Abstract: A sampling phase detector for a data bit synchronizer produces a constant level in the absence of data bit transitions. Reference voltages are provided and a switch selects between these reference voltages to provide an output which changes only when a data bit is detected and otherwise remains at a constant level. A loop filter operates together with the sampling phase detector to provide the constant voltage output in the absence of data bit transitions.

Abstract: A spread-spectrum noise canceller (390) is provided for cancelling user code noise from a spread-spectrum communication channel. The spread-spectrum noise canceller (390) includes a receiver for receiving a spread-spectrum signal (302) including a first and at least a second signal as well as a noise canceller (390) operatively coupled to the receiver for reducing spread-spectrum noise in the first received signal by substantially processing the at least second received signal out of the received spread-spectrum signal (302).In addition, a method is provided which cancels user code noise from a spread-spectrum communication channel. The method includes receiving a spread-spectrum signal (302) including a first and at least a second signal and subsequently reducing spread-spectrum noise in the first received signal by substantially processing the at least second received signal out of the received spread-spectrum signal (302).

Abstract: A symbol state trellis maximum likelihood detection method greatly limits the number of possible interfering symbols which require examination. This method has considerable processing advantages over other optimal maximum likelihood detection methods. For practical configurations, the symbol state trellis maximum likelihood detection method provides a performance which is less than 1 dB from the optimal maximum likelihood detection method while simultaneously providing for a similar bit error rate. The symbol state trellis maximum likelihood detection method calculates the phase errors for all paths from a present state to a previous state. Next, total path distances are calculated for previously selected paths to the previous state. The phase error associated with each of the paths from two states previous to the present state are calculated. For each symbol of the present state, only one path is selected to each symbol. This path corresponds to the path with the minimum phase error.

Abstract: A spread-spectrum noise canceller is provided for cancelling user code noise from a spread-spectrum communication channel. The spread-spectrum noise canceller including a receiver for receiving a spread-spectrum signal including a first and at least a second signal as well as a noise canceller operatively coupled to the receiver for reducing spread-spectrum noise in the first received signal by substantially processing the at least second received signal out of the received spread-spectrum signal.In addition a method is provided which cancels user code noise from a spread-spectrum communication channel. The method includes for receiving a spread-spectrum signal including a first and at least a second signal and subsequently reducing spread-spectrum noise in the first received signal by substantially processing the at least second received signal out of the received spread-spectrum signal.

Abstract: A multiple phase shift keyed data coherent carrier recovery system wherein a coherent carrier tracking loop has attached thereto a signal generator for providing a signal with non-stationary zero-crossing times (e.g. a noise generator), which signal generator chops, or alters the phase of, signals within the loop to prevent the loop from locking on harmonics or subharmonics and to allow AC coupling with DC response therein.

Abstract: An improved quadraphase shift keyed (QPSK) adaptive demodulator includes a Costas loop modified to independently cross couple the inphase (I) and quadraphase (.phi.) channels so that minimum cross talk takes place between the I and Q channels. Advantageously, the improved QPSK adaptive demodulator separates the feedback control for correcting the phasor errors in the I and Q phasors. Advantageously, the improved demodulator permits independent phase adjustment of the I and Q demodulator outputs.

Abstract: A quadriphase shift keyed (QPSK) adaptive equalizer includes baseband inphase (I) and quadrature (Q) adaptive filters for receiving demodulated OPSK signals. The I and Q channel filters are designed to operate independent of each other and adapt their characteristics continuously in a predetermined manner in response to an incoming received QPSK signal, distorted in an unknown time varying manner.