Abstract: The present disclosure provides methods and apparatuses for nonlinear channel identification and estimation of the distorted signals in digital data transmission systems that include signals traversing a dispersive nonlinear channel that produces noisy distorted signals. The identification and estimation are accomplished with an amplitude-based signal expansion and are adapted for changing nonlinear distortion effects using a Least-Means Square direct solution that includes a precomputed matrix.

Abstract: The present disclosure provides methods and apparatuses for demodulating discrete-time desired signals in a period-Td bandpass desired signal in the presence of interference that results from a period-T bandpass interference signal that has been nonlinear distorted. Estimation of the nonlinear-distorted interference and subsequent cancellation from a received signal, that includes the interference and desired signal, produces residual-interference signals. The demodulation of the residual-interference signals uses an equalization technique when Td is not equal to T. The estimation, cancellation, and demodulation are adapted for changing nonlinear distortion effects.

Abstract: A method and apparatus at a local terminal are described for demodulating a remote-terminal signal located at a subband offset frequency in a frequency subband of relayed interference from a transponder satellite link. The demodulation of the remote-terminal signal is accomplished by transferring the digital data that produced the local-terminal transmit signal to the local-terminal receiver. The digital data is time-delayed and converted to a narrowband offset-constellation signal that cancels the relayed interference in an adaptive equalizer. Providing cancellation in the subband of the relayed interference produces larger interference cancellation factors than those obtained in conventional broadband cancellation systems. A phase-noise error signal is also generated and used to increase cancellation levels limited by phase noise generated in the satellite link frequency converters.