MXPA98005804A - Ntsc video signal receivers with reduced sensitivity to the interference of digital television signals of co-ca - Google Patents

Abstract

The present invention relates to a video signal receiver with reduced sensitivity to the interference of co-channel digital television signals, the video signal receiver is characterized in that it comprises: first input circuits for selecting an amplitude modulation signal descriptive residual sideband of a video signal, which converts the selected residual sideband amplitude modulation signal to a first intermediate frequency signal and which amplifies the first intermediate frequency signal to provide a first amplified intermediate frequency signal, the residual sideband amplitude modulation signal as originally received by the first input circuit includes a video carrier and full sideband in addition to a residual sideband, the selection of the residual sideband amplitude modulation signal is from any of a plurality of channels at least one of which is likely to contain sometimes co-channel interference of a digital television signal; video synchronization circuits for synchronously detecting the first amplified intermediate frequency signal with respect to the carrier signal of video and with respect to a phase quadrature carrier with the video carrier signal, to generate a first phase synchronized detection response and to generate a first phase quadrature synchronized detection response; first phase shift circuits for the phase shift, by substantially 90% of all frequency components of the first phase quadrature synchronized detection response above a prescribed frequency to generate a first phase shift circuit response, and first linear combination circuits that linearly combine the first synchronized detection response in phase and first response of the phase shift circuits to recover the lower frequency portions of the video signal described in the full sideband and in the residual sideband, substantially free of artifacts of any digital interference television signal of co-can

Description

NTSC VIDEO SEEK RECEIVERS WITH REDUCED SENSITIVITY TO THE INTERFERENCE OF DIGITAL TELEVISION SIGNALS DE CO-CHANNEL Description of the invention The invention relates to NTSC television signal receivers and more particularly to improvements in such receivers to make them substantially less sensitive to the interference of co-channel digital television signals.

BACKGROUND OF THE INVENTION U.S. Patent No. 5,122,879 issued June 16, 1992 to Katsu Ito and entitled "TELEVISION SYNCHRONOUS RECEIVER WITH PHASE SHIFTER FOR REDUCING INTERFERENCE FROM A LOWER ADJACENT CHANNEL" describes a receiver for the video portion of a signal of analog television that synchronously detects the analog television signal received in phase and in quadrature phase. To improve the noise figure by avoiding amplifiers with varactor diode tuning, the Ito receiver synchronizes the response of the radio frequency (RF) amplifier directly to the baseband, such that an adjacent lower channel can appear with an image. The phase quadrature synchronized detection response is shifted in phase 90 ° to all video frequencies REF: 27963 greater than 750 KHz and linearly combined with the phase synchronized detection response to suppress the image frequency components translated to the baseband during the synchronized detection of the 5 video portion of the received NTSC signal. In US Patent No. 5,122,879 Ito does not describe the fact that this procedure also cancels video components greater than 750 KHz. The concurrent loss of frequencies of * High luminance is acceptable in television receivers small display screen, however, such as those used in pulse watches. By modifying the band-limited video signal receiver described by Ito in such a way that the synchronized quadrature detection response on the basis of is displaced in phase 90 ° in all frequencies of In video, the artifacts of digital co-channel interference television signals are removed from the band-limited NTSC signal in the band, as indicated herein. Assuming that the circuit time constant Since the automatic gain control in the receiver is a few horizontal scan lines, the phase quadrature synchronized detection response needs to be shifted in the 90 ° phase only for frequencies greater than a few kilohertz (KHz) to prevent artifacts of the digital television signals of co-channel interference in the band-limited video signal, are visible »On the television or interference display screen with horizontal synchronization.

BRIEF DESCRIPTION OF THE INVENTION A video signal receiver with reduced sensitivity to the interference of co-channel digital television signals is constructed in accordance with a main aspect of the invention in such a way that it includes input circuits for selecting a residual sideband amplitude modulation signal descriptive of a video signal, which converts the selected residual sideband amplitude modulation signal to an intermediate frequency signal and amplifies the signal of intermediate frequency to provide an amplified intermediate frequency signal. The residual sideband amplitude modulation signal as originally received includes a video carrier and a full sideband in addition to a residual sideband. The The residual sideband amplitude modulation signal is selected from any of a plurality of channels, at least one of which is prone to contain, at some time, co-channel interference of a digital television signal. Video synchronization circuits detect in a synchronized manner the amplified intermediate frequency signal with respect to the video carrier signal, to generate a base synchronized detection response and to generate a synchronized phase quadrature detection response. All frequency components of the phase quadrature synchronization detection response above a prescribed frequency are shifted in phase substantially by 90 ° by an inverse Hilbert transformation filter and are combined linearly with the phased detection response in phase, appropriately delayed to recover the lower frequency portions of the described video signal in the full sideband and in the residual sideband of the residual sideband amplitude modulation signal, substantially free of artifacts of any digital television signal of Co-channel interference. The term "linear combination" as used in this specification and the claims appended hereto is a generic term for "additive combiner" or additive and for "differential combiner", or subtracter. According to further aspects of the invention, the video signal receiver includes circuits for recovering higher frequency portions of the described video signal in the full sideband of the residual sideband amplitude modulation signal, but not in its residual sideband. The residual sideband amplitude modulation signal, as supplied to this circuit for recovering the higher frequency portions of the video signal is selectively filtered to eliminate the pilot carrier signal component of any digital television signal from channel. This is done to prevent any artifact from such a pilot carrier signal from being generated when the higher frequency portions of the video signal are recovered. The video signal receiver further includes circuits for linearly combining those higher frequency portions of the video signal with the lower frequency portions of the video signal, which are described in the full sideband and the residual sideband. of the residual sideband amplitude modulation signal and which are substantially free of artifacts of any digital co-channel interference television signal.

BRIEF DESCRIPTION OF THE DRAWINGS Figures 1, 2, 3, 4, 5, 6, and 7 are each a schematic diagram of a respective television receiver that is capable of receiving analog television signals from NTSC as well as DTV signals, which receiver employs the method of the invention to detect the presence in the DTV signals of analog TV signals of NTSC of co-channel interference. Figure 8 is a graph of the preferred spectral responses for the portions of the television receivers 5 of Figures 1, 2, 3, 4 and 5. Figure 9 is a schematic diagram of the synchronization circuit, as it may be. employed in any of the television receivers of Figures 1, # 2, 3, 4, 5, 6 and 7. FIG. 10 is a graph of the preferred spectral response for a portion of the television receivers of FIGS. 6 and 7.

DETAILED DESCRIPTION 15 Figure 1 shows a television receiver that is capable of receiving analog TV signals from NTSC, also as DTV signals. The television broadcast signals of the air type, as received by an antenna 1 are amplified by an amplifier 2 of radio frequency properly tuned and are supplied to a first detector 3. The RF amplifier 2 and the first detector 3 have adjustable tuning and work together as a tuner to select the digital television signal from one of the channels in different locations in a frequency band. The first detector 3 * includes a first local oscillator that supplies first tunable local oscillations over a frequency range above the ultra high frequency TV (UHF) broadcast band and a first mixer to mix the first 5 local oscillations with one TV signal selected by the RF amplifier 2 tuned in an adjustable manner, to up-convert the selected TV signal to generate a signal of # intermediate frequency of UHF in a frequency band intermediate UHF 6 MHz wide, located at higher frequencies of the assigned channels in the UHF TV broadcast band. The first detector 3 supplies the high IF band signal to an intermediate frequency amplifier 4 of UHF band for the NTSC audio signal, to a UHF band intermediate frequency amplifier 5 for the full band NTSC video signal and to a UHF band intermediate frequency amplifier 6 for the high video signals of NTSC. The answers of the UHF band IF amplifiers 4, 5 and 6 are supplied to respective second detectors 7, 8 and 9 to be descendingly converted to respective intermediate VHF band frequency signals in a VHF band smaller than the very high frequencies. assigned highs as TV broadcast channels. The second detectors 7, 8 # and 9 share a second common local oscillator to generate second local oscillations and have respective second mixers to mix those second local oscillations with the responses of the 5 band IF amplifiers of UHF 4, 5, and 6 respectively. The VHF band IF signals of the second detectors 7, 8 and 9 are respectively supplied to the VHF band intermediate frequency amplifier 10 for the audio signal # of NTSC or an intermediate frequency amplifier 11 of VHF band for the full-band NTSC video signal and a VHF mid-frequency amplifier 12 for the high video signal of NTSC. The band IF amplifiers of UHF 4, 5 and 6 include surface acoustic wave (SAW) filters for the UHF IF band NTSC audio signal, for the UHF IF band full band NTSC video signal and for the UHF IF band NTSC video high signals, respectively. SAW filters with steep rejection skirts, but with pass bands that have a linear group delay and flat amplitude response, are implemented more easily in UHF than in VHF. This is the reason to prefer determine the global IF response for the UHF IF band NTSC audio signal for the UHF IF full-band NTSC video signal and for the high-band NTSC video signal of UHF IF in the UHF IF band instead of in the VHF IF band. The SAW filter in the IF amplifier 5, to determine the overall IF response for the full-band NTSC video signal 5 preferably has a substantially flat amplitude response for those portions of the fluctuating VSB AM signal. between frequencies from 500 KHz to at least 3.5 MHz above the lower limit of the 6 MHz wide TV broadcast channel since that # 10 VSB AM signal is translated to the UHF IF band, which rejects the NTSC channel and adjacent channel audio signals and has a substantially linear phase response through its passband. The SAW filter in the IF amplifier 5 can suppress or reject the carrier pilot of any ATSC DTV signal of co-channel interference, as long as the linear phase response is maintained at 750 KHz of the NTSC video carrier frequency. The self-resonance of the IF filtering for the full-band NTSC video signal, which are stimulated by impulse noise, they are close to the middle part of the IF bandpass. Thus, the ringing effects caused by the impulse noise are less apt to affect the baseband video response at a lower level of 750 KHz if the IF filtering has at least a bandwidth of 3 MHz.

The SAW filter in the IF amplifier 6 to determine the overall IF response for the high NTSC video signal rejects the NTSC audio signals in the adjacent channel and channel and preferably this 5 SAW filter exhibits an attenuation Progressive for the lower 1.75 MHz or so of the 6 MHz wide TV broadcast channel as it is translated to the UHF IF band and has a substantially linear phase response over its entire pass band. The progressive attenuation for the lower 1.75 MHz or so of the 6 MHz broadband TV broadcast channel as it is translated to the intermediate frequencies, rejects the adjacent channel NTSC audio signal, the pilot carrier of any ATSC DTV signal of co-channel interference and the NTSC video carrier on the channel. The filter SAW in the IF amplifier 6 preferably exhibits a progressive attenuation for the upper 550 KHz or so of the 6 MHz broadband TV broadcast channel as it is translated to the UHF IF band and rejects the sound signal in the channel. Figure 8 shows the desired global receiver responses, as referenced to the lower frequency of the original transmission channel, in the output gates of the UHF amplifiers 5 and 6.

The UHF 4, 5 and 6 band IF (intermediate frequency) amplifiers can include bandwidth constant balance amplifiers to drive their component SAW filters through source impedances that minimize multiple reflections and to overcome insertion losses of its component SAW filters. The VHF band IF amplifiers 10, 11 and 12 include respective gain controlled amplifiers that provide an amplification of up to 60 dB or more. The VHF band IF amplifiers 10, 11 and 12 each include stages with forward automatic gain control derived in response to the output signal level of the IF amplifier 11, the front AGC is preferred for the best noise figure that it provides. . The RF amplifier 2 is provided with delayed reverse automatic gain control in response to the output signal level of the IF amplifier 11. The response of the VHF IF amplifier 10 is applied to an intercarrier sound detector 13, which supplies intermediate intercarrier sound frequency signals of 4.5 MHz to an intercarrier sound intermediate frequency amplifier 14, which amplifies and in most designs symmetrically limits the amplified response for its application to an FM detector 14. The FM detector 15 reproduces the baseband composite audio signal supplied to the sound reproduction portion 16 of the NTSC receiver according to conventional practice. The sound reproduction portion 16 of the NTSC receiver normally includes a stereophonic decoder circuit. If the NTSC audio signals are selected with narrow band filtering in the IF amplifiers 4 and 10 passing only the FM audio carrier as translated to the intermediate frequencies, the intercarrier sound detector 13 can be provided. by a multiplier that multiplies the response of the IF amplifier 10 by a video carrier supplied from a third local oscillator in the circuits 17 to tune the full-band NTSC video signal to the baseband. Alternatively, if the NTSC audio signals are selected with filtering in the IF 4 and 10 amplifiers that pass the NTSC video and audio carriers as translated to the intermediate frequencies, to implement the "nearly parallel" sound, the intercarrier sound detector 13 may be a simple rectifier or may be a square law device. Then, a video carrier is no longer supplied with a third local oscillator in the circuits 17 to synchronize the full-band NTSC video signal to the baseband.

* The output signal of the VHF IF amplifier 11 is applied to the circuits 17 to synchronize the NTSC video carrier modulation to the baseband, which circuits can take the form shown in Figure 9. A synchronized detector in phase and a synchronized phase quadrature detector are used in the circuits 17 to synchronize the NTSC video carrier modulation to the baseband. The synchronization is carried out in the analogous regime in the specific circuits 17 to synchronize the modulation of the NTSC video carrier to the baseband shown in, and the responses of the phase-locked detector 170 and the phase-locked synchronous detector 171 used for this purpose and transformed to the digital lage using respective analog to digital converters 172 and 173. The third local oscillator 174 in circuit 17 supplies oscillations in phase of 0 ° to the detector 170 synchronized in phase and supplies oscillations in + 90 ° of phase or in -90 ° via a network 175 of phase shift to detector 171 synchronized phase quadrature. The third local oscillator 174 is a controlled oscillator provided with automatic frequency and phase control signal (AFPC) responsive to the unwanted appearance of the low frequency components in the response of the synchronized square detector 171 of phase. Figure 9 shows the AFPC signal that is generated using the common Coastal cycle array in which the responses of the phase locked detector 170 and the phase quadrature synchronized detector 171 are filtered by low pass filters 176 and 177 , the 5 responses of the low pass filters 176 and 177 are multiplied in a mixer 178 and the resulting product is filtered by a low pass filter 179 to generate the AFPC signal for the third * local oscillator 174. 10 Alternatively, synchronization of the NTSC video carrier modulation to the baseband can be performed in the digital mode after converting to a final intermediate frequency band just above the baseband, such way that the intermediate frequency final can be transformed into digital lage. This avoids any problem with the two analog to digital converts 172 and 173 which differ somewhat in the conversion gain. The digital response Q of the detector 171 synchronized quadrature phase is the Hilbert transform of the individual sideband components of the NTSC signal (that is, those components greater than 750 KHz in frequency) plus the artifacts of the DTV signal as they appear in the response I of detector 170 synchronized in phase. Now, the reader's attention is again directed to Figure 1. This Hilbert transform provided by the Q response of the synchronized phase quadrature detector in the synchronization circuits 17 is shifted in phase to provide a delay of 90 ° to 5 °. all frequencies above a few kilohertz by the inverse Hilbert transform circuit 18. The finite impulse response digital filters suitable for the inverse Hilbert transform circuits 18 are known in the art of receiver technology. digital television. The response of the inverse Hilbert transform of circuit 18 are combined linearly in a linear combiner 19, with the digital response I of the detector synchronized in phase, to generate a luminance signal that cuts a bit above 750 KHz. This luminance signal is generally free of DTV artifacts, due to its individual sideband character, as it relates to the NTSC video carrier frequency. If the linear combiner 19 is an additive or subtracter, it depends whether the operation of the phase quadrature synchronized detector is chosen to lead to the operation of the detector synchronized in phase or to retard it. The output signal of the VHF amplifier 12 IF is applied to a synchronized quadrature detector 20. phase for synchronization to the baseband of the NTSC video carrier modulation which is descriptive of the higher frequency portions of the composite video signal. The synchronized phase quadrature detector 20 supplies a digital response Q '. By way of example, if synchronous phase quadrature detection is carried out in the analogous regime, an analog-to-digital converter is cascaded after the synchronized detector to transform its response to the digital lage. The carrier * synchronized for the synchronized quadrature detector 20 of phase is supplied from the same source in circuit 17 to synchronize the NTSC video carrier modulation to the baseband as it supplies the synchronized phase quadrature detector within the synchronization circuit 17 (eg, from the 175 network phase shift). The Q 'response of the synchronized phase quadrature detector 20 is the Hilbert transform of the individual sideband components of the NTSC signal (that is, those components greater than 750 KHz in frequency) plus the artifacts of the portion of the DTV signal which is passed through the SAW filter in the IF amplifier 6. This Hilbert transform provided by the Q 'response of the phase quadrature synchronization detector 20 is shifted in phase to provide a delay of at least 90 ° to the frequencies greater than 500 KHz or in such a manner by the inverse Hilbert transform circuit 21. This method generates a response that is the same at higher frequencies as the response of an NTSC video detector in phase, but which exhibits a low frequency cutoff that is complementary to the high frequency cut of the linear combiner 19. linear combiner 22 combines the responses of the linear combiner 19 and the synchronized phase quadrature detector 20 to generate a composite video signal * 10 full band for apption to portion 23 of the NTSC receiver used to reproduce images on a display screen. This portion 23 of the NTSC receiver normally includes synchronization separation circuits and signal reproduction circuits of . color; in a combination of NTSC and HDTV receiver circuits, which will also be included to adapt the 4: 3 aspect ratio of the NTSC image for presentation on a 16: 9 display screen used to display DTV images. The reverse Hilbert transform circuits 18 require a substantial amount of latency (or insertion delay) in order to provide a 90 ° delay for frequencies as low as a few kilohertz (KHz). By providing a 90 ° delay for the frequencies that are a fraction of the horizontal scan line speed means that the uncapped artifacts of the DTV signals will be of sufficiently low frequency that the AGC receiver will operate to suppress them. An adjustment delay is necessary in the connection of the signal I of the synchronization circuit 17 to the linear combiner 19 to compensate for the latencies of the I and Q signals supplied to the linear combiner 19. The adjustment delay must be cascaded with the * circuits 21 of Hilbert transform inverse to the that its latency is less than that of the reverse Hilbert transform circuits 18. By making the reverse Hilbert transform circuits 21 similar to the inverse Hilbert transform circuits 18, it is possible to avoid the need for such an adjustment.

When such modification is made, the circuits can be subjected to a reduction technique that eliminates the need for the separate reverse Hilbert transform circuit 18 and 21. Figure 2 shows a television receiver that is capable of receiving analog TV signals from NTSC also as DTV signals, which receiver results from such reduction. The elements 18-22 of the television receiver of Figure 1 are replaced by an adder 24 to combine the output signal Q of the circuit 17 of synchronization and the output signal Q 'of the synchronized quadrature detector 20, the inverse Hilbert transform circuit 25 to the addition output signal of the adder 24 - and the linear combination circuit 26 to linearly combine the response of the circuit 25 5 inverse Hilbert transform with the output signal I of the synchronization circuit 17 to generate a luminance signal that cuts off somehow to a value greater than 750 KHz. This luminance signal is generally free from DTV artifacts due to its unique band character as it relates to the NTSC video carrier frequency. If the synchronized quadrature detector 20 and the synchronized quadrature detector within the synchronization circuit 17 is operated out of phase with each other, instead of in phase with each other as is assumed, the Adder 24 is replaced by a subtracter to obtain an equivalent operation. Synchronized detection of high video frequencies using the quadrature-phase video carrier is advantageous in that crossing between low frequencies video and high video frequencies is automatically corrected. In addition, the crossover is presented at the highest possible video frequencies, so that the cancellation of the DTV device is extended as high as possible.

Figure 3 shows a television receiver modification of Figure 1, which modification uses a phase-synchronized detector 27 for synchronized detection of the high video frequencies in place of the synchronized quadrature detector in phase. The synchronized phase quadrature detector 20 which arises together with the inverse Hilbert transform circuit 2 and the linear combiner 22. A crossover filter 28 filters the low passages of the response of the linear combiner 19 and the high-pass filters of the output signal I 'of the detector 27 synchronized in phase before combining them linearly to generate a composite video signal of full-band NTSC for application to the portion 23 of the NTSC receiver used to reproduce images in a display screen. The crossover frequency at which the low pass filtering and short high pass filtering in the crossover filter 28 is preferably at least 500 KHz. The television receiver of Figure 2 is more economical in physical components than the receiver of Figure 3, since the crossover filter 28 is not required in the receiver of Figure 2. In the television receivers of Figures 1, 2 and 3, it is assumed that the chroma demodulation circuits are included in the portion 23 of the NTSC receiver used to reproduce images on a display screen, the color signal is separated from the composite full band video signal applied to that portion 23 of the NTSC receiver used to reproduce images on a display screen. However, it is alternatively possible to separate the color signal of the high frequency component from the composite video signal before its combination with the low frequency component of the composite video signal. Figure 4 shows a variant of the receiver of television of Figure 3 having conventional color demodulation circuits 29 connected to be directly sensitive to the high baseband video frequencies as detected by the phase-synchronized detector 27. It is shown that circuits 29 of Chroma demodulation is separated from a portion 30 of the NTSC receiver used to reproduce images on a display screen. Color demodulation circuits 29 supply color difference signals to that portion 30 of the NTSC receiver, which portion 30 receives a composite video signal of full band the crossover filter 28. Figure 5 shows a variant of the television receiver of Figure 2 having the color demodulation circuits 29 connected to be directly sensitive to high baseband video frequencies as detected by the synchronized phase quadrature detector. Since the color chromatic synchronization as other color signal components is shifted in phase by 90 °, the fact of the 5 Hilbert transform of the color signal instead of the actual color signal that is detected in a synchronized manner does not it has a substantial effect on the recovery of the color difference signal. The television receiver of Figure 6 differs of the television receiver of Figure 2 in which the UHF band IF amplifier 5 is replaced by a UHF band IF amplifier 31 with a passband for the full frequency spectrum of the carrier modulation of the UHF band. VSN's NTSC video, the second NTSC video bass detector 8 is replaced by a second detector 32 for the full frequency spectrum of the NTSC AM video carrier modulation of VSB and the VHF band IF amplifier 11 is replaced by a IF band amplifier VHF with a pass band for full frequency spectra of VSB's NTSC AM video carrier modulation. Figure 10 shows the overall response of the desired receiver, as required at the lowest frequency of the original transmission channel, in the gate of output of the UHF IF amplifier 33-. This full bandwidth response allows the UHF band IF amplifier 6, the second NTSC video high detector 9, the UHF band 1F amplifier 12, the high-speed video quadrature synchronized detector 20 NTSC, and the reverse 21 Hilbert transform circuit 21 are fully assorted. Instead, a high pass filter 34 extracts the high video frequencies from the response of the inverse Hilbert transform circuit 18 for application to the linear combiner 22, to be combined linearly with the low video frequencies provided from the linear combiner 19. The television receiver of Figure 7 differs from the television receiver of Figure 3 in that the UHF band IF amplifier 5 is replaced by a UHF band IF amplifier 31 with a passband for the full frequency spectrum of the VSB NTSC video carrier modulation, the second NTSC video bass detector 8 is replaced by a second detector 32 for the full frequency spectrum of the AMS NTSC video carrier modulation of VSB and VHF band IF amplifier 11 is replaced by a VHF band IF amplifier 33 with a passband for the full frequency spectrum of carrier modulation NTSC video from VSB. The Figure 10 shows the overall response of the receiver, as referenced to the lowest frequency of the original transmission channel, in the output gate of the IF amplifier 33 of U? F. This full bandwidth response allows the UHF band 5 IF amplifier 6, the second NTSC video high detector, the VHF band IF amplifier 12 and the synchronized detector 27 in high video phase of NTSC are fully stocked. Instead, the response I of the detector synchronized in phase in the circuits 17 of The synchronization is applied to the crossover filter 28 to supply it with high video frequencies. In the variants of the television receiver of Figure 1, the color demodulation circuits can be arranged to respond directly to the response of the detector synchronized quadrature phase or circuit 21 of reverse Hilbert transform. In the variants of the television receivers of Figure 6 and Figure 7, the color demodulation circuits can be arranged to respond directly to either the signal output I or the output signal Q of the synchronization circuit 17 or to directly respond to the response of the inverse Hilbert transform circuit 18; these arrangements are also possible in the television receivers of Figure 1, 2 and 3, if their amplifiers IF -s of video are modified to have a * complete global band response as shown in Figure 10. The effect of the digital signal artifacts of co-channel interference on the results of the 5 color demodulation they can (like other forms of random noise) be reduced by cross filtering, since digital television signals are random from scan line to scan line while chrominance signals tend to exhibit strong anticorrelation from line to line before demodulation and strong line-to-line correlation after demodulation. An NTSC receiver as described above can be incorporated into a digital television receiver as described in the application for Patent Serial No. 08 / 821,944 filed by the inventor on March 21, 1997 and entitled "USING VIDEO SIGNALS FROM AUXILIARY ANALOG TV RECEIVERS FOR DETECTING NTSC INTERFERENCE IN DIGITAL TV RECEIVERS". Modifications of television receivers so far described for The use of PAL or SECAM signals instead of the NTSC signals is easily effected by those skilled in the television receiver design technique in recognizing the present disclosure. While the above description describes television receivers of NTSC that reproduce sound and image, the invention has * application to NTSC television receivers that do not reproduce sound and image, such as those incorporated in video tape recorders or in NTSC signal cancellation filters for receivers of digital television. Those experienced in television receiver design, in light of the present description will be enabled to design many variants of the receivers described as the preferred embodiments and this should be kept in mind when determining the ranges of the claims that follow. It is noted that, in relation to this date, the best method known by the applicant to carry out the aforementioned invention is the conventional one for the manufacture of the objects to which it refers. Having described the invention as above, property is claimed as contained in the following

Claims (20)

1. Claims 1. A receiver of video signals with reduced sensitivity to the interference of co-channel digital television signals, the video signal receiver is characterized in that it comprises: first input circuits for selecting an amplitude modulation signal of residual lateral band descriptive of a video signal, which converts the signal from # modulation of residual sideband amplitude 10 selected at a first intermediate frequency signal and that amplifies the first intermediate frequency signal to provide a first amplified intermediate frequency signal, the residual sideband amplitude modulation signal as originally received by the The first input circuit includes a video carrier and full sideband in addition to a residual sideband, the selection of the residual sideband amplitude modulation signal is from any of a plurality of channels at least one of the channels. which is prone to 20 sometimes contain co-channel interference of a digital television signal; video synchronization circuits for synchronously detecting the first amplified intermediate frequency signal with respect to the carrier signal 25 of video and with respect to a phase quadrature carrier with the video carrier signal, to generate a first phase-synchronized detection response and to generate a first synchronized phase quadrature detection response; 5 first phase shift circuits for the phase shift, by substantially 90 ° of all frequency components of the first phase quadrature synchronized detection response above # a prescribed frequency to generate a first response 10 phase shift circuit; and first linear combination circuits that linearly combine the first phase-synchronized detection response and the first response of the phase shift circuits to recover the portions of 15 lower frequency of the video signal described in the full sideband and in the residual sideband, substantially free of artifacts of any digital co-channel interference television signal.
2. 2. The receiver of conformance video signals 20 with claim 1, characterized in that the input circuits select the residual sideband amplitude modulation signal descriptive of a video signal to include the entire residual sideband and a portion of the full sideband extending up to 25 at least 1.75 MHz of the video carrier.
3. 3. The video signal receiver according to claim 2, characterized in that it further comprises: circuits for recovering the upper frequency portions of the video signal described in the entire sideband, but not in the residual sideband; and second linear combination circuits to recover the video signal by linearly combining the # 10 portions of the lower frequency of the video signal and the higher frequency portions of the video signal.
4. The video signal receiver according to claim 3, characterized in that the circuits for recovering the highest frequency portions of the The video signal comprises: second input circuits for selecting a portion of the entire sideband of the residual sideband amplitude modulation signal, which converts the selected portion to a second signal of 20 intermediate frequency and amplifying the second intermediate frequency signal to provide a second amplified intermediate frequency signal; a synchronous detector for synchronously detecting the second intermediate frequency signal 25 amplified with respect to the quadrature carrier phase with the video carrier signal, to generate a second synchronized phase quadrature detection response; and second phase shift circuits for 5 phase displacement substantially at 90 ° of all frequency components of the second phase quadrature synchronized detection response above a prescribed frequency to generate a second response of the circuits of phase shifting to recover the higher frequency portions of the video signal.
5. The video signal receiver according to claim 2, characterized in that it further comprises: second input circuits for selecting a portion of the full sideband of the residual sideband amplitude modulation signal, converting the selected portion to a second intermediate frequency signal and amplifying the second intermediate frequency signal to provide a second amplified intermediate frequency signal; a synchronous detector for synchronously detecting the second intermediate frequency signal amplified with respect to the quadrature carrier with the video carrier signal, to generate a second synchronized phase quadrature detection response; and an adder to add the second phase quadrature synchronized detection response to the first 5 phase quadrature synchronized detection response for application to the first phase shift circuits, the first phase shift circuits are operative to shift in phase, by substantially 90 °, all the components of The frequency of the first and second phase quadrature synchronized detection responses above a prescribed frequency, to generate the first response of the phase shift circuits; which first response of phase shift circuits 15 conditions the first linear combination circuits to further recover, from the lowest frequency of the video signal described in the full sideband and the residual sideband, the highest frequency portions of the video signal described in the sideband complete, but 20 not in the residual sideband.
6. The video signal receiver according to claim 2, characterized in that it further comprises: second input circuits to select a The entire sideband portion of the residual sideband amplitude modulation signal, which converts the selected portion to a second intermediate frequency signal and amplifies the second intermediate frequency signal to provide a second amplified intermediate frequency signal; a synchronous detector for synchronously detecting the second amplified intermediate frequency signal with respect to the video carrier signal, * to generate a second synchronized detection response 10 in phase to recover the higher frequency portions of the video signal; and a crossover filter for recovering the video signal by combining the lower frequency portions of the video signal and the higher frequency portions of the video signal.
7. The video signal receiver according to claim 1, characterized in that it also comprises: circuits for recovering the portions of 20 highest frequency of the video signal described in the full sideband, but in the residual sideband; and second linear combination circuits for recovering the video signal by linearly combining the lower frequency portions of the video signal and the higher frequency portions of the video signal. *
8. 8. The video signal receiver according to claim 7, characterized in that the circuits for recovering the higher frequency portions of the video signal comprise: 5 second input circuits for selecting a portion of the full sideband of the residual sideband amplitude modulation signal, converting the selected portion to a second intermediate frequency signal and amplifying the second frequency signal 10 intermediate to provide a second amplified intermediate frequency signal; a synchronous detector for synchronously detecting the second amplified intermediate frequency signal with respect to the quadrature carrier of 15 phase with the video carrier signal, to generate a second synchronized phase quadrature detection response; and second phase shift circuit for shifting in phase, by substantially 90 °, all the 20 frequency components of the second phase quadrature synchronized detection response above a prescribed frequency to generate a second response of the phase shift circuits to recover the higher frequency portions of the video signal.
9. 9. The video signal receiver according to claim 1, characterized in that it further comprises: second input circuits for selecting a portion of the entire sideband of the residual sideband amplitude modulation signal, which convert the selected portion to a second intermediate frequency signal and amplifying the second intermediate frequency signal to provide a second signal of 10 intermediate frequency amplified; a synchronous detector for synchronously detecting the second amplified intermediate frequency signal with respect to the quadrature carrier with the video carrier signal, to generate a 15 second phase quadrature synchronized detection response; and an adder to add the second phase quadrature synchronized detection response with the first synchronized quadrature detection response 20 phase for its application to the first phase shift circuits, the first phase shift circuits are operative to shift in phase, by substantially 90 °, all the frequency components of the first and second responses of 25 phased quadrature detection in phase above # a prescribed frequency, to generate the first response of the phase shift circuits; which first response of the phase shift circuits conditions the first linear combination circuits 5 to further recover, from the lowest frequency of the video signal described in the full sideband and the residual sideband, the frequency portions more High of the video signal described in the full sideband, but not in the residual sideband. #
10. 10. The video signal receiver according to claim 1, characterized in that it further comprises: second input circuits for selecting a portion of the full sideband of the signal from 15 residual sideband amplitude modulation, which converts the selected portion to a second intermediate frequency signal and amplifies the second intermediate frequency signal to provide a second amplified intermediate frequency signal; 20 a synchronous detector for synchronously detecting the second amplified intermediate frequency signal with respect to the video carrier signal, for generating a second phase synchronized detection response for recovering the higher frequency portions 25 of the video signal; and * a crossover filter for recovering the video signal by combining the lower frequency portions of the video signal and the higher frequency portions of the video signal.
11. 11. The video signal receiver according to claim 1, characterized in that the input circuits select the entire descriptive residual sideband amplitude modulation signal. # of a video signal, but rejects the sound signal on 10 channel, companion and the pilot carrier of any co-channel digital interference video signal.
12. The video signal receiver according to claim 11, characterized in that it further comprises: a high-pass filter that supplies a high-pass filter response to the first response of the phase-shift circuits; and second linear combination circuits to recover the video signal by linearly combining the 20 portions of the lower frequency of the video signal and the high pass filter response to the first response of the phase shift circuits.
13. 13. The video signal receiver according to claim 11, characterized in that it comprises 25 further: a crossover filter for recovering the video signal by combining the lower frequency portions of the video signal with the higher frequency portions of the video signal taken from the first video response. 5 synchronized detection in phase.
14. The video signal receiver according to claim 1, of the plural conversion type, characterized in that the first input circuits comprise: a first detector for selecting one of the plurality of channels and converting an NTSC signal to the same to an ultra high frequency intermediate frequency signal; a first amplifier that provides selective frequency amplification for a portion of the ultra high frequency intermediate frequency signal, to generate a first response of the amplifier comprising response to the residual sideband, the video carrier and at least a portion of the full lateral band 20 descriptive of the lower frequency portions of the video signal; a second detector for converting the first response of the amplifier to a first intermediate frequency signal of very high frequency; a second amplifier that provides a selective amplification of the frequency for the first intermediate frequency signal of very high frequency, to generate a second response of the amplifier supplied as the output signal of the first input circuits to the video synchronization circuits and which comprise responses to the residual sideband, the video carrier and at least a portion of the full descriptive sideband of the lower frequency portions of the video signal.
15. 15. The video signal receiver according to claim 14, characterized in that it further comprises, as components of the second input circuits, including the first detector: a third amplifier that provides a selective amplification of the frequency for a portion of the ultra high frequency intermediate frequency signal, to generate a third response of the amplifier only to a portion of the full sideband; a second additional detector for converting the third response of the amplifier to a second intermediate frequency signal of very high frequency; a fourth amplifier that provides selective frequency amplification for the second intermediate frequency signal of very high frequency, to generate a fourth response of the amplifier only to a portion of the complete sideband, supplied as the output signal of the second circuits of entry.
16. 16. A video signal receiver according to claim 15, characterized in that it further comprises: a synchronous detector for detecting S > synchronized the fourth response of the amplifier with respect to the carrier in quadrature phase with the signal 10 video carrier, to generate a second synchronized detection response in quadrature of phase; second phase shift circuits for shifting by substantially 90 °, all frequency components of the second phase quadrature synchronized detection response 15 above a prescribed frequency, to generate a second response of the phase shift circuits for recover the highest frequency portions of the video signal; and second linear combination circuits for recovering the video signal by linearly combining the lower frequency portions of the video signal and the higher frequency portions of the video signal.
17. 17. A video signal receiver according to claim 15, characterized in that it comprises In addition: # a synchronous detector for synchronously detecting the response of the fourth amplifier with respect to the carrier in quadrature phase with the video carrier signal, to generate a second response of 5 phase quadrature synchronized detection; and an adder to add the second phase quadrature synchronized detection response to the first phase quadrature synchronized detection response for application to the first phase circuits 10 phase shift, the first phase shift circuits are operative to shift in phase, by substantially 90 °, all the frequency components of the first and second quadrature phase synchronized detection responses above 15 a prescribed frequency to generate the first response of the phase shift circuits; which first response of the phase shift circuits conditions the first linear combination circuits to recover, in addition to the lowest frequency of the signal 20 of video described in the full sideband and the residual sideband, the higher frequency portions of the video signal described in the full sideband but not in the residual sideband. #
18. 18. A video signal receiver according to claim 15, characterized in that it further comprises: a synchronous detector for synchronously detecting the response of the fourth amplifier with respect to the video carrier signal, to generate a second response of Synchronized detection in phase to recover the highest frequency portions of the signal * Of video; and a crossover filter for recovering the video signal by combining the lower frequency portions of the video signal and the higher frequency portions of the video signal.
19. 19. A video signal receiver according to claim 14, characterized in that it further comprises: a high-pass filter that supplies a high-pass filter response to the first response of the phase-shift circuits; and 20 seconds of linear combination circuits to recover the video signal by linearly combining the lower frequency portions of the video signal and the response of the high pass filter to the first response of the phase shift circuits.
20. 20. A video signal receiver according to claim 14, characterized in that it further comprises: a crossover filter for recovering the signal from 5 video by combining the lower frequency portions of the video signal with the higher frequency portions of the video signal, taken from the first synchronized detection response, in phase. SUMMARY OF THE INVENTION A video signal receiver with reduced sensitivity to interference from co-channel digital TV signals is described, which includes circuits for selecting "a residual sideband amplitude modulation signal, descriptive of a video signal, which converts the AM signal of VSB (residual sideband) selected to an intermediate frequency signal and amplifies the IF signal to provide an IF signal 10 amplified. The AM signal of VSB is selected from any of a plurality of channels which may contain co-channel interference of a digital television signal. The amplified IF signal is detected in a synchronized manner with respect to the carrier frequency 15 of video to generate a synchronized detection response in phase and to generate a phase quadrature synchronized detection response. All frequency components of the quadrature phase synchronized detection response above one The prescribed frequency is shifted in phase by substantially 90 ° and is combined linearly with the phased detection response in order to recover the lower frequency portions of the video signal, substantially free of artifacts of any signal from 25 digital television co-channel interference. In some embodiments of the video signal receiver, the higher frequency portions of the video signal, described in the full sideband of the VSB AM signal, but not in its residual sideband, are retrieved by detecting in a synchronized the VSB AM signal after selective filtering to separate the component of the pilot carrier signal from any co-channel digital TV-signal. Selective filtering prevents any artifact of such a pilot carrier signal from being generated when the higher frequency portions of the video signal are recovered. The frequency, lower and higher frequency portions of the video signal are combined to obtain a full band video signal.