JPH0722413B2 - Signal processor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a signal processing device using an analog delay line such as a CCD (Charge Coupled Device) delay line or a glass delay line, and more particularly to a comb-shaped delay means. The present invention relates to a signal processing device shared by a filter circuit and a dropout compensation circuit.

[Conventional technology]

Conventionally, a VTR has used a delay circuit that gives a delay amount corresponding to one horizontal synchronization period (1H) of a video signal to be handled, thereby performing crosstalk removal and dropout compensation of a reproduced video signal.

For example, in FIG. 2 showing the configuration of a comb filter system in a general VTR, a reproduction luminance signal is supplied from a signal input terminal 21 to a 1H delay line 23 via a switch circuit 22, and the first and second The signal is supplied to the second signal subtractors 25 and 27, and is further provided with a delay amount of 1H by the 1H delay line 23, and then the first pass signal is passed through a low pass filter (LPF) 24.
Signal subtractor 25.

The first signal subtractor 25 detects the crosstalk component by subtracting and synthesizing the input luminance signal supplied to the signal input terminal 21 and the luminance signal provided with the delay amount of 1H. The crosstalk component detected by the first signal subtractor 25 is suppressed to a large level by the limiter circuit 26 and supplied to the second signal subtractor 28.

The second signal subtractor 27 subtracts and synthesizes the input luminance signal and the crosstalk component to output a reproduction luminance signal from which the crosstalk component is removed, from the signal output terminal 28.

The switch circuit 22 is switched and controlled by the detection output of a dropout detection circuit (not shown), and returns the delayed luminance signal output from the 1H delay line 23 to the input side of the 1H delay line 23 when a dropout occurs. By doing so, dropout compensation is performed.

Here, as the 1H delay line 23, an analog delay line such as a CCD delay line or a glass delay line has been conventionally used.

[Problems to be solved by the invention]

As described above, in a delay circuit using an analog delay line, the gain of the delay line has a temperature characteristic of ± 0.5 dB, and the comb depth of the comb filter becomes shallower depending on the temperature, and the dropout compensation level fluctuates. There is a problem.

In order to improve the above problems, as shown in FIG. 3, a delay line 31 which gives a delay amount of (1H + nbit) is used in place of the 1H delay line 23, and the first and second delay lines 31 are used.
A method of compensating the temperature of a comb filter is also proposed, in which a delay line 32 that gives a delay amount of (nbit) is provided in the line that supplies the input luminance signal to the signal subtractors 25 and 27 of. It was not possible to correct the temperature characteristic of the out compensation signal.

In view of the conventional problems as described above, the present invention compensates for the temperature characteristics of the gain of the analog delay line, so that a dropout compensation signal and a filter output signal with stable signal level can be obtained. The present invention provides the signal processing device.

[Means for solving problems]

A signal processing device according to the present invention comprises a comb filter circuit using a delay means for delaying an input signal by a predetermined amount, a variable gain amplifying means to which an output signal of the delay means is supplied, and an output signal level of the delay means. The signal level comparing means for comparing the output signal level of the variable gain amplifying means with the input signal level of the delay means to generate the control signal of the variable gain amplifying means and the input signal of the comb filter circuit are missing. At this time, an input signal switching means for inputting the output signal of the variable gain amplifying means to the delay means is provided, and the comb filter circuit and the signal compensating circuit when the input signal is missing share the delay means and It is characterized in that the level variation by the delay means is corrected.

[Action]

In the signal processing device according to the present invention, the difference between the input and output levels of the analog delay line is detected by the level comparator, and the gain of the variable gain amplifier provided on the output side of the analog delay line is controlled. An automatic gain control loop operates to output a dropout compensation signal having a stable signal level and a filter output signal.

〔Example〕

An embodiment of a video tape recorder to which the present invention is applied will be described below in detail with reference to the drawings.

In the embodiment shown in FIG. 1, the present invention is applied to a VTR comb filter system. In this embodiment, a reproduction luminance signal is supplied from a signal input terminal 1 to a first clamp circuit 2 and the clamp circuit 2 is used. The first CCD which is clamped by the circuit 2 and then supplied to the level comparator 13 and which provides the delay amount of (1H + nbit) through the switch circuit 3
It is supplied to the delay line 4 and a second CCD delay line 5 which gives a delay amount of (nbit).

The first CCD delay line 4 has a (1H) delay output terminal and a (1H) delay output terminal.
(+ Nbit) delay output end, which is (1H + nbit)
The delayed signal is supplied to the first signal subtractor 6, and the (1H) delayed signal is supplied to the second clamp circuit 12 via the first voltage-controlled variable gain amplifier 11. Also, the second CCD
The delay line 5 supplies the (nbit) delayed signal to the first and second signal subtractors 6 and 8.

The first signal subtractor 6 detects the crosstalk component by subtracting and combining the (1H + nbit) delayed signal and the (nbit) delayed signal. The crosstalk component detected by the first signal subtractor 6 is suppressed to a large level by the limiter circuit 7 and supplied to the second signal subtractor 8. The second signal subtractor 8 subtracts and synthesizes the (nbit) delayed signal and the crosstalk component, and the reproduced luminance signal from which the crosstalk component is removed is passed through a second voltage control type variable gain amplifier 9. Output from the signal output terminal 10.

The second clamp circuit 12 clamps the (1H) delay signal supplied via the first voltage control type variable gain amplifier 1 and supplies it to the level comparator 13 and also to the switch circuit 3. Supply.

The switch circuit 3 is switched and controlled by the detection output of a dropout detection circuit (not shown), and when the dropout occurs, the (1H) delay signal is used as a dropout compensation signal to the first and second CCD delay lines 4,5. Dropout compensation is performed by returning to each input side of.

Then, the level comparator 13 is provided with the first and second levels.
The signal levels of the clamp output signals of the clamp circuits 2 and 12 are compared, and the comparison error output is used to output the first and second signals.
The gain control of the voltage-controlled variable gain amplifiers 11 and 9 is performed.

The first voltage-controlled variable gain amplifier 11 ensures that the clamp output signals of the first and second clamp circuits 2 and 12, that is, the input signal of the CCD delay line 4 and the output signal level always match. Further, automatic gain control (AGC) is performed by the level comparator 13 to output a dropout compensation signal having a stable signal level.

By detecting the difference between the input and output levels of the analog delay line and applying AGC as in this embodiment, it is possible to effectively compensate for the fluctuation of the signal level due to the temperature characteristics of the gain of the analog delay line. .

Here, in this embodiment, the signal level of the dropout compensation signal is the first voltage controlled variable gain amplifier 11
However, the output signal of the second signal subtractor 8, that is, the output signal of the comb-shaped filter is influenced by the temperature characteristics of the gains of the first and second CCD delay lines 4 and 5. Therefore, the output voltage of the second signal subtractor 8 is supplied to the second voltage-controlled variable gain amplifier 9 which is stable by multiplying the comparison error output from the level comparator 13 by the feedforward AGC. The reproduced luminance signal of the specified signal level is obtained.

By detecting the difference between the input and output levels of the analog delay line and applying AGC as in this embodiment, it is possible to effectively compensate for the fluctuation of the signal level due to the temperature characteristics of the gain of the analog delay line. .

In the above embodiment, (1H + nbit) delay line 4 and (nbi)
t) The present invention is applied to a comb-shaped filter using two analog delay lines of the delay line 5, but the present invention is not limited to the above embodiment, and for example, one (1H) delay line is provided. In the conventional example shown in FIG. 2 which is used only, a variable gain amplifier is provided on the output side of the low-pass filter 24, the difference between the input and output levels of the analog delay line is detected, and AGC is applied. By compensating the fluctuation of the signal level due to the temperature characteristic of the gain of the delay line and the like, it is possible to obtain the dropout compensation signal and the reproduction luminance signal of the stable signal level.

〔The invention's effect〕

As is apparent from the above description of the embodiments, in the delay circuit according to the present invention, the difference between the input and output levels of the analog delay line is detected by the level comparator, and the variable gain provided on the output side of the analog delay line is detected. By controlling the gain of the amplifier,
Since a so-called automatic gain control loop operates, it is necessary to compensate the level variation of the delayed output signal due to the temperature characteristic of the gain of the analog delay line and output the dropout compensation signal and the filter output signal with stable signal levels. You can

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment in which a delay circuit according to the present invention is applied to a VTR comb filter system. FIG. 2 is a block diagram showing a conventional example of a VTR comb filter system using a conventional delay circuit, and FIG. 3 is a block diagram showing another conventional example. 1 …… Signal input terminal 2,12 …… Clamp circuit 4,5 …… CCD delay line 9,11 …… Voltage control type variable gain amplifier 13 …… Level comparator

Claims (1)

[Claims] 1. A comb filter circuit using a delay means for delaying an input signal by a predetermined amount, a variable gain amplifying means to which an output signal of the delay means is supplied, an output signal level of the delay means or the variable gain amplification. The signal level comparing means for comparing the output signal level of the means with the input signal level of the delay means to generate the control signal of the variable gain amplifying means, and the variable level when the input signal of the comb filter circuit is missing. Input signal switching means for inputting the output signal of the gain amplifying means to the delay means, the comb filter circuit and the signal compensating circuit when the input signal is missing share the delay means, and the level by the delay means is provided. A signal processing device characterized by correcting fluctuations.