JPH0789427B2 - Magnetic recording / reproducing device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a magnetic disk whose reverse wavelength characteristic exhibits a single peak,
The present invention relates to a magnetic recording / reproducing apparatus that records an FM-modulated signal of a video signal, reproduces it, and demodulates it by FM.

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 by the solid line in FIG. 9 (only the level is represented by logarithm), the levels of the upper sideband and the lower sideband are significantly reduced as shown in FIG. 10 (only the level is represented by logarithm). Therefore, there is a drawback that the high frequency band of the video signal obtained by FM demodulation during reproduction is lowered.

Also, in the case of a magnetic disk in which the magnetic recording medium is rotated at a constant number of revolutions, the linear velocity increases toward the outer circumference and decreases toward the inner circumference, so the carrier frequency is kept constant and the FM modulated image is When the signal is recorded on such a magnetic disk, reproduced and FM demodulated,
The frequency characteristic in the figure changes from the broken line to the solid line from the outer circumference to the inner circumference of the magnetic disk.

In view of such a point, the present invention is rotated at a constant linear velocity,
In a magnetic recording / reproducing apparatus in which an FM-modulated signal of a video signal is recorded on a magnetic disk whose reverse wavelength characteristic exhibits a single peak and is then reproduced for FM demodulation, the high There is no risk of lowering the range, and high range S /
The purpose of the present invention is to propose a magnetic recording / reproducing apparatus capable of suppressing the deterioration of N.

SUMMARY OF THE INVENTION According to the present invention, an image signal is modulated by an FM modulator and recorded on a magnetic disk which is rotated at a constant linear velocity and has a single-peaked inverse wavelength characteristic. In a magnetic recording / reproducing device that reproduces a modulated video signal and supplies it to an FM demodulator for demodulation, the carrier frequency of the FM-modulated video signal has a single peak, and the peak response frequency of the frequency characteristic of the reproduction output. An emphasis circuit is installed in front of the FM modulator to detect the rotation speed of the magnetic disk while selecting a value larger than the vicinity and enhancing the band above a predetermined frequency determined according to the difference between the carrier frequency and the peak corresponding frequency. Then, a detector for controlling the carrier frequency of the FM modulator and the FM demodulator according to this rotation speed is provided.

According to the present invention, the FM-modulated signal of the video signal is recorded on the magnetic disk which is rotated at a constant linear velocity and has a single-peaked inverse wavelength characteristic, and the reproduction signal is FM-demodulated. In a magnetic recording / reproducing device, there is no fear that the high frequency range of the video signal demodulated by FM during reproduction will decrease, and the S / N ratio of the high frequency range will be reduced.
It is possible to obtain a magnetic recording / reproducing apparatus capable of suppressing deterioration of

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 magnetic recording / reproducing apparatus according to the present invention. (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 a changeover switch (5).
Is supplied to the FM modulator (6) through the recording side fixed contact R and the moving side contact M, and the FM-modulated video signal obtained from this is recorded via the recording side fixed contact R and the moving contact M of the changeover switch (7). After being supplied to (8) and amplified, its output is supplied to a magnetic head (also used for recording and reproduction) (9), and this FM-modulated video signal has a reverse wavelength characteristic of a single-peaked magnetic disk. Recorded in (10).
The magnetic head (9) is moved in the radial direction of the disk (10) by the drive device (9A).

Next, the reproducing system (2) will be described. The FM modulated video signal reproduced by the magnetic head (9) is supplied to the reproducing amplifier (12) and amplified, and its output is on the reproducing side of the changeover switch (13). The video signal is supplied to the FM demodulator (14) through the fixed contact P and the movable contact M and is FM demodulated, and the original video signal is output to the output terminal (15).

Reference numeral (11) is a detector that detects the number of revolutions of the magnetic disk (10) and controls the carrier frequencies of the FM modulator (6) and the FM demodulator (14) according to the number of revolutions. This detector (11)
Detects the number of rotations of the disk (10) according to the position on the radius of the disk (10) of the drive device (9A), and the disk (10)
The carrier frequency of the FM modulator (6) and the FM demodulator (14) is variably controlled in a step substantially proportional to or close to the number of revolutions.

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.
The frequencies fc and fm change substantially in proportion to the rotation speed of the magnetic disk (10). Thus, the video signal is FM-modulated and recorded on a magnetic disk that rotates at a constant linear velocity, and the reproduced signal is recorded.
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). In addition, (16) is a changeover switch provided between the FM demodulator (14) and the de-emphasis circuit (17). The output of the FM demodulator (14) is fixed to the movable contact M and the reproducing side of the changeover switch (16). The de-emphasis circuit (17) is supplied through the contact point P, and its output is obtained at the output terminal (15). However, during monitoring, the movable contact M of the changeover switch (16) becomes the fixed contact E on the monitor side. The output of the FM demodulator (14) is switched to the direct output terminal (1
It is designed to be obtained in 5).

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 / reproducing apparatus described above, an FM-modulated signal of a video signal is recorded on a magnetic disk which is rotated at a constant linear velocity and has a single-peaked reverse wavelength characteristic, and the FM-modulated signal is reproduced to reproduce the FM signal.
In a magnetic recording / reproducing apparatus that is designed to demodulate, it is possible to compensate for the drop in the high frequency range of the reproduced signal,
The deterioration of N can be suppressed. Also, the video signal is enhanced above a predetermined frequency determined by the difference between the carrier frequency of the FM-modulated video signal and the peak frequency of the reproduction frequency characteristic corresponding to the unimodal inverse wavelength characteristic of the magnetic disk. After FM
Since the modulation is performed, over-modulation does not occur and the amount of emphasis can be increased.

EFFECTS OF THE INVENTION According to the present invention described above, an FM-modulated signal of a video signal is recorded on a magnetic disk that is rotated at a constant linear velocity and has a single-peaked inverse wavelength characteristic, and is reproduced for FM demodulation. In such a magnetic recording / reproducing apparatus, it is possible to compensate for deterioration of the reproduced video signal in the high frequency range,
The deterioration of N can be suppressed. Also, the video signal is enhanced above a predetermined frequency determined by the difference between the carrier frequency of the FM-modulated video signal and the peak frequency of the reproduction frequency characteristic corresponding to the unimodal inverse wavelength characteristic of the magnetic disk. After FM
Since the modulation is performed, over-modulation does not occur and the amount of emphasis can be increased.

[Brief description of drawings]

FIG. 1 is a block diagram showing a main part of a circuit of an embodiment of a magnetic recording / reproducing apparatus according to the present invention, FIG. 2 is a block diagram showing a part of another example of the apparatus of FIG. 1, and FIG. FIGS. 4 and 5 are characteristic curve diagrams for explaining the device of the present invention, and FIGS. 5 to 10 are characteristic curve diagrams for explaining the present invention. (1) is a recording system, (4) is a reproducing system, (4) is an emphasis circuit, (6) is an FM modulator, (9) is a magnetic head, and (1)
0) is a magnetic disk, (11) is a detector, and (14) is an FM demodulator.

Claims (1)

[Claims] 1. An FM-modulated image recorded on a magnetic disk, which is rotated at a constant linear velocity and whose reverse wavelength characteristic exhibits a single peak, by modulating an image signal with an FM modulator and recording the signal. In a magnetic recording / reproducing apparatus that reproduces a signal and supplies it to an FM demodulator for demodulation, the carrier frequency of the FM-modulated video signal is higher than the vicinity of the peak corresponding frequency of the frequency characteristic of the reproduction output exhibiting a single peak. And an emphasis circuit that enhances a band of a predetermined frequency or higher, which is determined according to the difference between the carrier frequency and the vicinity of the peak-corresponding frequency, is provided before the FM modulator, and after the video signal is emphasized, FM modulation is not performed, and a detector for detecting the rotation speed of the magnetic disk and controlling the carrier frequency of the FM modulator and the FM demodulator according to the rotation speed is provided. A magnetic recording / reproducing apparatus characterized by being punctured.