Method and apparatus for demodulation of a desired signal by constellation-independent cancellation of nonlinear-distorted interference

1. A receiving apparatus for use in a satellite ground terminal that generates in a source-transmitter a digital-data source signal that is modulated to a modulated-source signal and subsequently, filtered and converted to a bandpass signal and distorted in a nonlinear power amplifier to produce a bandpass distorted-interference signal, the receiving apparatus comprising:

a receiver filter/sampler with a receiver-timing clock for filtering, with a matched filter, a received signal containing a bandpass desired signal, which has a modulation period of T D seconds, is filtered with a waveform filter, and is derived from desired-signal digital-data and the delayed bandpass distorted-interference signal to produce a period-T R , T R <T D , discrete-time receiver signal, wherein the matched filter has a complex conjugate, time-inverted impulse response of the waveform filter, wherein T D and T R are nonzero real numbers less than unity;

a synchronizer/sampler for sampling at a rate of 1/T R the modulated-source signal and comparing the sampled modulated-source signal with the period-T R discrete-time receiver signal to produce a transmission time delay that is applied to the sampled modulated-source signal to produce a synchronized-interference signal;

a vector power series generator that produces a power vector with components that depend on the magnitude of the synchronized-interference signal;

a source multiplier that multiplies the synchronized-interference signal and the power vector to produce an interference vector;

a matched filter that filters the interference vector with the waveform filter to produce a matched-interference vector;

a weight generator that produces a vector of distortion weights that depend on the matched-interference vector;

a vector processor that produces from the vector of distortion weights a distorted-interference signal that depends on the interference vector;

a combiner that sums the distorted-interference signal and the discrete-time receiver signal to produce a residual-interference signal; and

a desired-signal demodulator for demodulating the residual-interference signal to produce estimates of the desired-signal digital-data.

2. The receiving apparatus of claim 1 , wherein the vector processor multiplies the interference vector and the vector of the distortion weights to produce a dot product that is filtered and sampled with the matched filter to produce the distorted-interference signal.

3. The receiving apparatus of claim 2 wherein the interference filter is time-division multiplexed to perform one filtering operation in each multiplex step for each of the components of the interference vector.

4. The receiving apparatus of claim 1 , wherein the power vector components produced by the power series generator include matched-interference signal magnitude values raised to the n−1 power, where n is an integer that is greater than unity.

5. The receiving apparatus of claim 1 , wherein the weight generator includes an estimated-gradient algorithm updated with the product of the matched-interference vector and the residual-interference signal.

6. A method for producing a bandpass distorted-interference signal in a satellite-transponder communication system that includes, at a local terminal, a digital-data source signal that is modulated to a modulated-source signal and, subsequently, filtered and converted to a bandpass signal and distorted in a nonlinear power amplifier to produce a bandpass distorted-interference signal, the method comprising:

filtering at the local terminal a received signal containing a bandpass desired signal;

deriving by waveform filtering modulated desired-signal digital-data produced at a remote terminal and the delayed bandpass distorted-interference signal;

producing a discrete-time receiver signal;

sampling the modulated-source signal and comparing the sampled modulated-source signal with the discrete-time receiver signal to produce a transmission time delay that is applied to the sampled modulated-source signal to produce a synchronized-interference signal;

power generating a power vector with components that depend on the magnitude of the synchronized-interference signal;

multiplying the synchronized-interference signal and the power vector to produce an interference vector;

interference filtering the interference vector to produce a filtered-interference vector;

weight generating a vector of distortion weights that depend on the filter-interference vector;

vector processing with the vector of distortion weights to produce a distorted-interference signal that depends on the interference vector;

combining the distorted-interference signal and the discrete-time receiver signal to produce a residual-interference signal; and

demodulating the residual-interference signal to produce estimates of the remote-terminal desired-signal digital-data.

7. The method of claim 6 , wherein the vector processing step multiplies the interference vector and the vector of the distortion weights to produce a dot product.

8. The method of claim 7 , further comprising a step of filtering the dot product to produce the period-T S distorted-interference signal.

9. The method of claim 8 , where the received signal filtering, interference filtering, and dot product filtering steps perform the same filtering that corresponds to the complex conjugate, time-inverted impulse response of the waveform filtering at the remote terminal.

10. The method of claim 6 , wherein the power vector components produced in the power generating step includes filtered-interference signal magnitude values raised to the n- 1 power, where n, integer, is greater than unity.

11. The method of claim 6 , wherein the weight generating step includes an estimated-gradient algorithm that is updated with the product of the filtered-interference vector and the residual-interference signal.

12. A transceiver for generation of a bandpass-interference signal, non-linear distortion interference cancellation, and demodulation of a cancelled signal, the transceiver comprising:

a source modulator that produces the bandpass-interference signal from a modulated-source signal;

a receiver filter/sampler, with a receiver-timing clock having a matched filter for filtering a received signal containing a bandpass distorted-interference signal, which results from passing the bandpass-interference through a nonlinear amplifier, and containing a bandpass desired signal, which is derived from desired-signal digital-data, and which has a modulation period of T D seconds and is filtered with a waveform filter, which produces a period-T R , T R <T D , discrete-time receiver signal, wherein the matched filter has a complex conjugate, time-inverted impulse response of the waveform filter, wherein T D and T R are nonzero real numbers less than unity;

a synchronizer/sampler that samples at a rate of 1/T R the modulated-source signal and compares the modulated-source signal with the period-T R discrete-time receiver signal to produce a transmission time delay applied to the modulated-source signal thereby producing a synchronized-interference signal;

a vector power series generator that produces a power vector having components dependent on the magnitude of the synchronized-interference signal;

a source multiplier that multiplies the synchronized-interference signal and the power vector to produce an interference vector;

a matched filter that filters the interference vector with the waveform filter to produce a matched-interference vector;

a weight generator that produces a vector of distortion weights dependent on the matched-interference vector;

a vector processor that produces from the vector of distortion weights a distorted-interference signal depending on the interference vector;

a combiner that sums the distorted-interference signal and the discrete-time receiver signal to produce a residual-interference signal; and

a desired-signal demodulator for demodulating the residual-interference signal to produce estimates of the desired-signal digital-data.