Methods and devices are described for reducing the audible effect of pre-responses in an audio signal. The pre-responses are effectively delayed by employing a digital non-minimum-phase filter, which includes a zero lying outside the unit circle in its z-transform response. This zero is not paired with another zero at a reciprocal position inside the unit circle, as this would linearise the phase modification. The filtering can introduce a greater group delay at the pre-response frequency than at a low frequency, such as 500 Hz or even 0 Hz. The technique can be used to reduce pre-responses in an existing audio signal and also to pre-empt pre-responses that would be introduced to the audio signal by subsequent processing.

The present disclosure relates to a concept of nonlinear signal processing which may be used for predistortion for RF power amplifiers. The concept includes generating time variant filter coefficients for a linear filter circuit based on a nonlinear mapping of an input signal, and filtering the input signal with the linear filter circuit using the time variant filter coefficients in order to generate a filtered output signal. Thus, it is proposed to implement a non-linear filter by a time-varying linear filter where the time-varying coefficients are derived from the input signal.

A mechanism is included for jointly determining filter coefficients for Finite Impulse Response (FIR) filters in a Linear, Memory-less Non-linear (LNL), Linear compensator. Calibration signals are applied to a signal converter input in a test and measurement system. Non-linear signal components are determined in signal output from the signal converter. Non-linear filter components are determined at the LNL compensator based on the calibration signals. The non-linear signal components are then compared to the non-linear filter components. The comparison is then resolved to determine filter coefficients for first stage Finite Impulse Response (FIR) filters and second stage FIR filters in the LNL.

The present invention is a computationally-efficient compensator for removing nonlinear distortion. The compensator operates in a digital post-compensation configuration for linearization of devices or systems such as analog-to-digital converters and RF receiver electronics. The compensator also operates in a digital pre-compensation configuration for linearization of devices or systems such as digital-to-analog converters, RF power amplifiers, and RF transmitter electronics. The multi-dimensional compensator effectively removes linear and nonlinear distortion in these systems by accurately modeling the state of the device by tracking multiple functions of the input, including but not limited to present signal value, delay function, derivative function (including higher order derivatives), integral function (including higher order integrals), signal statistics (mean, median, standard deviation, variance), covariance function, power calculation function (RMS or peak), or polynomial functions. The multi-dimensional compensator can be adaptively calibrated using simple arithmetic operations that can be completed with low processing requirements and quickly to track parameters that rapidly change over time, temperature, power level such as in frequency-hopping systems.

Methods and devices are described for reducing the audible effect of pre-responses in an audio signal. The pre-responses are effectively delayed by employing a digital non-minimum-phase filter, which includes a zero lying outside the unit circle in its z-transform response. This zero is not paired with another zero at a reciprocal position inside the unit circle, as this would linearise the phase modification. The filtering can introduce a greater group delay at the pre-response frequency than at a low frequency, such as 500 Hz or even 0 Hz. The technique can be used to reduce pre-responses in an existing audio signal and also to pre-empt pre-responses that would be introduced to the audio signal by subsequent processing.

Method and apparatus for nonlinear signal processing include mitigation of outlier noise in the process of analog-to-digital conversion and adaptive real-time signal conditioning, processing, analysis, quantification, comparison, and control. Methods, processes and apparatus for real-time measuring and analysis of variables include statistical analysis and generic measurement systems and processes which are not specially adapted for any specific variables, or to one particular environment. Methods and corresponding apparatus for mitigation of electromagnetic interference, for improving properties of electronic devices, and for improving and/or enabling coexistence of a plurality of electronic devices include post-processing analysis of measured variables and post-processing statistical analysis. Methods, processes and apparatus for secure communications include low-power communications and physical-layer steganography.

Methods and devices are described for reducing the audible effect of pre-responses in an audio signal. The pre-responses are effectively delayed by employing a digital non-minimum-phase filter, which includes a zero lying outside the unit circle in its z-transform response. This zero is not paired with another zero at a reciprocal position inside the unit circle, as this would linearise the phase modification. The filtering can introduce a greater group delay at the pre-response frequency than at a low frequency, such as 500 Hz or even 0 Hz. The technique can be used to reduce pre-responses in an existing audio signal and also to pre-empt pre-responses that would be introduced to the audio signal by subsequent processing.

A nonlinear compensator is provided to include a decomposition circuit and a plurality of filter elements. The decomposition circuit has a nonlinear frequency response characteristic and the decomposition circuit is configured to receive an input signal and decompose the input signal into decomposed signals corresponding to positive and negative frequency signal components of the input signal. Each of the plurality of filter elements is configured to receive at least portions of the decomposed signals and apply filter element characteristics to the decomposed signals with the filter element characteristics that are matched to the nonlinear frequency response of the decomposition circuit.

A mechanism is included for jointly determining filter coefficients for Finite Impulse Response (FIR) filters in a Linear, Memory-less Non-linear (LNL), Linear compensator. Calibration signals are applied to a signal converter input in a test and measurement system. Non-linear signal components are determined in signal output from the signal converter. Non-linear filter components are determined at the LNL compensator based on the calibration signals. The non-linear signal components are then compared to the non-linear filter components. The comparison is then resolved to determine filter coefficients for first stage Finite Impulse Response (FIR) filters and second stage FIR filters in the LNL.

Methods and devices are described for reducing the audible effect of pre-responses in an audio signal. The pre-responses are effectively delayed by employing a digital non-minimum-phase filter, which includes a zero lying outside the unit circle in its z-transform response. This zero is not paired with another zero at a reciprocal position inside the unit circle, as this would linearise the phase modification. The filtering can introduce a greater group delay at the pre-response frequency than at a low frequency, such as 500 Hz or even 0 Hz. The technique can be used to reduce pre-responses in an existing audio signal and also to pre-empt pre-responses that would be introduced to the audio signal by subsequent processing.