Abstract: The invention proposes the separate processing of the phase and amplitude of multi-amplitude digital modulation techniques, such as a QAM. The phases are differentially modulated and the amplitudes coherently processed. Also proposed is a method to correct the amplitude distortion of the symbols on each subcarrier, either from the QAM signal itself or from any PSK signal, if available. The invention shows that differential modulation/demodulation of multi-amplitude signals with no equidistant phases such as QAM is possible. Complex equalizer means to perform a channel estimation is no more needed as for coherent systems. Further, no pilot sucarriers are needed, thus the bandwidth efficiency is much higher. Furthermore, the frequency snychronization of differential demodulated signals is less complex. An implementation proposal of the new modulation/demodulation technique is described.

Abstract: A baud clock (15) for use by a serial communication interface (67) is generated by dividing a base clock of the serial communication interface by one of a plurality of possible composite divisors (DEG). Each composite divisor is indicative of a minimum time interval by which adjacent pulses of the baud clock are to be separated, and further indicates that at least one pair of adjacent pulses within each symbol interval of the baud clock are to be separated by an extended time interval which is longer than the minimum time interval.

Abstract: A bandwidth efficient advanced modulation waveform modem using concatenated iterative turbo coding and continuous phase modulation is disclosed. A demodulator in the modem has a turbo decoder and a decision feedback carrier and time tracking algorithm to track a carrier and adjust timing. The decision feedback carrier and time tracking algorithm may use an APP decoder as a decision device to provide symbol decisions at a high error rate and low latency for a coded input data stream. A symbol phase estimator produces a symbol phase error estimate from the symbol decisions. An erasure decision function decides which symbol decisions are correct and which symbol decisions are erasures. A carrier tracking function receives the symbol phase error estimates when the symbol decisions are correct and receives erasure inputs when the symbol decisions are erasures to maintain carrier tracking.

Abstract: An impulse response matrix of a received signal in a TDMA communications system is approximated using a plurality of indirect variables of a linear complex vector. The indirect variables are used for synchronizing to the received signal and for tracking and frequency offset estimation during successive samples of the received signal, the samples being equalized in dependence upon the indirect variables. A demodulated signal is derived from the equalized received signal samples. Individual synchronization and tracking units, and a single equalizer, can be provided for a two-antenna receiver. Tracking errors can be used to adapt a parameter of the equalizer to reduce interference in the received signal.

Abstract: A digital signal receiver and a method for receiving a digital signal. The receiver includes an equalizing unit for compensating for an amplitude distortion of a received signal, an original signal decision unit for deciding an original signal from a signal which is compensated for the amplitude distortion, a carrier recovering and phase lock detecting unit for detecting a phase error between an input of the original signal decision unit and the decided original signal, and outputting a phase lock signal, a re-rotating unit for restoring the signal from the original signal decision unit to its original state and outputting a restored signal to the equalizer, and a coefficients updating unit for receiving the phase lock signal from the carrier recovering and phase lock detecting unit and the restored signal from the re-rotator unit, generating an error for updating the coefficients of the equalizer, and updating the coefficients of the equalizer.

Abstract: A method, apparatus and system detects a loss of synchronization between a transmitter and a receiver in a multiple-carrier communication system such as an OFDM system. A phase-frequency synchronization detector determines when the receiver has lost synchronization with the transmitter based on a phase-frequency relationship of plurality of pilot signals transmitted at different frequencies from the transmitter and received at the receiver. A loss of synchronization is detected when a slope of a line defined by the phase-frequency relationship exceeds a timing threshold more at a rate in excess of an occurrence threshold within a time period.

Abstract: A synchronizing signal processing circuit for use in a video apparatus such as a display apparatus and an information recording/reproducing is disclosed. The synchronizing signal processing circuit is capable of not only removing false synchronizing pulses included in incoming synchronizing signals and compensating for missing signals, but also causing its output to follow its input quickly after a phase of the incoming synchronizing signals has shifted abruptly.

Abstract: A subscriber device (2) includes a long code generator (12) and a modifier (30) for generating a spread bit stream with a predetermined error pattern that is transmitted by a transmitter (16) at the subscriber device (2) to a base station (3). The base station (3) identifies the current subscriber device properties by identifying the error pattern and subsequently compares the current subscriber device properties with a knowledge base of subscriber device software properties associated with the error pattern in the spread bit stream. The knowledge base is stored in a memory source (4).

Abstract: A GPS receiver receives GPS spread spectrum communication signals subject to carrier demodulation and code phase autocorrelation using tightly coupled Kalman filter residual estimation based on Ricatti matrix computation for generating code phase errors and carrier phase errors for improved code phase tracking and carrier phase tracking in feedback loops for use in navigation systems.

Abstract: The frame synchronizing circuit establishes frame synchronization by detecting a sync pattern laid in an incoming frame. The frame synchronization circuit comprises a first frame synchronizing unit and a second frame synchronizing unit. The first and second synchronizing units synchronize with a first pattern, a second pattern at a first position and a second position, respectively. Thereafter, when the first position used for the synchronization by the first frame synchronizing unit is found to be in error, the first frame synchronizing unit synchronizes with the second pattern at the second position used by the second frame synchronization unit.

Abstract: A network receiver is configured for receiving a modulated carrier signal representing a data frame from a network transmitter via a network medium, the receiver includes an adaptive equalizer with a finite impulse response filter for filtering the received signal. The filter utilizes a plurality filter coefficients. A cache stores a plurality of sets of coefficients for use by the filter and the equalizer selects a set of coefficients for receiving the data frame.

Abstract: A programmable matched filter bank comprises a sliding integrator and compensation calculation circuits. The integrator receives a chip stream of samples derived from a received spread-spectrum signal and integrates a number of the most recent samples, to form a common integration value. Each of the compensation calculation circuits receives the same most recent samples and receives a respective one of the possible reference spreading code sequences. In operation, each compensation calculation circuit derives a compensation value, and an associated circuit modifies the common integration value by the respective compensation value. The result is a value of correlation between the predetermined number of most recent samples, for each respective reference code sequence. The inventive approach reduces the number of bit adders and inverters in the implementation of a matched-filter, a programmable matched filter and a programmable matched filter bank for spread spectrum receivers.

Abstract: An improved modem architecture and associated method are disclosed that integrate modem and line-isolation circuitry so as to achieve modem functionality and system-side isolation functionality on a single integrated circuit. The combined modem and line isolation system has both on-hook and off-hook intrusion detection for use with parallel connected phone line connection devices. During on-hook intrusion detection, when the combined modem and line isolation system is on-hook the system can detect if other parallel connected phone line connection devices are already off-hook. During off-hook intrusion detection, when the combined modem and line isolation system is off-hook the system can detect if other parallel connected phone line connection devices are attempting to go off-hook.

Abstract: A network device configured to detect a framing pattern includes a data scanner and a frame detector. The data scanner examines parallel bytes of data and detects portions of a framing pattern in the parallel bytes of data, identifies the phase of the framing pattern and outputs alignment information and phase information when a framing pattern has been detected. The frame detector receives the alignment information and phase information and determines whether framing patterns having the same phase relationship have been detected within a predetermined number of frames.

Abstract: A digital frame determination method and apparatus are provided which collect a data frame from a digital data stream starting at an initial frame start and a nominal frame frequency, test the data frame for alignment based on a set of rules, determine an adjustment value in accordance with the set of rules when the data frame is not aligned, adjust the frame start in accordance with the adjustment value, and repeat until the data frame is aligned and the alignment is verified.

Abstract: Disclosed is a method for wireless signal transmission of signals from an array of two or more antennas, in which each signal to be transmitted is selected from a constellation of unitary space-time signals. Each unitary space-time signal is a unitary matrix, in which each column represents a respective antenna, each row represents a respective time interval, and each element represents a complex amplitude to be transmitted by a given antenna during a given time interval. In specific embodiments of the invention, the matrices of the signal constellation form a non-Abelian group having a positive diversity product, or a coset of such a group. In other embodiments, the signal constellation is a subset of such a group, and its multiplicative closure forms a finite non-Abelian group having a positive diversity product.

Abstract: The invention is a communication system having a series of output modules that provide continuous synchronization output signals. Each output module has a driver assembly has a driver output and a backup selector output that is capable of driving a failed next driver assembly. A sensor detects the failure of the driver output and generates a select signal in the failure state. A selector receives the driver output, a backup driver output, the select signal, and a select signal from the next driver assembly. The selector normally selects the driver output, but in response to a failure state from the select signal, isolates the failed driver output. The previous driver assembly transmits a backup selector output to the failed driver assembly to maintain a continuous driver output. The transformers are preferably placed on a separate card to reduce the thermal degradation of nearby electronics. As transformers rarely fail, replacing them when a card fails is wasteful.

Abstract: A technique for encoding a signal used in a digital communication system in which individual traffic channel data rates may be adapted to specific channel conditions. In particular, a forward error correction coding rate is adapted for individual channels while at the same time maintaining a fixed block size independent of the FEC coding rate. This allows the system data rate to adapt to the channel conditions experienced by a specific user. Thus, users experiencing good communication conditions with low multipath distortion may be allocated higher capacity, whereas users with significant multipath distortion may make use of lower rate (higher levels of coding) error codes to maintain high quality. Messages are sent from a transmitter to a receiver to inform the receiver of the coding rate implemented at any given point in time.

Abstract: Improved decision feedback equalizer and decision directed timing recovery systems and methods suitable for use in connection with a dual mode QAM/VSB receiver system are disclosed. A trellis decoder operates in conjunction with a decision feedback equalizer circuit on trellis coded 8-VSB modulated signals. The trellis decoder includes a 4-state traceback memory circuit outputting a maximum likelihood decision as well as a number of intermediate decisions based upon the maximum likelihood sequence path. Any number of decisions, along the sequence, may be provided as an input signal to timing recovery system loops, with the particular decision along the sequence chosen on the basis of its delay through the trellis decoder. Variable delay circuitry is coupled to the other input of the timing recovery system loops in order to ensure that both input signals bear the same timestamp.

Abstract: An improved modem architecture and associated method are disclosed that integrate modem and line-isolation circuitry so as to achieve modem functionality and system-side isolation functionality on a single integrated circuit. The combined modem and line isolation system has both on-hook and off-hook intrusion detection for use with parallel connected phone line connection devices. During on-hook intrusion detection, when the combined modem and line isolation system is on-hook the system can detect if other parallel connected phone line connection devices are already off-hook. During off-hook intrusion detection, when the combined modem and line isolation system is off-hook the system can detect if other parallel connected phone line connection devices are attempting to go off-hook. On-hook intrusion detection may be accomplished by monitoring the phone line voltage through a pin utilized for setting DC termination characteristics.