JPH0486079A - Video processor - Google Patents

Abstract

PURPOSE:To stably and quickly issue the response of a main video intermediate frequency amplifier circuit by providing an AGC(Automatic Gain Control) means with a variable feedback time constant, and varying the feedback time constant by detecting the state of a reception signal. CONSTITUTION:A first AGC means 7 filters a first AGC signal fetched from a first composite video signal by an AGC filter means 9 with variable time constant, and feeds it back to a first video intermediate amplifier means 3, and a second AGC means 27 feeds back a second AGC signal fetched from a second composite video signal at a sub route to a second video intermediate frequency amplifier means 23. An AGC filter control means 29 detects the level range of the second composite video signal or that of the second AGC signal, and performs control to vary the time constant of the AGC filter means 9. Thereby, it is possible to stably and quickly issue the response of the first video intermediate frequency amplifier means 3 even when the reception signal receives disturbance due to ghost or flattering.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a video processing device, and particularly relates to AGC control and A/PC control configuration of a television receiver.

[Prior Art] Includes AGC control, APC control elliptical configuration, video intermediate frequency amplification circuit, synchronous detection circuit, etc.

Conventionally, a predetermined AGC (Auto
The AGC control signal is filtered by a low-pass filter with a constant time constant and fed back to a video intermediate frequency amplification circuit or the like. Therefore, stable video intermediate frequency amplification characteristics that are not affected by the high frequency components of the AGC signal and noise can be obtained.

Furthermore, in the past, APC (^Utomati
A VCO (Voltage Controlled 0
scillator) circuit to keep it phase-locked.

Therefore, stable synchronous detection characteristics that are not affected by high frequency components of the APC signal or noise can be obtained.

[Problems to be Solved by the Invention] However, when the received signal is interfered with by ghosts and flutter, the forms of this interference are various, so filters with a constant time constant are often unable to cope with the problem, and video intermediate frequency amplification and synchronization are difficult. There was a drawback that the detection operation became unstable.

The present invention was made under these circumstances, and an object of the present invention is to provide a video processing device that can obtain stable video intermediate frequency amplification characteristics even if a received signal is interfered with by ghosts or flutter.

Another object of the present invention is to provide a video processing device that can obtain stable synchronous detection characteristics even if a received signal is interfered with by ghosts or flutter.

A further object of the present invention is to provide a video processing device that can provide a stable video detection output even if a received signal is interfered with by ghosts or flutter.

[Means for Solving the Problems] The first aspect of the present invention is such that stable video intermediate frequency amplification characteristics can be obtained even if the received signal is interfered with by ghosts or flutters, and the first AGC means , second AG
It is equipped with C means and AGC filter control means.

The first AGC means filters the first AGC signal extracted from the first composite video signal using an AGC filter means with a variable time constant, and feeds it back to the first video intermediate frequency amplification means; 2nd AG
C means is the second AG extracted from the second composite video signal.
The C signal is fed back to the second video intermediate frequency amplification means. The AGC filter control means detects the level range of the second composite video signal or the second AGC signal and performs control to change the time constant of the AGC filter means.

The second aspect of the present invention is such that stable synchronous detection characteristics can be obtained even if the received signal is disturbed by ghosts or flutter, and the first phase control means, the second phase control means, and the APC filter It is equipped with control means.

The first phase control means converts the first APC signal extracted based on the first phase difference between the carrier wave of the first video intermediate frequency signal and its detection signal into an AP having a variable time constant.
The filter is filtered by the C filter means and fed back to the first voltage controlled oscillation means, and the second phase control means is configured to filter the second video intermediate frequency signal between the carrier wave of the second video intermediate frequency signal and the detection signal. The second APC signal collected based on the phase difference is fed back to the second voltage controlled oscillation means. The APC filter control means is
The level range of the signal based on this second phase difference or the second APC signal is detected to perform control to change the time constant of the APC filter means.

The third aspect of the present invention is to obtain stable video detection output even if the received signal is interfered with by ghost or flutter.
That is, stable video intermediate frequency amplification characteristics and stable synchronous detection characteristics can be obtained, and both the above-mentioned means according to the first and second aspects of the present invention are provided.

U effect] In the first aspect of the present invention, in the main route, the first AGC means filters the first AGC signal extracted from the first composite video signal using the AGC filter means having a variable time constant. It feeds back to the first video intermediate frequency amplification means, and in its subsidiary route, the second AG
C means is a second AG extracted from the second composite video signal.
The C signal is fed back to the second video intermediate frequency amplification means.

The A, GC filter control means detects the level range of the second composite video signal or the second AGC signal and performs control to change the time constant of the AGC filter means.

Therefore, even if the received signal is disturbed by ghost or flutter, the first video intermediate frequency amplifying means responds stably and quickly.

In addition, in the second invention, in its main route,
The first phase control means uses an APC filter means with a variable time constant to extract the first APC signal based on the first phase difference between the carrier wave of the first video intermediate frequency signal and its detection signal. It is filtered and fed back to the first voltage controlled oscillation means, and in its secondary route,
The second phase control means generates a second APC signal based on a second phase difference between the carrier wave of the second video intermediate frequency signal and its detection signal, and generates a second voltage-controlled oscillation signal. Feedback to the means.

Then, the APC filter control means detects the level range of the signal based on this second phase difference or the second APC signal, and performs control to change the time constant of the APC filter means.

Therefore, even if the received signal is interfered with by goose 1- or flutter, the first phase control means responds stably and quickly.

The third invention is a combination invention of the first and second inventions, and each means performs the same function as the corresponding means of the first and second inventions.

Therefore, even if the received signal is interfered with by ghost I or flutter, a stable video detection output can always be obtained in the main loops 1 to 1.

Embodiment] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a video processing device according to the present invention.

In FIG. 1, a tuner circuit 1 has a conventionally known circuit configuration for converting a tuned reception signal into an intermediate frequency, and includes a first (main route) video intermediate frequency amplification circuit 3 and a second video intermediate frequency amplification circuit 3.
(Secondary route) video intermediate frequency signal F! ! 423.

The first video intermediate frequency amplification circuit 3 has a conventionally known circuit configuration for amplifying the video intermediate frequency signal from the tuner circuit 1 and outputs the first video intermediate frequency signal. and connected to the first APC times &@1.5.

The first video detection circuit 5 detects the input first video intermediate frequency signal using a first detection signal synchronized with the carrier wave of the first video intermediate frequency signal, and outputs a first composite video signal. The first AGC forming circuit 7 has a conventionally known circuit configuration.
It is connected to the.

Further, this first composite video signal is outputted to a subsequent stage (not shown) as a main composite video signal.

The first AGC forming circuit 7 detects the amplitudes of the horizontal and vertical synchronizing signals in the first composite video signal and outputs the corresponding first AGC signal.
It has a conventionally known circuit for forming a GC signal, and is connected to an AGC filter circuit 9.

The AGC filter circuit 9 is an AGC filter means,
This is a low-pass filter that suppresses high frequency components and noise components of the first AGC signal and outputs a first AGC control signal converted to direct current.

Specifically, it has a first filter element having a predetermined time constant and a second filter element (both not shown) having a smaller time constant than this, and has an AGC filter control circuit 29 described later. The configuration is such that these first and second filter elements are switched and selected by an AGC filter control signal from.

A first AGC means 11 is formed by the first AGC forming circuit 7 and the AGC filter circuit 9.

An AGC amplifier circuit 13 is connected to the AGC filter circuit 9, and this AGC amplifier circuit 13 is connected to the first A
The first video intermediate frequency amplification circuit 3 amplifies the C control signal.
and a conventionally known circuit E@M configuration for feeding back to the tuner circuit 1.

On the other hand, the first APC circuit B15 receives the carrier wave of the first video intermediate frequency signal and the first
The phase difference (error component) of the detection signals is compared, and an error signal (first
It has a conventionally known configuration for outputting an APC signal (APC signal), and is connected to an APC filter circuit 17.

The APC filter circuit 17 is an APC filter means, and is a loop filter that suppresses high frequency components and noise components contained in the first APC signal and outputs a first APC control signal converted into a direct current. The time constant of this APC filter circuit 17 determines the lock range of the oscillation frequency of the first CO circuit 21.

Specifically, it has a third filter element with a predetermined time constant and a fourth filter element with a smaller time constant (none of which are shown). By the APC filter control signal of
It has a configuration in which the third and fourth filter elements are switched and selected.

A first phase control means 19 is formed by the first APC circuit ii'815 and the APC filter 4E@17.

The first ■CO circuit 21 has a conventionally known circuit configuration that oscillates and outputs a first detection signal whose phase changes according to the APC control signal from the APC filter circuit 17, and includes a first video detection circuit. 5 and the first APC circuit 15.

On the other hand, the second video intermediate frequency amplification circuit 23 has a conventionally known circuit configuration that amplifies the video intermediate frequency signal from the tuner circuit B1 and outputs a second video intermediate frequency signal, and has a second video intermediate frequency amplification circuit 23. It is connected to the circuit 25 and the second APC circuit 31.

The second video detection circuit 825 detects the input second video intermediate frequency signal using a second detection signal synchronized with the carrier wave of the second video intermediate frequency signal, and outputs a second composite video signal. It has a conventionally known circuit configuration and is connected to the second AGC forming circuit 27.

The second AGC forming circuit 27 is a second AGC means that detects the amplitudes of the horizontal and vertical synchronizing signals in the second composite video signal, forms a corresponding second AGC signal, and amplifies this. This circuit feeds back the signal to the second video intermediate frequency signal circuit 823.

Further, the AGC filter control circuit 29 is connected to the second AGC formation circuit 827.

The AGC filter control circuit 29 is an AGC filter control means that detects the level range of the second AGC signal and
This circuit performs control to change the time constant of the GC filter circuit 9. That is, the level of the second AGC signal is compared with a predetermined level range, and when the level of the AGC signal is within the predetermined level range, the first filter element with a large time constant is selected, and the first filter element with a large time constant is selected. When the time constant is exceeded, the second filter element with a smaller time constant is selected.

Although not shown, the AGC filter control circuit 29 includes:
The configuration may be such that the level range of the second composite video signal is detected and the time constant of the AGC filter circuit #19 is controlled to be changed. That is, for example, the level of the noise signal superimposed on the horizontal and vertical synchronizing signals of the second composite video signal is detected, and if this is below a predetermined level, the second composite video signal with a smaller time constant is detected.
It is also possible to select a filter element having a larger time constant, and to select a first filter element having a larger time constant when a predetermined value is exceeded.

On the other hand, the second APC clock signal 31 is a second phase control means, which controls the carrier wave of the second video intermediate frequency signal and the second
■Compare the phase difference (error component) of the second detection signal from the CO circuit 35, form an error signal (second APC signal) such that the phase difference error approaches a predetermined level, and This circuit feeds back the signal to the second VCO #I35.

Further, an APC filter control circuit 33, which will be described later, is connected to this second APC circuit 3H.

The second VCO circuit 35 has a conventionally known circuit configuration that oscillates and outputs a second detection signal whose phase changes according to the second PC signal, and includes a second video detection port 825 and a second detection signal. 2
It is connected to the APC circuit 31 of.

An APC filter control unit 33 is an APC filter control means that detects the level range of the second APC signal and
PC filter episode fl! This circuit performs control to change the time constant of 417. That is, the level of the second APC signal is compared with a predetermined level range, and when the level of the APC signal is within the predetermined level range, the third filter element having a large time constant is selected, and the third filter element with a large time constant is selected. The fourth filter element having a smaller time constant is selected when the time constant is exceeded.

Although not shown, the APC filter control circuit 33 includes:
AP detects the level range of the signal based on the second phase difference.
The configuration may be such that control is performed to change the time constant of the C filter circuit 17. That is, for example, when the level of the error signal based on the second phase difference is detected and the level is below a predetermined value, the fourth filter element with a smaller time constant is selected, and when it exceeds the predetermined value, the third filter element with a larger time constant is selected. The filter element may be configured to be selected.

Next, the present invention configured as described above will be explained in detail.

The video intermediate frequency signal that has been tuned and frequency-converted by the tuner circuit 1 is applied to first and second video intermediate frequency amplification circuits 3.23.

The first video intermediate frequency amplification circuit 3 amplifies the video intermediate frequency signal from the tuner circuit H1 and outputs the first video intermediate frequency signal, and the first video detection circuit 4 Fl@5 outputs the first video intermediate frequency signal. The first video intermediate frequency signal is detected to obtain a first composite video signal.

The first AGC forming circuit 7 detects the amplitudes of the horizontal and vertical synchronizing signals in the first composite video signal and outputs the first AGC signal, and the AGC filter circuit 9 detects the high frequency components of the first AGC signal and outputs the first AGC signal. The first AG that suppresses noise components and converts to DC
C control signal is output. Then, the AGC amplifier circuit 13 amplifies the first AGC control signal and feeds it back to the video intermediate frequency signal circuit n3 and the tuner circuit 1, thus providing the main loop!・First video intermediate frequency amplification circuit F
I@3 performs a stable video intermediate frequency amplification operation that is not affected by the high frequency components of the first AGC signal or noise.

On the other hand, the first APC circuit 15 compares the phase difference between the carrier wave of the first video intermediate frequency signal and the first detection signal from the first CO circuit 21, and adjusts the phase difference error to a predetermined level. The APC filter circuit 17 outputs a first APC control signal that suppresses high frequency components and noise components contained in the first APC signal and converts it into a direct current. Then, the first VCO circuit 21 oscillates and outputs a first detection signal whose phase changes according to the APC control signal from the APC filter circuit B17. Generates a stable detection signal that is unaffected by the high frequency components and noise of the APC signal.

Appropriate, second v! The image intermediate frequency amplification circuit 23 amplifies the image intermediate frequency signal from the tuner circuit 1 and outputs a second image intermediate frequency signal, and the second image detection circuit 25 outputs a second image intermediate frequency signal using the second detection signal. A second composite video signal is output by detecting the video intermediate frequency signal.

The second AGC forming circuit 127 detects the amplitudes of the horizontal and vertical synchronizing signals in the second composite video signal to form a corresponding second AGC signal, and amplifies this to generate a second video intermediate frequency signal. It is fed back to the amplifier circuit 23. Thus,
In the second video intermediate frequency amplification circuit 23 of the sub-route, a video intermediate frequency amplification operation with a relatively fast response is performed in accordance with the second AGC signal.

Then, in the AGC filter control circuit 29, the second AG
The C signal level is compared with a predetermined level range, and if the second AGC signal level is within the predetermined level range, the first filter element with a large time constant in the AGC filter circuit 9 is selected, and the predetermined filter element is selected. If the range is exceeded, select a second filter element with a smaller time constant. Therefore, even if the received signal is interfered with by ghost or flutter, the first video intermediate frequency amplification circuit can quickly respond to the interference.

The AGC filter control circuit 29 detects the noise level of the second composite video signal, and if the noise level is below a predetermined value, the second composite video signal with a smaller time constant in the AGC filter cycle FIII9 is detected.
If the configuration is such that when the time constant exceeds a predetermined value, the first filter element with a larger time constant is selected, noise is superimposed on the received signal in the first video intermediate frequency amplification circuit 3. It can operate stably in any case.

On the other hand, the second APC circuit 31 compares the phase difference (error component) between the carrier wave of the second video intermediate frequency signal and the second detection signal from the second VCo circuit 35, and calculates the phase difference error. An error signal approaching a predetermined level (second APC
signal> and feeds it back to the second vCO circuit 3, etc.

The second VCO circuit 35 oscillates and outputs a second detection signal whose phase changes depending on the second APC signal. AP
The C filter control circuit 33 compares the second APC signal level with a predetermined level range, and changes the time constant in the APC filter circuit 17 when the second APC signal level is within the predetermined level range. Select a large third filter element, and when the predetermined range is exceeded, select a fourth filter element with a smaller time constant.
Select the filter element. Therefore, the first VCO circuit 21 follows relatively smoothly when the change in the phase difference is small, and quickly follows when the change in the phase difference is large.

Note that the APC filter control circuit 33 detects the level of the error signal based on the second phase difference, and when the level is below a predetermined value, selects a fourth filter element with a smaller time constant in the APC filter circuit 17, and If the configuration is such that a third filter element with a large time constant is selected when the time constant exceeds F!, the first VCO times F! In @21, the lock range is narrow while the phase difference is small, and when the phase difference becomes large, the lock range is set wide, allowing stable operation.

[Effects of the Invention] As explained above, the first aspect of the present invention has a configuration in which an AGC means with a variable feedback time constant is provided in its main route, and the feedback time constant is changed by detecting the state of the received signal. Therefore, even if the received signal is interfered with by ghost or flutter, the main video intermediate frequency amplification circuit responds stably and promptly.

Further, the second invention has a configuration in which a phase control means with a variable feedback time constant is provided in the main route, and the feedback time constant is changed by detecting the state of the received signal, so that the received signal does not become a ghost. The main phase control means responds stably and quickly even when disturbed by noise or flutter.

Furthermore, the third aspect of the present invention has a configuration in which AGC means and phase control means with variable feedback time constants are provided in the main route, and the feedback time constants are changed by detecting the state of the received signal. Even if the received signal is interfered with by ghosts or flutter, a stable video detection output can always be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a video processing device according to the present invention. DESCRIPTION OF SYMBOLS 1... tuner circuit, 3... 1st video intermediate frequency amplification circuit, 5... 1st video detection circuit, 7... 1st AGC formation circuit, 9... AGC filter circuit, 11・
...First AGC means, 13...AGC amplification circuit, 1
5... First APCPCl37... APC filter circuit, 19... First phase control means, 21... First VCO circuit, 23... Second video intermediate frequency amplification circuit,
25...21st video detection circuit, 27...2nd A
GC forming means (second AGC forming circuit), two...A
GC filter control means (AGC filter control circuit), 3
1...Second APC means (second APCPCl333
. . . APC filter control means (APC filter control circuit), 35 . . . second VCO circuit.

Claims (3)

[Claims] (1) First AGC extracted from the first composite video signal
a first AGC means for filtering the signal by means of an AGC filter means having a variable time constant and feeding it back to the first video intermediate frequency amplifying means; a second AGC means for feeding back a second AGC signal extracted from the obtained second composite video signal to a second video intermediate frequency amplification means; and the second composite video signal or the second AGC signal. and AGC filter control means for detecting a level range of and controlling a time constant of the AGC filter means to change the time constant of the AGC filter means. (2) The first A extracted based on the first phase difference between the carrier wave of the first video intermediate frequency signal and its detection signal.
a first phase control means for filtering a PC signal by an APC filter means having a variable time constant and feeding it back to the first voltage-controlled oscillation means; A second APC signal extracted based on a second phase difference between the carrier wave of the second video intermediate frequency signal obtained by processing and the detection signal thereof is fed back to the second voltage-controlled oscillation means. and APC filter control means that detects a level range of the signal based on the second phase difference or the second APC signal and controls to change the time constant of the APC filter means. An image processing device characterized by: (3) First AGC extracted from the first composite video signal
a first AGC means for filtering the signal by means of an AGC filter means having a variable time constant and feeding it back to the first video intermediate frequency amplifying means; a second AGC means for feeding back a second AGC signal extracted from the obtained second composite video signal to a second video intermediate frequency amplification means; and the second composite video signal or the second AGC signal. AGC filter control means that performs control to detect a level range of and change the time constant of the AGC filter means; and a first phase difference between the carrier wave of the first video intermediate frequency signal and the detection signal thereof. a first phase control means for filtering the first APC signal taken out by the APC filter means having a variable time constant and feeding it back to the first voltage-controlled oscillation means; and obtaining the first video intermediate frequency signal. The second APC signal extracted based on the second phase difference between the carrier wave of the second video intermediate frequency signal obtained by processing the same input signal as the second video intermediate frequency signal and its detection signal is applied to the second voltage. a second phase control means for feeding back to the controlled oscillation means; and detecting a level range of the signal based on the second phase difference or the second APC signal to perform control to change the time constant of the APC filter means. A video processing device comprising: APC filter control means.