JPH0334148B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a magnetic recording and reproducing device, which records an FM modulated signal on a magnetic tape and FM demodulates the reproduced signal to obtain the original signal. Regarding a playback device.

Conventional technology When recording, a conventional magnetic recording/reproducing device pre-emphasizes a luminance signal, clamps the obtained signal, and uses a clip circuit to eliminate overshoot above a specified level, undershoot below a specified level, etc. After that, the luminance signal is FM-modulated, a low-frequency converted carrier color signal is mixed therein, and the signal is recorded on a magnetic tape. Also, during playback, the FM brightness signal extracted from the playback signal is
The luminance signal is extracted by demodulating and de-emphasizing the obtained signal.

Problems to be Solved by the Invention In the conventional device, when pre-emphasis is performed on a luminance signal as shown in FIG. It will be done. As a result, the information on the rising edge of the luminance signal is lost, and the luminance signal obtained by demodulating the reproduced signal and performing de-emphasis lacks the rising edge as shown in Figure 3B. The signal waveform before recording cannot be faithfully reproduced. Since the waveform at such a sharp rise portion is blunted, there are problems such as smearing in the reproduced image.

Therefore, in the present invention, the part from which the overshoot is removed is inverted and added immediately before the edge, and then recorded, and the added part is extracted from the reproduced signal and inverted, so that the added part and the overshoot are removed. It is an object of the present invention to provide a magnetic recording/reproducing device that solves the above-mentioned problems by adding the above-described problems.

Means and Effects for Solving the Problems The present invention extracts the portion removed due to the overshoot level limit, inverts it, and adds it just before the edge of the signal from the clip circuit to generate the reproduced signal.
It is constructed so that the added part immediately before the edge is extracted from the demodulated signal obtained by FM demodulation, inverted, and added to the added part of the demodulated signal and the part from which the overshoot has been removed. An example will be explained.

Embodiment FIGS. 1A and 1B show block system diagrams of an embodiment of each of the recording system and reproduction system of the apparatus of the present invention.

In FIG. 1A, reference numeral 1 denotes a terminal to which a luminance signal separated from a video signal is input, and the luminance signal input here is supplied to an emphasis circuit 2.
The emphasis circuit 2 has a predetermined frequency characteristic in which the amplification degree of the high frequency range is, for example, about five times the amplification degree of the low frequency range, and the high frequency component of the luminance signal is enhanced here, as shown in FIG. 2A. The signal a is supplied to the clip circuit 3 and the lower limiter circuit 4. In this signal a, the fall timing of the horizontal synchronization signal is defined as time t ₀ . The clip circuit 3 detects the portion where the level difference from the sync chip to the white peak exceeds, for example, 160%, as shown by the broken line in FIG. A portion of the difference below -40%, for example, is level limited to obtain signal b shown in FIG. 2B. This signal b
is delayed by a certain time τ (τ is, for example, several tens to hundreds of nanoseconds) in the delay circuit 5, and the signal c shown in FIG. 2C is supplied to the mixer 6.

Further, the lower limit limiter circuit 4 limits the signal a to the level shown by the broken line, sets the DC component to 0V, and generates a signal d having the waveform shown in FIG.
supply to. The mixer 6 subtracts and mixes the signal d with the signal c to obtain the signal e shown in FIG. 2E. This signal e
is supplied to the clip circuit 7, where the portion below the level indicated by the two-dot chain line in Fig. 2E (this level is the same as the level indicated by the one-dot chain line in Fig. 2A) is clipped to produce the signal shown in Fig. 2F. f is generated. After this signal f is clamped at the sync chip level by a clamp circuit 8, it is supplied to an FM modulator 9, and the signal f is used to FM modulate the carrier wave.
The modulated wave is output from terminal 9 and, after subsequent processing, is recorded on a magnetic tape, for example by a rotating head. In other words, the portion of the overshoot at the rising edge of signal a that is removed by the clip circuit 3 is the portion of signal d that is removed by the clip circuit 3.
This signal d is inverted, outputted from the clip circuit 3, and added just before the edge of the delayed signal c to obtain the signal e. Note that the clipping circuit 7 clips the portion added immediately before the edge, thereby preventing unnecessary sidebands of the luminance signal from being mixed into the chrominance signal band.

A reproduced signal reproduced from the magnetic tape by the rotary head enters the terminal 11 in FIG. 1B and is supplied to the FM demodulator 12. The signal demodulated by the FM demodulator 12 is taken out by the low-pass filter 13.
The signal g shown in FIG.
It is supplied to each of the mixers 16. In this signal g, the fall timing of the horizontal synchronization signal is defined as time _t1 . The delay circuit 14 has the same delay time τ as the delay circuit 5, and delays the signal g and supplies it to the sampling circuit 17 as a signal h shown in FIG. 2H. Further, the clamp circuit 15 clamps the sync chip level of the signal g and supplies it to the comparator 18. The comparator 18 has a reference level slightly lower than the level of 160% of the white peak of the signal g, as shown by the broken line in FIG. 2 Generating and extracting the signal i shown in FIG. 1 17
supply to.

The sampling circuit 17 extracts the signal h supplied from the delay circuit 14 during the H level period of the signal i,
Signal j shown in Figure 2 J assuming that the DC component is 0V
is generated and supplied to mixers 16 and 19, respectively. Mixer 16 subtracts and mixes signal j with demodulated signal g to obtain signal k shown in FIG. 2K, which is supplied to delay circuit 20. Delay circuit 20 has the same delay time τ as delay circuits 5 and 14, and delays signal k to produce signal l shown in FIG. 2L, which is supplied to mixer 19. This signal l is delayed by time 2τ compared to signal g. The mixer 19 subtracts and mixes the signal j with the signal l to generate a signal m shown in FIG. 2M. This signal m is supplied to a de-emphasis circuit 21, where the high frequency enhancement performed by the emphasis circuit 2 during recording is restored to its original characteristics, and the signal from the de-emphasis circuit 21 is outputted via a terminal 22. That is, the sampling circuit 17 extracts the added portion immediately before the edge from the demodulated signal g, and this extracted signal j is inverted and added to the added portion of the signal g and the portion from which the overshoot has been removed. A signal m substantially similar to the original signal a is obtained.

In this way, a part of the overshoot that was removed in the conventional method is restored, so the rising edge of the signal after de-emphasizing the signal m is not blunted, and for example, when the signal shown in FIG. 3A is recorded, When reproduced, a signal as shown in FIG. 3C is obtained, and the occurrence of smear in the reproduced image can be prevented.

In FIG. 1A, since the clip circuit 7 performs dark clipping, the clipping circuit 3 may perform only white clipping at the level shown by the broken line I, and is not limited to the above embodiment.

Effects of the Invention As described above, the magnetic recording/reproducing apparatus according to the present invention limits the level of the overshoot of the rising edge of a signal using a clip circuit, performs FM modulation, and records the signal on a magnetic recording medium. In a magnetic recording/reproducing device that obtains the original signal by FM demodulating the reproduced signal, the part that is removed due to the overshoot level limit is taken out, inverted, and added just before the edge of the signal from the clip circuit to generate the reproduced signal.
The added part just before the edge is extracted from the demodulated signal obtained by FM demodulation, inverted, and added to the added part of the demodulated signal and the part from which the overshoot has been removed, so the edges of the reproduced signal are not dulled. It is restored in the same manner as before recording, and has the advantage that, for example, when the signal is an image signal, it is possible to prevent the occurrence of smear in the image obtained by the reproduced signal.

[Brief explanation of drawings]

FIG. 1 is a block system diagram of an embodiment of the device of the present invention, FIG. 2 is a waveform diagram of each part of the device shown in FIG.
The figure is a waveform diagram of an example of a signal recorded and reproduced in a conventional apparatus and an apparatus according to the present invention. 1, 10, 11, 22... terminal, 2... emphasis circuit, 3, 7... clip circuit, 4... lower limit limiter circuit, 5, 14, 20... delay circuit, 6, 16,
19... Mixer, 8, 15... Clamp circuit, 9...
FM modulator, 12...FM demodulator, 13...Low pass filter, 17...Sampling circuit, 18...Comparator, 2
1...De-emphasis circuit.

Claims (1)

[Claims] 1. Magnetic recording/reproduction: After level-limiting the overshoot of the rising edge of the signal using a clip circuit, it is FM modulated and recorded on a magnetic recording medium, and the reproduced signal from the recording medium is FM demodulated to obtain the original signal. In the device, the part removed due to the level limit of the overshoot is taken out, inverted, and added to the signal from the clip circuit just before the edge, and the demodulated signal obtained by FM demodulating the reproduced signal is added just before the edge. 1. A magnetic recording and reproducing apparatus characterized in that the additional portion of the demodulated signal is extracted, inverted, and added to the additional portion of the demodulated signal and the portion from which the overshoot has been removed.