JPS6259950B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a signal processing device for correcting and extracting a received signal waveform using a waveform equalizer in a television receiver or other receiving device.

2. Description of the Related Art Conventionally, in a receiving apparatus, a waveform equalizer has been used to correct a received signal waveform into a waveform in which distortion caused in a transmission path has been removed. Specific examples include a ghost removal device in the video signal circuit stage of a television receiver, and an echo canceller in a telephone receiving station.

For example, a configuration shown in FIG. 1 has been considered as the ghost removal device for a television receiver. This uses a transversal filter, and its general operation is as follows.

That is, the television video signal input to the input terminal 1 is supplied to the transversal filter 2. The transversal filter 2 includes a delay element (for example, a charge transfer element such as a CCD) 2a having a plurality of taps, and an arbitrary weighting coefficient (hereinafter referred to as tap gain) for applying a video signal to each tap of the delay element 2a. The output of this weighting circuit 2b is connected to a delay element 2a.
is added to each tap so as to be added to the signal passing through the delay element 2a. The signal taken out from the final stage of the delay element 2a is input to the subtracter 2c, where the difference between the signal and the video signal sent to the input terminal 1 is calculated, and the signal is taken out as an output to the output terminal 4. In this case, by appropriately controlling the tap gain, a video signal from which ghost signal components have been removed can be obtained at the output terminal 4.

The tap gain control described above is performed, for example, as follows. That is, the reference waveform in the output signal of the transversal filter 2 and Input terminal 1
The reference waveforms in the video signals are detected by difference circuits 5 and 6, respectively. The difference circuits 5 and 6 are each composed of delay circuits 5a and 6a and subtracters 5b and 6b, and output a difference signal corresponding to the reference waveform, and also input a ghost signal component corresponding to the reference signal. If there is a ghost signal component, a difference signal corresponding to this ghost signal component is also output. The respective output signals of these difference circuits 5 and 6 are input to the output signal of the difference circuit 5 via a shift register 7 to a correlator 8, and the correlation is taken. The correlator 8 is a type of multiplier, and includes two sets of delay elements (for example, charge transfer elements) 8a and 8b each having a plurality of taps, and a shift register 7 added to each tap of the delay element 8a.
A weighting circuit 8c which gives a tap gain to the output of the differential circuit 6, a switch 8d and a holding capacitor 8e for sequentially controlling each tap gain with each tap output of a delay element 8b which receives the output of the differential circuit 6 as an input. Ru. A correlation output of a waveform in which the time interval between the difference signal of the reference waveform and the difference signal of the ghost signal is clarified is taken out from the correlator 8.
This correlation output waveform is converted into a "1" or "0" signal depending on its polarity by the positive/negative determination circuit 9, and then stored in a digital memory (shift register) 12 via a shift register 10 and an adder 11. . Note that the adder 11 adds the output of the shift register 10 and information already stored in the digital memory 12. After the output of this digital memory 12 is converted into an analog signal by a D/A converter 13, it is sent to the transversal filter 2 via a switch 15 which is controlled to turn on sequentially by a shift register 14. It is applied to the weighting circuit 2b as a tap gain control voltage. Capacitor 3 is used to hold this tap gain control voltage. Further, the timing circuit 16 is connected to the digital memory 1
2. Control the operation of the shift register 14, etc.

By the way, in general, in such a ghost removal device, the output video signal is often not in a state in which good image quality can be obtained from the time the device starts operating until the device reaches a stable state. Additionally, depending on the location where the television receiver is installed, if the number of ghost signals is very large or the amplitude is large, the ghost removal device will go into oscillation, which will actually deteriorate the quality of the video signal. Sometimes.

In order to avoid these inconveniences, the inventors have proposed a signal processing method as shown in FIG.
This means that the input signal f(t) to the input terminal 20, for example, a television signal received by a television receiver, and the waveform equalizer 2 as shown in FIG.
The signal g(t) whose waveform has been corrected by passing through the waveform equalizer 21 is guided to the switch 22, and the residual distortion of the output signal g(t) of the waveform equalizer 21 is measured by the residual distortion measuring circuit 23. When the value exceeds a certain value, the switch 22 selects the input signal f(t), and otherwise selects the output signal g(t).

However, even in such a method, the following problems may occur. An example in which the waveform equalizer 21 is a television ghost removal device as shown in FIG. 1 will be explained. Figure 3a
is the waveform near the fall of the vertical synchronization signal when moving from the third line to the fourth line used as a reference waveform in the waveform equalizer 21, b is the inverted difference waveform thereof, c is the delay time of 35 μsec, This figure shows inverted differential waveforms when an in-phase ghost with a relative level of 0.2 exists. When the vertical synchronization signal is used as a reference waveform, the total delay time of the delay element 2a in the transversal filter 2 is, for example, 27
Since the delay time is set to μsec, ghosts with a delay time of 27 μsec or more cannot be removed, but such ghosts may exist in reality. Now, the input signal f containing such a ghost signal component of the waveform equalizer 21 is
(t) is input, the waveform equalizer 21 operates to flatten the section indicated by the arrow A in FIG. 3c. That is, in FIG. 1, when the shift clock of the transversal filter 2 is 10 MHz (the delay time between taps is 0.1), the taps have delay times of 3.3 μsec and 5.8 μsec with respect to the final tap of the delay element 2a of the transversal filter 2, for example. μsec), incorrect tap gains are given to the 33rd tap and 58th tap counting from the last tap. In this case, as the waveform equalizer 21 continues to control the tap gain, the third
The part indicated by arrow A in Figure 3 becomes flat, and the ghost signal component is removed after the fall of the vertical synchronization signal as shown in Figure 3D (However, since the level of so-called grandchild ghosts is small, (Illustration is omitted). However, on the other hand, the third
A new ghost signal component (pseudo-ghost signal component) is generated as shown in FIG. d. In other words, originally
Ghost signal components with a delay time of 27 μsec or more cannot be removed, but in reality, for example,
When a ghost signal component with a delay time of 35 μsec is input, control is performed to remove the ghost signal component in the synchronization signal waveform used as a reference waveform, and as a result, the ghost signal component is removed in the video signal portion. Rather than being removed,
On the contrary, a new pseudo-ghost signal component is added and extracted as the output signal g(t), which causes the inconvenience.

Here, in the signal processing method shown in FIG. 2, when measuring the residual distortion of the output signal g(t) in the residual distortion measurement circuit 23, the reference waveform used in the waveform equalizer 21 is vertically Since the waveform after the fall of the synchronization signal was used, it is determined that the waveform equalization has been performed correctly in the case of the operation example described above, and the output signal g(t ). Therefore,
When a television signal containing a ghost signal component having a long delay time of about 30 μsec or more as described above is input, the image quality deteriorates significantly.

The present invention has been made in view of the above points, and
The residual distortion of the output signal of the waveform equalizer is measured using a signal waveform different from the reference waveform used in the waveform equalizer as a reference waveform, and the input and output signals of the waveform equalizer are calculated according to the measurement results. By making this selection, no matter what state of the signal is input, an output signal that is worse than the input signal will not be extracted, and the waveform equalizer will always select the one with better quality between the input signal and the output signal. The present invention provides a signal processing device that can be taken out.

The present invention will be explained in detail below using examples.

Figure 4 shows an overview of a signal processing system to which the method of the present invention is applied.
It has a configuration in which second timing circuits 25 and 26 are added. Here, when the input signal f(t) is a television signal, the first timing circuit 25 detects, for example, the falling point of the vertical synchronizing signal, and the waveform equalizer 21 operates at this timing. That is, the waveform equalizer 21 uses the waveform after the fall of the vertical synchronization signal as a reference waveform to perform waveform equalization (removal of ghost signal components) as described above.

On the other hand, the second timing circuit 26 receives the input signal f
detecting a signal other than the vertical synchronization signal during (t), for example, the leading edge of a certain horizontal synchronization signal during the vertical retrace period;
The residual distortion measuring circuit 23 is controlled by the second timing circuit 26 and measures the residual distortion of the output signal g(t) of the waveform equalizer 21. That is, the residual distortion measuring circuit 23 measures the residual distortion of g(t) in the approximately 27 μsec period of the flat part that exists immediately after the color burst signal in the horizontal synchronizing signal shown in FIG. Controls the switch 22.

FIG. 5 shows a specific example of the residual distortion measuring circuit 23, and its operation will be explained with reference to FIGS. 7 and 8. The output signal g of the waveform equalizer 21 shown in FIG. 7a input to the input terminal 30 in FIG.
(t) first includes the delay circuit 311 and the subtraction circuit 312.
The differential circuit 31 (which may also be a differentiating circuit) is used to calculate the difference as shown in FIG.
become that way. Then, the output of the absolute value circuit 32 is integrated by an integrator 33 controlled by the second timing circuit 26 over a period of about 27 μsec immediately after the burst signal, and this integrated value is compared with a predetermined constant value by a comparator 34. be done. This comparator 34
The output of is supplied to the switch 22 in FIG. 4 as a control signal for switching operation. As a result, the switch 22 selects the output signal g(t) when the waveform equalizer 21 is performing good waveform equalization, but for example, before the waveform equalizer 21 reaches a stable state. , or when the input signal f(t) contains a ghost signal component that cannot be removed by the waveform equalizer 21 as described above, the comparator 34 calculates the integral value of the integrator 33. As a result of exceeding a predetermined constant value, the input signal f(t) is switched to be selected.

The ghost signal components shown in Fig. 7 all have a relatively short delay time of 27 μsec or less.
It can be erased by the waveform equalizer 21 as described above.
That is, the above ghost signal component is removed by waveform equalization in the waveform equalizer 21, and a flat horizontal synchronization signal as shown in FIG. 6 is obtained. Further, at this time, the vertical synchronizing signal also does not include a ghost signal component as shown in FIG. 3a.

On the other hand, if the input signal f(t) contains a ghost signal component that cannot be removed by the waveform equalizer 21 and has a delay time of 35 μsec, for example, the vertical The synchronization signal is expressed as an inverted differential waveform as shown in Figure 3c, and after waveform equalization, it becomes as shown in Figure 3d, and during the period indicated by arrow A, the ghost signal component is removed and the signal becomes flat. It becomes a waveform. However, when looking at the horizontal synchronizing signal at this time, before waveform equalization it becomes as shown in FIG. 8a, and even after waveform equalization it becomes as shown in FIG. 8b, and the ghost signal component is not removed. Therefore, the ghost signal component remains without being removed even in the video signal part, and a new pseudo ghost is added, so the output signal g(t) of the waveform equalizer 21 becomes the input signal f(t). The quality will be worse than that.

In such a case, according to the present invention, the residual distortion measurement circuit 23 measures the ghost signal component of the output signal g(t) of the waveform equalizer 21 during the period of the horizontal synchronization signal which remains without being removed. Therefore, the input signal f(t) with better quality can be selected by the switch 22.

In the above embodiment, the vertical synchronization signal was used as the reference waveform used in the waveform equalizer, and the horizontal synchronization signal was used as the reference waveform used in the residual distortion measurement circuit for the output signal of the waveform equalizer. It is not limited. For example, if the input signal to be waveform equalized is a television signal, any two of the vertical synchronization signal, horizontal synchronization signal, equalization pulse signal, or specially inserted reference signal may be used as the respective reference waveforms. Can be done.

In addition, although an example is shown in FIG. 2 in which only the output signal g(t) of the waveform equalizer 21 is used as the residual distortion meter 23, the input signal f(t) and the output signal g
The switching device 22 may be controlled by comparing the residual distortions of both (t).

As described above, according to the present invention, by making the reference waveform for waveform equalization and the reference waveform for residual distortion measurement different, the output signal of the waveform equalizer is degraded more than the input signal. This eliminates the risk of selecting the signal as the final output even though it is in the same state as the waveform equalizer. It has the advantage of being able to

[Brief explanation of the drawing]

Fig. 1 is a diagram showing a configuration example of a television ghost removal device that is an example of a waveform equalizer, Fig. 2 is a block diagram showing an example of a signal processing device using a waveform equalizer, and Fig. 3 is a block diagram of the same. A waveform diagram for explaining the operation, FIG. 4 is a block diagram showing an embodiment of the present invention, FIG. 5 is a block diagram showing a specific configuration example of the residual distortion measuring circuit in FIG. 4, and FIGS. FIG. 8 is a waveform diagram for explaining the operation of the same embodiment. 21...Waveform equalizer, 22...Switcher, 23...Residual distortion measuring circuit, 25, 26...Timing circuit.

Claims (1)

[Claims] 1. A waveform equalizer that corrects the waveform of an input signal, and means for measuring residual distortion of the output signal of the waveform equalizer using a signal waveform different from the reference waveform used in the waveform equalizer as a reference waveform; A signal processing device comprising means for selectively extracting the input signal and the output signal of the waveform equalizer according to the measurement result obtained by the means.