JPH033163A - Rotary head type magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To most suitable set a slice level of a limiter to each head by providing a limiter slice level selecting circuit for selecting a comparison reference input of a voltage comparator as the slice level of the limiter in accordance with each head and giving it accordingly. CONSTITUTION:At the time of reproducing, a regenerative FM signal is read out of a tape 1 by heads 2a and 2b respectively and amplified by head amplifiers 3a and 3b, and the regenerative FM signal of each head which is under contact with the tape is selected by a head selecting circuit 4 according to a head selecting pulse P and synthesized to output one regenerative signal, which is then inputted to the limiter 6 via a regenerative equalizer 5. The limiter 6 is connected with the limiter slice level selecting circuit 9 as its comparison reference input. Then, while the head 2a is under contact with the tape 1, a voltage Ea of a 1st variable resistor 10a is selected by a switch circuit 11, and is given to the limiter 6 for its comparison reference, and while the head 2b is under contact with the tape 1, a 2nd variable resistor 10b of the circuit 11 is closed, and hence a voltage Eb is inputted.

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.

[Conventional technology]

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, with FIG. 5(a) showing a recording system and FIG. 5(b) showing a reproducing 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; 4 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 head 2b is in contact with the tape; 5 is a head selection circuit that combines the outputs of head amplifier 3a and head amplifier 3b into one signal; a reproduction equalizer for compensating the frequency characteristics of the synthesized reproduction FM signal, 6
numeral 7 is a limiter that removes the amplitude fluctuation component of the reproduced FM signal output from the reproduction equalizer, 7 is an FMi tuning circuit, and 8 is a de-emphasis circuit having a characteristic of attenuating the high-frequency component of the video signal emphasized during recording.

FIG. 6 is a top view of a rotating head used in a video tape recorder, and 15 is a rotating drum on which heads 2a and 2b are attached at an interval of 180°;
Reference numerals a and 16b are guide pins for winding the tape 1 around the rotating drum.

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' 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 7 from the tape 1, and amplify it with the head amplifiers 3a and 3b. Next, as shown in FIG. 8, the head selection circuit 4 selectively combines the reproduced FM signals of the heads in contact with the tape 1 according to the head selection pulse to form one reproduced FM signal.

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

Therefore, when the reproduction equalizer 5 suppresses the lower sideband and emphasizes the upper sideband with a frequency characteristic as shown in FIG. 10, for example, the constriction of the reproduced FM signal is reduced as shown in FIG. 9(C).

For the reproduced FM signal with this amplitude fluctuation component, the 11th
As shown in the figure, the limiter 6 consisting of a voltage comparator allows
The comparison reference input level (slice level) is shown in Figure 9 (C).
By setting the limiter near the center of the constricted portion, a reproduced FM signal from which amplitude fluctuation components have been removed can be obtained as the limiter output, as shown in FIG. 9(d).

Then, when the FM demodulation circuit 7 performs FM fill and the de-emphasis circuit 8 attenuates the high-frequency components emphasized during recording, a reproduced video signal in which high-frequency noise is also attenuated is obtained.

[Problem to be solved by the invention]

Since the conventional rotary head type magnetic recording/reproducing device is configured as described above, if the constriction of the reproduced FM signal differs depending on the head, as shown in FIG. If Ea (V) is also set, the constriction of the FM signal reproduced by the second head does not intersect with the slice level, so high frequency information is lost and becomes a low frequency, which becomes a white level when FM demodulated. There is a problem in that a phenomenon where the black level is lower than that, 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 to solve the problem]

The rotary head type magnetic recording/reproducing apparatus according to the present invention is provided with a limiter slice level selection circuit that selects and supplies the slice level of the limiter, that is, the comparison reference input of the voltage comparator, in accordance with each head.

(Function) In this invention, the limiter slice level selection circuit is configured to select and apply the slice level of the limiter, that is, the comparison reference input of the voltage comparator according to each head. The slice level can be set at the center value of the constriction of the signal, and the occurrence of the inversion phenomenon can be suppressed.

〔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.
2 is a tape, 2a and 2b are heads, 3a and 3b are head amplifiers, 4 is a head selection circuit for selecting the head amplifier output, and 5 is a reproduction equalizer. 6 is a limiter, and a limiter slice level selection circuit 9 is connected to the comparison reference input. 7 is an FM demodulation circuit, and 8 is a de-emphasis circuit.

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

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, in the head selection circuit 4, the reproduced FM signals of the heads in contact with the tape are selectively combined in accordance with the head selection pulse to form one reproduced FM signal, which is applied to the signal input of the limiter 6 via the reproduction equalizer 5. A limiter slice level selection circuit 9 is connected to the comparison reference input of the limiter 6, and a specific example thereof will be described below.

FIG. 2 is a diagram showing an example of the configuration of the limiter slice level selection circuit used in this embodiment.
is the first variable resistor, 10b is the second variable resistor, 11
is a switch circuit. The first variable resistor 10a and the second
The variable resistor tab is the power supply terminal ■ as shown in the figure. and ground, and the contacts of the variable resistors are each connected to a switch circuit 11.

Here, it is assumed that the waist portion of the reproduced FM signal output from the reproduction equalizer 5 is different between the head 2a and the head 2b as shown in FIG. While the head 2a is in contact with the tape 1, the switch circuit 11 is closed to the first variable resistor 10a, and the comparison reference input of the limiter 6 is given Ea (V) in FIG. The operation is performed normally. Furthermore, while the head 2b is in contact with the tape 1, the switch circuit 11 is closed to the second variable resistor 10b, and Eb (V) in FIG. 3 is applied to the comparison reference input of the limiter 6. , the limiter operation is performed normally in this case as well.

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 shown 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.

Furthermore, in the above embodiment, it has been explained that setting the slice level of the limiter for each head individually can suppress the occurrence of the reversal phenomenon. If the limiter slice level is not set for each head, a secondary amount will occur at the limiter output, causing carrier leak and degrading the video signal. Therefore, setting the limiter slice level for each head individually is an effective way to keep carrier leak to a low level. But it's effective.

[Effects of the Invention] As described above, according to the present invention, the limiter slice level selection circuit that selects and supplies the limiter slice level, that is, the comparison reference input of the voltage comparator according to each head, is provided. The slice level can be optimally selected for each head, which has the effect of suppressing the occurrence of an inversion phenomenon and reducing interference components such as carrier leakage.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a reproduction system in a magnetic recording and reproducing apparatus according to an embodiment of the present invention, FIG. 2 is a diagram illustrating an example of a limiter slice level selection circuit in the above embodiment,
FIG. 3 is a diagram for explaining the operation of the limiter in the above embodiment, FIG. 4 is a block diagram showing a reproducing system in another embodiment of the present invention, and FIG. 5 is a block diagram showing a conventional magnetic recording/reproducing device. Figure 6 is a view of the rotating drum viewed 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 a reproduction equalizer. FIG. 10 is a diagram showing an example of reproduction equalizer characteristics, FIG. 11 is a diagram showing the configuration of the limiter, and FIG. 12 is a diagram for explaining the operation of a limiter in a conventional example. It is a diagram. In the figure, ■ is the tape, 2a, 2b are the heads, 3a,
3b is a head amplifier, 4 is a head selection circuit, 5 is a reproduction equalizer, 6 is a limiter, 9 is a limiter slice level selection circuit, 10a and 10b are variable resistors, and 11 is a switch circuit. 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 reproduced FM A rotation device comprising: a limiter comprising a voltage comparator that limits the amplitude of a signal; and a limiter slice level selection circuit that selects a limiter slice level corresponding to each of the heads and applies it to a comparison reference input of the limiter. Head-type magnetic recording and reproducing device.