JPH07222107A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To realize a circuit without a deteriorated high frequency component of a recording signal with simple configuration by reducing only a higher harmonic component generated by a clip circuit. CONSTITUTION:A high frequency component of a video signal (a) is emphasized by using an emphasis circuit 12. An emphasized output signal (b) is clipped by a clip circuit 13. A clip detection circuit 16 detects it that an output signal c' is clipped by the clip circuit 13. As a result, an output of a low pass filter 14 or an output of a delay circuit 15 is selected by a switch 17. An output signal (e) whose band is limited based on a filter characteristic is processed via a demodulation processing circuit 18 and a recording processing circuit 19 by the changeover of the switch 17 and the processed signal is recorded on a magnetic tape 21.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing apparatus for obtaining a recording signal in which high frequency components are not deteriorated.

[0002]

2. Description of the Related Art As a conventional technique for obtaining a recording signal in which a high frequency component is not deteriorated, there is JP-A-2-182808. This will be described with reference to FIG. In FIG. 5, the recording signal a input to the input terminal 51 is input to the emphasis circuit 52 and then to the clipping circuit 53, the low-pass filter 54, the FM modulation circuit 55, the recording processing circuit 56, and the magnetic head 57. The signal is processed and recorded on the magnetic tape 58.

FIG. 6A shows a recording signal a and FIGS.
In (d), the signal waveforms of the output signals b to d of the emphasis circuit 52, the clipping circuit 53, and the low-pass filter 54,
FIG. 7 shows a spectrum diagram of each of the signals a to d, and the operation of FIG. 5 will be described with reference to FIGS. 6 and 7.

The emphasis circuit 52 emphasizes the high frequency component of the recording signal a and outputs it as an emphasis signal b, which is input to the clipping circuit 53. Since a whisker as shown in FIG. 6 (b) which causes an inversion phenomenon occurs in the emphasis signal b, it is input to the clipping circuit 53 and the white side and the dark side are clipped at a predetermined level. Since the recording signal of the clipped portion has a sharp waveform, the output signal d of the clipping circuit 53 has a harmonic component as shown in FIG. 7C. Since such a harmonic component is generated in a band higher than the high frequency component of the baseband signal, it causes aliasing distortion from DC during FM modulation and also causes crosstalk between adjacent tracks when the signal after FM modulation is reproduced. Since it is recorded as a low-frequency signal having a large level, noise is generated, which causes deterioration of image quality.

Therefore, the output signal c of the clipping circuit 53
Is input to the low-pass filter 54 to reduce the harmonic component. The output signal d of the low-pass filter 54 in which the harmonic components have been reduced is subjected to processing necessary for recording through the FM modulation circuit 55 and the recording processing circuit 56, and then recorded on the magnetic tape 58 via the magnetic head 57.

In this way, the reproduction of the video signal in which the noise due to the harmonics generated at the time of clipping is reduced is performed. However, regardless of not being clipped as shown in FIGS. 6D and 7D, since the high-pass signal component is always subjected to the low-pass filter, the high-pass signal component is also reduced, There is a problem of degrading frequency characteristics. Further, when a low-pass filter having a sufficiently wide band for the signal component is used, the reduction of the harmonic component generated by the clipping becomes insufficient.

[0007]

In the above-mentioned conventional system, when the harmonic components generated by the clipping are reduced, the high frequency component of the recording signal is also deteriorated, and the frequency characteristic of the high frequency is deteriorated. There is a problem of causing it.

According to the present invention, only the higher harmonic component generated by the clipping circuit is reduced, and a circuit which does not deteriorate the high frequency component of the recording signal is realized with a simple structure.

[0009]

In order to solve the above-mentioned problems, the present invention comprises emphasis means for emphasizing a high frequency component of a video signal, and clipping means for clipping an output signal emphasized by the emphasis means. It is characterized by further comprising detection means for detecting that the output signal is clipped by the clipping means, and switching means for switching the band limiting filter characteristic according to the result of the detection means.

[0010]

By the above means, only when clipped
Since the low-pass filter is applied, it is possible to attenuate only the higher harmonic component generated by clipping without attenuating the high frequency component of the recording signal.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a circuit configuration diagram showing an embodiment of the present invention. The recording signal a input to the input terminal 11 is input to the emphasis circuit 12. The output signal b of the emphasis circuit 12 is input to the clipping circuit 13, the signal c clipped here is input to the low-pass filter 14 and the delay circuit 15, respectively, and the clipping circuit 13
A clip detection signal c ′ for detecting the portion clipped by is input to the clip detection circuit 16. The detection result of the clip detection circuit 16 is input as a detection signal d to a switch 17 that selects either the low-pass filter 14 or the delay circuit 15. The output of the switch 17 is input to the FM modulation circuit 18 and then recorded on the magnetic tape 21 via the recording processing circuit 19 and the magnetic head 20.

The operation of FIG. 1 will be described with reference to FIG. 2. As in the conventional example, the recording signal a is output from the emphasis circuit 1.
After the high frequency component is emphasized by 2, the clipping circuit 13 clips it. At this time, the clip detection signal c ′ is output from the clip circuit 13 to the clip detection circuit 16. The clip detection circuit 16 detects whether the output signal c of the emphasis circuit 12 is clipped by the clip detection circuit 16. When the clip is detected, the switch 17 is switched to select the low-pass filter 14 to switch the filter characteristic so as to narrow the pass band. This reduces the harmonic components generated during clipping. At the time of non-detection, the switch 17 is switched to the delay circuit 15 side to widen the pass band so that the signal is not attenuated. By matching the delay times of the low-pass filter 14 and the delay element 15, a time shift at the time of switching can be prevented.

An example in which a comparator is used as the clip detection circuit 16 will be described with reference to FIG. The emphasis output signal b is input to the clip circuit 13 and the comparator 31. The reference voltage Vref generated by the reference voltage generation circuit 32 is input to the clip circuit 13 as a clip voltage,
The clipping operation is performed with this voltage to output the clipping output signal c ″. Similarly, the reference voltage Vre is also supplied to the comparator 31.
f is input, the reference voltage Vref is compared with the emphasis output signal b, and the result is output as the clip detection signal d ′.

FIG. 4 shows the clip circuit 13 and the comparator 3 of FIG.
1 shows a specific circuit example. The emphasis output signal b is compared with the reference voltage Vref by using the comparator 31 composed of the transistors Q1 and Q2 and the resistor R, and the low voltage side clipped signal Sa and the low voltage side clip detection signal S are compared.
b and are output. This makes it possible to detect clips and clips.

In this embodiment, since only the harmonic component generated at the time of clipping can be adaptively reduced, deterioration of the high frequency component of the recording signal does not occur.

[0016]

As described above, according to the magnetic recording / reproducing apparatus of the present invention, only the harmonic component generated by the clipping circuit can be attenuated without affecting the high frequency signal component.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram for explaining an embodiment of the present invention.

FIG. 2 is a signal waveform diagram for explaining the operation of FIG.

3 is a configuration diagram for explaining a configuration of a clip detection circuit in FIG.

FIG. 4 is a circuit diagram specifically showing a clip circuit and a comparator shown in FIG.

FIG. 5 is a conventional circuit configuration diagram in which deterioration of a conventional high frequency component is suppressed.

6 is a signal waveform diagram for explaining the operation of FIG.

7 is a characteristic diagram for explaining the operation of FIG.

[Explanation of symbols]

12 ... Emphasis circuit, 13 ... Clip circuit, 14 ...
Low-pass filter, 15 ... Delay circuit, 16 ... Clip detection circuit, 17 ... Switch, 18 ... FM demodulation processing circuit, 1
9 ... Recording processing circuit, 20 ... Magnetic head, 21 ... Magnetic tape.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H04N 5/208 5/922

Claims (3)

[Claims] 1. An emphasis means for emphasizing a high frequency component of a video signal, a clipping means for clipping an output signal emphasized by the emphasis means, and a detection for detecting that the output signal is clipped by the clipping means. A magnetic recording / reproducing apparatus comprising: a means and a switching means for switching a band limiting filter characteristic according to a result of the detecting means. 2. A band limiting means for switching the characteristic,
2. A magnetic recording / reproducing apparatus according to claim 1, wherein a band limiting element having a fixed characteristic and a delay element having the same delay time are switched. 3. The magnetic recording / reproducing apparatus according to claim 1, wherein said clip detecting means is performed by a comparator for comparing a reference voltage of said clipping means with said emphasized output signal.