Abstract: An encoder-modulator for coupling a digital baseband television signal to a VSB digital television receiver that includes filters, equalization circuitry, and forward error correction circuitry for correcting signal impairments that are below a given threshold. The encoder-modulator processes the baseband signal for low power transmission on an RF channel with less-than-nominal bandpass characteristics. A coaxial cable or other low noise communication link directly connects the RF signal to the RF input of the television receiver. Any errors or signal impairments in the transmitted signal that are below the predetermined threshold are corrected by the filters and equalization circuitry built into the VSB digital television receiver.

Abstract: An analog television is digitally enabled so that both analog video received in an analog broadcast signal and data received in data packets of a digital broadcast signal can be displayed on the same display. The analog television is digitally enabled by including digital television tuning and demodulation equipment either in the cabinet of the analog television or in a set top box coupled to the analog television.

Abstract: A transmitter transmits, and a receiver receives, a data frame is transmitted into an 8 MHZ channel. The data frame contains a plurality of data segments, where each of the data segments contain DS symbols. The DS symbols include data symbols, priming symbols, and segment synchronization symbols. The transmitter trellis encodes the data symbols, priming symbols, and segment synchronization symbols. The receiver trellis decodes the 10 data symbols, priming symbols, and segment synchronization symbols. The data frame also contains a mode control ID which the receiver uses in trellis decoding the data symbols, priming symbols, and segment synchronization symbols.

Abstract: In a reduced memory MPEG decoder, drift caused by the application of ½ pixel resolution motion vectors during prediction filtering is reduced. Received P and B frame and field DCT coded blocks are down converted. Reference pixels are selected based upon a received motion vector. The selected reference pixels are prediction filtered in order to produce a prediction output. If the motion vector is a ½ pixel resolution motion vector, a drift compensation value is added to the prediction output. Then, the prediction output is added to the down converted P and B frame and field DCT coded blocks in order to form lower resolution reconstructed pixel blocks.

Abstract: A downsampling apparatus converts a received DCT coefficient macroblock to a reconstructed pixel block and includes an IDCT module that performs an inverse DCT on the received DCT coefficient macroblock to produce a first intermediate block. A horizontal downsampler horizontally downsamples the first intermediate block to produce a second intermediate block. A calculation module calculates first and second errors. The first and second errors are calculated based upon a difference between the first intermediate block and first and second downsampled/upsampled versions of the first intermediate block derived from corresponding first and second vertical downsampling filters. A filtering module vertically downsamples the second intermediate block using the first or second vertical downsampling filter depending upon whether the first or second error is smaller. A motion compensator adds prediction reference pixels to the horizontally and vertically downsampled block, as appropriate, to form reconstructed pixels.

Abstract: A transmitter transmits, and a receiver receives, a data frame is transmitted into an 8 MHZ channel. The data frame contains a plurality of data segments, where each of the data segments contain DS symbols. The DS symbols include data symbols, priming symbols, and segment synchronization symbols. The transmitter trellis encodes the data symbols, priming symbols, and segment synchronization symbols. The receiver trellis decodes the data symbols, priming symbols, and segment synchronization symbols. The data frame also contains a mode control ID which the receiver uses in trellis decoding the data symbols, priming symbols, and segment synchronization symbols.

Abstract: A switchable filter for passing one of a plurality of frequency bands has n bandpass filter sections coupled in parallel between a filter input terminal and a filter output terminal. Each of the n bandpass filter sections is arranged to pass a different frequency band. Each of n switches is coupled to a respective one of the n bandpass filter sections, and each of the n switches is operable in either an OFF state for activating a corresponding one of the n bandpass filter sections or an ON state for deactivating the corresponding one of the n bandpass filter sections. The n switches are arranged and controlled so that, when any one of then switches is operated to its off state, the remaining n−1 switches are operated to their ON states and form a series circuit for conducting a common current.

Abstract: A circuit for developing correction signals for on-line controlling a precorrection arrangement in an HDTV 8VSB digital signal transmitter. The transmitted signal is sampled, sorted, smoothed and sliced to determine the symbol amplitude levels of the transmitted multilevel symbols. The centers of the sliced clusters of sampled symbol levels are used to determine the symbol amplitude levels. Correction signals for compensating the precorrection arrangement are developed based upon the determined symbol levels and the known symbol levels.

Abstract: A receiver receives a signal containing data distributed in both time and frequency. The receiver includes a vector transform arranged to perform a transform on the received signal using a plurality of receiver transform vectors. The receiver transform vectors are based upon a corresponding plurality of transmitter vectors modified in accordance with channel effects so that the data can be recovered by the vector transform even in the presence of strong ghosts.

Abstract: A video projector is arranged with three color CRTs vertically aligned with respect to a forwardly located projection surface. The projection surface is in a room having opposite side walls on either side of said projection surface. The video projector is positioned closely adjacent either of said side walls, thus leaving the ceiling and floor areas of the room unobstructed. The arrangement facilitates non intrusive use of a video projector in a home environment.

Abstract: A television receiver includes a tuner for receiving either analog or digital signals. Separate analog and digital demodulators are selectively coupled to the tuner through an RF switch that is controlled by the signal from a sync detector in the output of the analog demodulator. The selected one of the demodulators develops an AGC signal that is coupled to the tuner through a current mirror. Operating potential for the demodulators is coupled through the RF switch so that the oscillator in the non-selected demodulator is disabled and precluded from interfering with the oscillator in the enabled demodulator.

Abstract: A method for selecting a next available identifier. A plurality of unique identifiers are assigned, preferably in blocks, to each of a plurality of banks. Within each of the banks, when empty, there is one available minimum value identifier and one available maximum value identifier. A number of resident identifiers are counted in each of the banks and at least one bank having a lowest counted number is identified. Within the first available bank, a highest value of all resident identifiers is determined. In the first available bank, the highest value is compared to a maximum value. If the highest value is less than the maximum value, then the next available identifier is equal to a sum of the highest value plus an incremental value. When a check bank counter is set at a value or when the next available unique identifier is a value outside of a range of the corresponding bank, the next available bank is selected and an iteration process begins in the next available bank.

Abstract: Circuits for removing clock related artifacts in an offset QAM generated VSB signal includes a transmitter arrangement and a receiver arrangement. In the transmitter, a detector detects the artifacts and a correlator determines whether the artifacts repeat over two symbols or over four symbols. A signal indicative of the artifacts is used to control processing circuits for adjusting the ratios and levels of the I and Q signal components of the QAM signal for substantially eliminating the artifacts. In the receiver, the received VSB signal is divided into four parallel signals. Each parallel signal is processed to develop an average symbol level that is subtracted before the parallel signals are recombined. The four symbol repeat rate artifacts reflect a DC offset of the VSB signal symbols, which are both positive-going and negative-going and which therefore average to zero for random signals. Averaging is done over N symbols where N is a power of 2.

Abstract: A television receiver includes a tuner for receiving either analog or digital signals. Separate analog and digital demodulators are selectively coupled to the tuner through an RF switch that is controlled by a sync detector in the output of the analog demodulator. The selected one of the demodulators develops an AGC signal that is coupled to the tuner through the RF switch. In one embodiment, a two pole RF switch is used with one pole switching the IF signal and the other pole switching the AGC signal In another embodiment, a single pole RF switch is used with the tuner signal and the AGC signal being multiplexed through the switch. This is accomplished by the provision of a high frequency path and a low frequency path between each of the RF switch and the tuner, the RF switch and the analog demodulator, and the RF switch and the digital demodulator.

Abstract: A fastener for removably attaching a speaker grill to a cabinet includes a head having a pair of outwardly directed wings that have inwardly directed ramps at their bottoms to aid in disengaging the speaker grille receptacle from the fastener. A pair of angled abutments beneath the head are arranged to sandwich the receptacle between the abutments and the ramps to provide a secure, yet readily removable, grill. The tree-like base of the fastener includes a plurality of resilient branches for frictionally engaging the inner surface of an aperture in a wood or wood composition cabinet. The end of the base includes a pair of resilient wings that expand to engage the bottom of an aperture in a plastic cabinet.

Abstract: A receiver receives a received signal containing a pilot up chirp and a pilot down chirp. The pilot up chirp has a frequency which increases from a time reference zero to a time reference tN, and the pilot down chirp has a frequency which decreases from the time reference tN to a time reference 2ttN. A sampler of the receiver is arranged to sample the received signal. A detector is arranged to correlate the received signal samples with a reference up chirp and a reference down chirp. The reference up chirp has a varying frequency substantially matching the pilot up chirp, and the reference down chirp has a varying frequency substantially matching the pilot down chirp. A sample adjuster is arranged to synchronize the received signal samples in response to the detector.

Abstract: A reference generator includes a memory that stores reference data which, when clocked out of the memory, produces an ATSC compliant VSB reference signal substantially free of sub-harmonics of the clock signal. A digital-to-analog converter converts the clocked out reference data to an analog signal. The analog signal may be at low IF. An up converter is arranged to upconvert the output of the digital-to-analog converter to an RF reference signal. The RF reference signal can be used, for example, to calibrate a VSB demodulator.

Abstract: Indoor UHF antennas for HDTV and ATSC television signals each include a reflector backplate from which is supported one or more dipoles. Both passive and active antennas are disclosed. The active antennas include: single amplifier with a single dipole; push-pull amplifier with a single dipole; two amplifiers with two parallel dipoles; and two push-pull amplifiers with crossed dipoles. The dipole plates comprise printed circuit boards with the amplifiers directly deposited on the obverse sides of the dipole plates.

Abstract: A testing arrangement tests an MPEG video decoder that decodes frames of digital video data. The testing arrangement receives a data message containing a plurality of test frames and a reference checksum for each test frame. A checksum calculator calculates a calculated checksum for each test frame as decoded by the MPEG video decoder. A comparator compares each calculated checksum to its corresponding reference checksum, and determines whether the MPEG video decoder has properly decoded the test frames based upon results of the comparison.

Abstract: A circuit for developing correction signals for on-line controlling a precorrection arrangement in an HDTV 8VSB digital signal transmitter. The transmitted signal is sampled, sorted, smoothed and sliced to determine the symbol amplitude levels of the transmitted multilevel symbols. The centers of the sliced clusters of sampled symbol levels are used to determine the symbol amplitude levels. Correction signals for compensating the precorrection arrangement are developed based upon the determined symbol levels and the known symbol levels.