eliminates the above-mentioned drawbacks and has extremely low fundamental wave components and unnecessary components.

An embodiment of the present invention will be described below.

FIG. 5 is a block diagram showing one embodiment of the present invention.

In FIG. 5, 28 is the input terminal for the signal to be multiplied, and 29
is a multiplier, and 30 is an output terminal.

That is, the reproduced carrier color signal to be frequency multiplied is applied to both input terminals of the multiplier 29.

Therefore, the signal applied to the input terminal 28 is f i (t
), then the output signal fo(t) of the multiplier 29 becomes: If only the vibration term is taken out, it becomes a signal with twice the frequency, and no fundamental wave component is generated at all.

Next, regarding the multiplier 29, there are various ways of configuring it.

For example, a function generator constituted by an operational amplifier, a ring modulator, a balanced modulator, etc. can be considered.

Therefore, a balanced modulator is shown in FIG. 6 as an example.

In FIG. 6, 31 is a power supply terminal, 35 and 36 are input terminals, 37 and 38 are output terminals, 32, 33 and 34 are transistors, 40 to 44 are resistors, and 39 is a constant voltage source.

This is a well-known balanced modulator, in which the product of the signal applied to input terminal 35 and the signal applied to input terminal 36 appears at output terminal 37.38.

Naturally, the configuration shown in Fig. 5 can only perform double multiplication, so it is sufficient to cascade a predetermined stage of multipliers depending on the multiplication number, or to set an arbitrary multiplication number depending on how each manual signal is combined. Is possible.

Another effective method is to distort at least one of the input signals input to the multiplier shown in Figure 5 by 1 to generate a spectrum that is an integer multiple of the fundamental wave. It is also possible to create a multiplier dog.

Of course, there is no need to add weight, just input it into the multiplier at a level higher than the rated level.

As described above, according to the present invention, it is possible to construct a frequency multiplier with good multiplication efficiency and extremely low fundamental wave components and unnecessary components, and to use SECAM-based magnetic recording with good carrier color signal spectrum inverse conversion characteristics. It becomes possible to configure the playback device.

[Brief explanation of the drawing]

Figures 1 and 2 are block diagrams of a magnetic recording and reproducing device for SECAM video signals that record and reproduce by lowering the carrier color signal frequency. FIG. 4 is a spectrum diagram of a conventional example of a frequency multiplier, FIG. 5 is a block diagram of essential parts showing an embodiment of the present invention, and FIG.
The figure is a circuit diagram showing an example of the configuration of a hanger.

Claims (1)

[Scope of Claims] 1. The frequency of the carrier color signal of a SECAM video signal to be recorded is stepped down and recorded, and during playback, the frequency is multiplied by the reproduced carrier color signal whose frequency has been stepped down to return to the original frequency. A recording and reproducing device for S E CAM video signals. 2. The frequency of the carrier color signal of the SECAM video signal to be recorded is stepped down and recorded, and during playback, the reproduced carrier color signal whose frequency has been lowered and the signal obtained by superimposing the reproduced carrier color signal are multiplied to produce the original signal. SECAM, which is characterized by returning to the frequency of
System video signal recording/playback device.