JPS61150472A - Ghost eliminator - Google Patents

Abstract

PURPOSE:To use a tap gain control part in common with plural ghost eliminating parts by separating the tap gain control part from the ghost eliminating part of a ghost eliminator using a transversal filter and holding the tap load amount needed for elimination of ghost at the tap gain control part. CONSTITUTION:An erasion signal obtained by producing an undesired signal and a signal having the adverse polarity as said undesired signal in response to the variance of time is added to the main signal for eliminating of a ghost signal. A transversal filter 10 is used for production of an erasion signal together with decision of the load amount. The tap load is corrected by means of the output data of a ghost detecting circuit 260 which detects the ghost out of video signal delivered as well as the reference data stored in a RAM230. The tap load is decided by a ZF method at the early stage of a ghost elimination mode. Then the tap load is calculated by a correlation operation at a stage where a certain degree of convergence is secured. When the load amounts are obtained successively to the tap of the filter 10, the RAM230 is rewritten to said load amount. Then a corrected tap load amount is stored finally in the RAM230.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a ghost removal device that uses a transversal filter to remove unnecessary signals caused by transmission distortion, etc.
In particular, after separating the ghost detection section and the ghost removal section in terms of circuit configuration, and determining the tap weight amount of the ghost removal section for the transversal filter, the ghost detection section can be used as a ghost detection section for the other ghost removal section. The present invention relates to a ghost removal device that can be used.

[Summary of the invention]

In the present invention, for example, as shown in FIG. 1, in a ghost removal device including a transversal filter 10,
The ghost removal unit 100 to which the transmission signal to be waveform-equalized is applied and the equalized signal is output, and the tap gain control unit 200 which calculates the tap load amount for the transversal filter 10 are configured to be separable. .

The tap gain control section 200 performs a correlation calculation between, for example, the input waveform and the output of the transversal filter 10, and stores this result in the storage means 230, 240, KCP U213, etc.
Store under the control of This stored data is stored at terminal Ts
, T4 and T5, the control of the CPU 19 is written to the tap gain RAM 15 and the ROM 18.
write to.

After the ghost removal section 100 and the tap gain control section 200 are separated, the transversal filter 10 is processed based on the data stored in the ROM 18K.
The tap gain is determined and the ghost removal operation is performed.

In addition, a ghost removal device is provided in which a tap gain control section can be shared by a plurality of ghost removal sections.

[Technical background of the invention and its problems]

Generally, when transmitting electrical signals, so-called transmission distortion occurs in the transmission path due to reflected waves, phase distortion, and the like. For example, ghost disturbances that occur in television receivers when reflected waves are superimposed on the main signal are also a type of transmission distortion. One image is displayed, and the reproduced image deteriorates significantly. In order to remove such distortion of the transmission signal, for example, transno (-
There is a ghost removal device that uses a monkey filter to select taps and control the amount of weighting. In this case, the selection of taps is determined by the delay time of the ghost signal with respect to the main signal, and the amount of weighting is determined by the polarity of the ghost waveform. and 0 defined according to the absolute value.To select these taps and control the tap weight amount, algorithms such as correlation calculation are determined depending on the system.

In this algorithm, calculations for determining the tap gain include calculations based on zero-forging, which has a fast convergence speed, and correlation calculations in which a temporal interval is determined and a partial correlation is calculated for the interval. Considering the convergence and stability of the system,
It is desirable to perform zero-forging, which has a fast convergence speed, at the initial stage of ghost signal cancellation, and then to perform correlation calculation, which has excellent stability. Through such arithmetic processing, the selection of the taps to be loaded with respect to the taps of the transversal filter and the amount of loading thereof are determined. Calculations for determining the tap load amount are performed sequentially to remove ghost signals.

However, if the external conditions that generate ghost signals are stable, it is necessary to perform the control operations related to ghost removal described above after performing control operations for detecting and removing ghost signals. There isn't. Examples of such cases include public listening systems and CATV systems. In these systems, it is desirable for the ghost removal device to stop the subsequent control operation once the tap load amount of the transversal filter is set.

On the other hand, in public listening systems and CATV systems, multiple channels are generally transmitted, and a ghost removal device is required for each channel. Each ghost removal device requires a ghost removal section having a transversal filter and a tap gain control section for determining the tap load amount of the transversal filter. In the above-mentioned public listening system or CATV system that does not change, the above-mentioned ghost removal section and tap gain control section are separated,
It is desirable that the ghost removal device for each channel has only a ghost removal section, and that a common circuit is used for the tap gain control section and that it is switched and shared for each channel.

In other words, in a public listening system or the like, it is desirable to provide a ghost removal section for each channel, and to use the tap gain control section of the transversal filter in common with the ghost removal section provided for each channel.

In addition, even in a transmission system that does not involve cables, such as a public listening system, in situations where there are few changes in ghost conditions, each receiver should be equipped with only a ghost removal section.
As a repair work for each of these ghost removal sections, it is desirable to set a type of tab gain control section to determine the tap load amount, and then separate the tap gain control sections.

Furthermore, such a configuration in which the ghost removal section and the tap gain control section can be separated in the ghost removal apparatus is desired from the viewpoint of system stability. In other words, due to changes in the characteristics of the tap gain control section of the ghost removal device due to aging, etc., a problem may occur in which control data is interposed in the control loop and the system oscillates. It is desirable to have a configuration in which the components can be separated.

[Embodiments of the invention]

Embodiments of the ghost removal device according to the present invention will be described below with reference to the drawings.

FIG. 2 shows the ghost removal device according to the present invention on a television set.
FIG. 2 is a circuit diagram showing an embodiment of the present invention applied to a public listening system for online broadcasting.

In the embodiment shown in FIG. 2, the ghost removal device uses a transversal filter l which generates a signal necessary for eliminating the ghost signal by determining the amount of tap load.
The ghost signal is generated by a main signal, and has a separate circuit arrangement consisting of a ghost removal section 100 having a frequency of This occurs because the main signal itself is weakened due to the influence of reflected waves, etc., or when unnecessary signals are added. Whether or not there is a ghost signal can be determined, for example, in the case of a television signal, by detecting the vertical synchronization signal period. Originally, the falling portion of the vertical synchronization signal is flat, but if a signal other than the main signal is generated due to a ghost signal or the like, the vertical synchronization signal period is not flat. The slippage is caused by the generation of an unnecessary ghost signal that is time-shifted from the main signal, and cancellation is obtained by generating a signal with the opposite polarity to the unnecessary signal according to this time shift. Ghost signals are removed by adding the signal to the main signal.

To generate this cancellation signal, a transversal filter is used, and the above-mentioned cancellation signal is obtained by determining the amount of weight for the taps of this transversal filter.

In order to generate the cancellation signal for removing the ghost signal, a timing signal for comparing the main signal and the ghost signal, an error signal detection calculation, and a tap load of the above transversal filter by this error signal detection calculation are required. A series of operations for rewriting the quantity is required.

In FIG. 2, the input terminal lN to which the video signal is applied
The video signal entering the IC is passed through a transversal filter 10.
is applied to the input terminal of the clock generating circuit 11.
added to. This clock generation circuit 11 uses a burst signal extracted from a video signal and triples a 3.58 MHz signal synchronized with the burst signal to generate a clock signal. This clock signal is used as a clock pulse for the entire system including the ghost removal section 100 and the tap gain control section 200. A clock pulse is applied to the tap gain control section 200 via a buffer circuit.

Further, it is necessary to generate a reference signal To of comparison timing for comparing the main signal and the ghost, and this reference is generated by the synchronization separation circuit 210 and the synchronization timing pulse generation circuit 211 of the tap gain control section 200. The original video signal input to the ghost removal section 100 is applied to a buffer circuit 14 via an adder 13. This buffer circuit 14 functions as an analog buffer, and sends the video signal to the sync separation circuit 210 of the tap gain control section 200 via the terminal TI. Here, the vertical and horizontal synchronization signals in the video signal are separated, and these synchronization signals and the buffer circuit of the ghost removal section 100 are combined.
A clock pulse (10
, 7μH2), a reference pulse To, which serves as a comparison timing reference when comparing the original signal and the ghost signal, and a control signal for the DMA circuit 2, which will be described later, are generated. .

Next, the operation of input waveform integration performed at the timing defined by the reference pulse To will be described. This input waveform integration operation is a process for generating a reference pulse for determining whether or not there is a ghost signal, and is a process before calculating the amount of ghost by a calculation such as a correlation calculation. When the obtained reference pulse To is applied to the DMA circuit 2, the DMA
The DMA circuit 2 that performs processing starts operating. D.M.A.
Circuit 2 is the reference pulse T mentioned above.

When , an interrupt request signal is generated to the CPU 213 and the input waveform integrating circuit 220 is controlled.

That is, the DMA circuit 2 controls the input waveform integration operation of the input waveform integration circuit 220. This manual waveform integration circuit 220 has a comparator 221 and a D/A conversion circuit 222, and the above sampling clock (lQ, 7h4Hz)
The input waveform integrating circuit 22 uses information in the vicinity of the reference pulse To in the video signal as reference data.
Integrate the waveform at 0. This waveform integration operation obtains data on the falling edge of the vertical synchronization signal, which serves as a reference for the ghost removal section. In this case, the ~Φ conversion for the falling edge portion of the vertical synchronization signal is performed by transferring the data stored in the negative RAM 230 to the waveform integration circuit 220 by the DMA circuit 2.
The comparator 221 compares the analog-converted signal transferred to the D/A conversion circuit 222 and the video signal.

Then, one type of error data as a comparison result by the comparator 221 is taken into the RAM 240, and this RAM 24
Using the error data written to 0, the RAM 230
The waveform integration operation is performed in one cycle of rewriting and correcting the data, and the access to the RAM 230.240K at this time is performed by the DMA circuit 2. In addition,
Waveform integral data by waveform integral operation is RAM 230
is stored in the comparator 22 during waveform integration operation.
The error data obtained at the output of 1 is stored in the RAM 240 under the control of the DMA circuit 221 as a buffer memory function. In this case, the control signal for controlling the DMA circuit 2 is 10. Received by boat 250.

The amount of ghost is detected based on the input reference data for ghost signal detection obtained by the waveform integration operation, and when initial data has been captured, the tap load amount for the transversal filter 10 is determined. .

Next, a description will be given of the operation of correcting the tap gain of the transpersion filter 10 performed on the reference output stored in the RAM 230.

The modification of the tap weight as the tap gain is the same as the RA described above.
Ghost detection circuit 26 for detecting ghosts from M230i stored reference data and incoming video signals
This is done using output data of 0. .

The ghost detection circuit 260 receives the video signal obtained through the buffer circuit 14 of the ghost removal section 100 and whose vertical synchronization signal is near the falling edge. This video signal is differentiated by a subtractor (not shown), and this differentiated data is binarized by a comparator or the like and output as ghost data to the output of the ghost detection circuit 260. This ghost data acts as a buffer.
M 240 and read as needed for modification operations.

There are various calculation methods for correcting the tap gain, but considering shortening the convergence time for ghost removal, method (1) is recommended at the initial stage of ghost removal.
It is preferable to correct the static load using the ZF (zero forcing) method shown in the equation, and then perform a partial correlation calculation.

CnL+1 = CnL+Δ・8gn'p+j −
fl) Once the tap load amount has been corrected to some extent by the ZF method according to equation (1) above, correction calculations are then performed by the correlation method using a program stored in the ROM 270.

Among the correlation methods, correction of the tap load by partial correlation calculation is shown by the following equation.

CnL+1 = (lnL+Δ-8gn(Σwk' ・
s′n+k ) −(2) In the partial correlation shown in equation (2) above, the correlation interval is calculated for 64 taps,
In determining the amount of correction for one tap, a correlation calculation is performed using reference data for 64 taps and corresponding ghost data. The calculation for the Lth time of each tap is completed only after this calculation is performed for the total number n of taps. Therefore, although the correlation calculation requires a large amount of calculation and takes a long time to converge, the correlation calculation is more stable when considering the stability of the system such as unerased areas. For this reason, at the initial stage of the ghost removal operation, the tap load amount is determined by the ZF method, and at a stage where it has converged to a certain extent, a calculation is performed to obtain the tap load by correlation calculation.

When the load amount for the tap of the transversal filter 10 is successively determined as described above, the RAM 230 is rewritten to this load amount, and finally the RAM
The corrected tap load amount is stored in 230.

The tap load amount for erasing the ghost signal obtained in this way is the tap gain RAM 1 of the ghost removal section 100.
5 to change the tap load amount of the transversal filter 10. This rewriting of the load amount of the tap of the transversal filter 10 is performed on the I10 boat 25.
0 to the DMA circuit 2, and when a data transfer pulse is applied from the synchronous timing pulse generation circuit 211, the DMA operation of the DMA circuit 2 causes the data to be transferred from the RAM 230 to the buffer circuit 280. This is done when the data is read out. The tap load data read out to the buffer circuit 280 is transferred to the buffer 16 of the ghost removal unit 100 via the terminal T3, and further transferred to the tap gain RAM 1 via the buffer 17.
5, the tap load amount of the transversal filter 10 is modified to remove ghost signals.

In this case, the ghost removal unit 100 and the tap gain control unit 200 have terminals T4. The control signal line and address line from the CPU 213 are coupled between the tap gain control section 200 and the ghost removal section 290 by T3. ' In the above embodiment, since the configuration is such that the ghost removal section 100 and the tap gain control section 200 can be separated, it is necessary to take measures to retain the data written in the tap gain KAM 15 even after separation. That is,
If the data content of the tap gain RAM 15 is destroyed by external noise such as a sudden power outage or a lightning strike, the tap load amount of the transversal filter 10 will no longer be an appropriate value, and ghost signals cannot be removed. In addition to disappearing, new ghost signals may also be added. Therefore, in the embodiment shown in FIG. 2, the tap gain control section 200 and the ghost removal section 100
In this state, the BPROM writer 290 of the tap gain control unit 200 is used to transfer the tap gain data of the tap gain RAM 15 to the FI
Write to PROMt8. This operation is performed at step 17 after the end of the ghost removal control operation. RAM230 data and CP
EPR, 0M program for operating U 19
This is done by writing 18.

When the ghost removing unit 100 and the tap gain control unit 200 are separated after the EFROM 18 is installed in the ghost removing unit 100, the electrical conduction through the terminal T6 is cut off, and the potential of the terminal P1 of the CPU 19 is becomes a high level, the CPU 19 starts operating, and the tap gain RA
While writing the data of M15 into the EFROM 18, a Puffer control signal qt- is generated from the terminal P2. After this buffer control signal stops the operation of the buffer circuit 16 and the ghost removal section 100 and tap gain control section 200 are separated, the function of the buffer circuit 16 is stopped. After this, ゛The above ghost removal section 1
00 CPU 19 has the tap gain RAM 1
The data of the EFROM in which the initial data of 5 is written is compared with the subsequent data of the tap gain filter AM15. For this reason, even if the data in the tap gain RAM 15 is corrupted due to the above-mentioned power failure, lightning strike, etc., the data written in the EPROM 18 is used to correct it.

As a result, even if the data in the tap gain RAM 15 is corrupted, the tap load amount for ghost removal is maintained at an appropriate value, and even after the ghost removal section 100 and the tap gain control section 200 are separated, the ghost removal operation is performed. will not be hindered.

Note that when noise arrives, the above tap gain RAM
In the operation of transferring data from the EPROM 18 to the EPROM 15, it is preferable to forcibly determine the data transfer timing in order to prevent malfunction.

In the example shown in FIG. 2, a vertical synchronization separation circuit is provided in the ghost removal section 100, and the CPU is activated only during the vertical synchronization signal period.
FIG. 3 is a circuit diagram showing another embodiment of the ghost removal device according to the present invention, in which only the ghost removal section 100 is shown. Portions having the same functions as those of the circuit shown in FIG. 2 are designated by the same reference numerals, and their explanations will be omitted.

The ghost removal section shown in FIG.
It is the same as the circuit shown in the figure, and the tap gain R, A M
The means for holding the 15 data are different. That is, in the example of FIG. 3, no BFROM is used.

The MNO8 nonvolatile ROM 21 is used in the ghost removal section 100. MNOS (Meta I Ni trid)
e 0xide 8em+ conductor) generally requires an interface circuit due to operating voltage, etc., and in Fig. 3, MNO8 nonvolatile ROM 21
An interface circuit ρ is provided for the ROM.
When the ghost removal section 100 and the tap gain control section 200 are separated according to the program stored in the tap gain control section 23, data transfer of the tap gain RAM 15 is performed when the potential of the terminal P1 of the CPU 19 becomes high level. By this data transfer, the data of the first tap gain RAM 15 is written into the MNO8 nonvolatile ROM 21. By configuring the ghost removal section ioo in this way, the ROM of the tap gain control section 200 shown in FIG.
The writer 290 becomes unnecessary.

FIG. 4 shows a circuit diagram when the ghost removal device according to the present invention is applied to a public listening system or a multi-channel reception system such as CATV. In the figure, for example, a television signal transmitted through a signal transmission path is input to an input terminal INK.
and is added to n channels (QTx, T2 . . . Tn), each of which receives a predetermined television channel signal. This is because the ghost signal distortion differs for each reception channel, so the ghost removal operation is performed separately for each channel signal. Therefore, each of the cheeses (TI, T2...Tn) is individually equipped with a ghost removal section 100(1) as shown in FIG. 2, FIG. 3, and the like.
1oor2).

. . 100(n), and the television signal from which ghost distortion has been removed in each ghost removal section is re-modulated by a respective modulator (Ml, M2...Mn) and then sent to a coupler 50[1]. The signals are added and then output to the output terminal OUT.The above ghost removal sections each have a transversal filter, but the load amount for the tap of this transversal filter is controlled by a single tap gain control. 200. That is, the tap gain control section 200 is connected to one of the ghost removal sections 100 by the switching means 60. Then, the tap gain control section 200 performs a tap gain control operation for each ghost removal section 100.

FIG. 5 is a perspective view showing the structure of an embodiment of the ghost removal device according to the present invention.

In FIG. 5, the rack 300 includes the ghost removal units 100(1) and 100(2) shown in FIG.
, -10αn) are stored. Each ghost removal section is provided with a power switch SW, a connector/lid CN, and a signal transmission bin PN1, PN2, . . . PN(→).

On the other hand, the tap gain control section 200 is provided with a pin PN and a connector CN that are conductively connected to the ghost removal section 100 through cables CBI and CB2, so that the ghost removal section 100 and the tap gain control section 200 are conductively coupled. Ru. The cable CBI has a tap gain control section 200
The connector CN is provided to synchronize and separate the synchronization signal from the video signal, and the connector CN is used to transmit data, control signals, and
Further, the tap gain control section 200 is connected to a power switch 70, an EPROM
Writer operation switch 71, control operation switch 72. A control operation start switch 73 and an IP ROM writer socket 74 are provided.

Now, when the ghost removal section 100 of one of the racks 300 and the tap gain control section 200 are connected and the control operation start switch 73 is pressed to start the ghost removal operation, a display indicating the start of the ghost removal operation will appear. FiL
x is displayed. At this time, check the monitor using the signal obtained at the monitor output terminal 75 that derives the signal from the output side of the transversal filter 10, confirm that the ghost signal has been removed, and press the control operation switch 72. to stop the ghost removal operation. After this BFROM
Insert the 74KBFROM (socket) and press the EPROM writer operation switch 71. After writing the tap gain data etc. to the BFROM from this K, the socket 74
From T! When the IPR and OM are removed from the tap gain control section 200, the ghost removal section 100K is attached, and the tables CBI and CB2 are removed, the ghost removal operation for one chip is completed. In addition, the above lPROM
While writing to the MPROMIC in the socket, the display E1 notifies you that there is a write in progress and displays a message to prevent you from accidentally removing it from the socket. In addition, the display ELa indicates that there has been a malfunction, and the lPROM
In addition, in the above-mentioned FIG. 5, an lPROM is used to function as an error display during erase check and verify check, and the tap gain control unit 200 writes a kind of tap gain amount etc. to be held in this lPROM, and then the ghost Although an example is shown in which the MNOS is installed in the removing section 100, if MNOS is used as the nonvolatile memory as shown in FIG. The data to be stored in the tap gain memory is stored in the ghost removal unit 100 without being written.

〔Effect of the invention〕

As described above, in the ghost removal device according to the present invention, there is a ghost removal device 1c using a transversal filter, and the tap gain control section and the ghost removal section can be separated. Also, since the tap gain control section is configured to hold the tap load amount necessary for ghost removal, the tap gain control section can be shared by a plurality of ghost removal sections.

As a result, even in the case of multi-channel transmission such as a public listening system or a CATV system, the tap gain control section can be shared by the ghost removal sections of a plurality of channels, and there is no need to provide multiple stages of tap gain control sections.

Additionally, when the transmission conditions change and the ghost signal state changes, the tap gain control unit can be reinstalled for the ghost removal unit of the corresponding channel to newly set the tap gain data for the transversal filter. .

This invention is applicable not only to public listening systems and CATV systems, but also to general television receivers, etc., by providing only a ghost removal section with a transversal filter, and reducing the tap load of the transversal filter as a repair work when installing an antenna. The present invention can also be applied to a case where a tap gain control section is attached to the ghost removal section to determine the tap gain data, and the tap gain data at this time is held in the ghost removal section.

Furthermore, the calculation and circuit configuration for determining the tap load amount described above are not limited to the above embodiments.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an overview of the present invention, FIG. 2, FIG. 3, and FIG. 4 are circuit diagrams showing an embodiment of the ghost removal device according to the invention, and FIG. 010... transversal filter, 15, 18, which is a perspective view showing the configuration of the device.
...Tap gain holding means, 10G...Ghost removal section, 230.240...Tsubu gain data storage means, 2
10.213, 220, 260... calculation unit. Agent: Patent attorney Noriyuki Chika (IT or 1 person)

Claims (1)

[Claims] A ghost removal device that performs waveform equalization on a transmission signal by controlling the tap gain of a transversal filter, comprising: tap gain holding that holds tap gain data for the tap of the transversal filter. A tap having a ghost removing section having a means for removing the ghost, and a calculating section for calculating a tap load amount to be applied to the tap of the transversal filter of the ghost removing section, and a tap gain data storage means for storing the calculation result. The gain control unit, the ghost removal unit, and the tap gain control unit are configured to be separable, and after separation, the tap gain of the ghost removal unit is held for the data in the tap gain data storage means of the tap gain control unit. A ghost removal device characterized in that data for the means is determined and waveform equalization operation is maintained even after separation of the tap gain control section.