JPH033161A - Rotary head type magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To most suitable select the slice level of a limiter corresponding to each head and to suppress the occurrence of reversal by providing a bias adjusting circuit for adjusting the DC level of regenerative FM signal in a DC component part before inputting a head selecting circuit and DC-coupling an output of the head selecting circiut and a signal input of the limiter. CONSTITUTION:At the time of reproducing with the rotary head type magnetic recording and reproducing device, the regenarative FM signal is read out of a tape 1 by heads 2a and 2b respectively and amplified by head amplifiers 3a and then given to the bias adjusting circuits 4a and 4b. A DC component is interrupted by capacitors 10 of these adjusting circuits 4a and 4b, and each DC bias is given again to the DC-interrupted regenerative FM signal by variable resistors 11 respectively. Then, the outputs of the circuits 2a and 2b are selected by the head selecting circuit 5 and DC-coupled with a regenerative equalizer 6 and the limiter 7, and the regenerative FM signal is limited to an amplitude by the limiter 7, and then the slice level of the limiter is most suitable selected for each head.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a rotary head type magnetic recording and reproducing device that records and reproduces video signals by FM modulating them, and particularly relates to a limiter that limits the amplitude of reproduced FM signals in the device. It is something.

[Prior Art] Fig. 5 is a block diagram showing an example of a video tape recorder, which is a conventional rotary head type magnetic recording/reproducing device. Fig. 5(a) shows the recording system, and Fig. 5(b) shows the reproducing system. Show the system. In FIG. 5(a), 12 is a pre-emphasis circuit that emphasizes the high-frequency components of the video signal, 13 is an FM modulation circuit that performs FM modulation on the video signal with the high-frequency components emphasized, and 14 is the output of the FM modulation circuit 13. Recording amplifier that amplifies FM signals, 2a
, 2b is a head for recording and reproducing signals, and 1 is a tape.

In addition, in FIG. 5(b), 3a and 3b are heads 2a,
2b is a head amplifier that amplifies the reproduced FM signal; 5 is a head selection circuit that selects and combines the outputs of head amplifier 3a and head amplifier 3b according to which head 2a or 2b is in contact with tape 1; and 6 is a head selection circuit that combines the outputs of head amplifier 3a and head amplifier 3b into one signal. Synthesized playback F
A playback equalizer that compensates for the frequency characteristics of the M signal, 7 a transmitter that removes the amplitude fluctuation component of the playback FM signal output from the playback equalizer, 8 an FM demodulation circuit, and 9 attenuates the high-frequency components of the video signal that are emphasized during recording. This is a de-emphasis circuit with characteristics that allow

FIG. 6 is a top view of a rotary head used in a video tape recorder, and 15 indicates that heads 2a and 2b are
The rotating drums 16 are attached at intervals of 80'', and numeral 16 is a guide pin for winding the tape 1 around the rotating drum 15.

Next, the operation will be explained using FIGS. 5 to 12.

A pre-emphasis circuit 12 emphasizes high-frequency components of the input video signal, and an FM modulation circuit 13 performs FM modulation. Thereafter, the signal is amplified by the recording amplifier 14 and recorded on the tape 1 by the heads 2a and 2b. At this time, the tape 1 is wound around the rotating drum 15 by more than 180 degrees as shown in FIG. This is only during the period in which it is in contact with 1. Therefore, the recording pattern on the tape 1 is recorded in two areas a and b for each head as shown in FIG.

During playback, the heads 2a and 2b each read out the playback FM signal from the tape 1, and the head amplifiers 3a and 3b amplify it.

Next, as shown in FIG. 8, the head selection circuit 5 selectively combines the reproduced FM signals of the heads in contact with the tape 1 to form one reproduced FM signal.

Generally, when an FM signal is recorded and reproduced using a t-magnetic conversion system using a tape and a head, the lower sideband is emphasized and the upper sideband is suppressed, causing imbalance in the sidebands at the same time as the modulation index changes. Therefore, the pre-emphasis circuit 12
The reproduced FM signal corresponding to the rising portion of the video signal (FIG. 9(a)) with its high-frequency components emphasized becomes greatly constricted as shown in FIG. 9(b).

Therefore, when the reproduction equalizer 6 suppresses the lower sideband and emphasizes the upper sideband with the frequency characteristic shown in FIG. 10, for example, the constriction of the reproduced FM signal is reduced as shown in FIG. 9(C).

The reproduced FM signal having the amplitude fluctuation component is processed by a limiter 7 consisting of a voltage comparator as shown in FIG. By setting , a reproduced FM signal from which the amplitude fluctuation component has been removed is obtained as the limiter output as shown in FIG. 9(d).

Then, the FM demodulation circuit 8 demodulates the FM, and the de-emphasis circuit 9 attenuates the high frequency components emphasized during recording.
A reproduced video signal in which high-frequency noise is also attenuated can be obtained.

[Problems to be Solved by the Invention] Since the conventional rotary head type magnetic recording/reproducing device is configured as described above, as shown in FIG. When the slice level of the second head is set to Ea (V) in accordance with the first head, the constriction of the reproduced FM signal of the second head does not intersect with the slice level, so high frequency information is lost and the frequency becomes low. There is a problem in that a phenomenon in which the white level becomes lower than the black level after FM demodulation, that is, an inversion phenomenon occurs for the second head.

This invention was made to solve the above-mentioned problems, and it provides a rotating head type magnetic recording and reproducing device that can optimally set the slice level of the limiter for each head and suppress the occurrence of reversal phenomena. The purpose is to obtain equipment.

[Means for Solving the Problems] A rotary head type magnetic recording/reproducing device according to the present invention includes a bias adjustment circuit that adjusts the DC level of a reproduced FM signal at a DC-coupled portion before inputting the head selection circuit. The selection circuit output and the limiter signal input are DC-coupled.

[Effect]

In this invention, a bias adjustment circuit is provided for adjusting the DC level of the reproduced FM signal at a DC-coupled portion before the input of the head selection circuit, and the output of the head selection circuit and the signal input of the limiter are configured to be DC-coupled. , the limiter can set the slice level at the center value of the constriction of the reproduced FM signal of each head, and can suppress the occurrence of the inversion phenomenon.

〔Example] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a reproducing system of a rotary head type magnetic recording and reproducing apparatus according to an embodiment of the present invention.
is a tape, 2a and 2b are heads, and 3a and 3b are head amplifiers. 4.4b is a bias adjustment circuit that applies a DC bias to the reproduced FM signal output from the head amplifier to adjust the DC potential; this is the head selection circuit 5.4b. It is DC-coupled to the reproduction equalizer 6° limiter 7. 8 is FM
Demodulation circuit 9 is a de-emphasis circuit.

Next, the operation will be explained using FIGS. 1 to 3.

During playback, heads 2a and 2b each read out a playback FM signal from tape 1, amplified by head amplifiers 3a and 3b, and applied to bias adjustment circuits 4a and 4b.

A specific example of the bias adjustment circuit will be described below.

FIG. 2 is a diagram showing an example of the configuration of the bias adjustment circuit used in this embodiment. In the figure, 10 is a capacitor that blocks a DC component, and 11 is a variable resistor. The variable resistor 11 is connected between ta+■, c and the ground as shown in the figure, and the voltage at the contact point of the variable resistor 11 is configured to give DC bias again to the reproduced FM signal whose DC component has been cut off. This is the head selection circuit 5. The reproduction equalizer 6 and limiter 7 are also DC-coupled.

Here, it is assumed that the constriction portion of the reproduced FM signal output from the reproduction equalizer 6 is different between the head 2a and the head 2b as shown in FIG. 3(b). and head selection circuit 5. Each bias adjustment circuit 4 is adjusted so that the center values of the constriction part of the reproduced FM signal that has passed through the reproduction equalizer 6 are equal.
Adjust a and 4b. With this bias adjustment, the output of the reproduction equalizer becomes as shown in FIG. 3(C).

Therefore, the limiter operation is performed at the optimum slice level for both the head 2a and the head 2b, so that the occurrence of the reversal phenomenon can be suppressed.

In the above embodiment, the case where the reproduction equalizer is located at the latter stage of the head selection circuit has been explained, but as in another embodiment of the present invention shown in FIG. Setting the equalizer characteristics accordingly is even more effective in reducing the occurrence of the inversion phenomenon.

In addition, in the above embodiment, it was explained that the limiter has the effect of suppressing the occurrence of the inversion phenomenon by setting the slice level to the center value of the fin portion of the reproduced FM signal of each head. If the limiter slice level is not set near the level where the duty ratio of Setting this value is also effective in keeping carrier leakage low.

〔Effect of the invention〕

As described above, according to the present invention, the bias adjustment circuit is provided to adjust the DC level of the reproduced FM signal at the DC-coupled portion before the head selection circuit input, and the head selection circuit output and the signal input of the limiter are connected to the DC-coupled portion. Because of the combined configuration, the slice level of the limiter can be optimally selected for each head, suppressing the occurrence of the reversal phenomenon, and having the effect of reducing interference components such as carrier leakage.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a reproducing system in a magnetic recording and reproducing apparatus according to an embodiment of the present invention, FIG. 2 is a diagram showing an example of a bias adjustment circuit in the above embodiment, and FIG. 3 is a diagram showing a limiter in the above embodiment. Diagram for explaining the operation, No. 4
FIG. 5 is a block diagram showing a reproducing system according to another embodiment of the present invention, FIG. 5 is a block diagram showing a conventional magnetic recording/reproducing device, and FIG.
The figure is a view of the rotating drum from above, Figure 7 is a diagram showing the recording pattern on the tape, Figure 8 is a diagram to explain the operation of the head selection circuit, and Figure 9 is the operation of the reproduction equalizer and limiter. FIG. 10 is a diagram showing an example of reproduction equalizer characteristics, FIG. 11 is a diagram showing the configuration of a limiter, and FIG. 12 is a diagram explaining the operation of a limiter in a conventional example. 1 is a tape, 2a and 2b are heads, 3a and 3b are head amplifiers, 4 is a bias adjustment circuit, 5 is a head selection circuit,
6 is a reproduction equalizer, 7 is a limiter, 8 is an FM demodulation circuit, 9 is a de-emphasis circuit, 10 is a capacitor, 11
is a variable resistor. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] (1) In a rotary head type magnetic recording and reproducing device that FM modulates a video signal and records and reproduces it using two or more rotary heads, the head selection circuit selects the reproduced FM signal of the head that is in contact with the tape, and the head a bias adjustment circuit that adjusts the DC level of the reproduced FM signal at a DC-coupled portion before inputting the selection circuit; and a bias adjustment circuit that is DC-coupled with the output of the head selection circuit, and a
A rotary head type magnetic recording and reproducing device comprising: a limiter that limits the amplitude of an M signal.