Abstract: A digital television signal receiver in a television set or in a digital video recorder digitizes received digital television signal as converted in frequency to a final intermediate-frequency band close to baseband, then performs equalization filtering on the digitized signal before demodulating it in the digital regime to regenerate baseband symbol coding. The equalization filtering is adaptive, and weighting coefficients for this filtering are adjusted in response to portions of the regenerated baseband symbol coding. Initial adjustment of the weighting coefficients is preferably done using selected portions of the data field synchronizing signal as a ghost cancellation reference signal, in order that convergence of the weighting coefficients to desired values proceeds more rapidly.

Abstract: An outdoor battery cabinet is formed to include a cooling system to extend the life of the housed batteries. The cooling system comprises a ventilation system including an air intake unit, an exhaust unit and a thermostat control. The interior surface of the cabinet is covered with a layer of insulative material. The ventilation system is configured to turn "on" when the outdoor temperature drops below the interior cabinet temperature, thereby cooling the housed batteries. Once the outdoor temperature rises above the cabinet temperature, the ventilation system is turned "off" and the insulation in the cabinet functions to maintain the cooler ambient temperature within the cabinet. To minimize the effects of wind forcing air through the ventilation openings, the intake and exhaust louvers are located on the same side of the cabinet.

Abstract: Training signal for channel equalization is located in the initial data segment of each DTV data field and in the nineteenth scan line of each NTSC field. Arranging for training signal separated from plural PN sequences near the beginnings of the initial data segments of DTV data fields improves post-ghost detection capability in the DTV system. In receivers for receiving NTSC signals and DTV signals, arranging for training signal to be separated from plural PN sequences near the beginnings of the nineteenth scan line of each NTSC field facilitates the same ghost-cancellation and channel-equalization filtering being used both during the reception of NTSC signals and during the reception of DTV signals.

Abstract: A radio receiver for receiving a selected DTV signal that can be a quadrature-amplitude-modulation (QAM) signal or a vestigial sideband (VSB) signal synchrodynes the received signal to baseband and supplies the baseband signal to an adaptive equalizer. The presence of the pilot carrier accompanying a selected VSB DTV signal is detected for automatically switching the radio receiver for operation in a VSB signal reception mode, in which operating mode the adaptive equalizer is conditioned to respond to training signals included in the initial data segment of each data field of the VSB signal. The absence of pilot carrier accompanying a selected QAM DTV signal is detected for automatically switching the radio receiver for operation in a QAM signal reception mode, in which operating mode the adaptive equalizer is conditioned to operate without relying on the training signals included in the VSB signal.

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 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: Digital HDTV signals are exemplary of vestigial sideband (VSB) signals, which signals include a pilot carrier and sidebands generated in response to symbol codes descriptive of digital signals. A radio receiver for such VSB signals includes automatic gain control (AGC) circuitry that generates AGC signal by synchronously detecting the pilot carrier.

Abstract: In a radio receiver for receiving vestigial sideband (VSB) signals including symbol codes descriptive of digital signals, HDTV signals being exemplary of such VSB signals, a tuner provides for selecting one of channels at different locations in a frequency band used for transmitting such VSB signals. The tuner also includes mixers for performing plural conversion of the selected channel to a final intermediate-frequency (IF) signal, which is digitized by an analog-to-digital converter. The pilot carrier is detected by a narrowband quadrature-phase synchronous detector operative in the digital regime, for controlling the frequency and phase of the local oscillations applied to one of the mixers in the tuner so that the pilot carrier component of the final IF signal is locked to a submultiple of symbol frequency. The fullband final IF signal is synchronously detected by an in-phase synchronous detector to detect symbol codes.

Abstract: A first composite video signal may include attendant ghosts and sometimes includes in a prescribed L.sup.th line of each field during the vertical blanking interval one of a cycle of M ghost-canceling reference (GCR) signals of prescribed magnitude and respective phasing. Filter circuitry generates a second composite video signal in response to the first composite video signal, which is adjusted in response to filter programming signals generated by a computer storing a ghost-free GCR signal. The computer receives a GCR signal with attendant ghosts and compares it to the stored ghost-free GCR signal, thereby carrying out correlation procedures for calculating the filter programming signals. The second composite video signal is a response to the first composite video signal in which the attendant ghosts are lessened.

Abstract: In a radio receiver for receiving vestigial sideband (VSB) signals including symbol codes descriptive of digital signals, HDTV signals being exemplary of such VSB signals, a tuner provides for selecting one of channels at different locations in a frequency band used for transmitting such VSB signals. The tuner also includes mixers for performing plural conversion of the selected channel to a final intermediate-frequency signal, which is digitized by an analog-to-digital converter. A phase tracker, operative on narrow-bandpass filtered portions of the digitized final intermediate frequency signal centering on its carrier frequency, suppresses an imaginary portion of the final intermediate-frequency signal, arising from multipath distortion or from phase incoherency in local oscillations used during frequency conversion.

Abstract: Composite video signal and a relatively low power phase-shift-keyed (PSK) signal encoding digital information are transmitted on respective phases of a video carrier in quadrature with each other. Selected scan lines of the composite video signal contain ghost-cancellation reference (GCR) signals. A digital signal receiver performs a first detection of the video carrier modulated in the two phases, down-converting to an intermediate-frequency (IF) signal. This IF signal is selectively amplified prior to respective second detection of the down-converted video carrier by in-phase and quadrature-phase synchronous video detectors. A first cascade filter connection of a first ghost-cancellation filter and a first equalization filter follows the in-phase video detector, and a second cascade filter connection of a second ghost-cancellation filter and a second equalization filter follows the quadrature-phase video detector.

Abstract: A radio receiver for receiving a selected digital HDTV signal, irrespective of whether it is a complex-amplitude-modulation (QAM) or a vestigial sideband (VSB) signal, using the same tuner. The final IF signal from the tuner is digitized for application to in-phase and quadrature QAM synchronous detectors and to in-phase and quadrature VSB synchronous detectors. The carrier frequencies of the QAM and VSB final IF signals are regulated to be submultiples of symbol frequency by applying automatic frequency and phase control signals developed in the digital circuitry to a local oscillator of the tuner. The mean average energy in the output samples of the quadrature VSB synchronous detector is sensed for automatically switching the radio receiver reception mode, for operation in a VSB HDTV signal reception mode when the mean average energy is below a threshold level, and for operation in a QAM signal reception mode when the mean average energy is not below the threshold level.

Abstract: A frequency-multiplexed video signal is generated in which a color-under signal and a second under signal are linearly combined with at least partially overlapping frequency spectra to form a composite under signal for an FM luma signal. The frequency-multiplexed video signal is suited for recording on magnetic tape using helical scanning methods and for being played back from the magnetic tape using helical scanning methods. The second under signal is generated in such way that line-comb filtering can be used during playback to separate color-under signal and second under signal each from the composite signal despite their frequency spectra being at least partially overlapping in the composite signal.

Abstract: A ghost canceling reference signal transmission and reception system utilizes a ghost canceling reference signal including a zero to seventy IRE step followed by a seventy to zero IRE (sin x)/x step.

Abstract: In a radio receiver for receiving vestigial sideband (VSB) signals including symbol codes descriptive of digital signals, HDTV signals being exemplary of such VSB signals, a tuner provides for selecting one of channels at different locations in a frequency band used for transmitting such VSB signals. The tuner also includes mixers for performing plural conversion of the selected channel to a final intermediate-frequency signal, which is digitized by an analog-to-digital converter. A phase tracker, operative on narrow-bandpass filtered portions of the digitized final intermediate-frequency signal centering on its carrier frequency, suppresses an imaginary portion of the final intermediate-frequency signal, arising from multipath distortion or from phase incoherency in local oscillations used during frequency conversion.

Abstract: A relatively low power phase-shift-keyed (PSK) subcarrier encoding digital information is admixed with composite video signal. The PSK subcarrier is at an odd multiple of half the scan line frequency of the composite video signal, and the symbol rate is at a multiple of the scan line frequency. The PSK subcarrier modulates the amplitude of a suppressed carrier which is the same frequency as the video carrier for the composite video signal and preferably is in quadrature phasing therewith. To reduce evidence of the PSK subcarrier in television picture generated from that composite video signal, the PSK subcarrier is interrupted after each of periods of one frame duration and repeated in anti-phase during the next period of one frame duration. This also provides a basis for separating the PSK subcarrier from static luminance signal components by bandpass frame-comb filtering.

Abstract: A new technique for channel characterization for Advanced Compatible TV (ACTV) broadcasting systems is hereby proposed that conforms to the current practice of transmitting a ghost cancellation reference (GCR) signal during the vertical blanking interval (VBI). A copy of the GCR signal is stored at the receiver, and is used to extract the effective ghost channel parameters via digital signal processing techniques. A pair of equi-length, binary (.+-.) sequences is said to be complementary if the sum of the linear autocorrelation functions of the sequences is identically zero for all shifts other than zero, and provides a high correlation gain at zero shift. Such sequences can be sequentially transmitted on the allotted VBI line in the appropriate fields, along with pairwise constant signals in the corresponding fields of a basic eighth field sequence. To conform to the positivity constraint of the transmitted signal for NTSC compatible systems, each complementary sequence is transmitted on a pedestal.

Abstract: A ghost-canceling reference signal for inclusion in a television signal is provided by cyclically inserting ones of extended-length complementary-sequence pairs into a prescribed scan line in each of the vertical blanking intervals of successive fields of the television signal. By definition, a pair of binary (.+-.1) sequences of similar length to each other are complementary sequences only if the sum of the linear autocorrelation functions of the sequences is identically zero for all shifts other than zero but provides a high correlation gain at zero shift.

Abstract: Ghosts accompanying composite video signals are suppressed using separate filters for suppressing macroghosts and microghosts, the filtering parameters of these filters being adjustable responsive to digital programming signals generated by a computer. Computation includes data acquisition and channel characterization steps followed by a decision step for comparing the most recent set of channel characterization results with the next most recent set to determine whether stable ghosting conditions obtain. Data acquisition and channel characterization steps are repeated until stable ghosting conditions obtain, so the subsequent calculations with respect to the filter used for suppressing macroghosts are accurately performed. Where the filter suppressing macroghosts includes IIR and FIR sections for suppressing post-ghosts and preghosts, respectively, these calculations are carried out substantially on a separable basis, simplifying the calculations.

Abstract: Noise estimation circuitry for estimating the noise in a small number of horizontal scanning lines of a video signal includes a lowpass line comb filter responding to said video signal, but not to chrominance-descriptive components thereof. The video signal free from chrominance-descriptive components is repeatedly sampled during the backporch interval of each horizontal scanning line, and the samples are accumulated to generate a revised noise estimate each successive horizontal scanning line.