Method and apparatus for suppressing 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 normal to the interference vector component as an indication of the bandspread communication signal, comprising the steps of:

• generating a signal corresponding to a phase angle of each sample based upon each sample's defined vector;
• transforming the phase angle for each sample into a corresponding phase vector signal based on a symmetric sampling of phase angles from previous and subsequent received signal samples, each phase vector signal containing a representation of 2n terms centered symmetrically about each sample's phase angle, wherein the first n terms represented in each phase vector signal are generated by successively subtracting signals representing the previous n sample's phase angles from each sample's phase angle, and wherein the second n terms represented in each phase vector are generated by successively subtracting signals representing the subsequent n sample's phase angles from each sample's phase angle;
• generating signals representing the sum of all terms of each corresponding phase vector to generate a corresponding phase gain signal for each sample;
• generating a signal representing the average of each corresponding phase gain over the symmetric sampling to generate a corresponding average phase gain signal for each sample;
• and
• generating a signal that represents the product of each corresponding average phase gain and a vector normal to the corresponding sample's defined vector to estimate the signal vector component that is normal to the interference vector component for each sample, wherein said method is applicable whenever the phase of the interference vector components is characterized as having a frequency of change that is less than 1/2T, where T is the time required to receive the symmetric sampling.

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 signal sample is defined by an input pair (x.sub.j,y.sub.j) and a phase angle .phi..sub.j, a method of estimating the communication signal when the signal samples contain interference, said method comprising the steps of:

• generating a signal representing an averaged sum ##EQU9## where the value of n is based on the radio's frequency of operation;
• generating a rotated input pair (-y.sub.j,x.sub.j) signal for each j-th signal sample;
• and
• generating a signal representing the product of each j-th signal sample's averaged sum and its corresponding rotated input signal pair to generate a transformed input signal pair for each sample as an estimate of the communication signal associated with each j-th sample.

An apparatus for suppressing interference from a sequence of bandspread communication signal samples in order to estimate a communication signal contained therein, wherein the signal samples have information bits that are spread by a factor of ten or more, and wherein each j-th signal 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 phase angle for each j-th signal sample in the sequence to generate a sequence of phase angle signals;
• second means operably coupled to said first means for generating a j-th phase vector signal for each j-th signal sample based on the sequence of phase angles, each j-th phase vector signal containing a representation of 2n terms centered symmetrically about each j-th signal sample's phase angle, wherein the first n terms represented in each j-th phase vector signal are generated by successively subtracting signals representing the previous n sample's phase angles from each j-th sample's phase angle, and wherein the second n terms represented in each j-th phase vector signal are generated by successively subtracting signals representing the subsequent n sample's phase angles from each j-th sample's phase angle;
• third means operably coupled to said second means for generating a signal representing the sum of the 2n terms for each j-th phase vector to generate a j-th composite gain factor signal for each j-th sample in the sequence and for generating a signal representing the average of each j-th composite gain factor over the 2n terms to generate a j-th average gain factor signal for each j-th sample in the sequence;
• fourth means for translating each j-th signal sample's defined input pair (x.sub.j,y.sub.j) to generate a translated input pair (-y.sub.j,x.sub.j) signal;
• and
• fifth means operably coupled to said fourth means for multiplying each j-th average gain factor signal by each j-th sample's translated input signal pair (-y.sub.j,x.sub.j) to generate a transformed input signal pair for each j-th sample in the sequence to suppress interference characterized as having a frequency of change that is less than 1/2T, where T is the time required to receive the 2n terms symmetric about each j-th sample.

In a phase filter for suppressing 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 signal sample is defined by an input pair (x.sub.j,y.sub.j) signal, said phase filter comprising:

• a coordinate transform network for determining magnitude and phase associated with each j-th signal sample from the sequence based on the input pair (x.sub.j,y.sub.j) signal, whereby a corresponding sequence of sample phase .phi..sub.j signals are generated;
• a serial-to-parallel converter for transforming each sample phase signal .phi..sub.j into a corresponding symmetric vector signal about j, each symmetric vector signal representing a vector having 2n sample phase differences (.phi..sub.j -.phi..sub.j-n, . . . , .phi..sub.j -.phi..sub.j-1, .phi..sub.j -.phi..sub.j+1, . . . , .phi..sub.j -.phi..sub.j+n), where n is a positive integer based on the phase filter's frequency of operation;
• means for generating a signal representing the sum of all terms of each vector of sample phase differences to form a corresponding sum signal for each j-th sample and for averaging each corresponding sum signal over the 2n sample phase differences to form a corresponding averaged sum signal;
• and
• a filter applier for multiplying each input pair (x.sub.j,y.sub.j) signal times the corresponding averaged sum signal for each j-th signal sample, wherein said phase filter suppresses interference characterized as having a frequency of change that is less than 1/2T, where T is the time required to receive 2n signal samples.