CN1242668A - Using special NTSC receiver to detect when Co-channel interfering NTSC signal accompanies digital TV signal - Google Patents
Using special NTSC receiver to detect when Co-channel interfering NTSC signal accompanies digital TV signal Download PDFInfo
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Abstract
The video portion of any co-channel interfering NTSC signal is synchrodyned to baseband, for generating an in-phase demodulation result including 1st artifacts of the digital television signal, and for generating a quadrature-phase demodulation result including 2nd one of the digital television signal. The quadrature-phase demodulation results are phase shifted by 90 deg. at frequencies in a prescribed frequency range before being linearly combined with the in-phase quadrature-phase demodulation results, to generate a linear combining result substantially free of 1 st and 2nd in the prescribed frequency range. an indication that the digital television signal is accompanied by co-channel interfering NTSC signal of substantial amplitude is generated by detecting whenever the amplitude of the linear combining result exceeds a prescribed value.
Description
The present invention relates in broadcast television bands by the Digital Television of radio wave transmission, relate more specifically in digital television receiver, detect the method when digital television signal is attended by co-channel interference NTSC (N system) signal by a relatively large margin.
The digital television standard of being announced by Advanced Television sub-committee (ATSC) September 16 nineteen ninety-five illustrated and has been used for the character of in 6MHz bandwidth television channel residual sideband (VSB) signal of transmitting digital TV (DTV) signal, and described television channel is such as those channels that are the anolog TV signals of the current national TV sub-committee (NTSC) that is used for air broadcast in the U.S..As long as the NTSC anolog TV signals continue broadcasting, just be necessary in the receiver of DTV signal to determine when that the NTSC anolog TV signals produce bigger co-channel interference to the DTV signal that is receiving.The DTV receiver can be designed as in response to aligning determining of this co-channel interference of appearance and changes its mode of operation so, so that can alleviate the undesired effect that this co-channel interference produces, this is normally finished by comb filtering.When such interference when not being very big, to be used for the comb filtering of DTV receiver preferably discontinuous in order to suppress the co-channel interference of NTSC, because this can be avoided the appearance of the additional Johnson noise that produced by the multipath by comb filter.Usually, if have enough energy and cause frequent error in data limit (data-slicing) operation from the co-channel interference of NTSC anolog TV signals, just think that the co-channel interference that comes from the NTSC anolog TV signals is big or significant, the symbol decoding process of DTV signal when described data limit is used for being synchronized to base band.The sequence number that the name of on March 21st, 1997 application is called " NTSC that uses the vision signal from secondary analog TV receiver to detect in the digital television receiver disturbs " is to describe a kind of like this DTV receiver in detail in 08/821944 the patent application, it is designed to determine to change its mode of operation according to what remarkable co-channel interference occurs, can alleviates the undesired effect that this co-channel interference causes like this.Think in this application in digital television receiver to the detection of the co-channel interference of NTSC any this NTSC disturb be synchronized to base band after easier finishing, rather than with the DTV signal Synchronization after base band.
Licensed to the U.S. Patent No. 5122879 that Katsu Ito name is called " being used to reduce the TV synchrodyne from the band phase shifter of the interference of low adjacent channel " on June 16th, 1992 and described a kind of like this simulated television receiver, it synchronously detects the homophase that received and the NTSC signal of quadrature phase.The Ito receiver directly is transformed into base band synchronously with the response of radio frequency (RF) amplifier, and the low channel of such vicinity can be used as image and occurs.Quadrature phase synchronous detecting response all video frequencies places on 500-750KHz are moved phase place 90 degree, and detect to respond linearly with in-phase synchronization and combine, between the synchronous detection period of the NTSC signal that receives, to suppress to be transformed into the picture frequency composition of base band.In United States Patent (USP) 5122879, Ito does not disclose such fact, and promptly this process is also cancelled the video composition on 750kHz.The loss of incident brightness high frequency only can be accepted in the television receiver neglecting screen, such as being used for those of wrist-watch.
A plurality of frequency inverted are adopted in current DTV receiver design, be converted into an intermediate frequency in hyperfrequency (UHF) frequency range on the channel of television broadcasting appointment with first conversion, and change and be converted into a intermediate frequency in very high frequency(VHF) (VHF) frequency range under the channel of television broadcasting appointment with second.This sampled images suppresses to be out of question.And then the carrier wave of VSB DTV signal has only only 310KHz from the channel edge, therefore compares with the NTSC signal, has only very few double-side band content.
The inventor points out: such synchronization video detection response with homophase responds the NTSC receiver that combines linearly with the quadrature phase synchronization video detection of contrary Hilbert (Hilbert) conversion, and reception remains valuable to DTV, can be used as an auxiliary receiver, be used for detecting the NTSC signal whether a digital television signal is attended by co-channel interference by a relatively large margin.Respond frequency enough little under the 750kHz by arranging contrary Hilbert conversion quadrature phase synchronization video to detect, such auxiliary receiver becomes insensitive basically to the artifcates (artifacts) of co-channel DTV signal.The inhibition of DTV artifcates has been simplified the amplitude of measuring co-channel interference NTSC signal.
According to one aspect of the invention, a kind of like this method is provided, be used for detecting the NTSC signal when digital television signal is attended by co-channel interference by a relatively large margin at a digital television receiver.This method comprises the steps.The video section of the NTSC signal of any co-channel interference is arrived base band by synchronous (synchrodyned), the homophase demodulation result that comprises the first artifcates of digital television signal with generation, and generation comprises the quadrature phase demodulation result of second artifcates of digital television signal.Homophase and quadrature phase demodulation result the frequency place on several kilo hertzs are thereafter moved 90 degree phase places respectively, combination linearly then, and to produce a kind of result of linear combination, it does not have first and second artifcates of digital television signal basically.Then, whether the amplitude that detects the result of described linear combination surpasses a setting, to produce the indication when digital television signal is attended by the NTSC signal of co-channel interference by a relatively large margin.
According to another aspect of the present invention, a kind of digital television receiver is provided, comprise being used to detect the circuit that occupies the time of TV broadcast channel than the anolog TV signals of large amplitude that this circuit more specifically is described as follows.Described receiver has input circuit, be used for select describing the vestigial sideband amplitudemodulation signal of the video signal portions of any anolog TV signals that occupy TV broadcast channel from TV broadcast channel, selected vestigial sideband amplitudemodulation signal is transformed into an intermediate-freuqncy signal, and amplify this intermediate-freuqncy signal so that the intermediate-freuqncy signal of an amplification to be provided.Except that residual sideband, the vestigial sideband amplitudemodulation signal that was transfused to the circuit reception originally also comprises video carrier and full sideband.For video carrier signal and for the be orthogonal carrier wave of phase place of video carrier signal, the audio video synchronization change-over circuit synchronously detects the intermediate-freuqncy signal of being amplified, in order to synchronous detecting response that produces homophase and the synchronous detecting response that produces quadrature phase.Being called the relevant phase-shift circuit of contrary Hilbert translation circuit in this manual will be at about 90 degree of all frequency content travel(l)ing phases of the response of the quadrature phase synchronous detecting on the assigned frequency, to produce the phase-shift circuit response.The linear combination circuit is response of the synchronous detecting of homophase and phase-shift circuit response combination linearly, the linear combination circuit of a part of vision signal of being described in the full sideband of the vestigial sideband amplitudemodulation signal of primary reception and the residual sideband responded recovering.This linear combination circuit response does not have the response to the digital television signal that has occupied current received TV broadcast channel basically.One threshold dector is included in the receiver, is used for determining when the response of the first linear combination circuit surpasses the threshold value of a regulation, to produce the indication of co-channel anolog TV signals by a relatively large margin.
Fig. 1 and 2 is a schematic diagram of television receiver, and this receiver can receive NTSC anolog TV signals and DTV signal, and this receiver uses method of the present invention, detects the appearance of the NTSC anolog TV signals of the co-channel interference among the DTV signal.
Fig. 3 be can pie graph 1 or both of 2 television receiver in the schematic diagram of any one modification.
Fig. 4,5,6 and 7 is the flow charts that show the step of this method, this method adopts the present invention in every respect, is used for detecting the co-channel interference NTSC signal when digital television signal is attended by big amplitude at a digital television receiver.
Fig. 1 shows the each several part of television receiver, and this receiver can receive NTSC anolog TV signals and DTV signal.The television broadcasting signal of the aerial transmission that is received by antenna 1 is amplified by tunable radio frequency amplifier 2, and is provided to first detector 3.RF amplifier 2 and first detector 3 have variable tuning and the allomeric function as tuner, to select a digital television signal in one of the channel from the diverse location place in the frequency band.First detector 3 comprises: first local oscillator, and it provides first local oscillation, and it can carry out tuning on hyperfrequency (UHF) television broadcast band; And first frequency mixer, be used for first local oscillation is mixed mutually with the TV signal of being selected by tunable RF amplifier 2, with to the selected TV signal of up conversion, thereby on the frequency that is arranged in the channel that the UHF television broadcast band distributes, produce the wide UHF medium-frequency band of 6MHz.
The response of very high frequency(VHF) IF amplifier 12 is added to intercarrier sound detection device 34, it provides 4.5MHz intercarrier sound intermediate-freuqncy signal to intercarrier intermediate frequency amplifier 35, and it amplifies and limit the response of its amplification symmetrically to be added to FM (frequency modulation) wave detector 36 in the great majority design.FM wave detector 36 reproduces the base band composite audio signal, and they are provided to the remainder of the simulated television receiver of DTV receiver.About the base band composite audio signal, the part of these remainders typically comprises the stereodecoder circuit.It is selected if the NTSC audio signal is passed through narrow-band filtering in IF amplifier 6 and 12, IF amplifier 6 and 12 is only by being transformed into the FM sound carrier of intermediate frequency, intercarrier sound detection device 34 can be provided by such multiplier, and this multiplier multiply by the video carrier of being selected for this multiplier according to the response of IF amplifier 10 or 11 by narrow band filter with IF amplifier 12 responses of video carrier.If the NTSC audio signal is selected by filtering in IF amplifier 6 and 12, ntsc video and the sound carrier of IF amplifier 6 and 12 by being transformed into intermediate frequency, be used for carrying out " quasi-parallel " (" quasi-parallel ") sound accompaniment, intercarrier sound detection device 34 can be a simple rectifier or square-law (square-law) device.
Be provided to very high frequency(VHF) intermediate frequency amplifier 41 from the very high frequency(VHF) IF signal of second detector 38, it comprises ride gain transistor amplifying stage, and they provide up to 60dB or bigger amplification.VHFIF amplifier 41 is provided with reverse automatic gain control, and its responds its output signal level and produces, and oppositely AGC is good for the gain linearity aspect is provided.RF amplifier 2 is provided with the reverse automatic gain control of delay, and it is in response to the output signal level of IF amplifier 47.
Be added to ATSC symbolic code detector 13 from the output signal of very high frequency(VHF) IF amplifier 47 outputs, it detects the baseband signalling sign indicating number from this signal.Symbolic code detector 13 is such devices, it utilizes the synchronous detector of homophase to detect the vestigial sideband amplitudemodulation of data carrier, and utilize the quadrature phase synchronous detector to produce automatic frequency and phase control (AFPC) signal and give controlled oscillator, this oscillator provides synchronizing signal to arrive synchronous detector.The synchronous detector of homophase is worked in the system in simulation, its output signal by analogue-to-digital converters 14 with 10 bit left and right sides resolution digitalization.Perhaps, symbolic code detector 13 and ADC subsequently 14 can be replaced by following circuit: third detector, it arrives the final medium-frequency band on base band just in order to the VHF frequency response of conversion IF amplifier 47, and analogue-to-digital converters are used to make the third detector responding digitalization; And digital synchronous circuits, the third detector that is used for synchronous digitalization responds base band.Such replacement circuit was authorized in December 26 nineteen ninety-five, people's such as C.B.Patel, name is called the United States Patent (USP) 5 of " as being included in the HDTV receiver; have the digital VSB wave detector of logical phase tracker ", 479,449 have description, and are called in the name that authorize August 20 nineteen ninety-five in the United States Patent (USP) 5548617 of " as being used in the HDTV receiver; use the digital VSB wave detector that leads to phase tracker that has of Rader filter " description is arranged, here as an example.When the DTV signal just is being received, a direct signal that causes from the synchronous detecting to pilot signal is followed on the symbolic code when base band is reproduced, and this direct signal is detected by pilot frequency carrier wave wave detector 15, to produce the DTV enable signal, the display part that it regulates the DTV receiver shows the DTV image, but not the ntsc television image.The pilot frequency carrier wave wave detector 15 that shows in Fig. 1 is such types, and promptly in response to digital input signals, perhaps it can be such type, and the analog input signal that directly provides from symbolic code detector 13 promptly is provided.
Fig. 1 has shown from the digitized baseband signalling sign indicating number of ADC 14 symbol decoder that is provided to 20, the type of this symbol decoder 20 the inventor on November 12nd, 1996 application, name is called in No. the 08/746th, 520, the U.S. Patent application of " having the digital television receiver that auto-adaptive filter circuit is arranged that is used to suppress the co-channel interference of NTSC " and describes in detail.Symbol decoder 20 comprises: data limiter (slicer) 21, carry out data limit to decoder 70 input signals, to produce the response of first symbol decoder; Eliminate NTSC artifcates comb filter 22, the response to symbol decoder 20 input signals is provided, this response suppresses the co-channel interference signal of any NTSC; Data limiter 23, data limit is carried out in 21 responses to comb filter, to produce a kind of symbol decoder response of mistake; The comb filter 24 of coupling is used for the symbol decoder response of error recovery, and produces the response of second symbol decoder; And a multiplexer 25, in order to select one of first kind and the response of second symbol decoder as final symbol decoder response, this final response is provided to typical lattice (trellis) decoder 16 in the DTV receiver by symbol decoder 20.Under the situation of the indication that does not have the bigger co-channel interference signal of NTSC of reception, multiplexer 25 is selected the response of first symbol decoder from data limiter 21, to provide symbol decoder 20 output signals to trellis decoder 16.Exist in indication under the situation of the co-channel interference signal reception of bigger NTSC, remove outside during the symbol decoder initialization interval, multiplexer 25 is selected second symbol decoder response from the comb filter 24 of coupling, to provide symbol decoder 20 output signals to trellis decoder 16.
The output signal of very high frequency(VHF) IF amplifier 47 is added to circuit 46, is used for the ntsc video carrier modulation is synchronized to base band.In-phase synchronization wave detector and quadrature phase synchronous detector all are used in the circuit 46, are used for the ntsc video carrier modulation is synchronized to base band; Suppose that after being transformed into a lucky final medium-frequency band on base band carry out synchronously, so last intermediate frequency can be digitized in digital system.Perhaps, the ntsc video carrier modulation is synchronized to base band can be finished in the system in simulation, and, utilizing analogue-to-digital converters separately, the response that is used for the synchronous wave detector of the in-phase synchronization wave detector of this purpose and quadrature phase can be digitized.The response Q of quadrature phase synchronous detector is the artifcates that the Hilbert transform of the single sideband composition (being frequency those compositions on 750kHz) of NTSC signal adds the DTV signal, when appearing at the response I of in-phase synchronization wave detector as these artifcates.This Hilbert conversion that is provided by the response Q of quadrature phase synchronous detector is by phase shift, so that the delays (except that the low-limit frequency that little response should be arranged) of 90 degree to be provided on all frequencies by contrary Hilbert translation circuit 47.
Addition and subtraction are thought the alternative form of linear combination.One is adder among the linear combiner 47 and 48, and another is a subtracter.The response of the contrary Hilbert conversion of circuit 47 in linear combiner 48 with the response linear combination of the synchronous detector of homophase, to produce a composite video signal with high frequency, its frequency is raised the level that is added to the remainder in the simulated television receiver circuit with correction.About the baseband composite video signal, the part of these remainders typically comprises synchronizing separator circuit, and colour signal regenerative circuit and the NTSC image modification that is used for 4: 3 length-width ratios are to be suitable for showing the circuit that shows on 16: 9 used screens of DTV image.
The contrary Hilbert conversion response of circuit 47 in linear combiner 49 with the homophase baseband response linear combination of synchronous circuit (synchrodyne circuitry) 16, to be created in the luminance signal I that ends a little on the 750kHz, this luminance signal does not have the DTV artifcates.Linear combiner 48 and 49 is respectively adder and subtracter, or linear combiner 48 and 49 is respectively that subtracter and adder depend on that the synchronous wave detector operation of selected quadrature phase is ahead of the operation of in-phase synchronization wave detector or lags behind it.
Fig. 1 shows the bandwidth constraints luminance signal from linear combiner 49, it is also had low pass filter 50 filtering of the cut-off frequency of about 1MHz, undertaken square by squarer 31 then, with the indication of the energy of the co-channel interference signal of NTSC that is created in the DTV reception period.Squarer 31 can be made of a digital multiplier, and it receives the signal as multiplier and multiplicand, but it realizes actual with read-only memory.The output signal of squarer 31 is the energy indication of the co-channel interference signal of NTSC at the DTV reception period.
One digital threshold detector 32 determines thisly to indicate whether that very strong being enough to surpass threshold value that under this threshold value, the co-channel interference signal of NTSC is considered to be not enough to cause uncorrectable error in the work of data limiter 21.Threshold dector 32 responses are provided to multiplexer control circuit 33.33 selections of control multiplexer 25 between the response of first and second symbol decoders of multiplexer control circuit, it determines the final symbol decoder response as symbol decoder 20 output signals.During the symbol decoder initialization interval, multiplexer control circuit 33 control multiplexers 25 are selected the output signal of first symbol decoder response as symbol decoder 20.At All Other Times, as long as the response of threshold dector 32 represents that the co-channel interference signal of NTSC is considered to be not enough to cause uncorrectable error in the work of data limiter 21, multiplexer control circuit 33 is just controlled multiplexer 25 and is selected the response of first symbol decoder as symbol decoder 20 output signals, otherwise control multiplexer 25 is selected the output signal of second symbol decoder response as symbol decoder 20.
The distortion of the device of Fig. 2 displayed map 1 is used for providing to digital threshold detector 32 response of linear combiner 49, and need not squarer 31 carries out square.The response of linear combiner 49 is the base band brightness that expands to 750kHz basically, so always has identical polarity, therefore, can omit squarer 31, and digital threshold detector 32 can replace with the digital threshold detector 032 of a threshold with regulation, and this threshold is the square root of the regulation threshold of digital threshold detector 32.That is, the regulation threshold of digital threshold detector 32 be digital threshold detector 032 the regulation threshold square.
In the television receiver of Fig. 1 and Fig. 2, comprising low pass filter 50 has alleviated the needs against Hilbert translation circuit 47, because accurate 90 degree postpone and needn't provide at the frequency place on the cut-off frequency of above-mentioned low pass filter 50, so that in this part of frequency spectrum, suppress the DTV artifcates.Wherein, contrary Hilbert translation circuit 47 is providing accurate 90 ° of hysteresis rationally up to about 4.2MHz, and this comes place of filters 50 with regard to available direct connection.Just contrary Hilbert transformed filter 47 responses in the linear combiner 48 are made up with regard to the high frequency that promotes composite video signal with the homophase baseband response I of change-over circuit 46 synchronously, contrary Hilbert translation circuit 47 needn't provide accurate quadrature lagging at the frequency place up to 4.2MHz, this is because video peak value circuit can be used for remedying the high-frequency rolling drop (roll-off) of composite video signal, this roll-offing causes incorrect hysteresis, if the error in lagging behind is not too serious.
Fig. 3 shows an any one modification between the two to the television receiver of Fig. 1 and 2.In the modification of Fig. 3, replace the quadrature phase baseband response Q that moves the synchronous circuit 46 that is used in two linear combiners 48 and 49 with contrary Hilbert translation circuit 47, contrary Hilbert translation circuit 51 moves the quadrature phase baseband response Q of the synchronous circuit 46 that only is used in the linear combiner 48; And another contrary Hilbert translation circuit 52 moves the quadrature phase baseband response Q of the synchronous circuit 46 that only is used in the linear combiner 49.From 0.5MHz to 4.2MHz, provide reasonably accurate quadrature lagging against Hilbert translation circuit 51,, still needn't under 0.5MHz, provide 90 hysteresis of spending in far frequency place to optimize the spectral response of composite video signal.This is avoided many frequencies far under 0.5MHz to sentence high digital sampling speed for the needed tap finite impulse response (FIR) of quadrature lagging (FIR) filter is provided, and provides the hysteresis of 90 degree also to need high digital sampling speed at the frequency place up to 4.2MHz.Owing to used low pass filter 50, contrary Hilbert translation circuit 52 need provide reasonably accurate quadrature lagging within only to about the 1.0MHz, but circuit 52 far frequency under 0.5MHz provides quadrature lagging, and is preferably low to being the mark of NTSC scan line speed.To be lower than digital sampling speed in the extraction of four times of digital sampling speed used in Hilbert translation circuit 51, can satisfy these needs, significantly reduce like this to the FIR filtering in the contrary Hilbert translation circuit 52 provides different delays and taken a sample the needs of scratchpad memory.Really, low pass filter 50 can be designed to have the lower cut-off frequency below 0.5MHz, is used for the comparable low octuple of digital sampling speed that is used for contrary Hilbert translation circuit 51 of extraction digital sampling speed of contrary Hilbert translation circuit 52 like this.The perhaps cut-off frequency of low pass filter 50 one or many that can further reduce by half, the extraction digital sampling speed that is used in contrary Hilbert translation circuit 52 can further extract from the digital sampling speed that is used for contrary Hilbert translation circuit 51.
Fig. 4 is the flow chart by the performed method of operating of the television receiver of Fig. 1.The initial step S0 of receiving digital television signal is by the unit 1,2,3,37,38 of Fig. 1 television receiver, and 41 execution, and described signal is attended by the anolog TV signals with video section of co-channel interference often.The step S1 that synchronous circuit 46 is carried out subsequently, it is synchronized to the video section of any co-channel interference simulation TV signal on the base band, comprise the homophase demodulation result of first artifcates of DTV signal with generation, and produce the quadrature phase demodulation result of second artifcates that comprises the DTV signal.The step S2 that contrary Hilbert converter circuit 47 is carried out subsequently, the frequency under 750kHz in the frequency range of a far regulation is with homophase and quadrature phase demodulation result 90 ° of phase difference ground phase shifts separately.Linear combiner 49 is execution in step 53 subsequently, homophase and quadrature phase demodulation result separately phase place in the assigned frequency scope by difference phase shift 90 degree after, this step makes up them linearly, to produce the result of linear combination, they do not have first and second artifcates of Digital Television basically in this assigned frequency scope.(upper bound by the frequency range that determines this regulation of low pass filter 50).Squarer 31 execution in step S4, it carries out square the result of linear combination; Simultaneously digital threshold detector 32 is carried out last step S5 then, it detect described linear combination result square whether surpass described setting square, be used for determining whether digital television signal is attended by co-channel interference simulation TV signal by a relatively large margin.
Fig. 5 is the flow chart by the method for operation of Fig. 1 television receiver execution, the step S2 that different with Fig. 4 flow chart is is carried out by contrary Hilbert converter circuit 47 more specifically is shown as step S2 ', and it is with quadrature phase demodulation result phase shift 90 degree in far below the frequency range of the regulation of 750kHz.
Fig. 6 is the flow chart by the method for operation of Fig. 2 television receiver execution.Method utilization described in Fig. 6 flow chart and identical step S0, S1, S2 and S3 described in Fig. 4 flow chart.Certainly, in the work of Fig. 2 television receiver, a square step S4 who is carried out by the squarer in Fig. 1 television receiver 31 is omitted.The step S5 that finishes by the digital threshold detector 32 in Fig. 1 television receiver in the work of the television receiver of Fig. 2 by step S5 ' replacement, whether the linear combination result that it detects in the assigned frequency scope surpasses the value of stipulating, to produce the indication when the DTV signal is attended by the anolog TV signals of co-channel interference by a relatively large margin.This step S5 is carried out by digital threshold detector 032 in Fig. 2 television receiver.
Fig. 7 is the flow chart by the method for work of Fig. 6 television receiver execution, different with Fig. 4 flow chart is more specifically to be shown as step S2 ' by the step S2 that contrary Hilbert converter circuit 47 is carried out, and it is with quadrature phase demodulation result phase shift 90 degree in far below the assigned frequency scope of 750kHz.
Claims (8)
1. method comprises step:
Receiving digital television signal, this signal are attended by the co-channel interference simulation TV signal with video section often;
The video section of any described co-channel interference simulation TV signal is synchronized to base band, comprise the homophase demodulation result of first artifcates of described digital television signal with generation, and produce the quadrature phase demodulation result of second artifcates that comprises described digital television signal;
Frequency place in the assigned frequency scope below 750 kilo hertzs a long way off is with 90 ° of described homophase and quadrature phase demodulation result's the phase shifts of phase difference separately;
After 90 ° of the frequency place phase shifts in described assigned frequency scope, described homophase and quadrature phase demodulation result are made up linearly, to produce the result of a linear combination, it does not have first and second artifcates of digital television signal basically in described assigned frequency scope; And
Whether the amplitude that detects described linear combination result surpasses the value of a regulation in described assigned frequency scope, to produce the indication when described digital television signal is attended by co-channel interference simulation TV signal by a relatively large margin.
2. according to the process of claim 1 wherein, the frequency place in described assigned frequency scope with homophase and quadrature phase demodulation result separately the step of phase difference phase shift 90 degree further comprise substep:
Described quadrature phase demodulation result is carried out contrary Hilbert transform.
3. according to the process of claim 1 wherein, the step whether result's of the described linear combination of described detection amplitude surpasses the value of a regulation further comprises substep:
Described linear combination result is carried out square; And
Square result who detects described linear combination result whether surpass described setting square.
4. method comprises step:
Receiving digital television signal, this signal are attended by the co-channel interference simulation TV signal with video section often;
The video section of any described co-channel interference simulation TV signal is synchronized to base band, comprise the homophase demodulation result of first artifcates of described digital television signal with generation, and produce the quadrature phase demodulation result of second artifcates that comprises described digital television signal;
Frequency place in the assigned frequency scope below 750 kilo hertzs moves 90 degree phase places with described quadrature phase demodulation result a long way off;
The quadrature phase demodulation result and the described inphase quadrature phase demodulating result of the phase shift of gained are made up linearly, and to produce a linear combination result, it does not have first and second artifcates of digital television signal basically in described assigned frequency scope; And
Result's the amplitude of the described linear combination of a setting is crossed in detection at described assigned frequency wide-ultra, be attended by the indication of co-channel interference simulation TV signal by a relatively large margin to produce a described digital television signal.
5. according to the method for claim 4, wherein, result's the amplitude of the described linear combination of a setting is crossed in described detection at described assigned frequency wide-ultra, further comprise substep to produce the step that digital television signal is attended by the indication of co-channel interference simulation TV signal by a relatively large margin:
Described linear combination result is carried out square; And
Detect described linear combination result when gained square surpass described setting square, be attended by the indication of co-channel interference NTSC signal by a relatively large margin to produce described digital television signal.
6. a digital television receiver comprises being used to detect the circuit that occupies the time of TV broadcast channel than the anolog TV signals of large amplitude, and this circuit comprises:
Input circuit, be used for select describing a vestigial sideband amplitudemodulation signal of the video signal portions of any anolog TV signals that occupy described TV broadcast channel from TV broadcast channel, selected vestigial sideband amplitudemodulation signal is transformed into an intermediate-freuqncy signal, and amplify described intermediate-freuqncy signal so that the intermediate-freuqncy signal of an amplification to be provided, except that residual sideband, the described vestigial sideband amplitudemodulation signal that is received by this input circuit also comprised video carrier and full sideband originally;
Video sync circuit, be used for for described video carrier signal and with the carrier wave of video carrier signal quadrature in phase, synchronously detect the intermediate-freuqncy signal of described amplification, with synchronous detecting response that produces homophase and the synchronous detecting response that produces quadrature phase;
First phase-shift circuit is used for all frequency content phase shift 90 degree with the described quadrature phase synchronous detecting response on the assigned frequency, to produce the response of first phase-shift circuit;
The first linear combination circuit, synchronous detecting response and described first phase-shift circuit response combination linearly with described homophase, respond a part to recover the first linear combination circuit in the vision signal described in described full sideband and the residual sideband, the response of this first linear combination circuit is basically without any the response to the digital television signal that occupies described TV broadcast channel, and
Threshold dector is used to determine when that the response of the first linear combination circuit surpasses the threshold value of a regulation, has by a relatively large margin indication to produce co-channel anolog TV signals.
7. according to the digital television receiver of claim 6, further comprise:
The second linear combination circuit is used for synchronous detecting response and described first phase shifts circuit response combination linearly with described homophase, responds all described vision signals to recover the second linear combination circuit.
8. according to the digital television receiver of claim 6, further comprise:
Second phase-shift circuit is used for all frequency content phase shift 90 degree with the described quadrature phase synchronous detecting response on 500KHz, to produce the response of second phase-shift circuit;
The second linear combination circuit is used for synchronous detecting response and described first phase-shift circuit response combination linearly with described homophase, responds all described vision signals to recover the second linear combination circuit.
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| Application Number | Priority Date | Filing Date | Title |
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| CN98117408A CN1110945C (en) | 1998-07-18 | 1998-07-18 | Using special NTSC receiver to detect when Co-channel interfering NTSC signal accompanies digital TV signal |
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| Application Number | Priority Date | Filing Date | Title |
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| CN98117408A CN1110945C (en) | 1998-07-18 | 1998-07-18 | Using special NTSC receiver to detect when Co-channel interfering NTSC signal accompanies digital TV signal |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101003209B (en) * | 2003-04-10 | 2011-06-29 | 佳能株式会社 | Printhead substrate, printhead and printing apparatus |
| CN106303344A (en) * | 2016-08-26 | 2017-01-04 | 高拓讯达（北京）科技有限公司 | The processing method and processing device of interference signal based on digital television receiver |
| WO2018068177A1 (en) * | 2016-10-10 | 2018-04-19 | 华为技术有限公司 | Method and device for eliminating noise by comb filtering and frequency domain adaptive equalization device |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NL8301179A (en) * | 1983-04-01 | 1984-11-01 | Philips Nv | HF SIGNAL RECEIVER FITTED WITH A PAIR OF PARALLEL SIGNAL ROADS. |
| US5450392A (en) * | 1992-05-01 | 1995-09-12 | General Instrument Corporation | Reduction of interchannel harmonic distortions in an analog and digital signal multiplex |
| US5479449A (en) * | 1994-05-04 | 1995-12-26 | Samsung Electronics Co. Ltd. | Digital VSB detector with bandpass phase tracker, as for inclusion in an HDTV receiver. |
| US5546132A (en) * | 1994-12-07 | 1996-08-13 | Goldstar Co., Ltd. | NTSC interference detector |
-
1998
- 1998-07-18 CN CN98117408A patent/CN1110945C/en not_active Expired - Fee Related
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101003209B (en) * | 2003-04-10 | 2011-06-29 | 佳能株式会社 | Printhead substrate, printhead and printing apparatus |
| CN106303344A (en) * | 2016-08-26 | 2017-01-04 | 高拓讯达（北京）科技有限公司 | The processing method and processing device of interference signal based on digital television receiver |
| WO2018068177A1 (en) * | 2016-10-10 | 2018-04-19 | 华为技术有限公司 | Method and device for eliminating noise by comb filtering and frequency domain adaptive equalization device |
Also Published As
| Publication number | Publication date |
|---|---|
| CN1110945C (en) | 2003-06-04 |
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