JPH0789426B2 - Magnetic recording device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a magnetic recording medium whose reverse wavelength characteristic exhibits a single peak,
The present invention relates to a magnetic recording device that records an FM-modulated signal of a video signal.

Background Art and Its Problems The inverse wavelength (1 / λ) characteristics of conventional magnetic tapes (cassette tapes) such as gamma-hematite and metal tapes are shown in Fig. 5 (1 / λ and level are expressed in logarithm). 1 / as shown
Since it exhibits a substantially monotonic decreasing characteristic in the direction in which λ becomes large,
The FM-modulated video signal (f) having a frequency (f) spectrum as shown in FIG. 7 (only the level is represented logarithmically)
(c: carrier frequency, fc + fp: upper sideband frequency, fc−fp: lower sideband frequency, fp: maximum frequency of video signal) is recorded on such a magnetic tape with a rotating magnetic head and reproduced. As shown in FIG. 8 (only the level is represented by a logarithm), the frequency characteristic of the reproduction output is such that the level of the lower sideband is increased and the level of the upper sideband is decreased, but the level of the upper sideband is decreased. Is compensated by increasing the level of
There is no fear that the high frequency band of the video signal obtained by FM demodulation during reproduction will decrease.

However, the reverse wavelength characteristic of the thin film magnetic recording medium is
As shown in the figure (1 / λ and level are expressed in logarithm), it has a single peak with a peak in the short wavelength region.
When an FM-modulated video signal as shown in FIG. 7 is recorded horizontally or vertically on such a magnetic recording medium and an attempt is made to reproduce it,
The reproduction frequency characteristic is shown in FIG. 6, and considering the relational expression of f = v / λ (where v is the relative speed between the head and the tape),
As shown in FIG. 9 (only the level is logarithmized), the levels of the upper sideband and the lower sideband are significantly reduced as shown in FIG. 10 (only the level is logarithmized). However, there is a drawback that the high frequency range of the video signal obtained by FM demodulation during reproduction is lowered.

SUMMARY OF THE INVENTION In view of the above, the present invention is a magnetic recording device configured to record an FM-modulated signal of a video signal on a magnetic recording medium exhibiting unimodal characteristics with an inverse wavelength characteristic, and an image demodulated by FM during reproduction. It is an object of the present invention to propose a magnetic recording device that does not reduce the high frequency range of a signal and can suppress the deterioration of S / N in the high frequency range.

SUMMARY OF THE INVENTION The present invention is a magnetic recording device adapted to record an FM-modulated signal of a video signal on a magnetic recording medium exhibiting a single-peaked inverse wavelength characteristic. The FM modulator is equipped with an emphasic circuit that selects a value greater than the vicinity of the peak corresponding frequency of the frequency characteristics of the reproduction output exhibiting a peak, and enhances a band above a predetermined frequency determined according to the difference between the carrier frequency and the peak corresponding frequency. It is characterized in that it is provided in the preceding stage.

According to the present invention, in the magnetic recording device adapted to record the FM-modulated signal of the video signal on the magnetic recording medium whose reverse wavelength characteristic exhibits a single peak, the video signal demodulated by FM at the time of reproduction. It is possible to obtain a magnetic recording apparatus that is free from the possibility of lowering the high frequency range and that can suppress the deterioration of the high frequency S / N.

Embodiment An embodiment of the present invention will be described below with reference to FIG. FIG. 1 shows a main part of a circuit of an example of a VTR to which the present invention is applied. (1) is its recording system and (2) is its reproducing system. The video signal supplied from the input terminal (3) to the emphasis circuit (4) is supplied to the FM modulator (6) through the recording side fixed contact R and the movable contact M of the changeover switch (5), and the image signal thus obtained is obtained. The FM-modulated video signal is supplied to the recording amplifier (8) through the movable contact M and the recording-side fixed contact R of the changeover switch (7) and amplified, and then the output is supplied to the recording magnetic head (9). This FM-modulated video signal is recorded on the thin-film magnetic tape (10) whose reverse wavelength characteristic exhibits a single peak.

Next, the reproducing system (2) will be described. The FM-modulated video signal reproduced by the reproducing magnetic head (11) is supplied to the reproducing amplifier (12) and amplified, and its output is output from the changeover switch (13). It is supplied to the FM demodulator (14) through the fixed contact P on the reproducing side and the movable contact M to be FM demodulated, and the original video signal is output to the output terminal (15).

The change-over switches (5), (7) and (13) each have a fixed contact E for monitoring, and when each movable contact M thereof is switched to the fixed contact E for monitoring, the input terminal (3)
The video signal to be recorded supplied to the recording system (1)
Output switch (5) -FM modulator (6) -selection switch (7) -selection switch (13) -FM demodulator (14) to the output terminal (15) for output to the monitor receiver ( (Not shown) for monitoring.

Therefore, the frequency characteristics and the band of the video signal supplied to the input terminal (3) of FIG. 1 are as shown in the curve (18) of FIG. 3 (only the level is logarithmic) (fp is 4 MHz, for example).
Then, the frequency characteristic of the emphasis circuit (4) is represented by the frequency fc as shown by the curve (19) indicated by the broken line in FIG.
The frequency spectrum of the FM-modulated video signal without the emphasis circuit (4) is set to the solid line in Fig. 4 (only the level is represented by logarithm) by setting it so that it is enhanced above -fm. The level of the both sidebands is lowered as shown by the curve (21) indicated by, but the both sidebands are flat as a whole by the curve (22) indicated by the broken line. Thus, the video signal is FM-modulated and recorded, and the reproduced signal is reproduced.
There is no fear that the high frequency band of the reproduced video signal obtained by FM demodulation will deteriorate.

Further, the frequency characteristic of the emphasis circuit (4) can be increased more than the curve (19) as shown by the curve (20) shown by the one-dot chain line in FIG. In that case, as shown in FIG. 2, the de-emphasis circuit (1
By providing 7), if there is no de-emphasis circuit (17), the FM demodulator (14) obtained at the output terminal (15)
The frequency spectrum of the FM-modulated video signal supplied to is over-enhanced in the lower sideband and the upper sideband as shown by the curve (23) in Fig. 4, and shows the frequency characteristics of this de-emphasis circuit (17). Depending on the selection, both sidebands can be suppressed to be flat as a whole as shown by the curve (22). Incidentally, (16) is a changeover switch provided between the FM demodulator (14) and the de-emphasis circuit (17), and the output of the FM demodulator (14) is fixed to the movable contact M and the reproducing side of the changeover switch (16). The output is supplied to the de-emphasis circuit through the contact P and the output is obtained at the output terminal (15). However, during monitoring, the movable contact M of the changeover switch (16) is switched to the monitor-side fixed contact E. The output of the FM demodulator (14) is directly obtained at the output terminal (15).

Thus, even if the emphasis degree of the emphasis circuit (4) is increased, this can be compensated by the de-emphasis circuit (17).

According to the magnetic recording device described above, in a magnetic recording device configured to record an FM-modulated signal of a video signal on a magnetic recording medium having a reverse-wavelength characteristic having a single-peaked characteristic, it is possible to compensate for a decrease in a high frequency range of a reproduction signal. It is possible to suppress the deterioration of S / N in the high frequency range. In addition, the wide area signal is enhanced above a predetermined frequency determined by the difference between the carrier frequency of the FM modulated wide area signal and the peak frequency of the reproduction frequency characteristic corresponding to the unimodal inverse wavelength characteristic of the magnetic recording medium. After that, FM modulation is performed, so that overmodulation does not occur and a large amount of emphasis can be taken.

Although the case where the magnetic recording medium is a magnetic tape has been described above, a magnetic disk is also possible.

EFFECTS OF THE INVENTION According to the present invention described above, in a magnetic recording apparatus configured to record an FM-modulated signal of a video signal on a magnetic recording medium whose reverse wavelength characteristic exhibits a single peak, It is possible to compensate for the deterioration in the high frequency range and to suppress the deterioration of the S / N in the high frequency range. Moreover, since the inverse wavelength characteristic of the magnetic recording medium is unimodal, over-modulation does not occur even when the emphasis is strongly applied, and the amount of emphasis can be increased.

[Brief description of drawings]

FIG. 1 is a block diagram showing an essential part of a circuit of an example of a VTR to which the present invention is applied, FIG. 2 is a block diagram showing a part of another example of the VTR of FIG. 1, FIG. 3 and FIG. FIG. 4 is a characteristic curve diagram for explaining the VTR to which the present invention is applied, and FIGS. 5 to 10 are characteristic curve diagrams for explaining the present invention. (1) is a recording system, (4) is an emphasis circuit, and (6) is
An FM modulator, (9) is a magnetic head, and (10) is a magnetic tape as a magnetic recording medium.

Claims (1)

[Claims] 1. A magnetic recording device for recording an FM-modulated signal of a video signal on a magnetic recording medium exhibiting a single-peaked inverse wavelength characteristic, wherein the carrier frequency of the FM-modulated signal is unimodal. The emphasis circuit of the FM modulator is selected to be larger than the vicinity of the peak corresponding frequency of the frequency characteristics of the reproduced output to be presented, and to enhance the band of the predetermined frequency or more determined according to the difference between the carrier frequency and the peak corresponding frequency. Installed in the front stage,
A magnetic recording device characterized in that FM modulation is performed after the video signal is emphasized.