US 4,843,583 AGranted

Nonlinear adaptive filter

AssigneeRockwell International Corporation

InventorsStanley A. White, Visvaldis A. Vitols

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Abstract

A nonlinear adaptive filter has an input and an output, and includes an adjustable linear filter and nonlinear filter connected serially between the input and output. The parameters for the adjustable linear filter are derived from signals on the adaptive filter output and from signals on the adaptive filter input. Preferably, the adjustable linear filter is coupled between the adaptive filter input and the nonlinear filter. A parameter computer for adjusting the parameters of the adjustable linear filter includes an input coupled to the output of the nonlinear filter, a processor for processing a signal received from the output of the nonlinear filter, and apparatus for applying the processed output signal to the parameters of the adjustable linear filter. A linear filter for shaping the spectrum of a signal received from the output of the nonlinear filter is preferably coupled between the nonlinear filter output and the parameter computer. In its preferred form, the nonlinear filter portion includes a first processor for generating from an input signal an intermediate signal having a uniform amplitude-density function, and a second processor for generating from the intermediate signal an output signal having a desired amplitude-density function.

Claims18

Dependent claims

A signal processor comprising:

a nonlinear processor having an input and an output, wherein said nonlinear processor maps a sequence of first signal samples from said input into a sequence of second signal samples, each said second signal sample having a value representing the amplitude distribution function of the value of said corresponding first signal sample, each said second signal sample being mapped into a corresponding output signal sample, each output signal sample having an output signal value representing the inverse of the desired output amplitude-distribution function of each corresponding second signal sample;
and,
each first signal sample being mapped into a corresponding first control signal sample, each first control signal sample having a value representing the amplitude density function of the value of each corresponding first signal sample;
each second signal sample being mapped into a corresponding second control signal sample, each second control signal sample having a value representing the derivative of the inverse of the desired output amplitude-distribution function of the value of each respective second signal sample;
a combiner having first input responsive to said first control signal, a second input responsive to said second control signal and an output providing a corresponding gain control signal;
an adjustable linear filter having a sample signal input, a plurality of tap weight inputs and an output wherein:
the sample signal input of said adjustable linear filter is coupled to the input of the signal processor and receives sample input signals;
the output of said adjustable linear filter providing said sequence of first signal samples to said nonlinear processor input;
and
said adjustable linear filter being characterized to perform a predictive deconvolution on a signal applied to said linear filter input with respect to the spectrum-shaped output signal;
and to provide said first signal to said nonlinear processor input;
a parameter computer having inputs coupled to the output of said nonlinear signal processor, to said combiner output and to the input to said adjustable linear filter, for computing the weights for said adjustable linear filter from said gain control signals, said sample input signals, and said output signal samples and for applying tap weight input signals to corresponding adjustable linear filter tap weight inputs.

9 more elements

A nonlinear adaptive filter comprising:

a nonlinear filter having an input and an output, and comprising:
a first processor for generating from an input signal an intermediate signal having a uniform amplitude-density function;
and
a second processor for generating from said intermediate signal an output signal having a desired amplitude-density function;
an adjustable linear filter having an input and an output, wherein said output of said adjustable linear filter is connected to the input of said nonlinear filter;
a processor coupled to the output of said nonlinear filter for shaping the spectrum of a signal received from said nonlinear filter output;
and
a parameter computer for adjusting the parameters of said adjustable linear filter, said parameter computer comprising;
an input coupled to the output of said processor;
and
means for applying said spectrum shaped output signal to the parameters of said adjustable linear filter;
and
wherein:
said first processor of said nonlinear filter comprises a RAM for storing the inverse of the amplitude-distribution function desired for the signal output from said nonlinear filter.

11 more elements

Dependencies are inferred from the claim text.