CN1115875C - NTSC co-channel interference detectors responsive to received Q-channel signals in digital TV signal receivers - Google Patents

NTSC co-channel interference detectors responsive to received Q-channel signals in digital TV signal receivers Download PDF

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CN1115875C
CN1115875C CN97198489A CN97198489A CN1115875C CN 1115875 C CN1115875 C CN 1115875C CN 97198489 A CN97198489 A CN 97198489A CN 97198489 A CN97198489 A CN 97198489A CN 1115875 C CN1115875 C CN 1115875C
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signal
channel
time
ntsc
baseband signal
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CN1232591A (en
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艾伦·L·林伯格
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Samsung Electronics Co Ltd
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
    • H04L1/0056—Systems characterized by the type of code used
    • H04L1/0057—Block codes
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N7/00—Television systems
    • H04N7/04—Systems for the transmission of one television signal, i.e. both picture and sound, by a single carrier
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
    • H04L1/0045—Arrangements at the receiver end
    • H04L1/0054—Maximum-likelihood or sequential decoding, e.g. Viterbi, Fano, ZJ algorithms
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
    • H04L1/0056—Systems characterized by the type of code used
    • H04L1/0071—Use of interleaving
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/14—Picture signal circuitry for video frequency region
    • H04N5/21—Circuitry for suppressing or minimising disturbance, e.g. moiré or halo
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/44—Receiver circuitry for the reception of television signals according to analogue transmission standards
    • H04N5/455—Demodulation-circuits
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/40—Client devices specifically adapted for the reception of or interaction with content, e.g. set-top-box [STB]; Operations thereof
    • H04N21/41—Structure of client; Structure of client peripherals
    • H04N21/426—Internal components of the client ; Characteristics thereof
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/14—Picture signal circuitry for video frequency region
    • H04N5/21—Circuitry for suppressing or minimising disturbance, e.g. moiré or halo
    • H04N5/211—Ghost signal cancellation

Abstract

An NTSC co-channel interference detector detects the presence of an interfering NTSC signal in the received Q-channel signal that is orthogonal to the received I-channel signal, rather than detecting the presence of an interfering NTSC signal in the received I-channel signal. By determining whether or not a significant amount of NTSC co-channel interference accompanies the received Q-channel signal, it is inferentially determined whether or not a significant amount of NTSC co-channel interference accompanies the received I-channel signal, such as to cause too many errors in the trellis decoding of equalized received I-channel signal to be corrected by the Reed-Solomon decoder following the trellis decoder. The accurate determination of co-channel NTSC interference levels is simplified, because essentially no direct bias arises from the quadrature-phase synchronous detection of the pilot carrier of the VSB AM digital television signal.

Description

The digital television signal receiver, handle the vestigial sideband amplitudemodulation signal and determine whether to adopt co-channel interference to suppress the method for filtering
The present invention relates to digital television system, relate in particular to the circuit whether co-channel interference is arranged in definite NTSC anolog TV signals that DTV receiver adopts.
Background of the present invention
The digital television standard regulation that Advanced Television standard on the 16th committee in September nineteen ninety-five (ATSC) announces, transmit 6MHz bandwidth television channel numeral TV (DTV) signal, identical as residual sideband (VSB) signal of National Television System Committee (NTSC) anolog TV signals used in the present air broadcast of the U.S..So the frequency spectrum of the VSB DTV signal of design may interweave with the frequency spectrum of co-channel interference NTSC analog tv signal.This is to realize by the odd-multiple that pilot frequency carrier wave frequency and main amplitude-modulation sideband frequency configuration with the DTV signal are NTSC analog tv signal 1/4 horizontal scanning line speed, described " odd bits " is positioned between " even-multiple " of NTSC analog tv signal 1/4 horizontal scanning line speed, on this " even-multiple ", most of energy of co-channel interference NTSC analog tv signal brightness and chromatic component can be decayed.The video carrier frequency of NTSC analog tv signal departs from the lower frequency limit 1.25MHz of television channel.Frequency shift (FS) between the carrier frequency of DTV signal and this video carrier frequency is 59.75 times of NTSC analog tv signal horizontal scanning line speed, makes the carrier frequency of DTV signal depart from the about 309877.6kHz of television channel lower frequency limit.Correspondingly, the carrier frequency of DTV signal departs from the about 2690122.4Hz of television channel intermediate frequency.
The closely coincide speed of digital television standard regulation is sound carrier frequency in the NTSC analog tv signal and 684/286 times of the frequency offset (4.5MHz) between the video carrier frequency.Wherein, 684 is the symbolic number in each each horizontal scanning line of NTSC analog tv signal, 286 is the multiplication coefficient of NTSC analog tv signal horizontal scanning line speed, and the effect of this coefficient is its video carrier frequency of the sound carrier frequency departure 4.5MHz that makes the NTSC analog tv signal.Character rate is per second 10.762238 million symbols (megasymbol), and it can be comprised by the VSB signal, and described VSB signal and DTV signal carrier are at a distance of 5.38119MHz.That is to say that this VSB signal can be limited in the lower frequency limit in an edge frequency and middle video road in the frequency band of 5.690997MHz.
In the U.S., the digital HDTV signal is used for terrestrial broadcasting, and it is 16: 9 high definition TV (HDTV) form that the ATSC standard of this digital HDTV signal can transmit two kinds of the ratio of width to height.A kind of HDTV display format adopts each scan line to get 1920 samples, has the 30Hz frame at 2: 1 intervals, and every frame has 1080 effective horizontal scanning lines.Another kind of HDTV display format adopts each scan line to get 1280 luma samples points, and 60Hz frame, every frame have 720 lines of lining by line scan.Except the HDTV display format, the ATSC standard also comprises the transmission of DTV display format, as compare the parallel transmission of four kinds of TV signal with normal definition with the NTSC anolog TV signals.
DTV by residual sideband (VSB) amplitude modulation (AM) transmission in U.S.'s terrestrial broadcasting process comprises a series of continuous in time data fields, and each time continuous data field comprises 313 time continuous data segments.This data field can be looked at as by mould 2 serial numbers, and each is very numbered data field and constitutes a Frame with subsequently idol numbering data field.Frame rate is per second 20.66 frames.The duration of each data segment is 77.3 microseconds, therefore, when character rate is 10.76MHz, just contains 832 symbols in each data segment.Each data segment begins with the synchronous code character of the row that comprises four symbols, the value of described four symbols is+S ,-S ,-S and+S.The level of+S value is lower than maximum positive according to amplitude, and the level of-S value is higher than maximum negative data amplitude.The initial row of each data field comprises the field synchronization code character to training signal (training signal) coding, and it is used for channel equalisation and multichannel suppresses.The start-up portion of this training signal is the pseudo noise sequence (or " PN sequence ") that comprises 511 samples, and aft section is 3 PN sequences that respectively contain 63 samples.The mid portion of 63 sample PN sequences in the field synchronization sign indicating number transmits according to first row, first logical specification of each strange numbering data field and first row, second logical specification of each idol numbering data field, and first logical specification and second logical specification are complimentary to one another.
Data in the data line are carried out the lattice coding with 12 lattice sign indicating numbers that interweave (trellis code), and each 2/3 speed lattice sign indicating number has a not bits of coded.The lattice sign indicating number that interweaves will stand Reed-Solomon (Reed-Solomon) forward error correction coding, and the Reed-Solomon forward error correction coding can be proofreaied and correct the error code of bursting (burst errors) that is caused by the noise source such as near not shielding automotive ignition system.For aerial transmission, the Reed-Solomon coding result transmits in 8 level, 3/symbol one dimension constellations (one-dimensional-constellation) symbolic coding mode, this transmission is to carry out under the situation of not carrying out the symbol precoding, and described symbol precoding process is separated with the lattice cataloged procedure.For CATV transmission, the Reed-Solomon coding result is with 16 level (4/symbol) one dimension constellation symbol coded system transmission, and this transmission is carried out under the symbol precoding situation not carrying out.The carrier wave that the VSB signal suppressing is intrinsic, its amplitude changes with percent modulation.
Intrinsic carrier wave can replace with the amplitude fixed amplitude pilot frequency carrier wave consistent with the percent modulation of regulation.This fixed amplitude pilot frequency carrier wave is to produce by inject DC bias component in being added to the modulation voltage of balanced modulator, and described balanced modulator produces amplitude-modulation sideband, and this amplitude-modulation sideband produces the VSB signal behind filter filtering.If in the carrier (boc) modulated signals 8 level of 4 bit signs codings have normalized value-7 ,-5 ,-3 ,-1 ,+1 ,+3 ,+5 and+7, just the normalized value of pilot carrier signal is 1.25 so.The normalized value of+S is+5, and the normalized value of-S is-5.
At the DTV technical development initial stage, once (it was arranged in before the data amplitude limiter of symbolic solution device circuit the comb filter of imagination in DTV broadcasting equipment and each DTV signal receiver, as the back encoder) when using together, must judge the symbol precoder that whether uses on the reflector by this DTV broadcasting equipment, this symbol precoder is followed in the back of symbol generation circuit and the symbol filtering of coupling is provided.This judgement can only depend on the interference that whether predicts from co-channel NTSC broadcasting station.The symbol pre-encode operation can not be used in the synchronous code character of data line or between the data line of transmission data field synchrodata.
Far away more from the NTSC broadcasting station, co-channel interference is more little, more co-channel interference may take place when satisfying certain ionosphere condition.Co-channel interference took place probably in the summer in high movable year of the sun.Certainly, if just do not have this interference with frequency NTSC broadcasting station.Disturb if NTSC in broadcast coverage areas, may occur, will use the symbol precoder so that HDVT signal and NTSC interference signal are separated just suppose the HDTV broadcasting equipment; Thereby comb filter will be used as encoder behind the symbol in the DTV signal receiver, to finish matched filtering.If the NTSC that may or not occur that not exists NTSC to disturb disturbs, differentiate for fear of the mistake that causes by white noise lattice encoder value of symbol, will stop using the symbol precoder just suppose the DTV broadcasting equipment; So each DTV signal receiver just can not use encoder behind the symbol.
The back coding comb filter that adopts No. 5260793 United States Patent (USP) that is entitled as " RECEIVER POSTCODER SELECTION CIRCUIT (encoder is selected circuit behind the receiver) " of authorizing people such as R.W.Citta on November 9th, 1993 suppress with digital high-definition television (HDTV) receiver in the composite output signal of demodulator in the meritorious or simultaneous NTSC of homophase base band component (I channel) disturb.By in the I channel component that detects demodulator output whether the NTSC interference signal being arranged, make control signal open automatically or stop for the work that suppresses the comb filter that the NTSC co-channel interference uses.Between each data field synchronization zone, the input signal of the pectination NTSC rejects trap in the HDTV signal receiver and output signal compare with coherent signal pre-determined and that extract from the memory of HDTV signal receiver respectively.If with the energy of input signal minimum comparative result relatively less than with the energy of NTSC rejects trap output signal minimum comparative result relatively, that just illustrates that causing the main cause different with expecting received signal is random noise rather than NTSC co-channel interference signal.With regard to the optional network specific digit television receiver, received signal is not preferably adopted the back coding in precoding and the system, therefore suppose that broadcasting equipment does not adopt precoding.If with the energy of input signal minimum comparative result relatively greater than with the energy of NTSC rejects trap output signal minimum comparative result relatively, that just illustrates that causing the main cause different with expecting received signal is NTSC co-channel interference signal rather than random noise.With regard to the optional network specific digit television receiver, received signal is preferably adopted the back coding in precoding and the system, therefore suppose that broadcasting equipment has adopted precoding.
The exercise question of authorizing people such as K.S.Kim on August 13rd, 1996 has been described for No. 5546132 United States Patent (USP) of " NTSC INTERFERENCEDETECTOR (NTSC interference detector) " and has been suppressed NTSC with back coding comb filtering and extract comb filter detected co-channel NTSC interference signal when responding the I channel.No. 5546132 United States Patent (USP) is not done explanation specially to the idle or quadrature base band component (Q channel) in the composite output signal of demodulator used in the digital HDTV signal receiver.Make the synchronous digital HDTV signal receiver of VSB AM signal and base band adopt a kind of like this demodulator usually, this demodulator comprises in-phase synchronization detector and quadrature phase synchronizing indicator, wherein, the in-phase synchronization detector is used to provide the I channel signals that receives to use (after the coding of back for lattice decoding, if used precoding in the reflector), the quadrature phase synchronizing indicator is used to provide the Q that receives channel signals.The Q channel signals that this receives produces automatic frequency and phase control (AFPC) signal through after the low-pass filtering, so that make local oscillator that sync carrier is provided.Authorized being entitled as of C.B.Patel and A.L.R.Limberg the explanation of No. 5479449 United States Patent (USP) of " DIGITAL VSB DETECTORWITH BANDPASS PHASE TRACKER; AS FOR INCLUSION IN AN HDTVRECEIVER (the digital VSB detector that has the logical phase tracker of band in the HDTV receiver) " and accompanying drawing on December 26th, 1996 herein as a reference, this patent has transferred Samsung (Samsung) electronics corporation.The reader should be specifically noted that in the 22-27 parts shown in Figure 1 of No. 5479449 patent accompanying drawing of the U.S. and this patent description the description to these parts.These parts are used in described HDTV signal receiver, and it is used for the final intermediate frequency of VSB AM (IF) signal is carried out compound demodulation.The compound demodulation of the final I-F signal of VSB AM that No. 5479449 United States Patent (USP) described to carry out under the digital situation, but the compound demodulation of the final I-F signal of VSB AM in other digital TV receiver is all carried out under simulated conditions.
In No. 5260793 United States Patent (USP) and No. 5546132 United States Patent (USP), do not exist with allowing the back coding during the NTSC interference signal frequently, otherwise just do not allow the back coding, this selectable start-up control signal is to obtain according to received I channel signals.Because co-channel NTSC interference signal is with Dc bias, thereby very difficult definite co-channel NTSC interference signal level, this Dc bias is caused by the pilot carrier signal in the VSB AM DTV signal being carried out the in-phase synchronization detection.This is the prominent question in the DTV signal receiver, and in the DTV signal receiver, automatic gaining controling signal is not closely regulated the amplitude that is detected the I channel signals that receives that is recovered by in-phase synchronization.
The video carrier frequency of NTSC signal is broadcast the edge 1.25MHz of channel from the 6MHz broadness, and the carrier frequency that is used for the DTV signal of terrestrial broadcasting is broadcast edges of signals from the 6MHz broadness and then is 310kHz.For vestigial sideband amplitudemodulation (VSB AM) carrier wave of transmitting digital information, co-channel NTSC signal can not present the amplitude-modulation sideband of symmetry.Thereby having eliminated frequency from the DTV signal carrier is the artefact (artifact) of the ntsc video carrier wave of 940kHz, but because synchronous with base band, its sideband artefact does not disappear from the DTV signal fully.Certainly, the artefact of NTSC sound carrier and sideband thereof does not have fully from the DTV blackout yet, and the NTSC sound carrier at 5.44MHz place has disappeared from the DTV signal carrier.
The digital television standard ATSC that announces September 16 nineteen ninety-five does not consider to compensate when utilizing comb filtering to suppress co-channel interferences of NTSC afterwards incident back encode in the DTV signal receiver by in the DTV reflector all data being carried out precoding, and just the original symbol in the lattice decoding is carried out precoding.This process itself suppresses the co-channel interference of NTSC to DTV signal receiver before carrying out in the data slicing process with comb filter and there is no help.The DTV digit receiver that can not before the data slicing process is carried out, suppress the co-channel interference of NTSC artefact may because of the DTV digit signal receiver away from the DTV digit emitter or because of near have the analog TV reflector to cause the co-channel disturbed condition of strong NTSC under can not finely receive.With the synchronous DTV signal of base band in, the artefact frequency of the video carrier in the colored TV signal of co-channel interference NTSC is 59.75f H, f HIt is the line-scanning frequency of the colored TV signal of NTSC.The artefact frequency of colour subcarrier is 287.25f H, the artefact frequency of unmodulated NTSC sound carrier is 345.75fH.The inventor points out, the comb filtering process also not exclusively is suitable for eliminating frequency modulation NTSC sound carrier artefact, especially all the more so under the bigger frequency modulation situation of carrier frequency drift, because the correlation (or anti-correlation) of the FM carrier wave sample that obtains in the sampling instant of any constant time lag might not be good especially.The inventor proposes, and the filtering that is used for bearing whole intermediate-frequency bandwidth amplification must be convenient to suppress the FM sound carrier of any co-channel NTSC analog tv signal.The comb filtering process is very suitable for isolating the baseband DTV signal near the artefact of the carrier chrominance signal frequency ntsc video carrier wave, low video frequencies and colour carrier.This is because have reasonable correlation between some specific time delay interval sample of these artefacts, has reasonable anti-correlation between some other specific time delay interval sample.
On November 12nd, 1996, the inventor has proposed to be entitled as No. 08/746520 patent application of " DTV RECEIVERWITH FILTER IN I-F CIRCUITRY TO SUPPRESS FM SOUND CARRIER OFNTSC CO-CHANNEL INTERFERING SIGNAL (the DTV receiver with filter of the I-F circuit that is used for suppressing FM sound carrier and the co-channel interference signal of NTSC) " in the U.S., the inventor proposes, when the co-channel interference of NTSC is big must be enough to influence data slicing conversely the time, just in the DTV signal receiver, pass through the advanced line data amplitude limit of comb filtering, thereby suppress the co-channel interference of NTSC.The inventor has also illustrated the influence how this comb filtering of compensation causes the symbolic coding of carrying out selectively in the symbol decoding process.In addition, it can also determine when the moment of the co-channel interference of NTSC during greater than setting, and described setting be for can receive minimum value, thereby this result of determination can be used for control comb filter is used selectively so that co-channel interference suppresses to NTSC.
When in the meritorious or homophase base band component (I channel) of the composite output signal of the used demodulator of DTV signal receiver, the co-channel interference of NTSC occurring, it is idle or quadrature phase base band component (Q channel) in also co-channel interference can appear.Therefore, the NTSC interference detector can be set like this, make its NTSC extraction filter play response rather than the I-channel signals that receives is played response the Q-channel signals that receives.By whether the co-channel interference signal of NTSC of big numerical value is arranged in the Q-channel signals of determining to receive, just can infer whether the co-channel interference signal of the NTSC of big numerical value is arranged in the I-channel signals that receives, so just a large amount of error codes that can in the lattice decoding process, produce with the I-channel signals that receives after the Reed-Solomon decoder correction equilibrium of trellis decoder back.Because the quadrature phase of VSBAM DTV signal pilot carrier wave is carried out synchronous detecting can not cause Dc bias basically, therefore the accurate mensuration of co-channel NTSC interference level is simplified.
General introduction of the present invention
The method that is used for handling the vestigial sideband amplitudemodulation digital television signal of digital television signal receiver according to one aspect of the invention a kind of comprises the following steps: the vestigial sideband amplitudemodulation digital television signal that is subject to co-channel NTSC interference effect is carried out compound demodulation, so that isolate the I channel baseband signal that is received and isolate the Q channel signals that is received with the orthogonal thereto relation of I channel baseband signal that is received; Then, disturb artefact whether to surpass setting by the co-channel NTSC that follows in the Q channel baseband signal of determining to be received, the co-channel NTSC that follows in the I channel baseband signal of estimating to be received disturbs artefact whether to reach significant level.
Be used for determining whether before lattice decoding, adopt comb filtering to suppress the method that co-channel NTSC disturbs according to of the present invention in DTV receiver, comprise the following steps: digital television signal is carried out compound demodulation, so that isolate the Q channel signals that is received of I channel baseband signal that is received and the orthogonal thereto relation of baseband signal of isolating and being received; Whether exist co-channel NTSC to disturb artefact in the Q channel baseband signal of determining to be received with significant level; If do not exist the co-channel NTSC of significant level to disturb artefact in the Q channel baseband signal of determining to be received, just make the I channel signals that is received under the situation of not carrying out comb filtering, directly carry out symbol decoding, thereby produce the decoded symbol of using for lattice decoding; If exist co-channel NTSC to disturb artefact in the Q channel baseband signal of determining to be received with significant level, just the I channel baseband signal that is received is carried out comb filtering, thereby produce the I channel baseband signal (co-channel NTSC wherein disturbs and is inhibited) that comb filtering is crossed, and the I channel baseband signal that this comb filtering is crossed carried out symbol decoding, symbol decoding result to the I channel baseband signal behind the comb filtering carries out the back coding then, thereby produces the decoded symbol of using for lattice decoding.
According to a kind of digital television signal receiver of the present invention, comprising: amplifier circuit is used to provide the vestigial sideband amplitudemodulation digital television signal of amplification of co-channel interference simulation TV signal of being easy to carry about with one; Compound demodulator, vestigial sideband amplitudemodulation digital television signal after the described amplification is responded, so that I channel baseband signal that contains any co-channel interference simulation TV signal artefact and the Q channel baseband signal that contains other artefact of any co-channel interference simulation TV signal to be provided; The symbol decoding device of described I channel baseband signal, comprise first data amplitude limiter that is used in the very first time, described I channel baseband signal being carried out symbol decoding, usually as long as the described artefact of any co-channel interference simulation TV signal is lower than the significant level of described I channel baseband signal, the error code among the first symbol decoding result of then described first data amplitude limiter output can be proofreaied and correct; With the co-channel interference detector of NTSC that described Q channel baseband signal is played response, those of described other artefact that are used for detecting any co-channel interference simulation TV signal are higher than the appearance of the artefact of described Q channel baseband signal significant level, and the described significant level of described Q channel baseband signal is consistent with the described significant level of described I channel baseband signal.
The interference NTSC signal that occurs in the co-channel interference detector of NTSC pair that embodies various aspects of the present invention and the Q channel of I channel quadrature detects.Further the co-channel codan of adaptive N TSC that embodies viewpoint of the present invention utilizes the co-channel interference detector of these NTSC to control whether suppressing the co-channel interference of NTSC with comb filtering before the data limit in DTV receiver.
Brief description of drawings
Fig. 1 is the block diagram of a DTV receiver part, it comprises the symbol decoder that has according to the co-channel codan of NTSC of the present invention, and it carries out work according to the response signal that the Q channel signals to the compound demodulator output of DTV signal plays the co-channel interference detector of NTSC of response;
Fig. 2 is the block diagram of the co-channel interference detector of NTSC that responds being used to of constituting the Q channel signals of the compound demodulator output of DTV signal according to the present invention;
Fig. 3 is the operational flowchart of part of the DTV receiver of Fig. 1, and how whether its expression disturbed and revised equalization operation according to utilizing comb filtering to suppress co-channel NTSC;
Fig. 4 is the details schematic block diagram that numeral electricity shown in Figure 1 divides when NTSC suppresses 12 symbols time-delays of comb filter employing;
Fig. 6 is the details schematic block diagram of the part of DTV signal receiver shown in Figure 1 when NTSC suppresses 6 symbols time-delays of comb filter employing;
Fig. 7 is the details schematic block diagram of the part of the co-channel interference detector of NTSC shown in Figure 2 when adopting 6 symbol time-delays;
Fig. 8 is the details schematic block diagram of the part of DTV signal receiver shown in Figure 1 when NTSC suppresses 2 video line time-delays of comb filter employing;
Fig. 9 is the details schematic block diagram of the part of the co-channel interference detector of NTSC shown in Figure 2 when adopting 2 video line time-delays;
Figure 10 is the details schematic block diagram of the part of DTV signal receiver shown in Figure 1 when NTSC suppresses 262 video line time-delays of comb filter employing;
Figure 11 is the details schematic block diagram of the part of the co-channel interference detector of NTSC shown in Figure 2 when adopting 262 video line time-delays;
Figure 12 is the details schematic block diagram of the part of DTV signal receiver shown in Figure 1 when NTSC suppresses 2 frame of video time-delays of comb filter employing;
Figure 13 is the details schematic block diagram of the co-channel interference detector part of NTSC shown in Figure 2 when adopting 2 frame of video time-delays;
Figure 14 and 15 represents to be used in the details schematic block diagram of the co-channel interference detector of NTSC of other type on the DTV signal receiver shown in Figure 1 respectively; And
Figure 16 is the schematic block diagram according to DTV receiver of the present invention, in this DTV signal receiver, has adopted a plurality of comb filter and the relevant co-channel interference detector of NTSC thereof, so that the co-channel interference of filtering NTSC artefact selectively.
The detailed description of the embodiment of the invention
Must insert calking time-delay (Shimming delay) on each position of circuit shown in the accompanying drawing, this can understand those people that are familiar with design of electronic circuits.To not relate to the calking time-delay in the following description, unless the calking time-delay is had specific (special) requirements.
Fig. 1 shows the digital television signal receiver that is used to recover error correction data, and described data adapting is in writing down with digital video cassette recorder (DVCR) or being suitable for MPEG-2 decoding and playing on television set.DTV signal receiver among Fig. 1 received tv broadcast signal from the reception antenna 8, but it also can be from received signal on the wired network.Television broadcasting signal is used as the input signal of " preposition " circuit 10." preposition " circuit 10 generally includes the radio frequency amplifier and first detector, and wherein, first detector is used for converting radio television signal to medium-frequency TV signal.This medium-frequency TV signal is as the input signal of intermediate frequency (IF) amplifier circuit 12, and intermediate frequency amplifier circuit 12 produces residual sideband DTV signal.The DTV signal receiver is preferably with the complex conversion type receiver of IF amplifier circuit 12, IF amplifier circuit 12 comprises IF amplifier, second detector and another IF amplifier, wherein, the IF amplifier is used for the superfrequency DTV signal that obtains after the conversion of first detector is amplified, second detector is used for the DTV conversion of signals after amplifying is become very high frequency(VHF) (VHF) signal, and another IF amplifier is used for the DTV signal that converts the VHF signal to is amplified.If carry out demodulation in digital scope, this IF amplifier circuit 12 will also comprise the 3rd detector that is used for the DTV conversion of signals one-tenth after amplifying is more approached the final midband of base band so.
UHF band IF amplifier preferably adopts surface acoustic wave (SAW) filter, so that channel selection is responded integer and suppresses adjacent channel.This SAW filter ends rapidly outside the 5.38MHz scope of the inhibition carrier frequency of distance VSB DTV signal and pilot signal, and these two signals have same frequency and fixed amplitude.Thereby this SAW filtering can be eliminated the frequency modulated sound carrier wave in a large amount of any co-channel interference simulation TV signals.In IF amplifier circuit 12, eliminate FM sound carrier in any co-channel interference analog tv signal and can avoid producing the artefact of this carrier wave when recovering baseband signalling detecting final I-F signal, and the data slicing mutual interference mutually that in the symbol decoding process, prevents these artefacts and those baseband signallings.In the symbol decoding process, avoid artefact that these and the data slicing of baseband signalling disturb mutually than the better off of before data slicing, avoiding these artefacts by comb filtering, particularly all the more so when the different delayed time in the comb filter postpones (epoch) greater than several symbol phase.
Be provided for compound demodulator 14 from the final IF output signal of IF amplifier circuit 12 outputs, the vestigial sideband amplitudemodulation DTV signal in 14 pairs of final midbands of compound demodulator carries out demodulation, to recover meritorious baseband signal and idle baseband signal.Can be described as for example No. 5479449 United States Patent (USP), after the final midband in several megahertz range is carried out analog-to-digital conversion, in digital scope, carry out demodulation.On the other hand, also can in simulation context, carry out demodulation, in this case, generally will carry out analog-to-digital conversion and be beneficial to further processing demodulation result.Compound demodulation is preferably finished by homophase (I) synchronous demodulation and quadrature phase (Q) synchronous demodulation.The numeric results of above-mentioned demodulation operation has the precision more than 8 or 8 usually, and it has described 2N level symbol of coding N bit data.Usually, the DTV signal receiver in Fig. 1 receives under the situation of air broadcast signal by antenna 12, and 2N equals 8, and the DTV signal receiver in Fig. 1 receives under the situation of cable TV signal, and 2N equals 16.The present invention is with to receive ground relevant in the face of empty broadcast singal, thus Fig. 1 do not draw the DTV signal receiver the symbol decoding part and be used to receive the error correction decoding part of CATV transmission signal.
Sign synchronization and equalizing circuit 16 receive the digital power sample of homophase (I channel) baseband signal from compound demodulator 14 at least; In DTV signal receiver shown in Figure 1, circuit 16 also receives the idle sample of digitlization of quadrature phase (Q channel) baseband signal.Circuit 16 comprises the digital filter with adjustable weight coefficient, and it is used for compensating the ghost image and the gradient of received signal.Sign synchronization and equalizing circuit 16 make sign synchronization or " go rotation " and make amplitude balanced and ghost image disappears.Sign synchronization that sign synchronization was finished before amplitude balanced and equalizing circuit can be recognized from No. 5479449 United States Patent (USP).In the design, demodulator 14 will provide the over-sampling demodulator response signal that contains meritorious and idle baseband signal to sign synchronization and equalizing circuit 16.After sign synchronization,, the over-sampling data are carried out 10 get 1 fen sample, thereby extract the baseband I channel signals of proper symbol speed for reducing the sampling rate that amplitude balanced and ghost image suppress digital filter.Sign synchronization that amplitude balanced is finished before sign synchronization, " go rotation " or " Phase Tracking " and equalizing circuit also be for the technical staff of digit signal receiver design field known.
10 of resolved one-tenth of each sample value of circuit 16 output signals or multidigit more, it is actually the numeral of single level (8 level in level) analog symbol and describes.The output signal of circuit 16 can be controlled meticulously with any method in known several gain control methods, so the typical ladder level of symbol is known.A kind of preferred gain control method (because the response speed of this gain controlling is fast especially thereby preferentially recommended) is that the DC component of meritorious baseband signal that compound demodulator 14 is provided is adjusted to+1.25 normalization level.No. 5479449 United States Patent (USP), particularly authorized people's such as C.B.Patel No. 5573454 United States Patent (USP) that is entitled as " AUTOMATIC GAIN CONTROL OFRADIO RECEIVER FOR RECEIVING DIGITAL HIGH-DEFINITIONTELEVISION SIGNALS (the automatic gain control of the radio receiver of receiving high-definition TV signal) " on June 3rd, 1997 and described this gain control method, herein with this gain control method as the reference method.
The output signal of circuit 16 is used as the input signal of data sync testing circuit 18, and data sync testing circuit 18 is used for from equalization base band I channel signals restore data field sync information F and data segment sync information S.On the other hand, the input signal of data sync testing circuit 18 can obtain before equilibrium.
Balanced I channel signals proper symbol rate samples in circuit 16 output signals is used as the input signal that NTSC suppresses comb filter 20.Comb filter 20 comprises first time-delay mechanism 201 and the linear combiner 202, wherein, first time-delay mechanism 201 is used to produce a pair of symbols streams with 2N level of different delayed time, and first linear combiner 202 is used for the different delayed time symbols streams is carried out linear combination so that produce the response signal of comb filter 20.As described in No. 5260793 United States Patent (USP), first time-delay mechanism 201 can provide the time-delay that equates with 12 2N level symbol cycles, and first linear combiner 202 can be a subtracter.10 of resolved one-tenth of each sample of comb filter 20 output signals or multidigit more, it is actually the numeral of single level (4N=15 a level in level) analog symbol and describes.
Suppose that sign synchronization and equalizing circuit 16 are used to suppress the DC bias component in its input signal (representing with numeral sample), the normalization level of this DC bias component is+1.25, owing to detect pilot frequency carrier wave, therefore this DC bias component occurred in the meritorious baseband signal of compound demodulator 14.Therefore, as each samples of circuit 16 output signals of comb filter 20 input signals be actually its level for certain normalization level (7 ,-5 ,-3 ,-1 ,+1 ,+3 ,+5 and+7) the numeral of analog symbol describe.These symbol level are named as " very " symbol level, and they produce 000,001,010,011,100,101,110 and 111 such centres respectively and meet decoded result after strange level data amplitude limiter 22 detects.
Each sample of comb filter 20 output signals be actually its level for certain normalization level (14 ,-12 ,-10 ,-8 ,-6 ,-4 ,-2,0 ,+2 ,+4 ,+6 ,+8 ,+10 ,+12+ and 14) the numeral of analog symbol describe.These symbol level are named as " idol " symbol level, and they produce 001,010,011,100,101,110,111,000,001,010,011,100,101,100 and 111 such pre-coded symbols decoded results respectively after even level data amplitude limiter 24 detects.
Data amplitude limiter 22 and 24 can be the sort of what is called " hard decision " the type data amplitude limiter of up to the present being supposed in explanation, perhaps can be the sort of what is called " soft decision " type amplitude limiter used when carrying out Viterbi (Viterbi) decoding scheme.It also is feasible replacing strange level data amplitude limiter 22 and even level data amplitude limit 24 with the individual data amplitude limiter, as long as with the multiplexer connecting circuit move it in circuit the position and be provided for revising the bias voltage of its amplitude limit scope, but because these scheme complicated operations, thereby preferably do not adopt these schemes.
Suppose that above-mentioned sign synchronization and equalizing circuit 16 are used to suppress the DC bias component in its input signal (representing with numeral sample), the normalization level of this DC bias component is+1.25, owing to detect pilot frequency carrier wave, this DC bias component occurred in the meritorious baseband signal of compound demodulator 14.On the other hand, sign synchronization and equalizing circuit 16 are used to keep the DC bias component in its input signal, and this has simplified the design of the equalization filter in the circuit 16 a little.In this case, the data slicing level of strange level data amplitude limiter 22 is offset, so that the DC bias component of following in its input signal data ladder is taken into account.Suppose that first linear combiner 202 is subtracters, no matter circuit 16 is used for suppressing or is used for keeping so, the data slicing level of the DC bias component antithesis level data amplitude limiter 24 in its input signal all is inessential.But, when the difference time-delay that provides when first time-delay mechanism 201 makes first linear combiner 202 become adder, consider the DC bias component of following in its input signal data ladder, the data slicing level of even level data amplitude limiter 24 should be offset.
Back in data amplitude limiter 22 and 24 produces the back coding filter response signal that the response signal of the precoder filter in the comb filter 20 is played response with comb filter 26.The time-delay of first time-delay mechanism 201 in the time-delay that comb filter 26 comprises 3 input multiplexers 261, second linear combiner 262 and second time-delay mechanism, 263, the second time-delay mechanisms 263 and the comb filter 20 is identical.If first linear combiner 202 is subtracters, just second linear combiner 262 is mould 8 adders so; If first linear combiner 202 is adders, just second linear combiner 262 is mould 8 subtracters so.First linear combiner 202 and second linear combiner 262 can constitute corresponding read-only memory (ROM), are enough to support related sample rate so that the linear combination service speed brought up to.The output signal of multiplexer 261 is exactly the response signal of back coding comb filter 26, and this signal is postponed by second time-delay mechanism 263.Second linear combiner 262 combines the pre-coded symbols decoded result of even level data amplitude limiter 24 outputs and the output signal of second time-delay mechanism 263.
During a kind of state of multiplexer 261 in the multiplexer control signal that provided by controller 28 of response first, second and the third state, its output signal is just reproduced an input signal in its three input signals.During data sync testing circuit 18 received data field synchronizing information F and data segment sync information S in the equalization base band I channel signals, first input port of multiplexer 261 received the standard symbol decoded result of self-controller 28 internal storages.During this period, controller 28 is input to first state of multiplexer control signal in the multiplexer 261, makes standard symbol decoded result that multiplexer 261 provides controller 28 internal storages as final decoded result (output signal).Strange level data amplitude limiter 22 provides the intermediate symbols decoded result to second input port of multiplexer 261.Second state of multiplexer control signal makes the final decoded result of multiplexer 261 reproduce this intermediate symbols decoded result.Second linear combiner 262 provides back coded identification decoded result as its output signal to the 3rd input port of multiplexer 261.The third state of multiplexer control signal makes multiplexer 261 reproduce for example this back coded identification decoded result.During data sync testing circuit 18 restore data field sync information F and data segment sync information S, the standard symbol decoded result that controller 28 internal storages provide has reduced the operation error code among the back coding and decoding result of back coding comb filter 26 outputs.
The output signal of the multiplexer 261 in the back coding comb filter 26 comprises the final symbol decoding result of parallel 3 hyte forms, and it is input in the data interleaver 32 behind Data Assembler 30 compilations.Data interleaver 32 becomes parallel data stream with assembled exchanges data, offers trellis decoder circuit 34 then.12 trellis decoders of trellis decoder circuit 34 general employings.The lattice decoding result of trellis decoder circuit 34 outputs is imported into and carries out inverse transformation in the data deinterleaver circuit 36.Byte analysis circuit 38 converts the output signal of data interleaver 36 to Reed-Solomon error correction coding byte, it is input in the Reed-Solomon decoder circuit 40 then, Reed-Solomon circuit 40 carries out the Reed-Solomon decoding to it, removes randomizer 42 thereby produce error correction stream and this error correction stream is offered data.Data go randomizer 42 data of reproducing to be offered the other parts (not shown) of receiver.The other parts of a complete DTV signal receiver will comprise information block grader, audio decoder, MPEG-2 decoder etc.The other parts of the DTV signal receiver in digital magnetic tape video tape recorder/player will comprise the circuit that is used for data transaction is become record format.
NTSC is co-channel, and interference detector 44 provides a co-channel interference strength indication of NTSC for controller 28, and whether the co-channel interference of its indication NTSC can produce can not be by the error code of proofreading and correct in the data slicing of data amplitude limiter 22.If the co-channel interference of detector 44 indication NTSC not have so big intensity, so controller 28 will be during data sync testing circuit 18 be carried out resuming work of data field sync information F and data segment sync information S in addition during provide second state of multiplexer control signal to multiplexer 261.This intermediate symbols decoded result that makes multiplexer 261 reproduce to be provided by strange level data amplitude limiter 22 is as its output signal.Can not be if the co-channel interference strength of decoder 44 indication NTSC is enough to produce by the error code of proofreading and correct in the data slicing of data amplitude limiter 22, so controller 28 beyond will be during data sync testing circuit 18 be carried out resuming work of data field sync information F and data segment sync information S during provide the third state of multiplexer control signal to multiplexer 261, the back coded identification decoded result that this makes multiplexer 261 reproduce second line combination by second linear combiner 262 provides is used as its output signal.
The disclosed invention of this specification and accompanying drawing thereof is characterised in that the co-channel interference detector 44 of NTSC, and the artefact of the co-channel interference of NTSC that occurs in the Q channel output signal of 44 pairs of compound demodulators 14 of DTV signal of this detector plays response.Detector 44 can be used for detecting the artefact of the co-channel interference of NTSC in the compound demodulator 44 Q channel output signals that sign synchronization and equalizing circuit 16 extract previously, but Fig. 1 shows the detector 44 that is used for detecting the artefact from the Q channel output signal that the response of sign synchronization and equalizing circuit 16 is extracted.
Fig. 2 shows a kind of form that the co-channel interference detector 44 of NTSC in one embodiment of the invention can be taked.The Q channel output signal of extracting from the response of sign synchronization and equalizing circuit 16 directly is added on the node 440, perhaps in that 441 filtering are added to later on the word point 440 through the bandwidth selective filter, bandwidth selective filter 441 provides one to node 440, and those more may contain the response of the part of NTSC channel interference artefact in to Q channel output signal.Signal on the node 440 is used as input signal and is added on the 3rd time-delay mechanism 442 and stands the 3rd time-delay.Trilinear combiner 443 has suppressed signal on the node 440 and one of generation after the signal linear combination of the 3rd time-delay mechanism 442 time-delays the comb filter response of the co-channel interference of NTSC artefact.The 4th linear combiner 444 contains signal on the node 440 and one of generation after the signal linear combination of the 3rd time-delay mechanism 442 time-delays the response of the co-channel interference of the NTSC artefact of selection.Have one to be digital adder in the 3rd and the 4th linear combiner, and another is a digital subtractor, its selection scheme depends on the time-delay that the 3rd time-delay mechanism 442 provides.The comb filter response amplitude of trilinear combiner 443 outputs is detected by amplitude detector 445, the comb filter response amplitude of the 4th linear combiner 444 outputs is detected by amplitude detector 446, and the amplitude testing result that amplitude detector 445 and 446 records by magnitude comparator 447 relatively.Amplitude detector 447 provides a carry-out bit, and whether the response of its indication amplitude detector 446 surpasses the response of amplitude detector 445 substantially.This carry-out bit is used for selection operation between second and the third state of multiplexer 261.For example, this carry-out bit of magnitude comparator 447 can be that controller 28 offers a control bit in two control bits of the multiplexer 261 in the back coding comb filter 26 of Fig. 1, and whether another control bit is used for signal that indicating controller 28 provides and occurs in the response of multiplexer 261.
For example, amplitude detector 445 and 446 can be the envelope detector with several data sampling constants cycle time, thereby the data component difference in their input signal finally is tending towards low value, supposes that they are at random.Random noise difference in linear combiner 443 and 444 the response finally also goes to zero.Therefore, when the magnitude comparator 447 of the amplitude detection response that is used for comparison amplitude detector 445 and 446 was indicated those response differences greater than setting, this illustrated that just the artefact of any co-channel interference simulation TV signal all surpasses the significant level of Q channel baseband signal.This Q channel baseband signal significant level is equivalent to the significant level of I channel baseband signal.As long as any co-channel interference simulation TV signal artefact is lower than the significant level of I channel baseband signal, the symbol decoding error code that is caused by the simple data amplitude limit to I channel baseband signal can obtain proofreading and correct by lattice and Reed-Solomon error correction so.
When the amplitude of the comb filter response (wherein containing the co-channel interference of selected NTSC artefact) of the 4th linear combiner 444 output during, can suppose that just this difference is owing to existing the co-channel interference of NTSC to cause in the signal on the node 440 basically greater than the amplitude of the comb filter response (wherein having suppressed the co-channel interference of NTSC artefact) of trilinear combiner 443 outputs.In this case, the carry-out bit that magnitude comparator 447 provides can not be operated multiplexer 261 under its third state, thus from multiplexer 261 occur final symbol decoding as a result the time just deselect fall back coded identification decoded result from second linear combiner 262.
Bandwidth selective filter 441 perhaps is unwanted, or even undesirable, and this decides on the time-delay length of the 3rd delay cell 442 and the design of amplitude detector 445 and 446.Except as the envelope detector, amplitude detector 445 and 446 also can detect the skew energy between its input signal and the symbolic coding level (releasing according to pilot frequency carrier wave intensity); Do not need bandwidth selective filter 441 in this case.If the time-delay length of the 3rd delay cell 442 can not make the complete obiteration of NTSC sound carrier artefact, but can make the artefact complete obiteration of NTSC sound carrier and colour subcarrier, if and amplitude detector 445 and 446 is envelope detector, just bandwidth selective filter 441 can adopt cut-off frequency shown in Fig. 7,9,11,13 and 14 to be not more than finite impulse response (FIR) the wave digital lowpass filter 4410 this forms of 5.4MHz so.
Fig. 3 shows DTV traffic filter among Fig. 1 and suppresses the flow chart that situation that co-channel NTSC disturbs is revised equalization operation according to whether with comb filtering.The inventor points out, bring error can for the calculating of equalization filter Kernel (nuclear) coefficient when occurring with NTSC interference frequently in the baseband signalling cataloged procedure, unless take special measure to make these artefacts invalid when calculating.
At initial step S1, compound demodulator 14 in the DTV signal receiver shown in Figure 1 is done compound demodulation to digital television signal continuously, so as to isolate the I channel baseband signal that received and with the Q channel baseband signal that is received of the I channel baseband signal quadrature that is received.Whether at determination step S2, the co-channel interference detector 44 of the NTSC in the DTV signal receiver shown in Figure 1 is also done compound demodulation to digital television signal continuously, have the co-channel NTSC of effective dose to disturb in the Q channel baseband signal of determining to be received.
Thereby to such an extent as to the co-channel NTSC in the DTV signal receiver disturbs effective value to be meant the level that can cause a large amount of error codes in the error correcting capability that can make a large amount of error code of lattice decoding generation can reduce the bidimensional Reed-Solomon decoding of lattice decoding back greatly under the normal noise reception condition in final data recovered.Co-channel NTSC in the DTV signal receiver of particular design disturbs effective value to be easy to determine by the prototype experiment of receiver.
If do not exist co-channel NTSC to disturb in the Q channel baseband signal of in determining step S2, determining to be received with effective value, just execution in step S3 and step S4, so that produce the symbol decoding result who uses for step S5, wherein, step S3 is used to regulate the Kernel weights of digital equalization filter, so that balanced response to I channel baseband signal; Step S4 is used for equalization filter response the carrying out symbol decoding to being provided by step S3; Step S5 is used for the symbol decoding result is made lattice decoding, so that proofread and correct error code wherein.Lattice decoding step S5 back is Reed-Solomon decoding step S6 and step S7, and step S6 is used for proofreading and correct lattice decoding result's error code, and step S7 is used to remove the form of Reed-Solomon decoded result.
If exist the co-channel NTSC of effective dose to disturb in the Q channel baseband signal of in determining step S2, determining to be received, just use suitable comb filter execution in step S8, received I channel baseband signal is carried out comb filtering, thereby produce the I channel baseband signal behind the comb filtering.In step S9, the digital equalization filter of cascade and the response of comb filter are consistent with this filter cascade normal response by the Kernel weights of regulating digital equalization filter.Execution in step S10 makes symbol decoding to this filter cascade response.Execution in step S11 decodes after response is done to symbol decoding then, thus the symbol decoding result after the correction that obtains using for lattice decoding step S5.Lattice decoding step S5 back is Reed-Solomon decoding step S6 and step S7, and step S6 is used for proofreading and correct lattice decoding result's error code, and step S7 is used to remove the form of Reed-Solomon decoded result.
In step S3, be used for regulating the Kernel weights of digital equalization filter so that make the Kernel weights control method of digital equalization filter of balanced householder method of digital equalization filter response and prior art similar.Adjusting is performed such: carry out discrete fourier transform (DFT) to the data field synchronous code that receives or to wherein established part, DFT with normal data field sync sign indicating number or its established part is cut apart it, thereby determines the DFT of DTV transmission channel.With respect to maximal term normalization, so that characterize this channel, the Kernel weights of selecting digital equalization filter are so that replenish the normalization DFT that characterizes this channel with the DFT of DTV transmission channel.For example the people's such as C.B.Patel that announced on July 19th, 1994 No. 5331416 United States Patent (USP) that is entitled as " METHODS FOR OPERATING GHOST-CANCELATION CIRCUITRY FOR TV RECEIVER OR VIDEORECORDER (ghost image of TV receiver or video recorder is eliminated the method for operation of circuit) " described this control method in greater detail.This method is preferably used in the initial adjustment of digital equalization filter Kernel weights, can make initial adjustment carry out sooner because this method is compared with adaptive equalization.After the initial adjustment of digital equalization filter Kernel weights, adopt the adaptive equalization method at last.Authorize people's such as J.Yang No. 5648987 United States Patent (USP) that is entitled as " RAPID-UPDATE ADAPTIVE CHANEL-EQUALIZATION FILTERINGFOR DIGITAL RADIO RECEIVERS, SUCH AS HDTV RECEIVERS (the quick renewal self-adaption frequency channel equalization filtering of digital radio receiver and HDTV receiver) " on July 15th, 1997 and described a kind of piece LMS method that is used to carry out adaptive equalization.In April, 1997, No. 08/832674 U.S. Patent application be entitled as " the DYNAMICALLY ADAPTIVE EQUALIZER SYSTEM AND METHOD (dynamic self-adapting equalizing system and method) " that propose of A.L.R.Limberg described a kind of continuous LMS method that is used to carry out adaptive equalization.
In step S9, when particularly before switching to adaptive equalization, carrying out quick initial equalization, can carry out householder method with DFT, regulate the Kernel weights of digital equalization filter, make the response of the digital equalization filter of cascade and comb filter consistent with the normal response of this filter cascade.Adjusting is performed such: carry out discrete fourier transform (DFT) to the data field synchronous code that receives or to wherein being suppressed the established part that comb filter 20 comb filterings cross by the NTSC artefact, DFT with normal data field sync sign indicating number or the established part wherein crossed by comb filtering is cut apart it, thereby determines the DFT of DTV transmission channel.Then, with respect to maximal term normalization, so that characterize this channel, the Kernel weights of regulating digital equalization filter are so that replenish the normalization DFT that characterizes this channel with the DFT of DTV transmission channel.After being made initial adjustment, the Kernel weights of digital equalization filter preferably adopt the adaptive equalization method.These adaptive equalization methods are different from method used when NTSC is co-channel to disturb artefact very little, and its difference is by suppressing the NTSC artefact with comb filter 20, makes possible useful signal state increase by one times.
Fig. 4 is the schematic diagram of the part details of expression DTV signal receiver shown in Figure 1, and wherein, NTSC suppresses comb filter and adopts 120 the sort of structures, and back coding comb filter adopts 126 the sort of structures.The subtracter 1202 that NTSC suppresses in the comb filtering 120 plays a part first linear combiner, and mould 8 adders 1262 in the coding comb filter 126 of back play a part second linear combiner.It is first time-delay mechanism 1201 that 12 symbol phase postpone that NTSC suppresses to have used in the comb filter 120 delay time, and having used delay time in the coding comb filtering 126 of back also is second time-delay mechanism 1263 that 12 symbol phase postpone.It is analog TV line-scanning frequency f that 12 symbol time-delays that each time-delay mechanism 1201 and 1263 is presented approximate frequency greatly HThe one-period time-delay of 59.75 times analog TV video carrier artefact.It is 287.25f that these 12 symbol time-delays approximate frequency greatly H5 cycles of analog TV chrominance carrier artefact.It is 345.75f that these 12 symbol time-delays approximate frequency greatly H6 cycles of analog TV sound carrier artefact.Here it is 1202 pairs of sound carriers of subtracter, to the video carrier and the reason that can reduce co-channel interference to those various combination responses that approach the frequency of the chrominance carrier after the different delayed time of first time-delay mechanism 1201.But, pass in that part of vision signal of horizontal scanning line at the edge, the correlative in the last analog TV vision signal of this horizontal space direction distance is very little.
When determining that the output signal that does not have the co-channel interference of enough NTSC can give data amplitude limiter 22 causes uncorrectable error code, multiplexer 1261 is subjected to second State Control of multiplexer control signal in most of times, when defining the co-channel interference of enough NTSC and cause uncorrectable error code can for the output signal of data amplitude limiter 22, multiplexer 1261 is controlled by the third state of multiplexer control signal in most of times.Multiplexer 1261 will feed back to adder 1262 as summand through time-delay mechanism 1263 mould 8 and the result that 12 symbol phase postpone that delayed time at the following of the third state of its control signal control.This is a modulus cumulative process (modularaccumulation procedure), and in this process, single error code is as the operation error propagation, and per 12 symbol phase postpone circulation primary.In 4 symbol phase that each data segment begins postpone and during each data segment contains field synchronization information integral body, multiplexer 1261 is in first state, and this has reduced the kinematic error in the back coded identification decoded result of back coding comb filter 126 outputs.When this control signal was first state, the output signal of multiplexer 1261 was just reappeared the output signal standard symbol decoded result that controller 28 interior magazine provide.The output signal of multiplexer 1261 adopts the standard symbol decoded result to block the operation error code.Because each data segment has the individual symbol of 4+69 (12), at each data segment, standard decoded result homophase returns sliding 4 symbol phase to postpone, and therefore, the duration of any operation error code all can not surpass three data segments.
Fig. 5 is the details block diagram of a kind of form 144 of the co-channel interference detector 44 of expression NTSC shown in Figure 2, it has the 3rd delay cell 1442, the three delay cells 1442 and 12 symbol time-delays is set for the Q channel signals from sign synchronization and equalizing circuit 16 that directly is added on the node 440.The trilinear combiner is a digital subtractor 1443, it will carry out difference combination back through the Q channel signals of sign synchronization after the difference time-delay and equalizing circuit 16 outputs and produce the comb filter response that does not contain the co-channel interference of NTSC artefact, and this response signal is added on the amplitude detector 445.The 4th linear combiner is a digital adder 1444, and the Q channel signals after it delays time difference carries out producing the comb filter response that contains the co-channel interference of selected NTSC artefact after the stack combinations, and this response is added on the amplitude detector 446.When the DTV signal receiver among Fig. 1 adopted 120 the sort of NTSC inhibition comb filter 20 and 126 the sort of backs to encode comb filter 26, this NTSC synchronization channels interference detector 144 just was particularly suitable for the DTV signal receiver among Fig. 1.Owing to adopt the comb filtering of subtracter 1443 to suppress the artefact that causes by NTSC sound carrier, ntsc video carrier wave and NTSC colour subcarrier, therefore do not need dedicated bandwidth selective filter 441 in the front of node 440.
Fig. 6 is the details schematic block diagram of the part of expression DVT signal receiver shown in Figure 1 under the situation that adopts 220 the sort of NTSC inhibition comb filter 20 and 226 the sort of back coding comb filter 26.It is first time-delay mechanism 2201 that 6 symbol phase postpone that NTSC suppresses to have used in the comb filter 220 delay time, and having used delay time in the coding comb filter 226 of back also is second time-delay mechanism 2263 that 6 symbol phase postpone.It is analog TV line-scanning frequency f that 6 symbol time-delays that each time-delay mechanism 2201 and 2263 is presented approximate frequency greatly H0.5 cycle time-delay of 59.75 times analog TV video carrier artefact, approximating frequency greatly is 287.25f H2.5 cycles of analog TV chrominance carrier artefact, and to approximate frequency greatly be 345.75f H3 cycles of any artefact of analog TV sound carrier.The adder 2202 that NTSC suppresses in the comb filter 220 plays a part first linear combiner, and mould 8 subtracters 2262 in the coding comb filter 226 of back play a part second linear combiner.Although near the frequency band of the idling frequency (nulls) the frequency that is converted to from the analog TV carrier frequency is narrower, but because the time-delay that time-delay mechanism 2201 and 2263 presents is less than time-delay mechanism 1201 and 1263 time-delays that presented, therefore, better by the anti-correlation that signal presented of adder 2202 stack combinations than the correlation that signal presented that makes up by subtracter 1202 difference.The sound carrier inhibition situation that NTSC suppresses in comb filter 220 responses is poorer than the sound carrier inhibition situation that NTSC suppresses comb filter 120 responses.But, if the sound carrier in the co-channel interference simulation TV signal suppresses with sound trap in the IF amplifier circuit 12 (sound trap) or SAW filtering, not problem just the low sound of comb filter 220 suppresses ability.NTSC in adopting Fig. 6 suppresses comb filter 220 rather than adopts under the situation of the NTSC comb filter 120 among Fig. 4, response to synchronous end (tip) just can reduce, therefore, can bring into play the error correction effect of lattice decoding and Reed-Solomon decoding basically.
When determining that the output signal that does not have the co-channel interference of enough NTSC can give data amplitude limiter 22 causes uncorrectable error code, 2261 the sort of multiplexers 261 are subjected to second State Control of multiplexer control signal in most of times, when defining the co-channel interference of enough NTSC and cause uncorrectable error code can for the output signal of data amplitude limiter 22,2261 the sort of multiplexers 261 are controlled by the third state of multiplexer control signal in most of times.Multiplexer 2261 will feed back to adder 2262 as summand through delayed time mould 8 and the result of the adder 2262 that 6 symbol phase postpone of time-delay mechanism 2263 under the control of the third state of its control signal.This is a modulus cumulative process, and in this process, single error code is as the operation error propagation, and per 6 symbol phase postpone circulation primary.In 4 symbol phase that begin at each data segment postpone and in each contains the whole data segment of data segment of field synchronization information, multiplexer 2261 all is in first state, and this has reduced the operation error code in the back coded identification decoded result of back coding comb filter 226 outputs.When this control signal was in first state, multiplexer 2261 just reappeared standard symbol decoded result that controller 28 internal storages provide as its output signal.The output signal of multiplexer 2261 adopts the standard symbol decoded result can block the operation error code.Because each data segment has the individual symbol of 4+138 (6), at each data segment, the standard decoded result postpones with 4 symbol phase of identical cunning, and therefore, the duration of any operation error code all can not super individual two data segments.In the coding comb filter 226 of back, although the operation error code circulates sooner and influence number of times is 12 twices that interweave the lattice sign indicating number, wherein moves the long-standing possibility of error code and will be lower than encode the long-standing possibility of operation error code in the comb filter 126 of back.
Fig. 7 is the details block diagram of a kind of form 244 of the co-channel interference detector 44 of expression NTSC shown in Figure 2, and it has the 3rd delay cell 2442, the three delay cells 2442 and 6 symbol time-delays is set for the Q channel signals that is added on the node 440.The trilinear combiner is a digital adder 2443, and it will produce the comb filter response that does not contain the co-channel interference of NTSC artefact after will carrying out stack combinations through the Q channel signals after the difference time-delay, and this response is added on the amplitude detector 445.The 4th linear combiner is a digital subtractor 2444, the sign synchronization after it delays time difference and the Q channel signals of equalizing circuit output carry out difference combination back generation and contain the co-channel comb filter response of disturbing artefact of selected NTSC, and this response is added on the amplitude detector 446.When the DTV signal receiver among Fig. 1 adopts 220 the sort of NTSC to suppress 226 the sort of back coding comb filter 26 of comb filter 20, this NTSC is co-channel interference detector 244 just is particularly suitable among Fig. 1 DTV signal receiver.
Fig. 8 is the schematic diagram of the part details of expression DTV signal receiver shown in Figure 1 under the situation that adopts 320 the sort of NTSC inhibition comb filter 20 and 326 the sort of back coding comb filter 26.It is first time-delay mechanism 3201 that 1368 symbol phase postpone that NTSC suppresses to have used in the comb filter 320 delay time, having used delay time in the coding comb filter 326 of back also is second time-delay mechanism 3263 that 1368 symbol phase postpone, wherein, 1368 symbol phase delay are substantially equal to two horizontal scanning line phase delays of analog tv signal.First linear combiner that NTSC suppresses in the comb filter 320 is an adder 3202, and second linear combiner in the coding comb filter 326 of back is mould 8 subtracters 3262.
When determining that the output signal that does not have the co-channel interference of enough NTSC can give data amplitude limiter 22 causes uncorrectable error code, 3261 the sort of multiplexers 261 are second State Control that are subjected to the multiplexer control signal in most of times, when defining the co-channel interference of enough NTSC and cause uncorrectable error code can for the output signal of data amplitude limiter 22,3261 the sort of multiplexers 261 are controlled by the third state of multiplexer control signal in most of times.The DTV signal receiver preferably includes the testing circuit that is used to detect variable quantity between the co-channel interference interlaced line of NTSC, so that controller 28 can not provide the third state of multiplexer 32613261 control signals in these cases.
Multiplexer 3261 will feed back to adder 3262 as summand through delayed time mould 8 and the result of the adder 3262 that 1368 symbol phase postpone of time-delay mechanism 3263 under the control of the third state of its control signal.This is a modulus cumulative process, and in this process, single error code is as the operation error propagation, and per 1368 symbol phase postpone circulation primary.This symbolic code length (span) is greater than the length of single Reed-Solomon code block, and therefore single operation error code is easy to obtain in the Reed-Solomon decode procedure proofread and correct.In 4 symbol phase that begin at each data segment postpone and in each contains the whole data segment of data segment of field synchronization information, multiplexer 3261 all is in its first state, and this has reduced the operation error code in the back coded identification decoded result of back coding comb filter 326 outputs.When this control signal was in its first state, multiplexer 3261 just reappeared standard symbol decoded result that controller 28 internal storages provide as its output signal.The output signal of multiplexer 3261 adopts the standard symbol decoded result can block the operation error code.Be that the ntsc video field of 16.67 microseconds exists phase drift with respect to the DTV data field that is 24.19 microseconds cycle time cycle time, and the DTV data segment that therefore contains field sync signal finally can scan whole NTSC frame grid (frame raster).NTSC frame grid comprise 525 row, and each provisional capital comprises that 684 symbol phase postpone, and always has 359100 symbol phase and postpones.Postpone because this is slightly less than 432 * 832 symbol phase that the DTV data segment that contains field sync signal comprised, have reason to infer therefore that the duration will be deleted by the multiplexer 3261 of reproducing standards symbol decoding result during comprising the DTV data segment of synchronizing signal greater than the operation error code of 432 data fields.Can obtain therein also having phase drift between the data segment of the initial code character of standard symbol decoded result and the ntsc video scan line.Can estimate during 89775 continuous data segments, can scan 359100 symbol phase and postpone, 89775 times of postponing of these 4 symbol phase that are initial code character comprises.Owing to 313 data segments are arranged in each DTV data field, have reason to infer therefore that the duration will be deleted by the multiplexer 3261 of reproducing standards symbol decoding result during initial code character greater than the operation error code of 287 data fields.These two operation error code inhibition sources are separate, so the duration fails to turn up for the show more than or equal to the operation of 200 data fields and is impossible to exist.Also have, if repeat so that the response of multiplexer 3261 playing data for broadcasting amplitude limiters 22 co-channel interference reduction of NTSC during, just can be than earlier error correction under other situation as its output signal at the operation error code.
NTSC shown in Figure 8 suppresses comb filter 320 can be suppressed at demodulation artefact and most demodulation artefact that produces of inhibition that response simulation TV horizontal synchronization phase time produces well when response simulation TV vertical sync pulse and equalizing pulse.These artefacts are the co-channel interference with ceiling capacity.In the video information of analog tv signal during twice line scanning, contain by this situation of scan line (scam-line-to-scan-line) variation, no matter the color of this video information how, NTSC suppresses comb filter 320 can both suppress this video information well.If the FM sound carrier in the analog tv signal is not suppressed by the tracking rejects trap in sign synchronization and the equalizing circuit 16, it also can obtain good restraining so herein.Suppress in the response of comb filter 320 at NTSC, the artefact of most of analog TV burst signal has also obtained inhibition.In addition, the NTSC filtering that suppresses comb filter 320 be set to NTSC in the lattice decoding process and disturb that to suppress be " quadrature ".
Fig. 9 is the details block diagram of a kind of form 344 of the co-channel interference detector 44 of expression NTSC shown in Figure 2, it has the 3rd delay cell 3442, the three delay cells 3442 and 2 video line time-delays that 1368 symbol phase postpone is set for the Q channel signals that is added on the node 440.The trilinear combiner is a digital adder 3443, and it will produce the comb filter response that does not contain the co-channel interference of NTSC artefact after will carrying out stack combinations through the Q channel signals after the difference time-delay, and this response is added on the amplitude detector 445.The 4th linear combiner is a digital subtractor 3444, the sign synchronization after it delays time difference and the Q channel signals of equalizing circuit output carry out difference combination back generation and contain the co-channel comb filter response of disturbing artefact of selected NTSC, and this response is added on the amplitude detector 446.When the DTV signal receiver among Fig. 1 adopts 320 the sort of NTSC to suppress comb filter 20 and 326 the sort of back coding comb filter 26, this NTSC is co-channel interference detector 344 just is particularly suitable among Fig. 1 DTV signal receiver.
Figure 10 is that expression DTV signal receiver shown in Figure 1 is adopting 420 the sort of NTSC to suppress the schematic diagram of the part details under comb filter 20 and 426 the sort of back coding comb filter 26 situations.It is first time-delay mechanism 4201 that 179208 symbol phase postpone that NTSC suppresses to have used in the comb filter 420 delay time, having used delay time in the coding comb filter 426 of back also is second time-delay mechanism 4261 that 179208 symbol phase postpone, wherein, 179208 symbol phase postpone 262 horizontal scanning line cycles that time-delay is substantially equal to analog tv signal.The adder 4202 that NTSC suppresses in the comb filter 420 plays a part first linear combiner, and mould 8 subtracters 4262 in the coding comb filter 426 of back play a part second linear combiner.
When determining that the output signal that does not have the co-channel interference of enough NTSC can give data amplitude limiter 22 causes uncorrectable error code, 4261 the sort of multiplexers 261 are subjected to second State Control of multiplexer control signal in most of times, when defining the co-channel interference of enough NTSC and cause uncorrectable error code can for the output signal of data amplitude limiter 22,4261 the sort of multiplexers 261 are controlled by the third state of multiplexer control signal in most of times.The DTV signal receiver preferably includes the testing circuit by the field variation that is used for detecting the co-channel interference of NTSC, so that controller 28 can forbid providing to multiplexer 4261 third state of control signal in these cases.
Multiplexer 4261 will feed back to adder 4262 as summand through delayed time mould 8 and the result of the adder 4262 that 179208 symbol phase postpone of time-delay mechanism 4263 under the control of the third state of its control signal.This is a modulus cumulative process, and in this process, single error code is as the transmission of operation error code, and per 179208 symbol phase postpone circulation primary.This symbolic code length is greater than the length of single Reed-Solomon code block, and therefore single operation error code is easy to obtain in the Reed-Solomon decode procedure proofread and correct.In 4 symbol phase that begin at each data segment postpone and in each contains the whole data segment of data segment of field sync signal, multiplexer 4261 all is in first state, and this has reduced the operation error code among the back coded identification result of back coding comb filter 426 outputs.When this control signal was in its first state, multiplexer 4261 just reappeared standard symbol decoded result that controller 28 internal storages provide as output signal.The output signal of multiplexer 4261 adopts the standard symbol decoded result can block the operation error code.It is roughly the same to eliminate the required maximum data field amount of operation error code in multiplexer 4261 output signals maximum data field amount required with eliminating operation error code in multiplexer 3261 output signals.But, the number of times that error code occurs during this drops to original 1/131.
NTSC shown in Figure 10 suppresses comb filter 420 and can suppress most demodulation artefact that produces and can suppress the demodulation artefact that all produce when response simulation TV vertical sync pulse and equalizing pulse when response simulation TV horizontal synchronization pulse.These artefacts are the co-channel interference with ceiling capacity.The comb filter 420 that suppresses NTSC can also suppress by those artefacts that do not cause with the video information by field or variation line by line in the analog tv signal, thereby eliminates and horizontal space frequency or the irrelevant still-mode of color.Suppress in comb filter 420 responses at NTSC, the artefact of most of analog TV burst signals has also obtained inhibition.
Figure 11 is the detailed diagram of a kind of form 444 of the co-channel interference detector 44 of expression NTSC shown in Figure 2, it has the 3rd delay cell 4442, the three delay cells 4442 and the time-delay of (promptly 179208 symbol phase postpone) of 262 video line is set for the Q channel signals that is added on the node 440.The trilinear combiner is a digital adder 4443, and it will produce the comb filter response that does not contain the co-channel interference of NTSC artefact after will carrying out stack combinations through the Q channel signals after the difference time-delay, and this response is added on the amplitude detector 445.The 4th linear combiner is a digital subtractor 4444, the sign synchronization after it delays time difference and the Q channel signals of equalizing circuit 16 outputs carry out difference combination back generation and contain the co-channel comb filter response of disturbing artefact of selected NTSC, and this response is added on the amplitude detector 446.When the DTV signal receiver among Fig. 1 adopts 420 the sort of NTSC to suppress comb filter 20 and 426 the sort of back coding comb filter 26, this NTSC is co-channel interference detector 444 just is particularly suitable among Fig. 1 DTV signal receiver.
Figure 12 is the schematic diagram of the part details of expression DTV signal receiver shown in Figure 1 under the situation that adopts 520 the sort of NTSC inhibition comb filter 20 and 526 the sort of back coding comb filter 26.It is first time-delay mechanism 5201 that 718200 symbol phase postpone that NTSC suppresses to have used in the comb filter 520 delay time, having used delay time in the coding comb filter 526 of back also is second time-delay mechanism 5261 that 718200 symbol phase postpone, wherein, the time-delay of 718200 symbol phase delays is substantially equal to two frame periods of analog tv signal.The subtracter 5202 that NTSC suppresses in the comb filter 520 plays a part first linear combiner, and mould 8 adders 5262 in the coding comb filter 526 of back play a part second linear combiner.
When determining that the output signal that does not have the co-channel interference of enough NTSC can give data amplitude limiter 22 causes uncorrectable error code, 5261 the sort of multiplexers 261 are subjected to second State Control of multiplexer control signal in most of times, when defining the co-channel interference of enough NTSC and cause uncorrectable error code can for the output signal of data amplitude limiter 22,5261 the sort of multiplexers 261 are controlled by the third state of multiplexer control signal in most of times.The DTV signal receiver preferably includes the testing circuit of the variation between the alternate frame that is used for detecting the co-channel interference of NTSC, so that controller 28 can forbid providing to multiplexer 5261 third state of control signal in these cases.
Multiplexer 5261 will feed back to adder 5262 as summand through delayed time mould 8 and the result of the adder 5262 that 718200 symbol phase postpone of time-delay mechanism 5263 under the control of the third state of its control signal.This is a modulus cumulative process, and in this process, single error code is as the transmission of operation error code, and per 718200 symbol phase postpone circulation primary.This symbolic code length is greater than the length of single Reed-Solomon code block, and therefore single operation sign indicating number is easy to obtain in the Reed-Solomon decode procedure proofread and correct.In 4 symbol phase that begin at each data segment postpone and in each contains the whole data segment of data segment of field sync signal, multiplexer 5261 all is in first state, and this has reduced the operation error code among the back coded identification result of back coding comb filter 526 outputs.When this control signal was in first state, multiplexer 5261 just reappeared standard symbol decoded result that controller 28 internal storages provide as its output signal.The output signal of multiplexer 5261 adopts the standard symbol decoded result can block the operation error code.It is roughly the same to eliminate the required maximum data field amount of operation error code in multiplexer 5261 output signals maximum data field amount required with eliminating operation error code in multiplexer 3261 output signals.But, the number of times that error code occurs during this drops to original 1/525.
NTSC shown in Figure 12 suppresses comb filter 520 can suppress the demodulation artefact that all produce when response simulation TV vertical sync pulse and equalizing pulse, and can suppress the demodulation artefact that all produce when response simulation TV horizontal synchronization pulse.These artefacts are the co-channel interference with ceiling capacity.The comb filter 520 that suppresses NTSC can also suppress the artefact that caused by those video informations that do not change with two frames in the analog tv signal, thereby eliminates and their spatial frequency or the irrelevant still-mode of color.Suppress in comb filter 520 responses at NTSC, the artefact of all analog TV burst signals has also obtained inhibition.
Figure 13 is the detailed diagram of a kind of form 544 of the expression co-channel interference detector 44 of NTSC shown in Figure 2, it has the 3rd delay cell 5442, the three delay cells 5442 and the time-delay of (promptly 718200 symbol phase postpone) of 2 frame of video is set for the Q channel signals that is added on the node 440.The trilinear combiner is a digital adder 5443, and it will produce the comb filter response that does not contain the co-channel interference of NTSC artefact after will carrying out stack combinations through the Q channel signals after the difference time-delay, and this response is added on the amplitude detector 445.The 4th linear combiner is a digital subtractor 5444, the sign synchronization after it delays time difference and the Q channel signals of equalizing circuit 16 outputs carry out difference combination back generation and contain the co-channel comb filter response of disturbing artefact of selected NTSC, and this response is added on the amplitude detector 446.When the DTV signal receiver among Fig. 1 adopts 520 the sort of NTSC to suppress comb filter 20 and 526 the sort of back coding comb filter 26, this NTSC is co-channel interference detector 544 just is particularly suitable among Fig. 1 DTV signal receiver.
The those of ordinary skill of television system design field it will be appreciated that other characteristic of analog tv signal correlation and anti-correlation, and these characteristics can obtain utilizing when the NTSC rejects trap of other type of design except that the NTSC rejects trap shown in Fig. 4,6,8,10 and 12.Utilization can make 2N level of baseband signal be increased to (8N-1) individual data level by the resultant NTSC rejects trap of two disclosed the sort of NTSC rejects traps cascade, and this has strengthened the difficulty of data slicing in the symbol decoding process.Although these filters can reduce the signal to noise ratio of the random noise disturbance of symbol decoding, they can be used for the special serious co-channel interference problem that solves.From this respect, the NTSC that is used to improve co-channel interference detector suppresses and what shortcoming the cascading filter of selective power does not almost have.
Figure 14 shows that the NTSC that is used to improve 644 the sort of co-channel interference detectors 44 suppresses and the cascade of the filter of selective power, and it can be considered to the improvement of co-channel interference detector 544 shown in Figure 13.4410 pairs of responses from the Q channel signals after the equilibrium of sign synchronization and equalizing circuit 16 of FIR wave digital lowpass filter are added on the node 440.If require the comb filter of maximum delay partly to be placed on cascade circuit foremost, just can save hardware, because same maximum delay element can be suppressed comb filter by NTSC and NTSC selects comb filter to use together.Identical with the co-channel interference detector 544 among Figure 13, in co-channel interference detector 644 shown in Figure 14, the signal on the node 440 is added on the delay cell 5442 that delay time is 2 frame of video; Resulting difference time delayed signal is carried out stack combinations and is carried out the difference combination by subtracter 5444 by adder 5443.
Adder 5443 export responses with value produce the response of NTSC inhibition comb filter after next stage NTSC suppresses filtering, this response is added on the amplitude detector 445.More particularly, time-delay mechanism 6441 is provided with the difference time-delay of 6 symbols for the response with value of adder 5443 outputs, responding with value of adder 5443 after the difference time-delay produces the response of NTSC inhibition comb filter after digital adder 6443 stack combinations, this response is added on the amplitude detector 445.
The difference response of subtracter 5444 outputs produces NTSC and selects the comb filter response after next stage NTSC suppresses filtering, this response is added on the amplitude detector 446.More particularly, time-delay mechanism 6442 is provided with the difference time-delay of 6 symbols for the difference response of subtracter 5444 outputs, the difference response of the subtracter 5443 after the difference time-delay produces NTSC and selects the comb filter response after the combination of digital subtractor 6444 difference, this response is added on the amplitude detector 446.The amplitude testing result that amplitude detector 445 and 446 obtains is compared by magnitude comparator 447.Magnitude comparator 447 provides a carry-out bit, and whether the response of this carry-out bit indication amplitude detector 446 surpasses the response of amplitude detector 445 substantially.This carry-out bit is used for selecting the mode of operation (second state or the third state) of the multiplexer 261 of DTV signal receiver shown in Figure 1, herein, DTV signal receiver shown in Figure 1 adopts co-channel interference detector 644 as its co-channel interference detector 44.Cascade filtering utilization in the co-channel interference detector 644 replaces instantaneous comb filtering between the ntsc video frame and suppresses the NTSC artefact that caused by synchronizing information and static video component.Cascade filtering in the co-channel interference detector 644 utilizes the interior space of frame comb filtering to suppress the NTSC artefact that is caused by the dynamic video component.
Figure 15 shows further that the NTSC that is used to improve 744 the sort of co-channel interference detectors 44 suppresses and the cascade of the filter of selective power, and it can be considered to the improvement of co-channel Interference Detection 544 shown in Figure 13.Directly be added on the node 440 from the Q channel signals after the equilibrium of sign synchronization and equalizing circuit 16, because the second level of comb filtering has suppressed the sound carrier artefact in any co-channel interference NTSC analog tv signal, does not therefore need the FIR wave digital lowpass filter.Identical with the co-channel interference detector 544 among Figure 13, in co-channel interference detector 744 shown in Figure 15, the signal on the node 440 is added on the delay cell 5442 that delay time is 2 frame of video; Resulting difference time delayed signal is carried out stack combinations and is carried out the difference combination by subtracter 5444 by adder 5443.
Adder 5443 export responses with value should produce the response of NTSC inhibition comb filter after next stage NTSC suppresses filtering, this response is added on the amplitude detector 445.More particularly, time-delay mechanism 7441 is provided with the difference time-delay of 12 symbols for the response with value of adder 5443 outputs, responding with value of adder 5443 after difference is delayed time produces the response of NTSC inhibition comb filter after the combination of digital subtractor 7443 difference, this response is added on the amplitude detector 445.
The difference response of subtracter 5444 outputs produces NTSC and suppresses the comb filter response after next stage NTSC suppresses filtering, this response is added on the amplitude detector 446.More particularly, time-delay mechanism 7442 is provided with the difference time-delay of 12 symbols for the difference response of subtracter 5444 outputs, the difference response of the adder 5443 after the difference time-delay produces NTSC and selects the comb filter response after digital adder 7444 stack combinations, this response is added on the amplitude detector 446.The amplitude testing result that amplitude detector 445 and 446 obtains is compared by magnitude comparator 447.Magnitude comparator 447 provides a carry-out bit, and whether the response of this carry-out bit indication amplitude detector 446 surpasses the response of amplitude detector 445 substantially.This carry-out bit is used for selecting the mode of operation (second state or the third state) of the multiplexer 261 of DTV signal receiver shown in Figure 1, herein, DTV signal receiver shown in Figure 1 adopts co-channel interference detector 744 as its co-channel interference detector 44.Cascade filtering utilization in the co-channel interference detector 744 replaces instantaneous comb filtering between the ntsc video frame and suppresses the NTSC artefact that caused by synchronizing information and static video component.Cascade filtering in the co-channel interference detector 744 utilizes the interior space of frame comb filtering to suppress the NTSC artefact that is caused by audio component and dynamic video component.
Figure 16 shows the modification of so far described DTV signal receiver shown in Figure 1, it constitutes according to a further aspect in the invention, it has adopted even level data amplitude limiter A24, B24 and the C24 of a plurality of parallel work-flows, the front of each even level data amplitude limiter is that corresponding N TSC suppresses comb filter, and the back is a corresponding back coding comb filter.The symbol decoding result that idol level data amplitude limiter A24 converts the response of first kind NTSC rejects trap A20 to first precoding for the first kind after coding comb filter A26 use.The symbol decoding result that idol level data amplitude limiter B24 converts the response of the second class NTSC rejects trap B20 to second precoding for second class after coding comb filter B26 use.The symbol decoding result that idol level data amplitude limiter C24 converts the response of the second class NTSC rejects trap C20 to the 3rd precoding for the 3rd class after coding comb filter C26 use.Strange level data amplitude limiter 22 provides the intermediate symbols decoded result for back coding comb filter A26, B26 and C26.When receiver partly adopted some part shown in Fig. 4,6,8,10 and 12, the prefix A of parts label, B, C corresponded respectively to integer 1,2,3,4 and 5 different integers among Figure 15.
The first kind is co-channel, and interference detector A44 determines the inhibition effect of first kind NTSC rejects trap A20 to the co-channel interference of the analog tv signal in the I channel signals of crossing from current equilibrium according to the Q channel signals.Second class is co-channel, and interference detector B44 determines the inhibition effect of the second class NTSC rejects trap B20 to the co-channel interference of the analog tv signal in the I channel signals of crossing from current equilibrium according to the Q channel signals.The 3rd class is co-channel, and interference detector C44 determines the inhibition effect of the 3rd class NTSC rejects trap C20 to the co-channel interference of the analog tv signal in the I channel signals of crossing from current equilibrium according to the Q channel signals.Inhibition to the pilot frequency carrier wave in the Q channel signals helps co-channel interference detector A44, B44 and C44 to provide NTSC to suppress the indication of the relative inhibition effect of comb filter A20, B20 and C20.
The correction symbol decoding best estimate that symbol decoding selects circuit 90 generations to use for Data Assembler 30.This best estimate is by to the standard symbol decoded result that comes self-controller 28, selected to produce from the intermediate symbols decoded result of strange level data amplitude limiter 22 and the symbol decoding result who crosses from the back coding of back coding comb filter A26, B26 and C26.Unless controller 28 selects circuit 90 to provide other symbol to select information to symbol decoding, definite this best estimate of inhibition effect indication that symbol decoding selects circuit 90 to provide according to co-channel interference detector A44, B44 and C44.Other symbol selection information that controller 28 provides comprises that synchronous code goes out indication information now, and this indication information is used to guarantee that best estimate is that the basis of the standard symbol decoded result that provides at controller 28 obtains.Symbol decoding result's best estimate is used for proofreading and correct coupling comb filter A26, the B26 of Figure 16 DTV signal receiver most preferred embodiment and the sum operation of C26.
Beyond synchronizing field goes out now, if indicating, co-channel interference detector A44, B44 and C44 do not have bigger NTSC synchronous interference artefact, just symbol decoding selects circuit 90 to select from the intermediate symbols decoded result of strange level data amplitude limiter 22 best estimate as the correction symbol decoded result.This has reduced the influence of Johnson (grandson John) noise to symbol decoding.
Beyond synchronous code goes out now, if have at least an indication that bigger NTSC synchronous interference artefact is arranged among co-channel interference detector A44, B44 and the C44, symbol decoding selects circuit 90 just to select certain NTSC inhibition comb filter A20, B20 and back coding comb filter A26, the B26 of C20 back or the back coded identification decoded result of C26 output, and described certain NTSC inhibition comb filter is meant by co-channel interference detector A44, B44 and C44 and is defined as that NTSC inhibition comb filter that the co-channel interference of NTSC artefact suppresses best results.
When NTSC inhibition comb filter A20 carried out stack combinations to replacing frame of video, all high energy demodulation artefacts that produce to analog TV lock-out pulse, equalizing pulse and burst signal response the time had all obtained inhibition.Also obtained inhibition by those the caused artefacts of indeclinable video information between two frames in the analog tv signal, thereby eliminated and their spatial frequency or the irrelevant still-mode of color.The sort of co-channel interference detector A44 shown in Figure 13 uses with the sort of symbol decoding circuit shown in Figure 12.
Remaining inhibition demodulation artefact problem is mainly considered to suppress on those some pixel locations in the analog tv signal grid by the caused demodulation artefact of frame difference.These demodulation artefacts can suppress with filtering technique in the frame.Can select NTSC to suppress comb filter B20 and utilize the correlation of horizontal direction to suppress remaining demodulation artefact, can select NTSC to suppress comb filter C20 and utilize the correlation of vertical direction to suppress remaining demodulation artefact with back coding comb filter C26 circuit with back coding comb filter B26 circuit.Consider other possible implementation method of this design philosophy below.
If the sound carrier in the co-channel interference simulation TV signal is not to suppress with SAW filtering or without the sound trap circuit in the IF amplifier circuit 12, elect the sort of NTSC inhibition comb filter 120 shown in Figure 4 and back coding comb filter 126 circuit as with back coding comb filter B26 circuit just can easily NTSC be suppressed comb filter B20.The sort of co-channel interference detector B44 shown in Figure 5 uses with the sort of symbol decoding circuit shown in Figure 4.
If the sound carrier in the synchronous interference analog tv signal suppresses with the SAW filter circuit or with the sound trap circuit in the IF amplifier circuit 12, elect the sort of NTSC inhibition comb filter 220 shown in Figure 6 and back coding comb filter 226 circuit as with back coding comb filter B26 circuit just can easily NTSC be suppressed comb filter B20.This is because the anti-correlation between the video component that 6 symbol phase of only being separated by each other postpone is better than the correlation between the video component of several symbol phase delays of being separated by each other usually.The sort of co-channel interference detector B44 shown in Figure 7 uses with the sort of symbol decoding circuit shown in Figure 6.
Suppressing comb filter C20 to NTSC, to make optimal selection with back coding comb filter C26 circuit be not the part nothing the matter, this be because must select (consider in the interference simulation TV signal field at interval) on NTSC suppresses to select among the comb filter C20 with the time in the same field nearer scan line and current scan line is combined or with the space in the previous field on nearer scan line and current scan line combined.Usually selecting preferably is the time of selecting in same to go up nearer scan line, because the saltus step between the field suppresses effect by the NTSC that (jump cuts) may damage comb filter C20 hardly.Concerning this selection, NTSC suppresses comb filter C20 will suppress comb filter 320 and back coding comb filter 326 circuit with the sort of NTSC shown in Figure 8 with back coding comb filter C26 circuit.The sort of co-channel interference detector C44 shown in Figure 9 uses with the sort of symbol decoding circuit shown in Figure 8.
Concerning another kind was selected, NTSC suppresses comb filter C20 will suppress comb filter 420 and back coding comb filter 426 circuit with the sort of NTSC shown in Figure 10 with back coding comb filter C26 circuit.The sort of co-channel interference detector C44 shown in Figure 11 uses with the sort of symbol decoding circuit shown in Figure 10.

Claims (19)

1. method that is used to handle the vestigial sideband amplitudemodulation digital television signal of digital television signal receiver said method comprising the steps of:
The vestigial sideband amplitudemodulation digital television signal that is subject to co-channel NTSC interference effect is carried out compound demodulation, so as to isolate the I channel baseband signal that received and with the Q channel baseband signal that is received of the described orthogonal thereto relation of I channel baseband signal that receives; With
Whether other artefact that disturbs by the co-channel NTSC that determines to follow in the described Q channel baseband signal that receives surpasses specified level, and whether the artefact that the co-channel NTSC that estimates to follow in the described I channel baseband signal that receives disturbs reaches significant level.
2. whether one kind be used to determine to adopt before the lattice decoding of digital television signal receiver co-channel NTSC to disturb the method that suppresses comb filtering, said method comprising the steps of:
The vestigial sideband amplitudemodulation digital television signal is carried out compound demodulation, so as to isolate the I channel baseband signal that received and with the Q channel baseband signal that is received of the described orthogonal thereto relation of I channel baseband signal that receives;
Determine whether to follow in the described Q channel baseband signal that receives co-channel NTSC to disturb artefact with significant level;
If determine not exist in the described Q channel baseband signal that receives described co-channel NTSC to disturb artefact with significant level, then the described I channel baseband signal that receives of not passing through comb filtering is carried out symbol decoding, thereby produce the decoded symbol of using for described lattice decoding;
If determine to exist in the described Q channel baseband signal that receives described co-channel NTSC to disturb artefact with significant level, just the described I channel baseband signal that receives is carried out comb filtering, thus the I channel baseband signal that comb filtering is crossed produced;
If determine to exist in the described Q channel baseband signal that receives described co-channel NTSC to disturb artefact, just the I channel baseband signal that described comb filtering is crossed is carried out symbol decoding with significant level; With
If determine to exist in the described Q channel baseband signal that receives described co-channel NTSC to disturb artefact with significant level, just the symbol decoding result of the I channel baseband signal that described comb filtering is crossed carries out the back coding, thereby produces the decoded symbol of using for described lattice decoding.
3. method according to claim 2, further comprising the steps of:
If determine to exist in the described Q channel baseband signal that receives described co-channel NTSC to disturb artefact with significant level, just before the I channel baseband signal that comb filtering is crossed was advanced described symbol decoding, it is consistent with the response of standard comb filter that described comb filtering is crossed the response of described I channel baseband signal; With
If determine to exist in the described Q channel baseband signal that receives described co-channel interference artefact with significant level, just before the described I channel baseband signal that receives of not passing through comb filtering is carried out described symbol decoding, the described I channel signals that receives that does not pass through comb filter is carried out equilibrium.
4. digital television signal receiver comprises:
Amplifier circuit is used to provide the vestigial sideband amplitudemodulation digital television signal of amplification of co-channel interference simulation TV signal of being easy to carry about with one;
Compound demodulator, vestigial sideband amplitudemodulation digital television signal after the described amplification is responded, so that I channel baseband signal that contains any co-channel interference simulation TV signal artefact and the Q channel baseband signal that contains other artefact of any co-channel interference simulation TV signal to be provided;
The symbol decoding device of described I channel baseband signal, comprise first data amplitude limiter that is used in the very first time, described I channel baseband signal being carried out symbol decoding, usually as long as the described artefact of any co-channel interference simulation TV signal is lower than the significant level of described I channel baseband signal, the error code among the first symbol decoding result of then described first data amplitude limiter output can be proofreaied and correct; With
Described Q channel baseband signal is played the co-channel interference detector of NTSC of response, those of described other artefact that are used for detecting any co-channel interference simulation TV signal are higher than the appearance of the artefact of described Q channel baseband signal significant level, and the described significant level of described Q channel baseband signal is consistent with the described significant level of described I channel baseband signal.
5. digital television signal receiver according to claim 4, wherein, the co-channel interference detector of described NTSC that described Q channel baseband signal is played response comprises:
Time-delay mechanism, the described Q signal baseband signal that is used to delay time is to produce the Q channel baseband signal of difference time-delay;
Adder is used for the Q channel baseband signal after the described difference time-delay is carried out stack combinations, to produce and value signal;
Subtracter is used for the Q channel baseband signal after the described difference time-delay is carried out the difference combination, to produce difference signal;
First amplitude detector is used to detect described and amplitude value signal, detects response to produce first amplitude;
Second amplitude detector is used to detect the amplitude of described difference signal, detects response to produce second amplitude; With
Magnitude comparator, be used for more described first and second amplitude and detect response, and show that described other artefact of any co-channel interference simulation TV signal is higher than the described significant level of described Q channel baseband signal during greater than setting when the difference of described first and second amplitude response.
6. digital television signal receiver according to claim 5, wherein, the described time-delay mechanism in the co-channel interference detector of described NTSC produces the Q channel baseband signal after the described difference time-delay with the time-delay of 12 symbol phase delay differences.
7. digital television signal receiver according to claim 5, wherein, the described time-delay mechanism in the co-channel interference detector of described NTSC produces the Q channel baseband signal after the described difference time-delay with the time-delay of 6 symbol phase delay differences.
8. digital television signal receiver according to claim 5, wherein, the described time-delay mechanism in the co-channel interference detector of described NTSC produces the Q channel baseband signal after the described difference with 1368 symbol phase delays or 2 ntsc video scan line difference time-delays is delayed time.
9. digital television signal receiver according to claim 5, wherein, the described time-delay mechanism in the co-channel interference detector of described NTSC produces the Q channel baseband signal after the described difference with 179208 symbol phase delays or 262 ntsc video scan line difference time-delays is delayed time.
10. digital television signal receiver according to claim 5, wherein, the described time-delay mechanism in the co-channel interference detector of described NTSC produces the Q channel baseband signal after the described difference with 718200 symbol phase delays or 2 ntsc video frame difference time-delays is delayed time.
11. digital television signal receiver according to claim 4, wherein, the co-channel interference detector of described NTSC that described Q channel baseband signal is played response comprises:
First time-delay mechanism, the described Q channel baseband signal that is used to delay time is to produce the Q channel baseband signal after difference is delayed time;
First adder is used for the Q channel baseband signal after the time-delay of described difference is carried out stack combinations, to produce first and value signal;
First subtracter is used for the Q channel baseband signal after the described difference time-delay is carried out the difference combination, to produce first difference signal;
Second time-delay mechanism is used to delay time described first and value signal, to produce first and value signal after the difference time-delay;
The 3rd time-delay mechanism, described first difference signal is used to delay time, producing first difference signal after the difference time-delay, the method that described the 3rd time-delay mechanism is delayed time to described first difference signal is similar to described second time-delay mechanism to described first and the value signal method of delaying time;
Second adder is used for first and value signal after the time-delay of described difference are carried out stack combinations, to produce second and value signal;
Second subtracter is used for first difference signal after the described difference time-delay is carried out the difference combination, to produce second difference signal;
First amplitude detector is used to detect described second and the amplitude of value signal, detects response to produce first amplitude;
Second amplitude detector is used to detect the amplitude of described second difference signal and produces second amplitude and detects response; With
Magnitude comparator, be used for that described first amplitude is detected response and detect response with second amplitude and compare, and when described first amplitude detects the difference of response between responding with the detection of second amplitude greater than setting, show that described other artefact of any co-channel interference simulation TV signal is higher than the described significant level of described Q channel baseband signal.
12. digital television signal receiver according to claim 4, wherein, the co-channel interference detector of described NTSC that described Q channel baseband signal is played response comprises:
First time-delay mechanism, the described Q channel baseband signal that is used to delay time is to produce the Q channel baseband signal after difference is delayed time;
First adder is used for the Q channel baseband signal after the time-delay of described difference is carried out stack combinations, to produce first and value signal;
First subtracter is used for the Q channel baseband signal after the described difference time-delay is carried out the difference combination, to produce first difference signal;
Second time-delay mechanism is used to delay time described first and value signal, to produce first and value signal after the difference time-delay;
The 3rd time-delay mechanism, described first difference signal is used to delay time, producing first difference signal after the difference time-delay, the method that described the 3rd time-delay mechanism is delayed time to described first difference signal and described second time-delay mechanism are identical with the value signal method of delaying time to described first;
Second adder is used for first difference signal after the described difference time-delay is carried out stack combinations, to produce second difference signal;
Second subtracter is used for first and value signal after the time-delay of described difference are carried out the difference combination, to produce second and value signal;
First amplitude detector is used to detect described second and the amplitude of value signal, detects response to produce first amplitude;
Second amplitude detector is used to detect the amplitude of described second difference signal, detects response to produce second amplitude; With
Magnitude comparator, be used for that described first amplitude is detected response and detect response with second amplitude and compare, and when described first amplitude detects the difference of response between responding with the detection of second amplitude greater than setting, show that described other artefact of any co-channel interference simulation TV signal is higher than the described significant level of described Q channel baseband signal.
13. digital television signal receiver according to claim 4 also comprises:
Data synchronization circuit is used for the specified data synchronizing symbol in moment that described I channel baseband signal occurs; With
Be used for occurring the circuit of the moment generation standard symbol decoded result of data sync symbol in described I channel baseband signal; Wherein said sign coding equipment also comprises:
First time-delay mechanism produces the time-delay that is used for described I channel baseband signal is risen first defined amount symbol phase delay of response, thereby produces the I channel baseband signal after the difference time-delay;
First linear combiner carries out linear combination to the I channel baseband signal after the described difference time-delay, and to produce the response of first comb filter, in this response, described any co-channel interference anolog TV signals are inhibited;
Second data amplitude limiter is used for symbol decoding is carried out in described first comb filter response, so that produce the symbol decoding result after first precoding;
Second linear combiner, corresponding first and second input signal that receives is carried out linear combination, thereby provide corresponding output signal to respond as second comb filter, described second linear combiner is used to receive symbol decoding result after described first precoding as corresponding first input signal, have one to be adder in described first linear combiner and described second linear combiner, another then is a subtracter;
Second time-delay mechanism is used for its respective input signals described first defined amount symbol phase of delaying time is postponed, so that produce described second input signal of described second linear combiner;
Input multiplexer more than first, be used for its corresponding output signal is offered described second input signal of described second time-delay mechanism as it, be used to receive described standard symbol decoded result as its first input signal, be used to receive described intermediate symbols decoded result as its second input signal, and be used to receive the described output signal of described second linear combiner as its 3rd input signal, when the data sync symbol occurring in definite described I channel baseband signal that and if only if, described first multiplexer reappears its first input signal as its output signal, when other artefact that detects described any co-channel interference simulation TV signal when the co-channel interference detector of described NTSC is higher than the described significant level of described Q channel baseband signal, described first multiplexer reappears the output signal of described second linear combiner as its output signal, when other artefact that does not detect described any co-channel interference simulation TV signal when the co-channel interference detector of described NTSC was higher than the described significant level of described Q channel baseband signal, described first multiplexer reappeared the output signal of described first data amplitude limiter as its output signal.
14. digital television signal receiver according to claim 13, wherein, the co-channel interference detector of described NTSC that described Q channel baseband signal is played response comprises:
The 3rd time-delay mechanism is used for described Q channel baseband signal first defined amount the symbol phase of delaying time is postponed, so that produce the Q channel baseband signal after the difference time-delay;
The trilinear combiner, with the Q channel baseband signal linear combination after the described difference time-delay, to produce the response of the 3rd comb filter, in this response, the artefact of any co-channel interference simulation TV signal all is tending towards being inhibited;
The 4th linear combiner, with the Q channel baseband signal linear combination after the described difference time-delay, to produce the response of the 4th comb filter, in this response, the artefact of any co-channel interference simulation TV signal all is tending towards being enhanced, have one to be adder in described trilinear combiner and described the 4th linear combiner, another then is a subtracter;
First amplitude detector is used to detect the amplitude that described the 3rd comb filter responds, and detects response to produce first amplitude;
Second amplitude detector is used to detect the amplitude that described the 4th comb filter responds, and detects response to produce second amplitude; With
Magnitude comparator, be used for that described first amplitude is detected response and detect response with second amplitude and compare, when the difference between described first amplitude response and second amplitude response shows that described any co-channel other artefact of interference simulation TV signal is higher than the described significant level of described Q channel baseband signal during greater than setting.
15. digital television signal receiver according to claim 14, wherein, described first, second delayed time with the difference that the 3rd time-delay mechanism all provides 12 symbol phase to postpone; Described first and the trilinear combiner be subtracter; The described second and the 4th linear combiner is an adder.
16. digital television signal receiver according to claim 14, wherein, described first, second delayed time with the difference that the 3rd time-delay mechanism all provides 6 symbol phase to postpone; Described first and the trilinear combiner be adder; The described second and the 4th linear combiner is a subtracter.
17. digital television signal receiver according to claim 14, wherein, described first, second and the 3rd time-delay mechanism all provide 1368 symbol phase to postpone or 2 ntsc video scan lines the difference time-delay; Described first and the trilinear combiner be adder; The described second and the 4th linear combiner is a subtracter.
18. digital television signal receiver according to claim 14, wherein, described first, second all provides 179208 symbol phase to postpone with the 3rd time-delay mechanism or the difference of 262 ntsc video scan lines is delayed time; Described first and the trilinear combiner be adder; The described second and the 4th linear combiner is a subtracter.
19. digital television signal receiver according to claim 14, wherein, described first, second all provides 718200 symbol phase to postpone with the 3rd time-delay mechanism or the difference of 2 ntsc video frames is delayed time; Described first and the trilinear combiner be adder; The described second and the 4th linear combiner is a subtracter.
CN97198489A 1996-10-02 1997-10-02 NTSC co-channel interference detectors responsive to received Q-channel signals in digital TV signal receivers Expired - Fee Related CN1115875C (en)

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