JPH0644326B2 - Magnetic recording / reproducing device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention records an FM modulated signal of a wide band signal such as a video signal on a thin film magnetic recording medium whose reverse wavelength characteristic exhibits a single peak and reproduces it. The present invention relates to a magnetic recording / reproducing device for FM demodulation.

Background Art and Its Problems Conventional magnetic tape (cassette tape) such as gamma-hematite and metal tape has a reverse wavelength (1 / λ) characteristic of
As shown in the figure (1 / λ and level are expressed in logarithm), it shows a substantially monotonic decreasing characteristic in the direction in which 1 / λ becomes large, so that it is shown in FIG. 8 (only level is expressed in logarithm). An FM-modulated video signal (fc: carrier frequency, fc + fp: upper sideband frequency, fc-fp: lower sideband frequency, fp: maximum frequency of video signal) having a frequency (f) spectrum as described above is generated by a rotary magnetic head. When recorded on such a magnetic tape and reproduced, 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 increased as shown in FIG. 9 (only the level is represented by logarithm). Although lowering, the lowering of the upper sideband level is compensated by the lowering of the lower sideband level, so there is no risk of lowering the high frequency range of the video signal obtained by FM demodulation during reproduction.

However, the reverse wavelength characteristic of the grooved magnetic recording medium is
As shown in the figure (1 / λ and level are expressed in logarithm), it exhibits a single peak having a peak in the short wavelength region. Therefore, an FM modulated video signal as shown in FIG. When horizontal or vertical recording is performed on a medium and an attempt is made to reproduce it, the reproduction frequency characteristic is as shown in FIG. 7 in consideration of the relational expression of f = v / λ (where v is the relative speed between the head and the tape). As shown in FIG. 10 (only the level is represented by logarithm), the levels of the upper sideband and the lower sideband are significantly reduced as shown in FIG. 11 (only the level is represented by logarithm). There is a drawback that the high frequency band of the video signal obtained by FM demodulation during reproduction is lowered.

SUMMARY OF THE INVENTION In view of the above problems, the present invention is a magnetic recording in which an FM-modulated signal of a wideband signal is recorded on a thin film magnetic recording medium whose reverse wavelength characteristic exhibits a single peak, and the signal is reproduced for FM demodulation. It is an object of the present invention to propose a magnetic recording / reproducing apparatus in which there is no fear that the high frequency band of the broadband signal demodulated by FM in reproduction will decrease.

SUMMARY OF THE INVENTION According to the present invention, an image signal is modulated by an FM modulator and recorded on a thin film magnetic recording medium whose reverse wavelength characteristic exhibits a single peak.
A magnetic recording / reproducing apparatus for reproducing an FM-modulated video signal recorded on the thin-film magnetic recording medium and supplying it to an FM demodulator for demodulation, wherein a reproduction frequency characteristic peak corresponding frequency corresponding to an inverse wavelength characteristic Is substantially equal to each other, and an equalizer circuit having substantially the opposite frequency characteristic is provided in the preceding stage of the FM demodulator. The equalizer circuit provides a signal current source to which an FM-modulated video signal is supplied and a signal current source therefor. A matching element to be connected, delay means for inputting the output of the matching element, and a first buffer circuit connected to the delay means,
A second buffer circuit connected to the matching element, and a second buffer circuit
A cosine equalizer composed of a variable attenuator connected to the buffer circuit and a combiner for combining the output of the variable attenuator and the output of the first buffer circuit. Is.

According to the present invention, an image signal is modulated by an FM modulator and recorded on a thin film magnetic recording medium whose reverse wavelength characteristic exhibits a single peak, and the F-subject recorded on the thin film magnetic recording medium is recorded.
In a magnetic recording / reproducing apparatus which reproduces an M-modulated video signal and supplies it to an FM demodulator for demodulation,
It is possible to obtain a magnetic recording / reproducing apparatus that can obtain stable reproduction characteristics without the possibility that the high frequency band of the demodulated wideband signal will decrease.

Embodiment An embodiment of the present invention will be described below with reference to FIG. FIG. 1 shows an essential 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 from the input terminal (3) is supplied to the FM modulator (4), and the FM-modulated video signal obtained from this is supplied to the recording amplifier (5) and amplified, and then the output is for recording. The FM-modulated video signal is supplied to the magnetic head (6) and recorded on the thin-film magnetic tape (7) whose reverse wavelength characteristic exhibits a single peak.

Next, the reproducing system (2) will be described. The reproducing magnetic head
The FM-modulated video signal reproduced by (8) is supplied to the reproduction amplifier (9) for amplification, and its output is supplied to the FM demodulator (11) through the equalizer circuit (10) for FM demodulation, The obtained original video signal is output to the output terminal (12).

As shown in FIG. 3, the equalizer circuit (10) has a peak and a peak corresponding frequency both coincident with the reproduction frequency characteristic curve (14) shown in FIG. 10, and exhibits an inverse frequency characteristic curve (15).

Thus, the frequency spectrum of the reproduced FM-modulated video signal has the level of both sidebands lowered as shown by the curve (16) shown by the solid line in FIG. 4 (only the level is represented by logarithm). , Both sidebands are flat as a whole, as shown by the curved line (17). Thus, there is no possibility that the high frequency band of the reproduced video signal obtained by FM-modulating and recording the video signal and demodulating the reproduced signal is deteriorated.

By the way, the equalizer circuit (10) may be composed of a cascade circuit of a high-frequency boost equalizer (10H) and a low-frequency boost equalizer (10L) as shown in FIG. Since the characteristics are non-linear, there is a drawback that stable reproduction characteristics cannot be obtained.

Therefore, it is desirable that the equalizer circuit (10) described above has a linear phase characteristic. A specific circuit example of such an equalizer circuit will be described with reference to FIG. This is a kind of cosine equalizer and has a characteristic that the phase characteristic is linear. Reference numeral (20) is a signal current source for the FM-modulated video signal, which is a delay circuit (matching the delay amount) for matching and opening the receiving end through a series circuit of a variable resistor (21) and a variable inductor (22) for matching. td) (23) and buffer circuit (2
6) Connected to each input side. The output of the delay circuit (23) is supplied to the combiner (amplifier) (25) through the buffer circuit (24). The output of the buffer circuit (26) is supplied to the combiner (25) through the variable attenuator (the attenuation rate is K) (27) and added to the output of the buffer circuit (24), and the added output is obtained. It is output to the output terminal (28).

If the signal current of the signal current source (20) is (1/2) sin2πft (however, f: frequency, t: time), the delay circuit (23)
And the input signal to the buffer circuit (26) is (1/2) sin2πf (t-2td) + (1/2) sin2πft The output signal of the buffer circuit (24) is (1/2) sin2πf (t-td ) The output signal of the variable attenuator (27) becomes k {(1/2) sin2πft + (1/2) sin2πf (t-2td)}, so the output signal of the output terminal (28) is (1 + k cos2πftd ) ・ Sin2πf (t-td). The peak corresponding frequency fm is represented by fm = 1 / 2td.

According to the present invention described above, an FM-modulated signal of a broadband signal is recorded on a magnetic recording medium whose reverse wavelength characteristic exhibits a single peak.
In a magnetic recording / reproducing apparatus for reproducing it and performing FM demodulation, a magnetic recording / reproducing apparatus capable of obtaining stable reproduction characteristics without a fear that the high frequency band of the FM demodulated wideband signal is lowered during reproduction is obtained. be able to.

[Brief description of drawings]

FIG. 1 is a block diagram showing a main 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 reference example of an equalizer circuit of the apparatus of FIG. 1, FIGS. FIG. 5 is a characteristic curve diagram for explaining a VTR to which the present invention is applied, FIG. 5 is a block diagram showing a concrete configuration example of an equalizer circuit of the apparatus of FIG. 1, and FIGS. 6 to 11 are explanations of the present invention. FIG. 3 is a characteristic curve diagram for use in FIG. (1) is a recording system, (2) is a reproducing system, (4) is an FM modulator, (6) is a magnetic head, (7) is a magnetic tape as a magnetic recording medium, and (1)
0) is an equalizer circuit, and (11) is an FM demodulator.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-52-131708 (JP, A) JP-A-56-81517 (JP, A) JP-A-51-67115 (JP, A)

Claims (1)

[Claims] 1. A video signal is modulated and recorded by an FM modulator on a thin film magnetic recording medium exhibiting a single-peak inverse wavelength characteristic, and the FM-modulated video signal recorded on the thin film magnetic recording medium is reproduced. A magnetic recording / reproducing apparatus for supplying to an FM demodulator for demodulation, wherein an equalizer circuit having reproduction frequency characteristic peak corresponding frequencies corresponding to the above-mentioned inverse wavelength characteristics and having substantially opposite frequency characteristics is provided. The equalizer circuit is provided in the preceding stage of the FM demodulator, and the equalizer circuit inputs a signal current source to which the FM-modulated video signal is supplied, a matching element connected to the signal current source, and an output of the matching element. Delay means, a first buffer circuit connected to the delay means, a second buffer circuit connected to the matching element, a second variable attenuator connected to the second buffer circuit, and the variable attenuation circuit. Magnetic recording and reproducing apparatus characterized in that it is constituted by the output and the cosine equalizer is composed of a combiner for combining the outputs of said first buffer circuit.