JPH0810942B2 - Magnetic recording / reproducing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing apparatus for separately recording a video input signal into a luminance signal and a chromaticity signal.

2. Description of the Related Art Conventionally, a TV signal is a luminance signal (Y signal) and a chromaticity signal (C).
As a means for separating signals, a 1H delay line is used and a comb filter is configured. Fig. 3 shows the conventional 1H
3 is a configuration diagram of a delay circuit of FIG.

First, the video signal is AM modulator 1, 28MHz oscillator 2
The carrier is received from AM, AM modulated, and amplified by the amplifier 3,
The output signal from the delay line 4 supplied to the 1H delay line 4 is attenuated and weakened, so that it is amplified by the amplifier 5 and sent to the AM detector 4 to be AM demodulated and returned to the 1H delayed video signal.

When the video signal is NTSC, it has a 1H delay line, but when it is PAL, it has a 2H delay line.

Problems to be Solved by the Invention An AM-modulated wave of a high-frequency carrier of 28 MHz passes through a delay line of 1H and its signal level is attenuated by about -20 to -30 dB. Also, the signal supplied to the 1H delay line is quite high at 28MHz, so sending it with a large amount of power would make the circuit bulky and difficult. Therefore, there is a problem in that the output signal of the 1H delay line becomes a weak signal, is likely to receive an interference wave from the outside, and the S / N in the demodulation output is easily deteriorated.

Means for Solving the Problem The present invention constitutes Y / C separation means by a comb filter, a pre-emphasis circuit is provided before entering the AM modulator of the delay circuit, and a de-emphasis circuit is provided after the AM detector. Is provided.

Action The pre-emphasis circuit has the function of increasing the gain for higher frequency components, and the de-emphasis circuit has the opposite characteristic. The high-frequency component of the video signal has a smaller signal level than the low-frequency component, and the decrease in the dynamic range of the circuit system and the transmission system due to the pre-emphasis operation is small.
Therefore, this emphasis operation can reduce the noise level from the outside and improve the S / N.

Embodiment First, FIG. 2 shows the structure of the main part of this embodiment. In this configuration, the pre-emphasis circuit 7 is provided in the front stage of the 1H delay circuit shown in FIG. 3, and the de-emphasis circuit 14 is added in the rear stage. Here, the circuits 8 to 13 correspond to the circuits 1 to 6 shown in FIG.

The high-frequency component of the input signal of the AM modulator 8 is temporarily gained up by the pre-emphasis circuit 7. On the other hand, in the output signal from the AM detector 6, the high-frequency component is gained down by the de-emphasis circuit 14. The noise that jumps into the output of the 1H delay line 11 is suppressed by the de-emphasis circuit 14. In the signal system, the high-frequency component is already leveled up by the pre-emphasis circuit 7, so that the high-frequency signal component does not become smaller than the original input by the de-emphasis circuit 14. For this reason, the S / N improves as much as the noise level is suppressed.

The specific emphasis amount is from 100KHz to 2MHz,
It is 3 to 5 dB.

FIG. 1 is a block diagram of a Y signal / C signal separation circuit using the 1H delay circuit with pre-emphasis and de-emphasis shown in FIG. This circuit is generally called a comb filter, and the bandpass filters 16 and 17 are
It is a bandpass filter that extracts the C signal band. Adder circuit 18
Adds the video signal and the output of the bandpass filter 16,
The subtracting circuit 19 subtracts the outputs of the bandpass filters 16 and 17 to obtain the Y signal at the output of the adding circuit 18 and the C signal at the output of the subtracting circuit 19, respectively.

The present invention can also be applied to a 1H delay circuit without an AM modulator. Therefore, in this case, there is no AM modulator and AM demodulator. Also in the PAL system,
It goes without saying that the same can be applied.

EFFECTS OF THE INVENTION Since the present invention is provided with a pre-emphasis circuit and a de-emphasis circuit before and after the 1H delay circuit, the S / N deterioration is reduced, and the Y
Since it can be applied to the / C separation circuit to prevent S / N degradation, it has the excellent feature of not degrading the S / N of the total recording / reproducing characteristics.

[Brief description of drawings]

FIG. 1 is a block diagram of a Y / C separation circuit in one embodiment of the present invention, FIG. 2 is a block diagram showing a main part including a 1H delay circuit of this embodiment, and FIG. 3 is a conventional 1H delay circuit. It is a block diagram. 7 ... Pre-emphasis circuit, 8 ... AM modulator, 9 ...
28MHz oscillator, 10 ... Amplifier, 11 ... 1H delay line, 12 ...
Amplifier, 13 …… AM detector, 14 …… De-emphasis circuit, 15 …… 1H delay circuit, 16,17 …… Band pass filter, 18 …… Adding circuit, 19 …… Subtracting circuit.

Claims (1)

[Claims] 1. A comb filter is constructed by using a delay line, and a Y / C separating means for separating a video signal into a Y signal and a C signal is provided, and a pre-emphasis means is provided in the preceding stage of the delay line. A magnetic recording / reproducing apparatus characterized in that a de-emphasis means is provided in a subsequent stage.