JPH03951B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a ghost removal device that receives a television detection output as input and performs ghost removal in a video stage.

Conventional configuration and its problems In recent years, when receiving television broadcasts,
Reception interference due to ghosts has increased, and various devices have been developed to remove ghosts. Among these, a method that uses a transversal filter to remove ghosts at the video stage is becoming mainstream.

FIG. 1 is a block diagram showing the configuration of an example of such a conventional ghost removal device. In the figure, numeral 1 is an adder circuit that adds the TV video detection signal A containing ghosts and the signal D obtained by passing the output of the transversal filter 2 through the low-pass filter 3 that removes the clock frequency component of the transversal filter. This constitutes a filter that removes ghosts. The output C of the adder circuit 1 is connected through a clamp and A/D conversion circuit 4. This output C is also connected to the input terminal of the transversal filter 2 and the AGC and video switching circuit 10.

The video detection signal A is connected to a synchronization separation and timing pulse generation circuit 9 and an AGC and video switching circuit 10. The synchronization separation and timing pulse generation circuit 9 generates pulses synchronized with the input video signal A necessary for the operation of the ghost removal device.

Microcomputer 5, program ROM
7. RAM6, DMA (Direct Memory access)
The controller 8 is connected by a data bus line 1 and an address bus line m, and constitutes a control section that controls the tap weighting coefficient of the transversal filter by adaptive equalization in order to remove ghosts. Clamp A/ to get ghost information
Bus lines l and m are also connected to the D conversion circuit 4. Transversal filter 2 and microcomputer 5 are connected by data bus line l and address bus line m, and tap weighting coefficients are controlled by microcomputer 5. The transversal filter 2 has tap weighting coefficient memories corresponding to the number of stages, and the amount of weighting of each tap changes depending on the value in the memory. The output n of the synchronous separation and timing pulse circuit 9 is a clock pulse having a frequency of 3 _sc ( _sc : chroma frequency). The clock pulse n is supplied as the address counter clock of the DMA controller circuit 8, the transversal filter 2 clock, and the sampling clock of the clamp A/D conversion circuit 4.

The output O of the synchronization separation and timing pulse circuit 9 is a signal indicating the falling edge (leading edge) of the vertical synchronization signal, and is connected to the DMA controller circuit 8 and the microcomputer 5. The output P of the synchronization separation and timing pulse circuit 9 is a signal obtained by calculating the logical sum of a signal indicating power-on clear when power is supplied to the ghost removal device and a signal indicating that the reception channel has been switched, and is a signal obtained by calculating the logical sum of a signal indicating power-on clear when power is supplied to the ghost removal device and a signal indicating that the receiving channel has been switched. 5.

The operation of the conventional ghost removal device configured as described above will be described below. The microcomputer 5 detects by the signal P that power is supplied to the ghost removal device or that the reception channel is switched, clears the tap weighting coefficient of the transversal filter, and outputs the transversal filter signal of D. becomes zero. The output O of the synchronization separation and timing pulse circuit 9 is a pulse that is generated by synchronization separation from the TV video detection signal A and indicates the position of the vertical synchronization signal, including the leading edge of the vertical synchronization, and puts the microcomputer in a hold state. Make it. During this period, the digital output of the clamp A/D conversion circuit 4 is written into the RAM 6 by the DMA controller 8. To RAM6
The microcomputer 5 calculates the position and size of a ghost on the DMA signal using the falling edge of the vertical synchronization signal as a reference.

Based on the ghost information calculated in this way, the microcomputer 5 performs a tap gain correction calculation of the transversal filter 2 by the zero-following method or the correlation method, so that the vertical synchronization signal after the fall becomes flat. controlled. The transversal filter 2 has tap weighting coefficient memories corresponding to the number of tap stages, and the output of each tap weighting coefficient memory is converted from a digital value to an analog value by an A/D converter corresponding to the number of tap stages. Addition and subtraction control is performed.

In such a ghost removal device, the maximum output and minimum resolution are limited by the number of bits in the tap weighting coefficient memory in the transversal filter 2 and the maximum value of each tap weighting coefficient. Therefore, for a fixed number of bits, if you try to remove a large ghost, the residual ghost after removal will be large for a small ghost, and if you try to make the resolution such that the residual ghost is sufficiently small for a small ghost, The drawback was that large ghosts could not be removed.

OBJECT OF THE INVENTION The present invention solves the above-mentioned conventional problems by using a transversal filter having a tap weighting coefficient memory of a fixed number of bits.
It is an object of the present invention to provide a ghost removal device that exhibits maximum ghost removal performance both in areas where strong ghosts exist and in areas where only weak ghosts exist.

Composition of the Invention The ghost removal device according to the present invention comprises a ghost removal filter that has a tap weighting coefficient memory and performs tap weighting control of a transversal filter by converting the tap weighting coefficient memory from digital to analog. A variable gain control amplifier is connected to the output, and its gain is controlled according to the strength of the ghost.
Even if the tap coefficient memory has a fixed number of bits, residual ghosts can be further reduced.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 shows a block diagram of a ghost removal device according to an embodiment of the present invention. In the figure, each block 1 to 10, signal lines l to p, signal A
-D are the same as the conventional example shown in FIG.

A variable gain amplifier circuit 11 that receives the output of the low-pass filter 3 as an input is connected, and its output serves as one input of the adder circuit 1 . Variable gain amplifier circuit 11
is connected to the microcomputer 5 by a data bus line l and an address bus line m.

FIG. 3 shows an embodiment of the variable gain amplifier circuit 11 in detail. Transistor 23 and transistor 24 constitute a differential amplifier. A DC power supply 22 is connected to the base of a transistor 23 and provides a bias voltage. A DC voltage generated by a digital-to-analog converter 33 is applied to the base of the transistor 24 . transistor 2
Resistors 26 and 27 are connected to emitters 3 and 24, respectively.
are connected, and each other end of the resistor is connected to the collector of the transistor 25. The emitter of transistor 25 is grounded via resistor 28. A signal E obtained by passing the output of the transversal filter 2 through a low-pass filter 3 is connected to the base of the transistor 25 via a capacitor 29.
The collector of the transistor 23 is connected to the power source F, and the collector of the transistor 24 is connected to the power source F via a load resistor 30. The collector of the transistor 24 is connected to the base of a transistor 31 forming an emitter follower. The collector of the transistor 31 is connected to a power supply, and the emitter is connected to ground via a resistor 32. The output of the transistor 31 is connected as a signal F through an inverting amplifier 35 to one input of the adder circuit. A signal CE obtained by address decoding data bus line l and address bus line m by an address decoder circuit 34 is connected to the digital-to-analog converter 33 .

Regarding the ghost removal device with the above configuration, the following is as follows.
The operation will be explained.

When the reception channel is changed or when power is input to the ghost removal device, the transversal filter 2 is controlled by the microcomputer 5.
All tap weighting coefficient memories are cleared and the signal output becomes zero. The output F of the variable gain amplifier 11 which receives this signal as input also becomes zero. Therefore, the output of the adder circuit 1 is a signal that still contains the ghost before the ghost is removed. This signal is digitized by the clamp analog-to-digital conversion circuit 4, including the falling edge of vertical synchronization, and the difference between adjacent sample points is calculated based on the data transferred to the RAM 6 by the DMA. Based on the size of this difference data, the microcomputer 5 calculates the required maximum output of the transversal filter,
Set the gain of the variable gain amplifier. Thereafter, ghosts are removed by performing the same control calculations for tap weighting coefficients as in the conventional example.

In this way, in this device, the maximum output of the transversal filter is set according to the size of the ghost, so even if a tap weighting coefficient memory with a fixed number of bits is used, the maximum resolution can be achieved with the required maximum output. can be obtained.

Effects of the Invention As described above, according to the present invention, even if a transversal filter having a tap weighting coefficient of a fixed number of bits is used, the gain of the variable gain amplifier can be set according to the strength of ghosts. Therefore, it is possible to reduce residual ghosts both in areas where strong ghosts exist and in areas where weak ghosts exist, and it is possible to provide a ghost removal device with good removal performance, which is useful.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a conventional ghost removal device, FIG. 2 is a block diagram of a ghost removal device according to an embodiment of the present invention, and FIG. 3 is a specific example of a variable gain control circuit in the same ghost removal device. It is a circuit diagram. 1...Addition circuit, 2...Transversal filter, 3...Low pass filter, 4...Clamp/A/D conversion circuit, 5...Microcomputer, 6...RAM, 7...Program ROM, 8
... DMA controller, 9 ... Synchronization separation and timing pulse circuit, 10 ... AGC and video switching circuit, 11 ... Variable gain amplifier, 23,
24, 25, 31...transistor, 26, 2
7, 28, 30, 32...Resistance, 33...D/A
Converter, 34...Address decoder circuit, 35...
...Inverting amplifier.

Claims (1)

[Claims] 1 A transversal filter equipped with a tap weighting coefficient memory, a variable gain amplifier that receives the output signal of this transversal filter, and an output signal of this variable gain amplifier and a TV video detection output signal containing a ghost component are added together. An adder circuit that outputs a video signal from which ghost components have been removed, an arithmetic control circuit that sets the gain of the variable gain amplifier based on a digital signal obtained by analog-to-digital conversion of the output signal of the adder circuit, and a transversal filter tap. A ghost removal device comprising a weighting coefficient control section.