Racal Data Communications Inc.

Rangarajan Srinivasagopalan

Raul F Fernandez

James D Pruett

Philip F Kromer, Iii

Henry H Parrish

Vedavalli G Krishnan

Luis V Farias

Philip F Kromer

Louis V Farias

Disclosed is a modem including a transmitter having a convolutional encoder for transforming each group interval digital data into an expanded bit sequence having symbol-selecting bits and subset-selecting bits forming a plurality of bit groups, with each bit group designating a 2-dimensional subset and the symbol-selecting bits being used to select one 2-dimensional symbol from each of the selected subsets, the transmitter further providing modulation of a carrier signal, and a receiver wherein synchronization of received frames of subset-selecting bits is provided by applying a parity check equation to a plurality of possible received frames of subset-selecting bits.

Frame synchronization

Disclosed is a modem including a transmitter having a convolutional encoder for transforming each group interval digital data into an expanded bit sequence having symbol-selecting bits and a frame of subset-selecting bits forming a plurality of bit groups, with each bit group designating a 2-dimensional subset and the symbol-selecting bits being used to select one 2-dimensional symbol from each of the selected subsets, the transmitter further providing modulation of a carrier signal, and a receiver wherein a commonality-seeking, branch cost calculator determines the candidate branch associated with the minimum cost N-dimensional symbol subset for each coset and a Viterbi decoder which determines the maximum likelihood path from a plurality of surviving paths formed from branches selected from the candidate branches.

Modem and method using multidimensional coded modulation

An apparatus for cancellation of sinusoidal varying phase jitter in a data modem is implemented in firmware using microprocessor technology. An estimate of the frequency and phase of the phase jitter is computed in a first stage. Substantially independently, an estimate of the amplitude of the phase jitter is computed in another stage. These estimates are combined to form a composite estimate of the phase jitter which is utilized to cancel out the sinusoidal phase jitter in the demodulator. Digital phase locked loop technology (DPLL) is utilized to lock onto the phase jitter components. The capture range of the phase locked loop is dynamically altered during a training sequence to allow for capturing a wide range of jitter frequencies. During the training sequence the damping factor of the loop is gradually altered thereby substantially reducing the capture range and response time of the loop once jitter acquisition has occurred. This results in enhanced noise performance while still retaining the capability of locking to a wide range of jitter frequencies. Quantization of the error signal is utilized to compute estimates of the frequencies and phase of the jitter signal so that continuous updating occurs virtualy without regard for the amplitude or change in amplitude of the jitter signal.

Method and apparatus for reduction of sinusoidal phase jitter in a high

Disclosed is a modulation-demodulation system and method for transmitting a plurality of sequentially received information bit sequences, the system including a transmitter having a state machine for expanding by a coding process each information bit sequence into an expanded bit sequence with a coded bit group portion and, in some cases, an uncoded bit group portion. The transmitter further includes a modulator for modulating a carrier signal by one of a plurality of multilevel symbols in a two-dimensional complex plane in response to each sequentially applied expanded bit sequence, with the coded bit group portion being used to specify a subset of the multilevel symbols which when rotated in the complex plane maps upon another subset for each adverse angular rotation and the uncoded bit group portion being used to specify for a selected multiple symbol subset the transmitted multilevel symbol of the carrier signal. The system further includes a receiver having a demodulator and slicer for demodulating and detecting the modulated carrier signal to obtain the expanded bit sequences; a phase rotation detector, coupled to the slicer, for uniquely identifying each adverse angular rotation by analyzing a plurality of sequentially applied coded bit group portions; and a phase corrector, coupled to the phase rotation detector, for compensating for the adverse angular rotation.

Carrier-phase adjustment using absolute phase detector

Disclosed is a modulation-demodulation system and method for transmitting a plurality of sequentially received information bit sequences, the system including a transmitter having a state machine for expanding by a coding process each information bit sequence into an expanded bit sequence with a coded bit group portion and, in some cases, an uncoded bit group portion. The transmitter further includes a modulator for modulating a carrier signal by one of a plurality of multilevel symbols in a two-dimensional complex plane in response to each sequentially applied expanded bit sequence, with the coded bit group portion being used to specify a subset of the multilevel symbols which when rotated in the complex plane maps upon another subset for each adverse angular rotation and the uncoded bit group portion being used to specify for a selected multiple symbol subset the transmitted multilevel symbol of the carrier signal. The system further includes a receiver having a demodulator and slicer for demodulating and detecting the modulated carrier signal to obtain the expanded bit sequences; a phase rotation detector, coupled to the slicer, for uniquely identifying each adverse angular rotation by analyzing a plurality of non-rotated and rotated sequentially received coded bit group portions; and a phase corrector, coupled to the phase rotation detector, for compensating for the adverse angular rotation.

Modified absolute phase detector

A digital transmitter wherein a read only memory (ROM) is addressed by subaddresses representing vector components of signal point positions of a desired transmit spectrum. In this manner, greatly reduced ROM storage requirements are achieved.

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Miami, FL, United States of America

Rangarajan Srinivasagopalan