CN1128538C - NTSC video signal receivers with reduced sensitivity to interference from Co-channel digital television signals - Google Patents
NTSC video signal receivers with reduced sensitivity to interference from Co-channel digital television signals Download PDFInfo
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Abstract
The present invention relates to a video signal receiver for reducing the interference sensibility from co-channel digital television signals. The present invention comprises a circuit which can make a selected vestigial sideband amplitude-modulation signal converted into an intermediate frequency signal and can amplify the intermediate frequency signal, wherein the vestigial sideband amplitude-modulation signal is selected from an interference channel. Subsequently, synchronous detection response and quadrature phase synchronous detection response are generated by the synchronous detection of the amplified intermediate frequency signal. Frequency components of the quadrature phase synchronous detection response higher than the preset frequency is shifted to 90DGE in a phase way to be combined with in-phase synchronous detection response for recovering lower frequency portions of the video signal, and the lower frequency portions hardly comprises the interference product. The low frequency portions and the high frequency portions of the video signal are combined so as to obtain a full band video signal.
Description
This is that the number of patent application of submitting on March 21st, 1997 is the continuation part of 08/821,944 patent application.
Technical field
The present invention relates to the ntsc television signal receiver, more specifically relate to the improvement in such receiver, be used to make them less basically sensitivity to be arranged disturbing from co-channel digital television signal.
Background technology
On June 16th, 1992 is by the U.S. Patent number 5 of Katsu Ito application, 122,879 exercise questions are for having described a kind of receiver of anolog TV signals video section, the anolog TV signals in homophase and quadrature phase that its synchronously detection received in " have with phase shifter and reduce the TV synchrodyne that disturbs from low adjacent channel ".By avoiding using the amplifier with variod tuning to improve noise factor, the Ito receiver directly is transformed into base band synchronously to radio frequency (radio frequency) amplifier response, and such one adjacently can be used as image than low channel and occurs.Be transformed into the picture frequency component of base band during the synchronous detection of the video section of the NTSC signal that above all videos of the 750KHz of this quadrature phase synchronous detection response receive to be suppressed at by 90 ° of phase shifts and with in-phase synchronization detection response linear combination.At U.S. Patent number 5,122, in 879, Ito does not disclose such situation: promptly this processing procedure has also been eliminated the video composition on 750KHz.In the small display screen television receiver, the high-frequency loss of this brightness of following can receive, and but, this situation can only be used for wrist-watch.
Summary of the invention
Here point out,,, from limit tape base band NTSC signal, eliminate the product of co-channel interference digital television signal so that on all videos frequency, the quadrature phase synchronous detection is responded 90 ° of phase shifts by improving this limit band video receiver of describing by Ito.The time constant of supposing automatic gain control circuit in receiver is several horizontal scan line, only to 90 ° of the frequency orthogonal phase-locked detection response phase shifts that are higher than several KHz just can stop limit be with the product of co-channel interference digital television signal in the vision signal to appear on the tv display screen or interference level synchronous.
The invention provides a kind of video receiver, have and reduced the sensitivity of disturbing from co-channel digital television signal, described video receiver comprises: first input circuit, be used to select a kind of vestigial sideband amplitudemodulation signal of describing vision signal, described this vestigial sideband amplitudemodulation conversion of signals of choosing is become first intermediate-freuqncy signal and amplify described first intermediate-freuqncy signal so that a kind of first intermediate-freuqncy signal of having amplified to be provided, except comprising a residual sideband, also comprise a video carrier and full sideband by the initial described vestigial sideband amplitudemodulation signal that receives of described first input circuit, described vestigial sideband amplitudemodulation signal is selected from a plurality of channels, and regular meeting comprises the co-channel interference from a digital television signal during wherein one or more channels; It is characterized in that, described video receiver also comprises: video sync circuit, be used for according to described video carrier signal and according on phase place, differing first intermediate-freuqncy signal that a carrier wave of 90 ° comes the described amplification of synchronous detection, be used to produce one first in-phase synchronization detection response and be used to produce one first quadrature phase synchronous detection response with described video carrier signal; First phase-shift circuit is used in the 90 ° of phase shifts of all frequency components that are higher than the described first quadrature phase synchronous detection response on the predetermined frequency, to produce one first phase-shift circuit response; First linear synthetic circuit, described first in-phase synchronization detection response and described first phase-shift circuit response are combined linearly to recover on described full sideband and the lower frequency part of the described vision signal of describing on described residual sideband, and it does not contain any co-channel interference digital television signal; Be used to recover on described full sideband rather than the circuit of the upper frequency of the described vision signal of on described residual sideband, describing part.
Employed term in this specification and its appended claims " linear synthesizer " is a kind of generic term of " addition synthesizer " or " adder " and " difference synthesizer " or " subtracter ".
According to a further aspect in the invention, this video receiver also comprises and is used to recover on the full sideband of vestigial sideband amplitudemodulation signal rather than the circuit of the upper frequency of the vision signal of describing on the residual sideband at it part.The vestigial sideband amplitudemodulation signal of sort circuit that offers the upper frequency part that is used to recover vision signal by filtering selectively to eliminate the pilot carrier signal composition of any co-channel digital television signal.Do the spawn that to avoid this pilot carrier signal that when recovering the upper frequency part of vision signal, produced like this.This video receiver also comprises and being used for the circuit of the upper frequency of vision signal part with the lower frequency partial linear ground combination of vision signal, this vision signal is both also to record and narrate on residual sideband on the full sideband of vestigial sideband amplitudemodulation signal, and contains the product of any co-channel interference digital television signal hardly.
Description of drawings
Fig. 1,2,3,4,5,6 and 7 each all be the block diagram that can receive the television receiver of NTSC analog tv signal and DTV signal respectively, this television receiver adopts method of the present invention to detect appearance at the co-channel (adjective) DTV signal that disturbs the NTSC analog tv signal.
Fig. 8 is a partial graph 1,2, the preferred spectral response curve of 3,4 and 5 television receiver.
Fig. 9 is can be at Fig. 1, the block diagram of the synchronous circuit that uses in any one television receiver in 2,3,4,5,6 and 7.
Figure 10 is the preferred spectral response curve of a part of the television receiver of Fig. 6 and 7.
Embodiment
Fig. 1 illustrates the television receiver that can receive NTSC analog tv signal and DTV signal.The air broadcast TV signal that is received by antenna 1 is amplified by tunable radio frequency amplifier 2 and is delivered to first detector 3.Radio frequency amplifier 2 and first detector 3 have tunable function and they constitute the function of tuner together, to select said digital television signal in the channel of diverse location from a frequency range.First detector 3 comprises first local oscillator and first blender, first local oscillator provides first local oscillator that may be tuned at the frequency range on hyperfrequency (UHF) the TV broadcast band, thus first blender with this first local oscillator with by tunable radio frequency amplifier 2 selected TV signal mixings so that the selected TV signal of upconvert produces the UHF intermediate-freuqncy signal of 6-MHZ-bandwidth UHF mf band at the frequency place that is arranged in the above-mentioned channel of UHF TV broadcast band.
Being used in intermediate frequency amplifier 5 determine full band ntsc video low signal the SAW filter of intermediate frequency overall response to scope at 500KHz at least as the response that those parts of this VSB AM signal between the 3.5MHz of VSB AM conversion of signals to the wide TV broadcasting channel of the 6MHz of the UHF mf band lower limit is preferably had substantially flat, give up in the channel and the NTSC audio signal of adjacent channel, and in its whole passband, have substantially linear phase response.As long as keep linear phase response from the ntsc video carrier frequency to 750KHz, then the SAW filter in intermediate frequency amplifier 5 just can suppress or not accept the pilot frequency carrier wave of any co-channel interference ATSC DTV signal.By the self-resonance of the intermediate-frequency filter of the full band ntsc video low signal that impulse noise encouraged, be the middle part that is close to IF passband.Therefore, if intermediate frequency filtering has the 3MHz bandwidth at least, then the ringing effect that is caused by impulse noise just seldom is easy to influence the base band video response below the 750KHz.
Being used in intermediate frequency amplifier 6 determines that the SAW filter of the intermediate frequency overall response of the high signal of ntsc video gives up in the channel and the NTSC audio signal of adjacent channel, and best this SAW filter present about to lower limit 1.75MHz as the wide TV broadcast singal of the 6MHz that is transformed into the UHF mf band one roll-off and whole passband in have substantially linear phase response.At ntsc video carrier wave in pilot frequency carrier wave that does not receive adjacent channel NTSC audio signal, any co-channel interference ATSC DTV signal as roll-offing about the 1.75MHz of the wide TV broadcasting channel of the 6MHz that is transformed into intermediate frequency and the channel.This SAW filter in intermediate frequency amplifier 6 is preferably to roll-offing and give up to fall audio signal in the channel as presenting one about the upper limit 550KHz that is transformed into the wide TV broadcasting channel of 6MHz in the UHF mf band.
Fig. 8 is illustrated in the output of UHF intermediate frequency amplifier 5 and 6, with reference to the desirable receiver overall response of the lower frequency of original transmitted channel.
UHF wave band intermediate frequency amplifier 4,5 and 6 can comprise the broadband fixed gain amplifier, is used for driving their part SAW filters to minimize multipath reflection and to be used to overcome the insertion loss of their part SAW filter from source impedance.VHF wave band intermediate frequency amplifier 10,11 and 12 comprises respectively provides the ride gain amplifier that reaches 60dB or bigger multiplication factor.Each VHF wave band intermediate frequency amplifier 10,11 and 12 comprises that the forward automatic gain of the output signal level that responds intermediate frequency amplifier 11 amplifies control section, forward AGC is preferably used in and bears better noise factor.Radio frequency amplifier 2 provides the reverse automatic gain control of the delay of response intermediate frequency amplifier 11 output signal levels.
The response of VHF intermediate frequency amplifier 10 provides to intercarrier sound detection device 13, wave detector 13 offers intercarrier sound intermediate frequency amplifier 14 with 4.5MHz intercarrier sound intermediate-freuqncy signal, and amplifier 14 amplifies and limits symmetrically in the great majority design to be provided to the response of the amplification of FM wave detector 15.FM wave detector 15 every routine operations just reveal the base band composite audio signal that offers NTSC receiver sound accompaniment reproducing part 16 again.The sound accompaniment reproducing part 16 of NTSC receiver generally comprises stereo decoding electrical equipment.If the NTSC audio signal is by only can choose as the narrow-band filtering that is transformed into intermediate frequency by the FM sound carrier in intermediate frequency amplifier 4 and 10, then intercarrier sound detection device 13 can provide a multiplier, and the response of intermediate frequency amplifier 10 and the video carrier that is used for full band ntsc video low signal is synchronized to the 3rd local oscillator in the circuit 17 of base band and is provided are multiplied each other.
In addition, when if the filtering that the NTSC audio signal is transformed into intermediate frequency by the conduct that ntsc video and sound carrier all can be passed through in intermediate frequency amplifier 4 and 10 is chosen, in order to realize " quasi-parallel " sound accompaniment, intercarrier sound detection device 13 can be a kind of simple rectifier or a kind of square law device.Then be used for no longer providing video carrier the 3rd local oscillator that full band ntsc video signal is synchronized in the circuit 17 of base band.
Output signal from VHF intermediate frequency amplifier 11 offers circuit 17 so that the ntsc video carrier modulation is transformed into base band synchronously, and this circuit can adopt structure shown in Figure 9.In-phase synchronization wave detector and quadrature phase synchronous detector all are used in and are used for changing the ntsc video carrier modulation synchronously in the circuit 17 and become base band as shown in the figure, carry out in the simulation field in specific circuit 17 synchronously so that the ntsc video carrier modulation is transformed into the base band shown in it, and utilization mould _ number converter 172 and 173 separately is the responding digitalizations that are used for the in-phase synchronization wave detector 170 and the quadrature phase synchronous detector 171 of this purpose.The 3rd local oscillator 174 in the circuit 17 offers the vibration of 0 ° of phasing in-phase synchronization wave detector 170 and the vibration of the vibration of+90 ° of phasings or-90 ° of phasings is offered quadrature phase synchronous detector 171 through phase shifter 175.The 3rd local oscillator 174 is a kind of controlled oscillators, is provided in the quadrature phase synchronous detector 171 phase control (AFPC) signal and automatic frequency in response to the low frequency component of not wishing to occur.Fig. 9 illustrates and utilizes common Coase tower phase-locked-loop configuration to generate the AFPC signal, wherein by the response filtering of low pass filter 176 and the 177 pairs of in-phase synchronization wave detectors 170 and quadrature phase synchronous detector 171, in frequency mixer 178, mix the response of low pass filter 176 and 177, thereby and be that the 3rd local oscillator 174 generates the AFPC signals by the output filtering as a result of 179 pairs of frequency mixers 178 of low pass filter.
In addition, the ntsc video carrier modulation is become base band synchronously when converting to after a last mf band on the base band, can in digital scope, carry out just, therefore can this last intermediate frequency of digitlization.Can avoid mould-number converter 172 and 173 that any problem of a difference is arranged in conversion gain a little like this.
The digital response Q of quadrature phase synchronous detector 171 is Hilbert conversions that the monolateral band component (that is the component of those frequencies more than 750KHz) of NTSC signal adds their products of DTV signal when appearing among the output I of in-phase synchronization wave detector 170 of being taken in.Reader's attentiveness is back to Fig. 1 now.Resulting this Hilbert changes by phase shift to provide 90 ° of hysteresis to all frequencies more than several KHz among the response Q of the quadrature phase detector device from synchronous circuit 17.Well-known in the digital television receiver field, finite impulse response digital filter is suitable for anti-phase Hilbert change-over circuit 18.
In linear synthesizer 19, the anti-phase Hilbert transition response of circuit 18 and the digital response I of in-phase synchronization wave detector are linear synthetic, produce a kind of by the luminance signal that is higher than 750KHz a little.Because it is monolateral band characteristic with reference to the ntsc video carrier frequency, therefore this luminance signal does not contain the DTV product usually.Linear synthesizer 19 is that adder or subtracter depend on the operation that the operation of quadrature phase synchronous detector is chosen as in advance or lags behind the in-phase synchronization wave detector.
Output signal from VHF intermediate frequency amplifier 12 is provided for the quadrature phase synchronous detector 20 of this ntsc video carrier modulation of the upper frequency part that is used for a description composite video signal to base band.Quadrature phase synchronous detector 20 provides digital response Q '.Give an example, if quadrature phase synchronous detector operation is carried out in simulation field, analog to digital converter of cascade behind synchronous detector then is to carry out digitlization to its output.Provide sync carrier from the circuit 17 that is used for the ntsc video carrier modulation is converted to synchronously base band to quadrature phase synchronous detector 20, this sync carrier be from offer synchronous circuit 17 within the identical source of quadrature phase synchronous detector (promptly from the phase-shift network 175) that provide.The response Q ' of quadrature phase synchronous detector 20 is a kind of Hilbert conversion that the monolateral band component (that is, those frequencies are higher than the component of 750KHz) of NTSC signal adds the product part of the DTV signal that the SAW filter in the intermediate frequency amplifier 6 is passed through.This Hilbert conversion that is provided from the response Q ' of quadrature phase synchronous detector 20 is provided 90 ° of hysteresis by anti-phase Hilbert translation circuit 21 in the frequency that is being higher than at least about 500KHz.This process produces a kind of and the response identical response of homophase ntsc video wave detector at identical upper frequency place, does additional low-frequency cutoff but present a kind of high-frequency cut-off to linear synthesizer 19.
In order to provide 90 ° of hysteresis to the so low frequency of several KHz, oppositely Hilbert translation circuit 18 needs a basic stand-by period amount (perhaps insert and postpone).To such an extent as to the product that provides 90 ° of hysteresis to mean the DTV signal of eliminating to the frequency of the part of horizontal scanning line frequency will not be that enough low frequency can suppress them through the operation of receiver AGC.The I signal that links from synchronous circuit 17 to linear synthesizer 19, need pad to postpone (shim delay), be used for balance the I that offers linear synthesizer 19 and the stand-by period of Q signal.Pad postpone must with anti-phase Hilbert translation circuit 21 cascades, make its stand-by period less than stand-by period of anti-phase Hilbert translation circuit 18.Anti-phase Hilbert translation circuit 21 is made the same needs that just may avoid this joint sheet with anti-phase Hilbert translation circuit 18.After changing this when carrying out, this circuit is benefited from the simplification technology and has been deleted the needs that separate anti-phase Hilbert translation circuit 18 and 21.
Fig. 2 illustrates the television receiver that can receive NTSC analog tv signal and DTV signal that is drawn by this simplification.The unit 18-22 of Fig. 1 television receiver is replaced by adder 24, anti-phase Hilbert translation circuit 25 and linear synthetic circuit 26, adder 24 is used for the Q output signal of synchronous circuit 17 is merged mutually with the Q ' output signal of quadrature synchronization detector 20, anti-phase Hilbert translation circuit 25 responses are from the total output signal of adder 24, and linear synthetic circuit 26 is used for the I output signal of anti-phase Hilert translation circuit 25 responses and synchronous circuit 17 is combined to the luminance signal that produces by being higher than 750KHz a little.Because theirs is the monolateral band characteristic of reference with the ntsc video carrier frequency, therefore this luminance signal does not conform to the DTV product usually.If the quadrature synchronization wave detector in quadrature phase synchronizing indicator 20 and the synchronous circuit 17 is operate out of phase each other, but not, then just replace adder 24 to finish balancing run with subtracter as the preceding homophase operation of supposing.
Utilize the advantage of the high-frequency synchronous detection of video of quadrature phase video carrier to be that overlapping between video low frequency and the video high-frequency is from dynamic(al) correction.In addition, the overlapping elimination that may occur in the such DTV product in maximum video frequency place trends towards high-frequency as far as possible.
Fig. 3 illustrates a kind of improvement of Fig. 1 television receiver, and this improvement comes the high-frequency detection of synchronization video without quadrature phase synchronous detector 20 with in-phase synchronization wave detector 27.Dispense quadrature phase synchronous detector 20 and reverse Hilbert translation circuit 21 and linear synthesizer 22.Crossover filter 28 linearly them synthetic before the I ' output signal of the response of the linear synthesizer 19 of low-pass filtering and high-pass filtering in-phase synchronization wave detector 27 be applied to a kind of full band composite video signal of the reconstruction of image part 23 of NTSC receiver with generation, this part 23 is used for reproduced image on display screen.The crossover frequencies that low-pass filtering and high-pass filtering end in crossover filter 28 is 500KHz at least preferably.Because Fig. 2 receiver does not need crossover filter 28, so Fig. 2 television receiver has more economical hardware than Fig. 3 receiver.
The hypothesis chrominance demodulation circuit is included in the reconstruction of image part 23 of the NTSC receiver that is used for reproduced image on display screen in Fig. 1, Fig. 2 and Fig. 3 TV are met sb. at the airport, and carrier chrominance signal is separated from the full band composite video signal of the reconstruction of image part 23 that offers the NTSC receiver that is used for reproduced picture on display screen.But, another kind being arranged may be just to isolate carrier chrominance signal from the high fdrequency component of composite video signal before the low frequency component of the high fdrequency component of composite video signal and composite video signal is synthetic.
Fig. 4 illustrates a kind of distortion of Fig. 3 television receiver, makes the conventional look demodulator circuit 29 that has be connected to the base band video high-frequency that directly responds by 27 detections of in-phase synchronization wave detector.Chrominance demodulation circuit shown in the figure 29 is separated with the NTSC receiver section 30 that is used for reproduced image on display screen.Chrominance demodulation circuit 29 provides the part 30 of color difference signal to the NTSC receiver, the full band composite video signal that this part 30 receives from crossover filter 28.
Fig. 5 illustrates a kind of distortion of Fig. 3 television receiver, and wherein chrominance demodulation circuit 29 is connected to and directly responds the base band video that is detected by quadrature phase synchronous detector 20.Because colour burst is the same as with other chroma signal component 90 ° of phase shifts, therefore, to the Hilbert conversion of carrier chrominance signal but not do not have essence to influence to recovering color difference signal to the synchronously detection of the carrier chrominance signal of reality.
The difference of Fig. 6 television receiver and Fig. 2 TV receiver is that UHF wave band intermediate frequency amplifier 31 has replaced UHF wave band intermediate frequency amplifier 5, second detector 32 has replaced ntsc video low signal second detector 8 and VHF wave band intermediate frequency amplifier 33 to replace VHF wave band intermediate frequency amplifier 11.Wherein, this VHF wave band intermediate frequency amplifier 31 has the passband of the entire spectrum of suitable VSB AM ntsc video carrier modulation, this second detector 32 has the passband of the entire spectrum of suitable VSB AM ntsc video carrier modulation, and this VHF wave band intermediate frequency amplifier 33 has the passband of the entire spectrum of suitable VSB AM ntsc video carrier modulation.Figure 10 illustrates the lower frequency with reference to the original transmitted channel, in the overall response of the desirable receiver of VHF intermediate frequency amplifier 33 outputs.This full bandwidth response allows to save fully UHF wave band intermediate frequency amplifier 6, high signal second detector 9 of ntsc video, VHF wave band intermediate frequency amplifier 12, the high signal in orthogonal phase-locked detection of ntsc video device 20 and anti-phase Hilbert translation circuit 21.Otherwise high pass filter 34 extracts the video high-frequency that is applied to linear synthesizer 22 from the response of reverse Hilbert translation circuit 18, and it is synthetic that the video low frequency that provides with linear synthesizer 19 is carried out linearity.
The difference of Fig. 7 television receiver and Fig. 3 TV receiver is: the UHF wave band intermediate frequency amplifier 31 of passband with entire spectrum of suitable VSB AM ntsc video carrier modulation has replaced UHF wave band intermediate frequency amplifier 5; The second detector of passband with entire spectrum of suitable VSB AM ntsc video carrier modulation has replaced ntsc video low signal second detector 8; Replaced VHF wave band intermediate frequency amplifier 11 with the VHF wave band intermediate frequency amplifier 33 of the passband of entire spectrum with suitable VSBAM ntsc video carrier modulation.Figure 10 illustrates the lower frequency with reference to the original transmitted channel, in the overall response of the desirable receiver of output of VHF intermediate frequency amplifier 33.This full bandwidth response allows to save fully UHF wave band intermediate frequency amplifier 6, the high signal second detector 9 of ntsc video, VHF wave band intermediate frequency amplifier 12 and the high signal in-phase synchronization of ntsc video wave detector 27.Otherwise the response I of the in-phase synchronization wave detector in synchronous circuit 17 is provided for crossover filter 28 to offer the high signal of its video.
In some distortion of Fig. 1 television receiver, can make chrominance demodulation circuit be arranged to directly respond the response of quadrature phase synchronous detector 20 or anti-phase Hilbert translation circuit 21.In some distortion of Fig. 6 and Fig. 7 TV receiver, the response that can make chrominance demodulation circuit be arranged to directly to respond the I output signal or the Q output signal of synchronous circuit 17 or directly respond anti-phase Hilbert translation circuit 18; If make their video low signal intermediate frequency amplifier be modified to overall response, in Fig. 1, Fig. 2 and Fig. 3 TV receiver, also can carry out these layouts with full base band as shown in figure 10.
Because digital television signal is that carrier chrominance signal trends towards presenting strong row and line correlation with the row non-correlation demodulation after presenting strong row before the demodulation at random the time on from scan line to scan line, so can reduce the influence (resemble other random noise form) of co-channel interference digital signal to the colourity demodulation result by horizontal filtering.Above-mentioned NTSC receiver can be 08/821 in the number of patent application of application on March 21st, 1997 with the applicant, digital television receiver described in 944 lumps together, and wherein this patent exercise question is " being used to disturb from the video signal detection NTSC of secondary analog TV receiver " in digital receiver.After having known the front disclosure, the technical staff in television receiver design field just can be easily to up to the present disclosed use PAL signal or SECAM signal but not the television receiver of NTSC signal is done change.When the disclosed content description in front reproduce after the ntsc television receiver of sound accompaniment and image, the present invention is applicable to the ntsc television receiver that does not reproduce sound accompaniment and image, such as those be contained in the video cassette recorder or be contained in the NTSC signal and eliminate and to be used for digital television receiver in the filter.After having known the disclosed content in front, a technician in the television receiver design field can design the many distortion as the described receiver of preferred embodiment, and when clear and definite after the scope of claims subsequently, this is to remember.
Claims (20)
1. a video receiver has and has reduced the sensitivity of disturbing from co-channel digital television signal, and described video receiver comprises:
First input circuit, be used to select a kind of vestigial sideband amplitudemodulation signal of describing vision signal, described this vestigial sideband amplitudemodulation conversion of signals of choosing is become first intermediate-freuqncy signal and amplify described first intermediate-freuqncy signal so that a kind of first intermediate-freuqncy signal of having amplified to be provided, except comprising a residual sideband, also comprise a video carrier and full sideband by the initial described vestigial sideband amplitudemodulation signal that receives of described first input circuit, described vestigial sideband amplitudemodulation signal is selected from a plurality of channels, and regular meeting comprises the co-channel interference from a digital television signal during wherein one or more channels;
It is characterized in that described video receiver also comprises:
Video sync circuit, be used for according to described video carrier signal and according on phase place, differing first intermediate-freuqncy signal that a carrier wave of 90 ° comes the described amplification of synchronous detection, be used to produce one first in-phase synchronization detection response and be used to produce one first quadrature phase synchronous detection response with described video carrier signal;
First phase-shift circuit is used in the 90 ° of phase shifts of all frequency components that are higher than the described first quadrature phase synchronous detection response on the predetermined frequency, to produce one first phase-shift circuit response;
First linear synthetic circuit, described first in-phase synchronization detection response and described first phase-shift circuit response are combined linearly to recover on described full sideband and the lower frequency part of the described vision signal of describing on described residual sideband, and it does not contain any co-channel interference digital television signal; With
Be used to recover on described full sideband rather than the circuit of the upper frequency of the described vision signal of on described residual sideband, describing part.
2. as the desired a kind of video receiver of claim 1, wherein said first input circuit selects to describe the described vestigial sideband amplitudemodulation signal of vision signal so that comprise whole described residual sideband and extend to the described full sideband of a part of 1.75MHz at least from video carrier.
3. as the desired a kind of video receiver of claim 2, also comprise:
Be used to recover at described full sideband but not the circuit of the upper frequency of the described vision signal described in described residual sideband part; With
Second linear synthetic circuit is used for recovering described vision signal by the described upper frequency partial linear ground combination the described lower frequency part of described vision signal and described vision signal.
4. as the desired a kind of video receiver of claim 3, the wherein said circuit that is used to recover the upper frequency part of described vision signal comprises:
Second input circuit is used to select the described full sideband of a part of described vestigial sideband modulation signal, the part of changing this selection to become one second intermediate-freuqncy signal and second intermediate-freuqncy signal of described second intermediate-freuqncy signal to provide one to amplify is provided;
Synchronous detector is used for differing 90 ° carrier wave with described video carrier signal come described second intermediate-freuqncy signal of having amplified of synchronously detection on phase place according to described, is used to produce one second quadrature phase synchronous detection response; With
Second phase-shift circuit, the 90 ° of phase shifts of whole frequency components that are used for the described second quadrature phase synchronous detection response on preset frequency are used to recover one second phase-shift circuit response of the described upper frequency part of described vision signal with generation.
5. as the desired a kind of video receiver of claim 2, also comprise:
Second input circuit, be used to select described vestigial sideband amplitudemodulation signal the described full sideband of a part, change this selection portion and be divided into one second intermediate-freuqncy signal and second intermediate-freuqncy signal of described second intermediate-freuqncy signal to provide one to amplify is provided;
A synchronous detector is used for described second intermediate-freuqncy signal of having amplified of carrier synchronization ground detection that differs 90 ° with described video carrier signal according to described on phase place, is used to produce one second quadrature phase synchronous detection response; With
An adder, be used for thereby described second quadrature phase synchronous detection response and described first quadrature phase synchronous detection response addition are applied to described first phase-shift circuit, all frequency components that described first phase-shift circuit responds described first and the described second quadrature phase synchronous detection that is higher than a preset frequency are carried out 90 ° of phase shifts to produce described first phase-shift circuit response; Described first phase-shift circuit response is determining described first linear synthetic circuit, this first linear synthetic circuit is used for recovering except both on the described full sideband also the described lower frequency part in the described vision signal of describing on the described residual sideband, also recovers at described full sideband but is not the described upper frequency part of the described vision signal on described residual sideband.
6. as the desired a kind of video receiver of claim 2, also comprise:
Second input circuit, be used to select described vestigial sideband amplitudemodulation signal the described full sideband of a part, change this selection portion and be divided into one second intermediate-freuqncy signal and second intermediate-freuqncy signal of described second intermediate-freuqncy signal to provide one to amplify is provided;
Synchronous detector is used for synchronously detecting described second intermediate-freuqncy signal of having amplified according to described video carrier signal, is used to generate one second in-phase synchronization detection response so that recover the described upper frequency part of described vision signal; With
Crossover filter is used for recovering described vision signal by the described lower frequency part of described vision signal is partly combined with the described upper frequency of described vision signal.
7. as the desired a kind of video receiver of claim 1, also comprise:
Second linear synthetic circuit is used for recovering described vision signal by the described upper frequency partial linear ground combination the described lower frequency of described vision signal part and described vision signal.
8. as the desired a kind of video receiver of claim 7, the wherein said circuit that is used to recover the upper frequency part of described vision signal comprises:
Second input circuit is used to select the described full sideband of a part of described vestigial sideband amplitudemodulation signal, the part of changing this selection to become one second intermediate-freuqncy signal and second intermediate-freuqncy signal of described second intermediate-freuqncy signal to provide one to amplify is provided;
A synchronous detector is used for differing 90 ° carrier wave with described video carrier signal come described second intermediate-freuqncy signal of having amplified of synchronously detection on phase place according to described, is used for producing one second quadrature phase synchronous detection response; With
Second phase-shift circuit is used for all frequency components that the described second quadrature phase synchronous detection that is higher than a preset frequency responds are carried out 90 ° of phase shifts are used for recovering described vision signal with generation described upper frequency one second phase-shift circuit response partly.
9. as the desired a kind of video receiver of claim 1, also comprise:
Second input circuit is used to select the described full sideband of a part of described vestigial sideband amplitudemodulation signal, changes this selection portion and is divided into a kind of second intermediate-freuqncy signal and amplifies described second intermediate-freuqncy signal so that a kind of second intermediate-freuqncy signal of having amplified to be provided;
A synchronous detector is used for described second intermediate-freuqncy signal of having amplified of carrier synchronization ground detection that differs 90 ° with described video carrier signal according to described on phase place, to produce one second quadrature phase synchronous detection response; With
An adder, be used for described second quadrature phase synchronous detection response and the described first in-phase synchronization detection are responded addition so that be applied to described first phase-shift circuit, whole frequency components that described first phase-shift circuit responds described first and the described second quadrature phase synchronous detection that is higher than a preset frequency are carried out 90 ° of phase shifts to produce described first phase-shift circuit response; Described first phase-shift circuit response is determining described first linear synthetic circuit, this first linear synthetic circuit is used for recovering except on the described full sideband also the described lower frequency part in the described vision signal of describing on the described residual sideband, also recovers on described full sideband but not the described upper frequency part of the described vision signal of describing on described residual sideband.
10. as the desired a kind of video receiver of claim 1, also comprise:
Second input circuit, be used to select described vestigial sideband amplitudemodulation signal the described full sideband of a part, change this selection portion and be divided into one second intermediate-freuqncy signal and second intermediate-freuqncy signal of described second intermediate-freuqncy signal to provide one to amplify is provided;
A synchronous detector is used for according to described video carrier signal described second intermediate-freuqncy signal of having amplified of detection synchronously, is used to produce one second in-phase synchronization detection response of the described upper frequency part that is used for recovering described vision signal; With
A crossover filter is used for recovering described vision signal by the described lower frequency part of described vision signal is partly combined with the described upper frequency of described vision signal.
11. as the desired a kind of video receiver of claim 1, wherein said first input circuit is selected to describe the whole described vestigial sideband amplitudemodulation signal of a vision signal but is given up the pilot tone of audio signal and any synchronous interference digital video signal in the channel of following.
12., also comprise as the desired a kind of video receiver of claim 11:
A high pass filter provides a high-pass filtering response to described first phase-shift circuit response; With
Second linear synthetic circuit is used for recovering described vision signal by the described lower frequency part of described vision signal is made up linearly with described high-pass filter response to described first phase-shift circuit response.
13., also comprise as the desired a kind of video receiver of claim 11:
A crossover filter is used for recovering described vision signal by the described lower frequency part of described vision signal is partly combined with the upper frequency of the described vision signal of taking out from described first in-phase synchronization detection response.
14. as the desired a kind of video receiver of claim 1, wherein said first input circuit comprises:
A first detector is used for selecting an independent channel of described many channels and conversion a kind of NTSC signal wherein to become a kind of hyperfrequency intermediate-freuqncy signal;
One first amplifier, provide frequency-selecting to amplify to the described hyperfrequency intermediate-freuqncy signal of a part, to produce first amplifier response, this first amplifier response comprises described residual sideband, described video carrier and the described full sideband response of at least a portion of describing described vision signal lower frequency part;
A second detector is used to transform described first amplifier response and becomes one first very high frequency(VHF) intermediate-freuqncy signal;
One second amplifier, provide frequency-selecting to amplify to the described first very high frequency(VHF) intermediate-freuqncy signal, producing second amplifier response, this second amplifier response is that the conduct that provides from described first input circuit outputs signal to described video sync circuit and comprises described residual sideband, described video carrier and the response of the described full sideband of at least a portion of describing the lower frequency part of described vision signal.
15., also comprise as the part of first input circuit that includes described first detector as the desired a kind of video receiver of claim 14:
The 3rd amplifier provides frequency-selecting to amplify to the described hyperfrequency intermediate-freuqncy signal of a part, to produce one the 3rd amplifier response at the described full sideband of a part;
Another second detector is used to change described the 3rd amplifier response and becomes one second very high frequency(VHF) intermediate-freuqncy signal;
One the 4th amplifier provides frequency-selecting to amplify to the described second very high frequency(VHF) intermediate-freuqncy signal, only to produce at the described full sideband of a part, one the 4th amplifier response as output signal is provided from described second input circuit.
16., also comprise as the desired a kind of video receiver of claim 15:
A synchronous detector is used for described the 4th amplifier response of carrier synchronization ground detection that differs 90 ° with described video carrier signal according to described on phase place, is used for producing one second quadrature phase synchronous detection response;
Second phase-shift circuit is used for all frequency components that the described second quadrature phase synchronous detection that is higher than a preset frequency responds are carried out 90 ° of phase shifts are used for recovering described vision signal with generation upper frequency one second phase-shift circuit response partly; With
Second linear synthetic circuit is used for by the described upper frequency partial linear ground of the described lower frequency part of described vision signal with described vision signal is made up to recover described vision signal.
17., also comprise as the desired a kind of video receiver of claim 15:
A synchronous detector is used for described the 4th amplifier response of carrier synchronization ground detection that differs 90 ° with described video carrier signal according to described on phase place, is used for producing one second quadrature phase synchronous detection response; With
An adder, be used in order to be applied to described first phase-shift circuit described second quadrature phase synchronous detection response being responded addition with the described first quadrature phase synchronous detection, all frequency components that described first phase-shift circuit responds described first and the described second quadrature phase synchronous detection that is higher than a preset frequency are carried out 90 ° of phase shifts to produce described first phase-shift circuit response; Described first phase-shift circuit response is determining described first linear synthetic circuit, this first linear synthetic circuit is used for recovering except both on the described full sideband also the described lower frequency in the described vision signal of describing on the described residual sideband, also has on described full sideband and the described upper frequency of the described vision signal of not describing on described residual sideband.
18., also comprise as the desired a kind of video receiver of claim 15:
A synchronous detector is used for coming described the 4th amplifier response of synchronously detection according to described video carrier signal, is used for producing upper frequency one the second in-phase synchronization detection response partly that is used to recover described vision signal; With
A crossover filter is used for partly combining to recover described vision signal with the described upper frequency of described vision signal by the described lower frequency part described vision signal.
19., also comprise as the desired a kind of video receiver of claim 14:
A high pass filter provides a high-pass filtering response to described first phase-shift circuit response; With
Second linear synthetic circuit is used for recovering described vision signal by the described lower frequency part of described vision signal is made up linearly with described high-pass filtering response to described first phase-shift circuit response.
20., also comprise as the desired a kind of video receiver of claim 14:
A crossover filter is used for by the described lower frequency part of described vision signal and the upper frequency of the described vision signal of taking out from described first in-phase synchronization detection response are partly combined to recover described vision signal.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 98117986 CN1128538C (en) | 1998-07-18 | 1998-07-18 | NTSC video signal receivers with reduced sensitivity to interference from Co-channel digital television signals |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 98117986 CN1128538C (en) | 1998-07-18 | 1998-07-18 | NTSC video signal receivers with reduced sensitivity to interference from Co-channel digital television signals |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1242672A CN1242672A (en) | 2000-01-26 |
| CN1128538C true CN1128538C (en) | 2003-11-19 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN 98117986 Expired - Fee Related CN1128538C (en) | 1998-07-18 | 1998-07-18 | NTSC video signal receivers with reduced sensitivity to interference from Co-channel digital television signals |
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| Country | Link |
|---|---|
| CN (1) | CN1128538C (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2006034142A2 (en) * | 2004-09-17 | 2006-03-30 | That Corporation | Direct digital encoding and radio frequency modulation for broadcast television application |
| CN107195263B (en) * | 2017-07-10 | 2019-11-08 | 京东方科技集团股份有限公司 | A kind of noise control modulating signal circuit, modulating method and display panel, display device |
| CN111416917B (en) * | 2020-03-30 | 2021-05-18 | 高拓讯达（北京）科技有限公司 | Analog television signal processing method and device |
-
1998
- 1998-07-18 CN CN 98117986 patent/CN1128538C/en not_active Expired - Fee Related
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| Publication number | Publication date |
|---|---|
| CN1242672A (en) | 2000-01-26 |
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