JPH02263359A - Magnetic recording/reproducing device - Google Patents

Abstract

PURPOSE:To obtain the optimum picture quality by varying the correction value of the characteristics of a reproduction RF equalizer, the noise cancel value of a NC circuit after FM demodulation, and the frequency (f) characteristics of a picture control circuit respectively. CONSTITUTION:The correction value of the characteristics of a reproduction RF equalizer, the noise cancel value of an NC circuit after demodulation, and the (f) characteristics of a picture control circuit 11 are based on the output of a carrier frequency detecting circuit 13 which detects the carrier frequency of a reproduction FM signal, the output of a comparator 16 which performs the comparison between two detection outputs of a side band frequency detecting circuit 15, and the output of an FM envelope level detecting circuit 17 which detects the envelope level of a reproduction FM signal. Thus it is possible to suppress the occurrence of inverted phenomena, the deterioration of S/N, and the variance of the (f) characteristics. Then the picture quality is extremely improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention is configured to improve image quality deterioration due to variations in heads during recording and playback when reproducing FM modulated signals. The present invention relates to a magnetic recording/reproducing device.

[Prior Art] Fig. 2 is a block diagram showing the configuration of a reproduction FM signal processing circuit in a conventional magnetic recording and reproduction apparatus. head, (2) is a switch circuit for head cutting base, (
3) is a beaking circuit for correcting the frequency characteristics of the reproduced FM signal, and (4) is an automatic gain control circuit (hereinafter referred to as AGC circuit) that keeps the gain constant.
5) is an RF equalizer for smoothing the frequency characteristics, (
6) is a limiter circuit that prevents the inversion phenomenon and removes AM components, (7) is an FM demodulation circuit, (8) is a de-emphasis circuit, and (8) is a low-pass filter that removes unnecessary high-frequency components (hereinafter referred to as LPF). , (10) is a noise canceller circuit (hereinafter referred to as N0 circuit), (11) is a picture control circuit, and (19) is an output terminal for a reproduced video signal.

Next, the operation of the above configuration will be explained.

The FM signal reproduced from the magnetic tape (18) via the video head (1) is input to the peaking circuit (3) via the head changeover switch circuit (2), where the frequency characteristics are corrected. , is fixed at a constant gain in the AGC circuit (4). Next, the AGC circuit (4
) is input to the RF equalizer (5) to correct the frequency characteristics, and then the limiter circuit (
6), and the limiter circuit (6) removes the AM acid component to prevent the inversion phenomenon.The FM demodulation circuit (7) demodulates the FM modulated signal, and the de-emphasis circuit (8) Triangular noise reduction,
The S/N ratio is improved. Next, L P F (
9) and removes unnecessary components in the high range.
The S/H is improved in the 0 circuit (lO) and the frequency characteristic (hereinafter referred to as f characteristic) is corrected in the picture control circuit (18), and the resultant signal is output as a reproduced video signal from the terminal (18). .

[Problems to be Solved by the Invention] Since the conventional magnetic recording/reproducing device is configured as described above, when reproducing an FM signal, due to variations in the head during recording and reproduction, the carrier frequency and The relationship with the sideband frequency may become unbalanced, or the playback FM
Large variations tend to occur in the level of the envelope amount of the signal, and if FM demodulation is performed as it is, 1 inversion phenomenon and S/
There was a problem in that the image quality deteriorated significantly due to deterioration of N and variations in f characteristics.

This invention was made to solve the above-mentioned problems, and it suppresses inversion phenomena, S/N deterioration, and f-characteristic variations caused by variations in heads during recording and playback, and improves the quality of a single image. An object of the present invention is to provide a magnetic recording/reproducing device that can improve the performance.

[Means for Solving the Problems] The magnetic recording and reproducing apparatus according to the present invention includes a comparator output that compares two detection outputs of a detection circuit that detects the carrier frequency of a reproduced FM signal and a detection circuit that detects the sideband frequency. The characteristics of the reproduction RF equalizer, the noise cancellation amount of the NC circuit after demodulation, and the f-characteristic correction amount of the picture control circuit are configured to be varied by the output of the envelope level detection circuit that detects the envelope level of the reproduction FM signal. It is characterized by

[Function] According to the present invention, during reproduction, the carrier frequency and sideband frequency of the reproduced FM signal are respectively detected, and the output obtained by comparing the two detection outputs;
The characteristics of the reproduction RF equalizer, the noise cancellation amount of the N0 circuit after FM demodulation, and the f-characteristic correction amount of the picture control circuit are varied by the output obtained by detecting the envelope level of the reproduction FM signal. Inversion phenomena, S/N deterioration, and variations in f characteristics are suppressed, and optimal image quality can be obtained.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described based on the drawings.

FIG. 1 is a block diagram showing the configuration of a reproduction FM@ number processing circuit in a magnetic recording and reproducing apparatus according to an embodiment of the present invention.
Since (113) has the same structure as the conventional example shown in FIG. 2, the same reference numerals are given and detailed explanation thereof will be omitted.

In Figure 1, (12) is a band pass filter (hereinafter referred to as BPF) for extracting the carrier frequency component of FM modulation from the reproduced FM signal, and (13) is this BPF.
P F A detection circuit detects the carrier frequency component extracted by (12), (14) detects the FM signal from the reproduced FM signal.
BPF for extracting sideband frequency components of modulation, (1
5) is a detection circuit that detects the sideband frequency component extracted by the BPF (14), and (16) is a comparator.
The output of the carrier frequency detection circuit (13) and the output of the sideband frequency detection circuit (15) are compared. (17)
is an FM envelope level detection circuit that detects the envelope level of an FM signal.

The output of the comparator (16) and the output of the FM envelope level detection circuit (17) are configured to be fed back to an RF equalizer (5), an NC circuit (10), and a picture control circuit (11), respectively. .

Next, the operation of the above configuration will be explained.

The FM signal reproduced from the magnetic tape (18) via the video head (1) is input to the peaking circuit (3) via the head changeover switcher circuit (2), where it is corrected for one frequency characteristic. , is fixed at a constant gain in the AGC circuit (4). This reproduced FM signal may have an unbalanced relationship between the carrier frequency and the sideband frequency due to variations in characteristics during recording, resulting in deterioration of image quality.

Here, according to the above configuration, carrier frequency B P F (12
) and sideband frequency B P F (14), the extracted frequencies are detected in the carrier frequency detection circuit (13) and the sideband frequency detection circuit (15), and the is converted from to DC. Then, the two detection output levels are compared by a comparator (IB), and outputs corresponding to the level difference between the two are fed back to the RF equalizer (5), NC circuit (10), and picture control circuit (11), respectively. , RF equalizer characteristics, noise cancellation amount, and picture control f-special correction amount are switched.

Similarly, the input FM (g
No. +7) The FM envelope level is detected by the FM enwelve level detection circuit (17), and the output corresponding to the magnitude of the detected envelope amount is sent to the RF equalizer (5), NC circuit (lO), and picture control. are fed back to the circuit (11) respectively, and the RF
The equalizer characteristics, noise cancellation amount, and picture control f-special correction amount are switched.

RF equalizer (
5) performs f-characteristic correction of the FM signal, removes the AM acid component in the limiter circuit (8), demodulates it in the FM demodulation circuit (7), reduces triangular noise in the de-emphasis circuit (8), and The reproduced video signal from which unnecessary high-frequency components have been removed in P F (9) is outputted from a terminal (19) via an NC circuit (10) and a picture control circuit (11).

In the above embodiment, B P F (12), (14) is used to extract the carrier frequency and sideband frequency.
However, even if peaking amplifiers for each of the carrier frequency and the sideband frequency are used, the same effects as in the above embodiment can be obtained.

Further, even if the peaking circuit (3) and the AGC circuit (4) shown in the above embodiments are omitted, the same effect can be obtained.

C. Effects of the Invention As described above, according to the present invention, when generating an FM signal, the carrier JAJ wave number and sideband frequency of the reproduced FM signal, which are generated due to head variations during recording and reproduction, etc. In addition to detecting imbalance, playback F
Detect the envelope level of the M signal and optimize the RF equalizer characteristics, noise cancellation l, and f special correction amount! ! By doing so, it is possible to suppress the occurrence of an inversion phenomenon, deterioration of S/N, and variation in f characteristics, and to significantly improve changes in image quality.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a reproduction FM signal processing circuit in a magnetic recording and reproduction apparatus according to an embodiment of the present invention;
FIG. 2 is a block diagram showing the configuration of a reproduction FM signal processing circuit in a conventional magnetic recording and reproduction apparatus. (5)...RF equalizer, (6)...Limiter circuit, (7)...FM demodulation circuit, (lO)...NC circuit, (11)...Picture control circuit, (12)...
), (14)... BPF, (13), (15)...
Detection circuit, (16... comparator, (+7)...
・FM envelope level detection circuit. Note that the same symbols in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] (1) A magnetic recording and reproducing device equipped with an RF equalizer that corrects the frequency characteristics of the reproduced FM signal, an FM demodulation circuit, a noise canceller circuit that removes noise from the demodulated FM signal, and a picture control circuit that corrects the frequency characteristics. , a detection circuit that extracts a carrier frequency component of FM modulation from an FM modulated playback signal and detects that frequency; a detection circuit that extracts a sideband frequency component of FM modulation and detects that frequency; and a detection circuit that extracts a sideband frequency component of FM modulation and detects that frequency; The RF equalizer is equipped with a comparator that compares the detection output of the circuit, and an FM envelope level detection circuit that detects the envelope level of the FM modulated reproduction signal, and the output of the comparator and the output of the FM envelope level detection circuit are used to control the RF equalizer. 1. A magnetic recording and reproducing apparatus characterized in that the characteristics, the amount of noise cancellation by the noise canceller circuit after FM demodulation, and the amount of frequency characteristic correction by the picture control circuit are respectively variable.