Abstract: A system and method are disclosed for securely transmitting and receiving a signal. A nonlinear keying modulator is used in the transmitter to encrypt the signal using a nonlinear keying modulation technique. A nonlinear keying demodulator is used in the receiver to decrypt the signal.

Abstract: A signal processing system includes a receiving terminal configured to receive a digital signal comprising a plurality of samples associated with a plurality of original sampling times, wherein the original sampling times have a period of T, and a compensation module coupled to the receiving terminal. The compensation module is configured to generate, based on the digital signal, a nominal phase shifted signal having a plurality of nominal phase shifted samples associated with a plurality of phase shifted sampling times, wherein the plurality of phase shifted sampling times correspond to fractional intervals of the original sampling times. The compensation module is further configured to generate a compensated signal based at least in part on the digital signal and the nominal phase shifted signal.

Abstract: A method of converting an input analog signal to a compensated digital signal comprises converting the input analog signal to an uncompensated digital signal, inputting the uncompensated digital signal to a distortion model, generating a modeled distortion signal based on the uncompensated digital signal, and subtracting the modeled distortion signal from the uncompensated digital signal to generate the compensated digital signal. A distortion compensating analog to digital converter (ADC) comprises an uncompensated ADC configured to convert an input analog signal to an uncompensated digital signal, and a compensation module coupled to the uncompensated ADC, configured to receive the uncompensated digital signal, generate a modeled distortion signal based on the uncompensated digital signal and subtract the modeled distortion signal from the uncompensated digital signal to generate the compensated digital signal.

Abstract: A system and method are disclosed for securely transmitting and receiving a signal. A nonlinear keying modulator is used in the transmitter to encrypt the signal using a nonlinear keying modulation technique. A nonlinear keying demodulator is used in the receiver to decrypt the signal.

Abstract: A system and a method are disclosed for converting analog signal to digital. An analog to digital converter system comprises an analog to digital converter (ADC) and an adaptive filter coupled to the ADC, wherein the adaptive filter is coupled to the ADC in a feedforward configuration. A method of generating a digital signal based on an analog signal comprises applying the analog signal to an analog to digital converter (ADC) to generate an ADC output and sending the ADC output to an adaptive filter, wherein the adaptive filter is coupled to the ADC in a feedforward configuration.

Abstract: A digital signal processor (DSP) comprises an input terminal configured to receive an input, an adaptive nonlinear phase filter coupled to the input terminal, the adaptive nonlinear phase filter having a time-varying phase response, and an adaptive nonlinear amplitude filter coupled to the input terminal, the adaptive nonlinear amplitude filter having a time-varying amplitude response. A method of processing a signal comprises receiving the signal, sending the signal to an adaptive nonlinear phase filter, the adaptive nonlinear phase filter having a time-varying phase response, and sending the signal to an adaptive nonlinear amplitude filter, the adaptive nonlinear amplitude filter having a time-varying amplitude response.

Abstract: A method of signal processing comprises receiving an unknown input signal that includes a distorted component and an undistorted component, the unknown input signal having a sampling rate of R; and performing self-linearization based at least in part on the unknown signal to obtain an output signal that is substantially undistorted, including by generating a replica distortion signal that is substantially similar to the distorted component, the generation being based at least in part on a target component having a sampling rate of R/L, L being an integer greater than 1.

Abstract: A method of signal processing includes receiving an unknown signal having a distorted component and an undistorted component, the distorted component and the undistorted component having a nonlinear relationship; and separating from the unknown signal a reference component and a target component. A signal processing system includes an input terminal configured to receive an unknown signal having a distorted component and an undistorted component, the distorted component and the undistorted component having a nonlinear relationship; and a separation block coupled to the input terminal, configured to separate from the unknown signal a reference component and a target component.

Abstract: A method of compensating for nonlinear distortions in a digital signal comprises receiving the digital signal, generating a nominal phase shifted signal based on the digital signal, generating a modeled distortion signal based on the digital signal and the nominal phase shifted signal, subtracting the modeled distortion signal from the digital signal, and generating a compensated signal. A compensating system comprises an input interface configured to receive a digital signal having nonlinear distortion, and a distortion model coupled to the interface, configured to generate a nominal phase shifted signal based on the digital signal, generate a modeled distortion signal based on the digital signal and the nominal phase shifted signal, subtract the modeled distortion signal from the digital signal, and generate a compensated signal.

Abstract: A system and method are disclosed for a nonlinear filter having a nonlinear transfer function. The nonlinear filter comprises a plurality of linear filters each having a filter output, a plurality of nonlinear elements each connected to one of the plurality of linear filters, and a combination network connected to the plurality of nonlinear elements. The nonlinear elements are used to produce nonlinear effects and generate a plurality of nonlinear outputs, and the combination network combines the nonlinear outputs.

Abstract: A method of converting an input analog signal to a compensated digital signal comprises converting the input analog signal to an uncompensated digital signal, inputting the uncompensated digital signal to a distortion model, generating a modeled distortion signal based on the uncompensated digital signal, and subtracting the modeled distortion signal from the uncompensated digital signal to generate the compensated digital signal. A distortion compensating analog to digital converter (ADC) comprises an uncompensated ADC configured to convert an input analog signal to an uncompensated digital signal, and a compensation module coupled to the uncompensated ADC, configured to receive the uncompensated digital signal, generate a modeled distortion signal based on the uncompensated digital signal and subtract the modeled distortion signal from the uncompensated digital signal to generate the compensated digital signal.

Abstract: A method of correcting for output distortion of an analog to digital converter (ADC) is disclosed. The method comprises estimating the output distortion and providing an estimated distortion. The method further comprises combining an output of the ADC with the estimated distortion to compensate for the output distortion and training a calibration module.

Abstract: A method for processing a signal propagated through a nonlinear channel is disclosed. The method comprises modeling the channel characteristics to produce a linearized channel model, wherein the linearized channel model has a linearized transfer function that includes a plurality of first order polynomials and nonlinear operators. The method further comprises deriving an inverse linearized channel model from the linearized channel model and filtering the signal using the inverse linearized channel model.

Abstract: A system and method are disclosed for correcting for output distortion of an analog to digital converter, comprising: estimating the output distortion, providing an estimated distortion, and combining an output of the analog to digital converter with the estimated distortion to compensate for the output distortion. The compensating module for correcting output distortion of an analog to digital converter comprises a calibration module configured to estimate the output distortion and a combiner configured to combine an output of the analog to digital converter with the estimated distortion to compensate the output distortion.

Abstract: A system and method are disclosed for correcting for output distortion of an analog to digital converter, comprising: estimating the output distortion, providing an estimated distortion, and combining an output of the analog to digital converter with the estimated distortion to compensate for the output distortion. The compensating module for correcting output distortion of an analog to digital converter comprises a calibration module configured to estimate the output distortion and a combiner configured to combine an output of the analog to digital converter with the estimated distortion to compensate the output distortion.

Abstract: A system and method are disclosed for securely transmitting and receiving a signal. A nonlinear keying modulator is used in the transmitter to encrypt the signal using a nonlinear keying modulation technique. A nonlinear keying demodulator is used in the receiver to decrypt the signal.

Abstract: A system and method are disclosed for processing a signal propagated through a nonlinear channel. The method includes modeling the channel characteristics to produce a linearized channel model, deriving an inverse linearized channel model from the linearized channel model, and filtering the signal using the inverse linearized channel model.

Abstract: A system and method are disclosed for a nonlinear filter having a nonlinear transfer function. The nonlinear filter comprises a plurality of linear filters each having a filter output, a plurality of nonlinear elements each connected to one of the plurality of linear filters, and a combination network connected to the plurality of nonlinear elements. The nonlinear elements are used to produce nonlinear effects and generate a plurality of nonlinear outputs, and the combination network combines the nonlinear outputs.

Abstract: Methods and apparatus for efficiently communicating across an asymmetric digital subscriber loop are disclosed. According to one aspect of the present invention, a method for communicating between a computer in a central office and a remote computer across DSL communications links involves sending a first set of data from the central office computer across a first DSL communications link. The first DSL communications link couples the central office computer to a switch. The method also includes selecting a second DSL communications link, which couples the switch and the remote computer, and sending the first set of data from the switch to the remote computer across the second DSL communications link.

Abstract: A Viterbi decoder circuit for decoding an encoded data signal containing Viterbi branch metric information includes a configurable memory which is alternately configured to have four stages of memory in which the incoming data signal is stored and selectively read out based upon Viterbi trellis address information contained therein. While the present data of the incoming data signal is being stored in one memory stage, individual bits from selected bytes of previously stored incoming data are read out from a second memory stage and used to form the next address for the second memory stage and an address for a third memory stage from which further previously stored incoming data are read out and decoded to form the final Viterbi-decoded data.