Abstract: A filter-combiner for combining television signals from adjacent channels is presented herein. The combiner has two inputs that respectively receive an NTSC combined visual and aural signal and a DTV signal wherein the NTSC signal and the DTV signal are in adjacent channels. The DTV signal is of greater frequency than the NTSC signal. A combined output signal is provided at an output of the combiner. The combiner has sharp tuned filtering interposed between the inputs and the output and tuned to pass the DTV signal while reflecting the NTSC signal such that the passed DTV signal and the reflected NTSC signal combine as the combined output signal.

Abstract: A method and apparatus for compensating for channel distortion is disclosed. In the present invention, equalization is performed in the treating sequence mode when the moving ghost does not exist in the channel and there is no possibility that the equalizer diverges, the data mode is cancelled and the equalization is carried out in the blind mode when the moving ghost does not exist in the channel but there is a possibility that the equalizer diverges, the equalizer is executed in the data mode when there is no possibility that the equalizer diverges but there exists the moving ghost including slowly moving ghosts in the channel, and the equalization is performed in the data mode and blind mode when the moving ghost exists and there is a possibility that the equalizer diverges.

Abstract: A method and apparatus for equalizing a signal containing high definition television information in the presence of co-channel NTSC interference employs an equalizer having feed forward and decision feedback filters. A comb filter is inserted ahead of the equalizer when NTSC co-channel interference is present. A selected tap of the decision feedback filter is set to a zero value when the signal is being equalized during an intitial blind operating mode. The decision feedback filter taps are updated afterwards, in a decision-directed operating mode.

Abstract: A method and system for detecting a VSB mode in a digital TV receiver is disclosed. The system includes first and second VSB mode detectors implemented before and after a channel equalizer. The first VSB mode detector detects a VSB mode from a signal before channel-equalization, the second VSB mode detector detects a VSB mode from a channel-equalized signal, and one of the detected VSB modes is output to the channel equalizer as the finally detected VSB mode.

Abstract: An NTSC co-channel interference detector (44) detects the presence of an interfering NTSC signal in the received Q-channel signal that is orthogonal to the received I-channel signal, rather than detecting the presence of an interfering NTSC signal in the received I-channel signal. By determining whether or not a significant amount of NTSC co-channel interference accompanies the received Q-channel signal, it is inferentially determined whether or not a significant amount of NTSC co-channel interference accompanies the received I-channel signal, such as to cause too many errors in the trellis decoding of equalized received I-channel signal to be corrected by the Reed-Solomon decoder (40) following the trellis decoder (34). The accurate determination of co-channel NTSC interference levels is simplified, because essentially no direct bias arises from the quadrature-phase synchronous detection of the pilot carrier of the VSB AM digital television signal.

Abstract: For use in a receiver capable of decoding trellis encoded signals of the type comprising a trellis decoder and a decision feedback equalizer coupled to each path memory output of said trellis decoder, wherein said decision feedback equalizer is capable of obtaining symbol values from each path memory output of said trellis decoder for use as estimates in channel equalization, an apparatus and method is disclosed for reconstructing symbol values from trace back path information stored within said trellis decoder. The apparatus and method of the present invention reconstructs a symbol stream from the trellis decoder using data signal selection circuitry to obtain bit values that represent the reconstructed symbols. In one embodiment of the present invention, each of a plurality of multiplexers selects one of four symbol value inputs to send to a first adaptive filter tap cell in a set of twelve adaptive filter tap cells.

Abstract: An apparatus for judging if a co-channel interference exists in a digital TV receiver is disclosed. The TV receiver includes a comb filter for removing NTSC interference of input data, and a selector for selectively outputting data which passed through the comb filter or data which did not pass through the comb filter according to a selection signal. The apparatus includes a gain controller for controlling the gain of noise which did not pass through the comb filter to change the point of time for turning on/off the comb filter, thereby optimizing the performance of the TV receiver for the channel noise and NTSC co-channel interference.

Abstract: A VSB reception system includes a sequence generator for decoding a symbol corresponding to the supplemental data and generating a predefined sequence included in the supplemental data at VSB transmission system. The reception system also includes a modified legacy VSB receiver for processing the data received from the VSB transmission system in a reverse order of the VSB transmission system by using the sequence, and a demultiplexer for demultiplexing the data from the modified legacy VSB receiver into the MPEG data and the supplemental data. The VSB reception system also includes a supplemental data processor for processing the supplemental data segment from the demultiplexer in a reverse order of the transmission system, to obtain the supplemental data, thereby carrying out the slicer prediction, decoding, and symbol decision more accurately by using the predefined sequence, to improve a performance.

Abstract: In a system for receiving a signal containing digital data representing HDTV image information in the form of multilevel symbols formatted into groups of successive fields, each field comprising a field segment, a plurality of data segments, and associated sync components, the received signal is demodulated to produce a demodulated signal. The demodulated signal is comb-filtered to reject NTSC co-channel interference to produce a filtered signal. The filtered signal is trellis decoded with a trellis decoder employing a truncated non-Euclidean metric.

Abstract: Adaptive equalizers for digital TV receivers in which the filter parameters are adjusted by decision-feedback are followed in cascade by filters for suppressing unwanted demodulation artifacts of NTSC co-channel interference. The decision-feedback signals are derived from the responses of the filters for suppressing unwanted demodulation artifacts of NTSC co-channel interference. This avoids erroneous adjustments of the filter parameters of the adaptive equalizers that results when the decision-feedback signals are accompanied by demodulation artifacts of carrier components of the NTSC co-channel interference.

Abstract: A video signal processing apparatus and method, and more particularly, digital broadcast signal processing apparatus and method in which channel interference by an analog broadcast is prevented, for effectively removing an analog broadcast signal mixed in a digital broadcast signal of a co-channel, are provided. According to the above apparatus and method, a frequency offset is corrected by operating the frequency offset of a carrier signal and automatically performing fine tuning and the characteristic of an NTSC rejection filter (NRF) is improved by processing the signal whose frequency offset is corrected by the NRF. Accordingly, it is possible to effectively prevent a co-channel interference phenomenon by the analog broadcast from occurring when the digital broadcast signal is processed, to thus reduce noise.

Abstract: A digital television receiver converts very-high-frequency intermediate-frequency digital television signal to a band with uppermost frequency in the lower portion of the high-frequency range. This facilitates RLC analog filtering, such as a Butterworth-Thomson-transition filter or a bridged-T trap filter, being used for suppressing the frequency-modulated audio carrier of co-channel NTSC analog television signal prior to the digital television signal being synchrodyned to baseband for recovering symbol code. The delay distortion introduced by this analog filtering is compensated for in substantial part in surface-acoustic-wave bandpass filtering of the very-high-frequency intermediate-frequency digital television signals. Remnant delay distortion is reduced by channel equalization filtering carried out in the digital regime.

Abstract: A method and apparatus for detecting the presence of a co-channel interference signal and, in response to detecting such an interference signal, utilizing a co-channel interference rejection filter. Specifically, the present invention monitors the status information generated by the error detecting/correcting circuitry of a signal receiver such as a high definition television (HDTV) receiver. A counter is used to determine an error rate. While this first error rate is being determined, the filter is not used within the signal path of the receiver. The filter is then switched into the signal path of the receiver and a second error rate is determined. The first and second error rates are then compared and if the first error rate is the same or lower than the second error rate, the co-channel interference rejection filter is not utilized.

Abstract: The frequency-modulated sound carrier of any co-channel interfering NTSC television signal that accompanies multiple-level symbols in a digital receiver, such as a digital television receiver, is suppressed using a surface-acoustic-wave (SAW) filter in the intermediate-frequency (I-F) amplifier circuitry. This reduces data-slicing errors during symbol decoding and improves bit error rate (BER) during subsequent trellis decoding. When a comb filter is used before data slicing to reduce the energy of co-channel interfering NTSC television signal, the SAW filter in the I-F amplifier circuitry eases the filtering requirements on the comb filter such that only video components of co-channel interfering NTSC television signal need be suppressed.

Abstract: A modulation/demodulation receiver having a reference signal in a digital communication system. A method for signal processing and co-channel interference signal removal in the receiver includes the steps of processing an input signal to be at a predetermined multilevel, feeding the processed signal to an adaptive equalizer, determining the type of multilevel from the signal applied to the adaptive equalizer and selecting an operation mode from at least two multilevel operation modes, for the adaptive equalizer and blocks downstream from the adaptive equalizer, and causing the adaptive equalizer to adaptively equalize the signal at the predetermined multilevel in the selected operation mode and remove co-channel interference.

Abstract: A digital television receiver has an equalizer filter and demodulates received ATSC digital television signal to recover a baseband signal. The ATSC digital television signal is subject to being accompanied at times by a co-channel NTSC analog television signal, which gives rise to undesirable demodulation artifacts in the baseband signal. Data field synchronizing signals extracted from a prescribed plural number of successive data fields in the baseband signal are combined to generate a training signal for the equalizer. This prescribed number is to chosen to reduce the energy of the undesirable demodulation artifacts as compared to the energy of the extracted training signal. In a receiver for the digital television signal prescribed in the 1995 ATSC standard, the prescribed number is preferably six or a multiple thereof.

Abstract: A data slicer for use in a digital television signal receiver in a television set or in a digital video recorder includes digital filtering for suppressing artifacts of NTSC co-channel interference in the symbol coding offered for data slicing. The artifacts are suppressed by combining baseband symbol coding with predicted estimates of those artifacts. Data slicing results are fed back and combined with symbol coding to generate a revised estimate of error that would arise from unsuppressed artifacts of NTSC co-channel interference. This revised estimate of error that would arise from unsuppressed artifacts of NTSC co-channel interference is delayed, to be used as a predicted estimate of error that would arise from unsuppressed artifacts of NTSC co-channel interference in a later symbol epoch.

Abstract: In a radio receiver for digital transmissions, an adaptive channel equalizer is clocked at a sampling rate higher than symbol rate by a factor k and employs decision feedback for adjusting the coefficients of its component filters. The channel equalizer response as supplied at the sampling rate k times symbol rate is decimated to symbol rate and quantized to generate a signal estimating the symbols transmitted to the receiver. The channel equalizer response as supplied at the sampling rate k times symbol rate is compared to the signal estimating the transmitted symbols as re-sampled to the sampling rate k times symbol rate, in order to develop decision-feedback error signal at the sampling rate k times symbol rate. This decision-feedback error signal has sufficient digital bandwidth to permit fractionally spaced equalization with all coefficients being optimally adjusted.

Abstract: A method of estimating symbol timing phase and rate offsets of a sampled digitally modulated signal having repetitive symbol sync sequences includes the steps of estimating symbol sync sequence locations in a block of signal samples using a cross-correlation with a reference pattern of ideal symbol sync sequences. Signal samples within subranges defining the symbol sync sequences in the block of signal samples are filtered for removing intersymbol interference. An iterative process of cross-correlation of the filtered signal samples within the subranges using the reference pattern of ideal symbol sync sequences and an ideal symbol sync correction pattern generates timing phase and rate offset values that are used to derive filter coefficients for resampling the filtered signal samples within the subranges using an interpolating filter. The rate offset value is derived using a linear model and performing an optimal estimation.

Abstract: A method is proposed that is used for terrestrial transmission of at least one digital signal, in particular a digital radio and/or TV broadcasting signal. In this method, the at least one digital signal, reduced in its data quantity by coding, is modulated, preferably by the OFDM method, and converted into the frequency position of at least one channel, adjacent to at least one occupied or unoccupied channel (30, 32) for transmitting an analog TV broadcasting signal, and is broadcast in this frequency position. The dynamic scope and the amplitude of the spectrum (41) of the at least one digital signal must undershoot a respectively predetermined value that is markedly less than the dynamic scope or amplitude of the video carrier of the spectrum (35, 36) of the analog TV broadcasting signal, so that there will be only slight intermodulation and cross modulation with other digital signals or with analog signals of other channels.

Abstract: In a system for receiving a signal containing digital data representing HDTV image information in the form of multilevel symbols formatted into groups of successive fields, each field comprising a field segment, a plurality of data segments, and associated sync components, the received signal is demodulated to produce a demodulated signal. The demodulated signal is comb-filtered to reject NTSC co-channel interference to produce a filtered signal. The filtered signal is trellis decoded with a trellis decoder employing a recursive non-Euclidean metric.

Abstract: An electronic, programmable filter is disclosed which selectively removes interference, noise or distortion components from a frequency band without perturbing any of the other signals of the band. An input frequency band such as a television channel spectrum is initially demodulated to baseband and applied to the input of the filter. The baseband spectrum is combined in a complex mixer with a synthesized frequency signal that shifts the spectrum a characteristic amount, in the frequency domain, so as to position an interference component in the region about DC. Once shifted, the frequency components about DC are removed by DC canceler circuit and the resulting spectrum is mixed with a subsequent synthesized frequency signal which shifts the spectrum back to its original representation and baseband. The frequency signals are developed by a programmable frequency synthesizer which a user may program with an intelligence signal that defines the frequency location of an interference signal within the spectrum.

Abstract: A system and method for transmitting advanced television signals such as digital television signals. The system and method controls the frequency of the RF signal by compensating for errors in the signal received from a transport system. The system and method also reduces the complexity of the transmission system by inserting a pilot frequency signal after the television signal has been filtered and shaped.

Abstract: Interference and/or nonlinear distortions are reduced in a signal communicated from a transmitter to a receiver. To reduce interference, the transmitter is momentarily disrupted, during which time the receiver analyzes interference on the communication path to determine the frequency of at least one peak thereof. Information is communicated from the receiver to the transmitter identifying the frequencies of the interference peaks. Based on this information, the transmitter pre-distorts the signal to accentuate the signal magnitude at the identified frequencies. The pre-distorted signal is then communicated to the receiver, where it is filtered to attenuate the signal magnitude at the identified frequencies. An adaptive scheme periodically determines the interference peak frequencies. For nonlinear distortion cancellation (e.g., CSO/CTB), there is no need to disrupt the transmitter since the frequencies of the distortion are already known.

Abstract: A wide-band overlay sequence generator adds an overlay signal to a television signal which is transmitted through a channel. At a receiver, a replica of the transmitted overlay sequence is generated and synchronized to the overlay signal in the received signal. An adaptive equalizer filter effectively adjusts the received television signal so that the channel perturbations are removed from the signal.

Abstract: A system and method for controlling the frequency of a signal being transmitted wherein the frequency of the signal received at the transmitter site is error corrected before being broadcast. The error in the frequency may be developed and applied to the intermediate frequency upconversion and/or the channel upconversion to reduce or eliminate the effects of the error. In the system and method, a pilot frequency signal can be added to the signal to be broadcast after the signal to be broadcast has been shaped and filtered.

Abstract: An adjacent channel combiner combines an analog television channel with an upper adjacent digital television channel using practical filter designs. An aural signal of the analog television channel is combined after both a visual signal and a digital signal have been combined. A directional filter combines the visual and digital signals and a diplexer or other means is used for combining the aural signal with the combined visual and digital signal.

Abstract: A wireless communication system (100) is disclosed in which a central office (102) generates a signal. A first base station (104) receives the central office signal and transmits a first broadcast signal in a first frequency range in response to the central office signal. A second base station (124) receives the first broadcast signal and transmits a second broadcast signal in a second frequency range in response to the first broadcast signal. A third base station (134) receives the second broadcast signal and transmits a third broadcast signal in the first frequency range in response to the second broadcast signal. In accordance with the present invention, a plurality of base stations are each able to provide one-way or two-way communication to a plurality of customers (110, 130, 140), with only one base station (104) receiving signals directly from the central office (102).

Abstract: A co-channel interference canceler and a method thereof. The co-channel interference canceler comprises: a co-channel interference rejection filter for outputting a second signal by performing co-channel interference rejection filtering on a first signal including co-channel interference; a selection signal generator for generating a selection signal which selects the signal with less error by calculating the error of each of the first and second signals with respect to a reference signal; a selection corrector for outputting a corrected selection signal by correcting the selection signal such that a predetermined one of the first and second signals is selected in a predetermined error region; and a selector for selecting one of the first and second signals according to the corrected selection signal.

Abstract: A linear filter for use in 8 MHZ television broadcast systems is provided having a frequency response which includes a notch corresponding to a television picture carrier fpix, a notch corresponding to approximately a television color subcarrier fcs, and a notch corresponding to approximately a television sound carrier fs. Accordingly, the linear filter substantially reduces co-channel interference in a digital signal received by a digital television.

Abstract: An apparatus and method for determining co-channel interference in a DTV system is disclosed including a first comb filter filtering the received digital data including a data field signal; a pattern generating unit generating a reference sync signal from the data field signal; a second comb filter filtering the reference sync signal; a selection unit receiving either the digital data that passed or have not passed the first comb filter to output one of the data in response to a selection signal; a determination unit determining the presence of a co-channel interference; a first counting unit counting up/down a counted value in response to an output signal of the determination unit; and a second counting unit counting the reliability of the counted value output from the first counting unit, and providing the selection signal to the selection unit.

Abstract: A receiver including an NTSC rejection filter for eliminating interference signals from a high definition signal. The ratio of the energy of an expected high definition signal to the energy of an NTSC signal is determined. An NTSC signal sequence is generated according to the determined ratio. The number of filter taps is determined, and an autocorrelation matrix of the NTSC signal is calculated using the generated NTSC signal sequence. The power of all interference noise in the output of the NTSC rejection filter is used as a cost function, with respect to the input NTSC interference signal, the additive Gaussian noise and the VSB signal. A filter coefficient equation, for minimizing the cost function, is obtained by differentiation, and then the autocorrelation matrix is substituted for the equation, to calculate coefficients of the NTSC rejection filter.

Abstract: An electronic, programmable filter is disclosed which selectively removes interference, noise or distortion components from a frequency band without perturbing any of the other signals of the band. An input frequency band such as a television channel spectrum is initially demodulated to baseband and applied to the input of the filter. The baseband spectrum is combined in a complex mixer with a synthesized frequency signal that shifts the spectrum a characteristic amount, in the frequency domain, so as to position an interference component in the region about DC. Once shifted, the frequency components about DC are removed by DC canceler circuit and the resulting spectrum is mixed with a subsequent synthesized frequency signal which shifts the spectrum back to its original representation and baseband. The frequency signals are developed by a programmable frequency synthesizer which a user may program with an intelligence signal that defines the frequency location of an interference signal within the spectrum.

Abstract: A system detects the presence of NTSC co-channel interference and enables NTSC comb-filtering when the NTSC signal is detected. The system comb-filters the baseband signal to generate a filtered baseband signal, and accumulates the noise power of the baseband and filtered baseband signals. The noise power of the baseband and filtered baseband signals is compared by forming a difference between the two noise powers, and the system detects the NTSC signal when the difference exceeds a threshold T. The threshold T is related to a product of a signal power of the baseband signal and a minimum carrier to noise ratio for the ATSC system.

Abstract: A DTV signal receiver includes an adaptive channel equalization filter, a comb filter for suppressing artifacts of co-channel NTSC interference, and an intersymbol-interference suppression filter compensating for the intersymbol interference introduced by the comb filter. The adaptation of the equalization filter coefficients is done so as to be insensitive to the presence or absence of the artifacts of co-channel NTSC interference. This avoids the channel equalization filter attempting to compensate for the intersymbol interference introduced by the comb filter, which compensation could not be fully accomplished and would make the intersymbol interference in the comb filter unpredictable. The adaptation of the equalization filter coefficients is done so as not to affect the intersymbol interference introduced by the comb filter. Consequently, the intersymbol interference can be properly compensated for by the intersymbol-interference suppression filter.

Abstract: An ATV receiver is provided with a 16-state trellis decoder to achieve improved performance in the presence of NTSC co-channel interference. In one embodiment, the ATV receiver comprises a tuner, a comb filter, and a trellis decoder. The tuner is configured to downmix a selected channel frequency signal to an intermediate frequency signal, where the comb filter is configurable to screen out most of the NTSC co-channel interference. The intermediate frequency receive signal is modified by the comb filter to resemble a partial response signal. The trellis decoder the demodulates the partial response signal in an improved fashion taking into account the state of the trellis encoder and the partial response channel. The trellis decoder may have a 16 state trellis comprised of four 4-state butterflies wherein each edge in the trellis is a single transition.

Abstract: A method and apparatus are provided for allowing two different television signals to be combined and sent to a common propagation device, such as a tower antenna. The apparatus utilizes a number of appropriately loaded hybrids, hybrid waveguide junctions, or other appropriate equivalent devices to combine the signals in such manner that there is a minimum of intersignal interference or distortion. The apparatus utilizes bandpass/reject filters and notch filters in conjunction with the hybrids to achieve the desired results. A television broadcast system using the hybrid combining apparatus is also provided.

Abstract: An N-level digitally encoded signal at a symbol rate fs substantially equal to three times the NTSC color subcarrier frequency, N being a plural integer, modulates a carrier signal of a frequency within a few hundred kilocycles of the NTSC audio carrier, for transmission through a channel subject at times to the presence of a co-channel NTSC analog television signal. The modulation is suppressed-carrier amplitude-modulation generating first and second amplitude-modulation sidebands. Any portion of the amplitude-modulation sidebands extending outside the channel is suppressed in the transmitted signal, thereby making the first amplitude-modulation sideband a vestigial sideband providing an image for only a portion of the second amplitude-modulation sideband closer in frequency to the carrier signal.

Abstract: A digital receiver (e.g., an ATV or HDTV receiver) which receives digital signals (e.g., ATV or HDTV signals), and which includes an equalizer for equalizing multipath channels having known co-channel interference (e.g., co-channel NTSC interference) present therein. A co-channel interference rejection filter is inserted in the digital receiver upstream of the equalizer, and the equalizer is modified in such a manner that it will not attempt to equalize the co-channel interference. Thus, co-channel interference cancellation is done primarily by the rejection filter, while multipath equalization (correction) is the exclusive function of the equalizer. This leads to better co-channel performance than that which can be obtained by relying on the equalizer alone to perform both functions. The co-channel interference rejection filter is preferably a multi-tap filter having fixed filter coefficients which are designed to optimize cancellation of the known co-channel interference.

Abstract: A color system determination circuit for use with an input video signal having a frequency component is disclosed. The circuit includes a color trap filter for attenuating the frequency component in the input video signal with the color trap filter providing a color burst output signal, a comparator for comparing the color burst output signal of the color trap filter and the frequency component of the input video signal, a maximum value detector which receives the color burst output signal of the color trap filter and a color burst sampling signal and detects a maximum value of the color burst output signal of the color trap filter during a period of the color burst sampling signal, and another maximum value detector which receives the video signal and the color burst sampling signal and detects a maximum value of the video signal during the period of the color burst sampling signal.

Abstract: Apparatus and method are provided by which television signals may be transmitted from adjacent NTSC and DTV channels. The NTSC television signals for a first channel are selected from a frequency band including a plurality of channels and wherein this first channel includes NTSC aural and NTSC visual signals. A source of DTV television signals are selected for a second channel in the same frequency band and wherein the second channel is adjacent the first channel. The NTSC visual signal and the DTV signal are combined to provide an intermediate combined signal. The intermediate combined signal and the NTSC aural signal are then combined to provide a combined output signal for application to antenna means for transmitting television signals.

Abstract: A co-channel interference canceler having a co-channel interference rejection filter and a driving method therefor are provided. The co-channel interference canceler is driven for removing co-channel interference of an NTSC signal existing in a co-channel on receiving of an HDTV signal. In doing so, an error rate of a direct signal path which does not pass the rejection filter and an error rate of a signal path passed through the rejection filter are compared. That is, the error rates, obtained for a predetermined period for each path, are compared using a reference signal, to output a driving signal for selecting the path having the smaller error rate. The error rate is obtained by integrating the number of symbol errors between the reference signal and each path signal. Therefore, the driving of the co-channel interference canceler is controlled according to the driving signal based on the error rate, thereby giving simple circuit structure and increased reliability.

Abstract: An MPEG-2 transport stream packet detection device includes a controller for generating a detection start control signal and a series/parallel output control signal, and a sync detector for detecting an MPEG-2 transport stream packet sync from MPEG-2 transport stream data transmitted from the network according to the detection start signal from the controller, and a packet counter for counting a predetermined number of bytes according to a sync detection signal from the sync detector and sending a packet reception completion signal to the sync detector when finishing counting the predetermined number of bytes during a declaration of the detection signal, and a bit counter for counting a predetermined number of bits according to the sync detection signal from the sync detector and generating a signal for converting series data to parallel data when finishing counting the bits during the declaration of the detection signal, and a buffer for converting the series data and clock from the sync detector into parall

Abstract: A method and device are provided for reducing RF transmission interference to a wanted signal of an interactive TV network which is impaired by an interfering signal present on a terrestrial and satellite RF network. The wanted signal is received in the presence of the interfering signal so as to obtain a received wanted signal in the presence of the interferer. The interfering signal transmitted by the satellite network is duplicated and delayed so as to obtain a received interfering signal similar to the interfering signal present with the wanted signal. The received interfering signal is subtracted from the wanted signal in the presence of the interfering signal, so as to deliver a received wanted signal free of interfering signal.

Abstract: A first comb filter differentially combines an I- or Q-channel baseband signal supplied as input signal to a co-channel NTSC interference detector for a DTV receiver with that signal as subjected to a first amount of differential delay. This generates a first comb filter response in which artifacts arising from synchronous detection of the co-channel interfering analog television signal are suppressed. The detector includes a second comb filter that combines the input signal with that signal as subjected to a second amount of differential delay to generate a second comb filter response in which artifacts of the co-channel interference are reinforced. The first and second comb filters both use the same type of linear combiner so the direct term of input signal is treated similarly in the first comb filter response and in the second comb filter response. First and second amplitude detectors detect the respective amplitudes of these comb filter responses.

Abstract: A digital television receiver includes a filter for minimizing NTSC interference with a received signal having a constant symbol rate. An equalizer has two one symbol delays for each tap. A filtered and a non-filtered version of the received signal are applied to a multiplexer at the input of the equalizer, which is operated at twice the symbol rate. The outputs of the multipliers in the equalizer are combined and applied to a demultiplexer. The filtered and non-filtered equalized signals are compared and a selection as to which of the filtered or non-filtered received signals is to be processed is made based upon the comparison.

Abstract: NTSC interference detectors include an NTSC extracting filter for supplying an NTSC extracting filter response that separates accompanying co-channel interfering NTSC signal component from the received I-channel baseband signal and its direct bias component. The NTSC extracting filter comprises a comb filter, which includes a delay circuit for supplying in response to said received I-channel baseband signal differentially delayed signals with a prescribed amount of differential delay equal to the duration of an even number of horizontal scanning periods of NTSC signal as will generate said co-channel interfering NTSC signal components. The comb filter further includes a subtractor for differentially combining the differentially delayed signals to generate the comb filter response.

Abstract: Within a desired service area, multiple transmitters at separately located sites simultaneously broadcast the same multi-channel, multi-program signal. Broadcast waves from the transmitters propagate substantially throughout the service area and overlap in a substantial portion of the area. The signals are broadcast as spread spectrum signals and the receivers include despreaders with rake capabilities to obtain enhanced output signals with multi-path reception. In the preferred implementation, the channels are 6 MHz wide channels broadcast in the super high frequency microwave portion of the spectrum. Each such channel carries a multiplexed digital data stream containing packets of information for a plurality of programs, e.g., television programs.

Abstract: Co-channel interference accompanying multiple-level symbols in a digital receiver, such as a digital television receiver, is suppressed by using a first comb filter to reduce the energy of the co-channel interference before data slicing. The first comb filter incidentally carries out a symbol re-coding procedure of first type that introduces error into the symbol decoding results generated by the data slicing. A second comb filter carries out a symbol re-coding procedure of second type after the data slicing is completed, to compensate for intersymbol error introduced by the symbol re-coding procedure of first type and generate corrected symbol decoding results. The symbol re-coding procedure of first type re-codes an input symbol stream through differential delay and first linear combination of the differentially delayed terms.

Abstract: A television signal transmission signal comprises a suppressed carrier, VSB signal having respective Nyquist slopes at the lower and upper edges of a 6 MHz television channel, the center frequency of the Nyquist slope at the lower edge of the channel being substantially coincident with the frequency of the suppressed carrier, and a pilot signal in quadrature relation with the suppressed carrier. The suppressed carrier is modulated by an N-level digitally encoded signal having a sample rate fs substantially equal to three times the NTSC color subcarrier frequency, with the frequency of the color subcarrier being less than the co-channel NTSC picture carrier by an amount equal to about fs/12. The received signal is demodulated by a synchronous detector in response to the received pilot signal and interfering NTSC beat components are attenuated by a linear filter having notches at fs/12, 5fs/12 and fs/2.