JPH04261291A - Energy spread signal elimination device - Google Patents

Abstract

PURPOSE:To realize the energy spread signal elimination device able to surely eliminate an energy spread signal included in a MUSE signal. CONSTITUTION:An energy spread signal included in a MUSE signal is clamped and suppressed by a clamp circuit 2. Then an energy spread signal detection circuit 4 detects a residual component of the energy spread signal. Moreover, a triangle wave signal generating circuit 8 generates a waveform signal of the same shape but inverted phase as the energy spread signal. An output of the energy spread signal detection circuit 4 is fed back to a variable gain circuit 7, which controls the amplitude of the waveform signal outputted from the triangle wave signal generating circuit 8. Then an adder 1 adds the inputted MUSE signal and an output of the variable gain circuit 7. Thus, the energy spread signal is forcibly cancelled.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an energy diffusion signal removal device used in various video equipment such as television receivers that handle FM modulated and demodulated television signals.

0002

2. Description of the Related Art HDTV broadcasting in which an FM-modulated MUSE signal is transmitted using one channel of satellite broadcasting has been put into practical use. The spectrum of the FM modulated carrier wave is M
In order to prevent energy from being concentrated at a frequency corresponding to a high time rate level in the USE signal, a triangular wave signal synchronized with the frame period called an energy diffusion signal is superimposed on the MUSE signal. MUSE
In a receiver equipped with a decoder, it is necessary to remove the energy spread signal superimposed on the MUSE signal. Conventionally, the energy spread signal has been reduced by clamping the MUSE signal with a horizontal synchronization period using a clamp circuit.

0003

By the way, if the energy diffusion signal remains in the video signal, it will cause flicker interference. The energy spread signal has a frame period (
Since it is a triangular wave of 1/30 Hz), by making the clamp time constant of the clamp circuit that clamps at the horizontal synchronization period relatively small, it is possible to suppress the energy spread signal to the extent that flicker interference is not a concern. However, the energy spread signal is not completely removed and remains slightly. Furthermore, if the clamp time constant of the clamp circuit is made small and the image is clamped strongly, there is a problem that the image is greatly influenced by noise, resulting in an unpleasant image with noise in the vertical direction.

The present invention was developed in view of this problem, and by adding a triangular wave signal that cancels the energy diffusion signal to the video signal, the energy diffusion signal is forcibly suppressed. It is an object of the present invention to provide an energy diffusion signal removal device that can have a large clamp time constant and is less susceptible to noise.

[0005]

[Means for Solving the Problems] In order to solve the problems of the conventional techniques described above, the present invention provides (1) a video signal on which an energy diffusion signal is superimposed, a waveform signal for canceling the energy diffusion signal; an addition (or subtraction) means for adding (or subtracting) , a clamping means for clamping the video signal that is the output of the addition (or subtraction) means, and a clamping means for clamping the video signal that is the output of the addition (or subtraction) means, and from the video signal clamped by the clamping means, the energy diffusion signal and a waveform generator capable of generating the waveform signal having the same shape and inverted phase (or the same phase) as the energy diffusion signal, and controlling the amplitude of the waveform signal. and controlling the signal amplitude of the waveform signal output from the waveform generation means so as to cancel the energy diffusion signal included in the video signal by the signal detected by the energy diffusion signal detection means. (2) The video signal is a video signal in which a portion with a prescribed level is superimposed within a horizontal or vertical blanking period, and the energy The spread signal detection means detects a first level of the defined portion of the level in a period in which the gradient of the energy spread signal in the video signal is positive, and a first level in a period in which the gradient of the energy spread signal in the video signal is negative. Consisting of a level extracting means for extracting a second level of a prescribed portion of the level in a period, and a level difference detecting means for determining the difference between the first and second levels obtained by the level extracting means. The present invention provides an energy spread signal removal device according to (1), characterized in that:

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The energy spread signal removal device of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a block diagram showing an embodiment of the energy spread signal removing device of the present invention, FIG. 2 is a block diagram showing a first embodiment of the energy spread signal detection circuit 4 in FIG. 1, and FIG. 3 is a block diagram showing a second embodiment of the energy spread signal detection circuit 4 in FIG. FIG. 2 is a block diagram illustrating an example. Further, FIG. 4 is an input/output waveform diagram of the clamp circuit 2 in FIG. 1.

First, the configuration of the energy spread signal removing device of the present invention will be explained using FIG. The MUSE signal detected by a tuner (not shown) is input to one input terminal of the adder circuit 1. The output of the adder circuit 1 is input to a clamp circuit 2, and the output of the clamp circuit 2 is input to an A/D converter 3. The output of the A/D converter 3 is then input to an energy spread signal detection circuit 4 and a MUSE decoding processing circuit 5. The output of the energy spread signal detection circuit 4 is inputted to a gain control terminal of a variable gain circuit 7 via an integration circuit 6. A triangular wave signal having the same shape and inverted phase as the energy diffusion signal is input from the triangular wave signal generating circuit 8 to the signal input terminal of the variable gain circuit 7 . Furthermore, the output of the variable gain circuit 7 is input to the other input terminal of the adder circuit 1.

Next, the configuration of a first embodiment of the energy diffusion signal detection circuit 4 in FIG. 1 will be explained using FIG. 2. The energy spread signal detection circuit 4 of the first embodiment includes a clamp level signal extraction circuit 21 as a level extraction means, average value calculation circuits 22 and 23, and a subtraction circuit 24 as a level difference detection means. The output of the A/D converter 3 is input to a clamp level signal extraction circuit 21. The output of the clamp level signal extraction circuit 21 is sent to the average value calculation circuit 2.
2 and 23, and the outputs of the average value calculation circuits 22 and 23 are input to the subtraction circuit 24. And subtraction circuit 2
The output of 4 becomes the output of the energy diffusion signal detection circuit 4 and is input to the integrating circuit 6.

Further, the configuration of a second embodiment of the energy diffusion signal detection circuit 4 in FIG. 1 will be explained using FIG. 3. The energy spread signal detection circuit 4 of the second embodiment includes a horizontal synchronization signal extraction circuit 31 as a level extraction means, average value calculation circuits 32 and 33, and a subtraction circuit 34 as a level difference detection means. The output of the A/D converter 3 is input to a horizontal synchronization signal extraction circuit 31. Horizontal synchronization signal extraction circuit 31
The outputs of the average value calculation circuits 32 and 33 are input to the average value calculation circuits 32 and 33, and the outputs of the average value calculation circuits 32 and 33 are input to the subtraction circuit . The output of the subtraction circuit 34 becomes the output of the energy diffusion signal detection circuit 4 and is input to the integration circuit 6.

The operation of the energy spread signal removing device of the present invention constructed as described above will be explained. The MUSE signal on which the energy spread signal (triangular wave) is superimposed is input to the adder circuit 1 together with the triangular wave signal from the variable gain circuit 7, and the energy spread signal in the MUSE signal is suppressed. Since the amplitude of the energy spread signal differs depending on the transmission system (broadcasting satellite, communication satellite, etc.), the residual component of the triangular wave that was not suppressed by the adder circuit 1 is detected in a subsequent circuit, and the residual component of the triangular wave signal generated by the triangular wave generator circuit 8 is detected. The amplitude is feedback-controlled by a variable gain circuit 7. This feedback control operation continues until the triangular wave component of the output of the adder circuit 1 is removed.

As mentioned above, the output of the adder circuit 1 is input to the clamp circuit 2. The clamp circuit 2 includes a capacitor 11, a resistor 12, an analog switch 13, and a clamp reference voltage source 14. The analog switch 13 is turned on during the horizontal synchronization period of the MUSE signal, and during this period, the DC voltage from the clamp reference voltage source 14 is charged and discharged into the capacitor 11 via the resistor 12. In order to reduce the influence of noise included in the horizontal synchronization period, the product of the resistor 12 and the capacitor 11 (clamp time constant) is increased and clamped weakly.

If the energy diffusion signal (triangular wave) remains at the input of the clamp circuit 2, the output of the clamp circuit 2 and the output of the A/D converter 3 will have a triangular wave as shown in FIG. A differential waveform, that is, a rectangular waveform appears. In FIG. 4, the value of d is the residual component of the energy spread signal. The energy spread signal detection circuit 4 detects the residual component d of the energy spread signal from the signal shown in FIG. 4 supplied by the A/D converter 3. Various means of this detection can be considered, but the level of a specified part of the level during a period in which the slope of the energy diffusion signal in the video signal is positive, and the level in a period in which the slope of the energy diffusion signal in the video signal is negative. What is necessary is to compare the level of the specified part of the level. For the MUSE signal, a reliable method is to detect it from the clamp level line and horizontal synchronization period signals.

Energy spread signal detection circuit 4 shown in FIG.
The first embodiment is a method of detecting the residual component d of the energy diffusion signal from the difference between the values of two clamp level lines in the MUSE signal. A MUSE signal is supplied from the A/D converter 3 to the clamp level signal extraction circuit 21. In the clamp level signal extraction circuit 21, line number 5
N samples of signals from two clamp level lines, line numbers 63 and 1125, are each extracted. The signal of line number 563 extracted by the clamp level signal extraction circuit 21 is supplied to the average value calculation circuit 22, and the signal of line number 1125 is supplied to the average value calculation circuit 23. The average value calculation circuits 22 and 23 are used for the purpose of removing noise components in the clamp level signal. The average value calculation circuits 22 and 23 calculate the average value of the signals of the two clamp level lines, and supply the average value to the subtraction circuit 24. The subtraction circuit 24 calculates the difference between the two clamp level signals, and outputs the residual component d of the energy diffusion signal shown in FIG.

Energy spread signal detection circuit 4 shown in FIG.
The second embodiment is a method of detecting the residual component d of the energy spread signal from the horizontal synchronization period signal in the MUSE signal. Horizontal synchronization signal extraction circuit 3 from A/D converter 3
1 is supplied with the MUSE signal. The horizontal synchronization signal extraction circuit 31 extracts N samples of the horizontal synchronization signal for each period in which the slope of the triangular wave of the energy diffusion signal is positive and the period in which the slope of the triangular wave is negative. The signal extracted by the horizontal synchronization signal extraction circuit 31 in which the slope of the triangular wave is positive is supplied to the average value calculation circuit 32, and the signal in which the slope of the triangular wave is negative in the period is supplied to the average value calculation circuit 33. The outputs of the average value calculation circuits 32 and 33 are supplied to a subtraction circuit 34. The subtraction circuit 34 calculates the difference between the horizontal synchronizing signals during the period in which the slope of the triangular wave is positive and the period in which it is negative, and outputs the residual component d of the energy spread signal shown in FIG.

The output of the energy diffusion signal detection circuit 4 is
It is input to the integrating circuit 6. This integrating circuit 6 is for stabilizing the feedback control response. The output of the integrating circuit 6 is input to a variable gain circuit 7, which controls the amplitude of the triangular wave supplied from the triangular wave generating circuit 8. That is,
The variable gain circuit 7 and the triangular wave generation circuit 8 constitute a waveform generation means capable of generating a waveform signal having the same shape and inverted phase as the energy diffusion signal and controlling the amplitude of the waveform signal. The triangular wave output from the variable gain circuit 7 is input to one terminal of the adder circuit 1 and cancels the energy diffusion signal superimposed on the MUSE signal input to the other terminal. In this way, the energy spread signal removal device of the present invention forcibly suppresses the energy spread signal by adding a triangular wave signal that cancels the energy spread signal to the video signal (MUSE signal).

In the embodiment of the energy spread signal removal device of the present invention shown in FIG. 1, the variable gain circuit 7 and the triangular wave signal generation circuit 8 generate a triangular wave signal having the same shape as the energy spread signal and an inverted phase. However, this waveform is input to the adder circuit 1 to cancel the energy diffusion signal contained in the MUSE signal, but a subtracter circuit is used instead of the adder circuit 1, and the variable gain circuit 7 and the triangular wave signal generator circuit 8, A triangular wave signal having the same shape and phase as the energy diffusion signal may be generated, and this waveform may be input to the above-mentioned subtraction circuit to cancel the energy diffusion signal included in the MUSE signal. Furthermore, the video signal is not limited to the MUSE signal, but may be any video signal in which a portion with a defined level is superimposed within the horizontal or vertical blanking period.

[0017]

Effects of the Invention As explained in detail above, the energy spread signal removing device of the present invention is configured as described above, and therefore can effectively remove energy spread signals, thereby eliminating problems caused by residual energy spread signals. This has an extremely excellent practical effect in that it can prevent interference (flicker, etc.) on the screen.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of an energy spread signal removal device of the present invention.

[FIG. 2] The first of the energy spread signal detection circuit 4 in FIG.
It is a block diagram showing an example.

[FIG. 3] The second energy diffusion signal detection circuit 4 in FIG.
It is a block diagram showing an example.

FIG. 4 is a waveform diagram for explaining the energy spread signal removal device of the present invention.

[Explanation of symbols]

1 Adder circuit 2 Clamp circuit 3 A/D converter 4 Energy diffusion signal detection circuit 5 MUSE decoding processing circuit 6 Integral circuit 7 Variable gain circuit 8 Triangular wave signal generation circuit

Claims (2)

[Claims] 1. Addition (or subtraction) means for adding (or subtraction) a video signal on which an energy diffusion signal is superimposed and a waveform signal for canceling the energy diffusion signal; clamping means for clamping the output video signal; energy diffusion signal detection means for detecting the residual component of the energy diffusion signal from the video signal clamped by the clamping means; waveform generating means capable of generating the waveform signal (or having the same phase) and controlling the amplitude of the waveform signal; An energy spread signal removing device, characterized in that the signal amplitude of the waveform signal output from the waveform generating means is controlled so as to cancel the energy spread signal contained therein. 2. The video signal is a video signal in which a portion with a defined level is superimposed within a horizontal or vertical blanking period, and the energy diffusion signal detection means detects the energy in the video signal. a first level of the defined portion of the level during a period when the slope of the spread signal is positive; and a second level of the defined portion of the level during the period when the slope of the energy spread signal in the video signal is negative. and a level difference detection means for determining the difference between the first and second levels obtained by the level extraction means. Spread signal removal device.