JPH04152790A - Delay circuit for magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To eliminate deterioration in a differentiating gain(DG) and a differentiating phase(DP) at recording and reproduction resulting from the deterioration in the linearity of a delay element by providing a switch and an inverting amplifier to an input and an output of the delay element so as to differentiate the polarity of a signal passing through the delay element at the recording and the reproduction state. CONSTITUTION:A video signal from an input terminal 7 is inputted to an inverting amplifier 2 at recording, in which the polarity is inverted and the result enters a switch 3 and a delay element 1. The video signal delayed by one horizontal period by the delay element 1 is inputted again into an inverting amplifier 4, the polarity is restored and the result is inputted to a switch 5. The video signal outputted from the switch 5 and delayed by one horizontal period is outputted to a next stage circuit from an output terminal 6. Then the switches 3, 5 are switched to the position of reproduction at the reproduction. The video signal is inputted to the delay element 1 while the polarity is not inverted. A signal shown in figure (a) passes through the delay element 1 at recording and a signal shown in figure (b) passes through the delay element 1 at reproduction.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a delay element (CCD) in a magnetic recording/reproducing device.
The present invention relates to means for improving the performance of a comb filter, a dropout compensation circuit, and a feedback line noise canceling circuit using the same.

[Prior Art] As described in Japanese Unexamined Patent Publication No. 63-308492, a conventional device combines a comb filter during recording, a dropout compensation circuit during playback, and a feedback line noise canceling circuit with a single delay element. It was composed of In particular, the polarity of the signal passing through the delay element is not made to differ between recording and reproduction, but the same polarity is used for recording and reproduction.

[Problems to be Solved by the Invention] The above-mentioned conventional technology does not take into consideration the poor DG (differential gain) and DP (IIl1 phase) caused by poor linearity of the delay element, and the problem is that the linearity is poor. There is a problem in that the use of a delay element doubles the DG and DP deterioration during recording and reproduction. This tendency is especially common in delay elements with low power consumption.

Also, the delay element has lower power consumption because it is of /11 type.

In particular, it is often used for movies with built-in cameras.

An object of the present invention is to provide DG in a delay element with poor linearity.
The object of the present invention is to use a delay element for both recording and reproduction without doubling the DP during the recording and reproduction process.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a switch circuit and an inversion circuit before and after a delay element so that the polarity of the signal passing through the delay element is different between recording and reproduction. This is what I did.

[Operation: During recording, the changeover switch and the inversion circuit are operated so that the polarity of the signal passing through the delay element is made positive or negative. Then, during reproduction, the changeover switch and the inverting circuit are operated so that the polarity is set to negative when the polarity is positive during recording, or positive when the polarity is set to negative during recording, contrary to the polarity during recording. As a result, the linearity of the delay element has opposite characteristics during recording and reproducing, and the DG and DP can be improved by combining recording and reproducing characteristics.

[Example] Hereinafter, examples of the present invention are shown in Figs. 1, 2, 3, and 4.
This will be explained using FIG. FIG. 1 shows a block diagram of a delay circuit of the present invention. FIG. 2 is a waveform diagram showing an example of a signal passing through the delay element 1 in FIG. 1. FIG. 3 shows an embodiment in which the delay circuit of the present invention is used when it operates as a comb filter circuit for separating luminance and color signals during recording, and as a feedback line noise cancellation circuit and dropout compensation circuit during playback. FIG. 2 is a block diagram illustrating an example. 4 and 5 are detailed explanatory views of the present invention. First, the operation shown in FIG. 3 will be explained. During recording, a composite video signal is input from input terminal 9,
input to switch 19. During recording and normal playback, the switch is switched to the R/P side, and the delay circuit 8, L
Input to PF18. The signal input to the delay circuit 8 is delayed by one horizontal scanning period and sent to the LPFIO to remove unnecessary components generated by the delay element. , adjust the timing so that the luminance signal and color signal can be separated. The color signal separated by the subtracter 13 is then recorded on the magnetic tape through the recording color signal output terminal 16 by a recording color signal processing circuit in the next stage. on the other hand,
The luminance signal component separated by the adder 12 is subjected to timing adjustment and band-limiting by the delay equalizer 14, and is then combined with the band-limited luminance signal from the LPF 18 and the adder 1.
5, and is recorded as a recording luminance signal from a recording luminance signal output terminal 17 onto a magnetic tape via a signal processing circuit at the next stage.

Next, the time of reproduction will be explained. The reproduced luminance signal is inputted from the input terminal 9 and further inputted to the switch 19 . During normal playback, the switch is switched to the R/P side, and the playback brightness signal is transferred to the delay circuit 8. The subtracter 21 and the subtracter 25 are inputted. The signal output from the delay circuit 8 is delayed by one horizontal scanning period and unnecessary components generated by the delay element are removed by the LPFIO. The signal from which unnecessary components have been removed enters the equalizer 11, where the timing is adjusted, and the level is adjusted by a factor of K1 by the attenuator 22. The attenuator 21 extracts uncorrelated signal components in the -horizontal period. The extracted signal enters a limiter 23 and is limited and enters an attenuator 24. The signal whose level has been adjusted twice by the attenuator 24 enters the subtracter 25 . The feedback type line noise cancellation circuit is thus configured. The noise-suppressed video signal output from the subtracter 25 is output from the reproduced luminance signal output terminal 26. Here, the amount of noise suppression can be adjusted by changing the value of K2.

Next, the operation of the dropout detection circuit will be explained.

At the time of dropout, the dropout detection circuit 20 detects the level of the FM video signal reproduced from the magnetic tape, and
When the signal is lost, a signal is generated and the switch 19 is switched to the O side.

As a result, a signal from one horizontal period ago is input to the delay circuit 8. Moreover, since there is a correlation in the output of the subtracter 21, nothing is output. As a result, a signal from one horizontal period ago is output to the reproduced luminance signal output terminal 26, and the dropout compensation circuit operates.

Next, the delay circuit of the present invention will be explained using FIG. FIG. 1 shows an internal block of the delay circuit 8 in FIG. First, I will explain the operation. During recording, the video signal is input from the input terminal 7 to the inverting amplifier 2 , the polarity of which is inverted by the inverting amplifier, and then input to the switch 3 and input to the delay element 1 . The video signal delayed by one horizontal period by the delay element 1 is again input to the switch 5 after its polarity is restored by four inverting amplifiers. The video signal outputted from the switch 5 and delayed by one horizontal period is outputted from the output terminal 6 to the next stage circuit. Next, during reproduction, switch 3 and switch 5 are switched to the reproduction side. The video signal is input to the delay element 1 without inverting its polarity.

This will be explained using FIG. 2. FIG. 2 shows an example of a signal passing through the delay element 1. When recording, see Figure 2 (
The signal a) passes through delay element 1.

During reproduction, the signal shown in FIG. 2(b) passes through.

Next, the effect when the polarity of the signal passing through the delay element 1 is made different for recording and reproduction will be explained. Currently, a CCD is used as a component of the delay element 1 for the purpose of improving the signal passband and reducing the size. Since CCDs generally consume a large amount of power, the power consumption is reduced at the expense of a certain degree of performance. Because of this sacrifice, the linearity of the circuit deteriorates.

Conventionally, the polarity of the signal passing through the delay element 1 during recording and reproduction was not made different, resulting in poor DG and DP.

FIGS. 4 and 5 show DG characteristics when recording and reproducing a ramp waveform. Figure 4 shows the DG when the polarity of the signal passing through delay element 1 is the same for recording and reproduction.
FIG. 5 shows the characteristics of the delay circuit 8 shown in FIG. 1 of the present invention.
This figure shows the DG characteristics when the polarity of the video signal passing through the delay element 1 is made different between recording and reproduction.

The characteristics shown in FIG. 4(a) show the DG characteristics from 0% to 100% of the hexagonal video signal level during recording. Next, see Figure 4 (
b) shows the DG characteristics when recording and reproduction signal processing is performed. In Figure 4, the polarity of the signal passing through delay element 1 is not different between recording and reproduction, so the video level is 0%~
It becomes a characteristic that increases DG up to 100%. On the other hand, in the case of the present invention, as shown in Figure 5, in the record (C)
The characteristics are the same as those shown in FIG. 4(a). However, during playback, the polarity of the signal passing through delay element 1 is different between recording and playback, resulting in opposite characteristics during playback, and as a result, as shown in Figure 5(d), In other words, compared to FIG. 4(b), D
G characteristics can be improved using the same delay element. In addition, DP
Improvements will also be made in the same way.

According to this embodiment, it is possible to improve the poor DG and DP characteristics in a combination of recording and reproduction caused by poor linearity of the delay element without changing the delay element.

Next, a second embodiment of the present invention will be described using FIG. 6. FIG. 6 shows a video signal processing circuit of a magnetic recording and reproducing apparatus using the delay circuit of the present invention, including a luminance signal separation comb filter, a color signal separation comb filter, a dropout compensation circuit, and a feedback line noise cancellation circuit. FIG. Here, the operations of the luminance signal/chrominance signal separation comb filter, dropout compensation circuit, and feedback type line noise canceling circuit are the same as in the first embodiment.

In this embodiment, during reproduction, the delay circuit is used for both luminance signal processing and color signal processing, and the circuit is configured with one delay circuit.In other words, the reproduction color signal separation comb filter is also used. This embodiment differs from the first embodiment in that

Next, the operation of the circuit will be explained based on the differences.

During recording, the composite video signal is input from the input terminal 9 and then input to the switch 33, as in the first embodiment. The switch 33 is switched to the R side and outputs a composite video signal to the primary stage. The rest of the operation is the same as in the first embodiment. Next, during reproduction, a reproduced luminance signal is input from the input terminal 9. The color signal band of the input reproduced luminance signal is limited by the LPF 28. On the other hand, the color signal band of the reproduced color signal inputted from the reproduced color signal input terminal 27 is limited by the BPF 29 . Color signal output from BPF29 and LPF
The reproduced luminance signal outputted from 28 is superimposed by an adder 34. The superimposed reproduced luminance signal and reproduced color signal are sent to a delay circuit 8. The subtracter 21 and the subtracter 25 are inputted. The same signal processing as in the first embodiment is applied to the luminance signal component of the superimposed reproduced video signal. Color signal is delay circuit 8, LPFI
O. The same signal processing as in the first embodiment is performed up to the equalizer 11. The color signal output from the equalizer 11 is BPF
31. Here, the reason why the output part of the equalizer 11 is different from the luminance signal is that if the signals are taken from the same output part, the timing will not match as the color signal comb filter. The BPF 31 removes unnecessary luminance signal components.

The output of the BPF 31 is input to the subtracter 30. On the other hand, the reproduced color signal input from the reproduced color signal input terminal 27 is input to the subtracter 30 . By subtracting the signals input to the subtracter 30 with a time difference of -horizontal period, a color signal comb filter is realized and adjacent crosstalk components during reproduction are removed. The color signal from which the adjacent crosstalk components have been removed, which is output from the subtracter 30, is output from the reproduced color signal output terminal 32 to the subsequent video signal processing circuit.

Next, regarding dropout, the operation is the same as in the first embodiment.

Here, the delay circuit 8 is a circuit shown in FIG. 1, and operates so that the polarity of the video signal passing through the delay element 1 is different between recording and reproduction. In this embodiment, since the luminance signal and the color signal are superimposed and the delay element 1 is used, the delay circuit 8 of the present invention
If the delay circuit 8 of the present invention is not used in the circuit of the first embodiment,
The luminance signal has a negative effect on the color signal, and DG and DP become worse than in the case where the chrominance signal is not used.

According to this embodiment, the improvement effect is greater than the improvement effect of DG and DP in the first embodiment.

[Effects of the Invention] According to the present invention, in a delay circuit of a magnetic recording/reproducing device, poor DG and DP during recording and reproduction caused by poor linearity of a delay element can be prevented.

Improvements can be made without significantly increasing the number of circuits.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a delay circuit according to an embodiment of the present invention, FIG. 2 is a waveform diagram showing an example of a signal passing through the delay element in FIG. 1, and FIG. 3 is an overall block diagram of the present invention. , FIG. 4 and FIG. 5 are detailed explanatory diagrams of the present invention, and FIG. 6 is a block diagram showing a second embodiment of the present invention. 1... Delay element, 2, 4... Inverting amplifier, 3
．． 5...Switch, 6...Output terminal. System 1 [21 Figure 2 Bore 30 No. 4 [21

Claims (1)

[Claims] 1. Has a recording and reproducing function, and includes a delay element that constitutes a luminance signal and color signal separation comb filter during recording, and a dropout compensation circuit and a feedback line noise canceling circuit during reproduction. In the delay circuit of a magnetic recording and reproducing device, a switch and an inverting amplifier are provided at the input and output portions of the delay element, and the polarity of the signal passing through the delay element is made different during recording and reproduction. Delay circuit for magnetic recording and reproducing equipment. 2. In claim 1, the delay element constitutes a comb-shaped filter for separating luminance signals and chrominance signals during recording, and during reproduction, the delay element is used to superimpose the luminance signal and the chrominance signal, and the comb-shaped filter for separating chrominance signals is used. and a delay circuit for a magnetic recording/reproducing device, in which the polarity of the signal passing through the delay element is different during recording and during reproduction when forming a dropout compensation circuit and a feedback type line noise canceling circuit.