Abstract: In a superheterodyne radio receiver designed for DTV reception, the IF amplifier chain for the VSB data modulation includes filtering having selective response to different portions of a received DTV signal, as translated to intermediate frequencies by a first detector. There is automatic fine tuning of a local oscillator included in the first detector to assure that the received DTV signal, as translated to intermediate frequencies by the first detector, is in proper alignment with the filtering having selective response to different portions of the received DTV signal. The bandpass filter used for extracting the frequencies near DTV carrier frequency for application to the AFT detector has a tilted amplitude response in passband that compensates for the roll-off of the DTV signal through the carrier region.

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 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 bandpass tracking demodulator for digital radio signals, such as DTV signals, provides an in-phase baseband demodulation result which is subjected to equalization and ghost-cancellation filtering before symbol decoding. The bandpass tracking demodulator also provides a quadrature-phase baseband demodulation result, which is processed to provide automatic frequency and phase control (AFPC) signal to a local oscillator used in downconverting the digital radio signal to the intermediate-frequency signal that is subsequently demodulated. Multi-path distortion of the in-phase baseband demodulation result is reduced by subjecting the quadrature-phase baseband demodulation result to equalization and ghost-cancellation filtering similar to that the in-phase baseband demodulation result is subjected to.

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 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 radio receiver includes first and second intermediate-frequency amplifier chains respectively supplying first and second final intermediate-frequency responses to a digital television (DTV) signal selected for reception; first and second analog-to-digital converters for digitizing the first and second final intermediate-frequency responses; QAM synchrodyning circuitry for generating real and imaginary sample streams of interleaved QAM symbol code by synchrodyning the digitized first final intermediate-frequency response to baseband, providing the selected DTV signal is a QAM signal; and VSB synchrodyning circuitry for generating a real sample stream of interleaved VSB symbol code by synchrodyning the digitized second final intermediate-frequency response to baseband, providing the selected DTV signal is a VSB signal. The first and second intermediate-frequency amplifier chains share at least one local oscillator.

Abstract: A radio receiver uses the same tuner for receiving a selected digital television (DTV) signal, irrespective of whether it is a quadrature-amplitude-modulation (QAM) or a vestigial sideband (VSB) signal. The tuner supplies a final IF signal in a 6-MHz-wide frequency band, the lowest frequency of which is not appreciably more than 2.69 MHz. The final IF signal is digitized at a rate that is a multiple of both the symbol frequencies of the QAM and VSB signals, for synchrodyning to baseband, with the 2.69 MHz difference between the carrier frequencies of QAM and VSB signals being taken into account in the digital synchrodyning circuitry. The carrier frequencies of the QAM and VSB final IF signals are regulated to be submultiples of the multiple of both the symbol frequencies of the QAM and VSB signals by applying automatic frequency and phase control signals developed in the digital circuitry to a local oscillator of the tuner.

Abstract: Television signal reception apparatus for receiving a television signal selected from among transmitted television signals of different types includes a respective receiver portion for each of the different types. Responsive to its respective type of television signal being received, each receiver portion supplies digitized baseband signal to adaptive digital filter circuitry shared by each receiver portion. The adaptive digital filter circuitry is operated for suppressing ghosts in that digitized baseband signal.

Abstract: During the reception of VSB DTV signal, the channel equalizer for a QAM/VSB DTV signal receiver the equalizer is operated to equalize only the real sample stream of VSB symbol code, rather than being operated as a complex equalizer. During the reception of QAM DTV signal, the real sample stream of QAM symbol code and the imaginary sample stream of QAM symbol code are time-division-multiplexed together on an alternate sample basis to generate input signal for the channel equalizer, which is operated as a dual-phase filter. After equalization, the time-division-multiplexed real and imaginary samples of QAM symbol code are de-multiplexed to recover parallel real and imaginary sample streams of QAM symbol code that are independent of each other, but have been subjected to similar equalization. Supposing that the QAM DTV symbol code rate is half the VSB DTV symbol code rate, the minimum sampling rate for operation of the channel equalizer is the same for both types of symbol code.

Abstract: Plural-conversion radio receivers for receiving DTV signals, in accordance with the Advanced Television Systems Committee (ATSC) standard, or analog TV, in accordance with the National Television Sub-Committee (NTSC) standard, utilize a first intermediate-frequency band spanning 917-923 MHz and a second intermediate-frequency band spanning 35.5-41.5 MHz. A local oscillator generates local oscillations at 958.5 MHz for mixing with signal in the first intermediate-frequency band to generate signal in the second intermediate-frequency band. These local oscillations do not interfere with the aeronautical navigation band or with channel 81 television broadcasting. The second harmonic of sound carrier in the second intermediate-frequency band falls below the 88-108 MHz FM broadcast band.

Abstract: Television signal reception apparatus for receiving a television signal selected from among transmitted television signals of different types includes a respective receiver portion for each of the different types. The current reception or non-reception of NTSC signal is detected by ascertaining whether or not 4.5 MHz intercarrier sound intermediate-frequency signal is generated in the receiver portion used for NTSC signal reception. When reception of NTSC signal is detected, the television signal reception apparatus is automatically conditioned for selecting the demodulated NTSC signal for further processing.

Abstract: The tuner in a digital TV receiver converts received signal to a penultimate intermediate-frequency signal. Penultimate local oscillations are supplied in a first phasing and in a second phasing in quadrature therewith, for heterodyning with the penultimate IF signal in first and second mixers respectively to generate real and imaginary components of an ultimate intermediate-frequency signal. The first and second mixers are of a switching type, switching in respective response to the penultimate local oscillations as supplied in first and in second phasing. First analog-to-digital conversion circuitry containing a number N of analog-to-digital converters digitizes the real component of the ultimate IF signal on an N-phase basis, N being at least one. Second analog-to-digital conversion circuitry, which contains a number N of analog-to-digital converters, digitizes the imaginary component of the ultimate IF signal on an N-phase basis.

Abstract: Training signal for channel equalization is located in the initial data segment of each DTV data field or in the nineteenth scan line of each NTSC field. The training signal comprises a pseudo-random noise sequence near the conclusion of the initial data segment of each DTV data field or the nineteenth scan line of each NTSC field and an earlier pseudo-random noise sequence. The later pseudo-random noise sequence is used in a television receiver for detecting pre-ghosts and the earlier pseudo-random noise sequence is used in a television receiver for detecting post-ghosts.

Abstract: A system for reproducing a luminance signal from a medium containing a previously recorded luminance signal with a high-frequency portion thereof compressed in dynamic range includes a circuit for recovering that luminance signal from the medium. Filtering is done to separate the low-frequency and compressed-in-dynamic-range high-frequency portions of the recovered luminance signal from each other. A corer responds to the separated compressed-in-dynamic-range high-frequency portion of the recovered luminance signal to provide a cored high-frequency portion with expanded dynamic range and reduced noise.

Abstract: Radio receivers for receiving DTV signals, in accordance with the Advanced Television Systems Committee (ATSC) standard, or analog TV, in accordance with the National Television Sub-Committee (NTSC) standard, each use a single first detector for both types of signal. This single first detector supplies its output signals to an intermediate-frequency amplifier chain for DTV signals and to another intermediate-frequency amplifier chain for analog TV signals. The response of the intermediate-frequency amplifier chain for DTV signals is synchrodyned to baseband and supplied to symbol decoding circuitry. The response of the intermediate-frequency amplifier chain for analog TV signals is supplied to a video detector. In some of the radio receivers the sound carrier of the NTSC signal has a separate, further intermediate-frequency amplifier chain. The intermediate-frequency chain for DTV signals comprises an intitial portion which has reverse AGC, a following mixer, and a final portion which also has reverse AGC.

Abstract: A radio receiver uses the same tuner for receiving a selected digital television (DTV) signal, irrespective of whether it is a quadrature-amplitude-modulation (QAM) or a vestigial sideband (VSB) signal. The final IF signal is digitized at a rate that is a multiple of both the symbol frequencies of the QAM and VSB signals, for synchrodyning to baseband. The carrier frequencies of the QAM and VSB final IF signals are regulated to be submultiples of the multiple of both the symbol frequencies of the QAM and VSB signals by applying automatic frequency and phase control (AFPC) signals developed in the digital circuitry to a local oscillator of the tuner. Baseband DTV signals obtained by synchrodyning the final IF signals have a sample rate higher than symbol rate to facilitate symbol synchronization. The baseband DTV signals are decimated to symbol rate before performing channel equalization to reduce the number of multipliers required in the channel equalization filter.

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.