Method and apparatus for suppressing linear amplitude interference from bandspread communication signals

For a sequence of received bandspread communication signal samples such that each sample is defined as a vector having a signal vector component and an interference vector component, a method of estimating a portion of the signal vector component that is parallel to the interference vector component as an indication of the bandspread communication signal, comprising the steps of:

• generating a signal corresponding to the amplitude of each sample's defined vector;
• using the signal corresponding to the amplitude to generate a signal approximating a quantity proportional to the second derivative for each sample based on the amplitudes of current, previous and subsequent samples to generate a pseudo second derivative signal;
• transforming the pseudo second derivative signal for each sample into a corresponding pseudo second derivative vector signal, each pseudo second derivative vector signal containing a representation of 2n terms centered symmetrically about each sample's pseudo second derivative, wherein the first n terms represented in each pseudo second derivative vector signal are generated by successively subtracting signals representing the previous n sample's pseudo second derivatives from each current sample's pseudo second derivative, and wherein the second n terms represented in each pseudo second derivative vector signal are generated by successively subtracting signals representing the subsequent n sample's pseudo second derivatives from each current sample's pseudo second derivative;
• generating signals representing the sum of all terms of each corresponding pseudo second derivative vector;
• generating a signal representing the average of the summed pseudo second derivative vector over 2n to generate a corresponding average enhanced gain signal for each sample;
• and
• generating a signal that represents the product of each corresponding average enhanced signal gain and a vector approximately parallel to the corresponding sample's interference vector component to estimate the signal vector component that is parallel to the interference vector component for each sample, wherein said method is applicable whenever the amplitude of the interference vector components is at least approximately linear.

For a radio receiving a sequence of bandspread communication signal samples whose information bits are spread by a factor of ten or more, wherein each j-th sample is defined by an input pair (x.sub.j,y.sub.j) and an amplitude A.sub.j, a method of estimating the communication signal when the signal samples contain linear amplitude interference comprising the steps of:

• approximating a quantity DA.sub.j proportional to the second derivative of the amplitude A.sub.j by generating a first signal that represents the sum
• 2A.sub.j -A.sub.j-1 -A.sub.j+1 ;
• using the first signal to generate a second signal representing an averaged sum ##EQU6## where the value of n is based on the radio's frequency of operation;
• and using the second signal to generate each j-th sample's averaged sum and a vector defined by the coordinate pair (x.sub.j /A.sub.j,y.sub.j /A.sub.j) wherein the resulting product is an estimate of the communication signal.

An apparatus for suppressing linear amplitude interference from a sequence of bandspread communication signal samples in order to estimate a communication signal contained therein, wherein the signal sample information bits are spread by a factor of ten or more and wherein each j-th sample is defined by an input pair (x.sub.j,y.sub.j), said apparatus comprising:

• first means for generating a signal corresponding to the amplitude of each j-th sample in the sequence;
• second means operably coupled to said first means for approximating a quantity proportional to the second derivative for each j-th sample based on the amplitudes of the j-th, (j-1)th and (j+1)th samples to generate a sequence of pseudo second derivative signals;
• third means operably coupled to said second means for generating a j-th pseudo second derivative vector signal for each j-th sample based on the sequence of pseudo second derivative signals, each j-th pseudo second derivative vector signal containing a representation of 2n terms centered symmetrically about each j-th sample's pseudo second derivative, wherein the first n terms represented in each j-th pseudo second derivative vector signal are generated by successively subtracting signals representing the previous n sample's pseudo second derivatives from each j-th sample's pseudo second derivative, and wherein the second n terms represented in each j-th pseudo second derivative vector signal are generated by successively subtracting signals representing the subsequent n sample's pseudo second derivatives from each j-th sample's pseudo second derivative;
• and
• fourth means operably coupled to said third means for generating a signal representing the sum of the 2n terms for each j-th pseudo second derivative vector to generate a j-th enhanced gain factor signal for each j-th sample in the sequence and for generating a signal representing the average of each j-th enhanced signal gain factor over the 2n terms as an indication of the communication signal.

In a filter for suppressing linear amplitude interference from a sequence of bandspread communication signal samples whose information bits are spread by a factor of ten or more, wherein each j-th sample is defined by an input pair (x.sub.j,y.sub.j), said filter comprising:

• a coordinate transform network for determining an amplitude A.sub.j and a quantity DA.sub.j proportional to the second derivative associated with each j-th sample from the sequence based on the input pair (x.sub.j,y.sub.j), whereby a corresponding sequence of signals representing pseudo second derivatives are generated;
• a serial-to-parallel converter coupled to said coordinate transform network for transforming each pseudo second derivative D.sub.j into a corresponding symmetric vector signal about j, each symmetric vector signal being a vector signal representing 2n pseudo second derivative differences (DA.sub.j -DA.sub.j-n, . . . , DA.sub.j -DA.sub.j-1, DA.sub.j -DA.sub.j+1, . . . , DA.sub.j -DA.sub.j+n), where n is a positive integer based on the filter's frequency of operation;
• a summer operably coupled to said serial-to-parallel converter for generating a signal representing the sum of all terms of each vector of pseudo second derivative differences to form a corresponding sum signal for each j-th sample and for averaging each corresponding sum signal over the 2n pseudo second derivative differences to form a corresponding averaged sum signal;
• and
• a filter applier operably coupled to said summer for generating a signal representing the product of a vector represented by the coordinate pair (x.sub.j /A.sub.j,y.sub.j /A.sub.j) and the corresponding averaged sum for each j-th sample.