Adaptive digital cancellation using probe waveforms
A method and apparatus for achieving simultaneous transmit and receive operation with digital cancelling based upon probe waveforms is described. Digital cancelling based upon probe waveforms enables adjacent transmitting and receiving channels to transmit and receive correlated signals.
1. A method for simultaneous transmit and receive (STAR) operation comprising:
emitting, by a transmit channel, a transmit signal, wherein the transmit signal includes at least a source signal portion and a probe signal portion;
coupling a portion of the transmit signal from an output of the transmit channel to an observation receive channel coupled to a same antenna element as the transmit channel;
determining an estimated observed probe signal portion based upon the coupled portion of the transmit signal;
generating a cancel signal based upon the estimated observed probe signal portion;
receiving, via a receive path, a receive signal comprising at least a portion of a signal of interest and at least a portion of the emitted transmit signal; and
combining the receive signal with the cancel signal to generate an estimate of the signal of interest.
2. The method of claim 1 , wherein the source signal portion and the portion of the signal of interest are correlated.
3. The method of claim 1 , further comprising:
generating, an estimate of the observation channel response based on the transmit signal and the coupled portion of the transmit signal;
wherein the estimated observed probe signal portion is generated further based on the estimate of the observation channel response.
4. The method of claim 3 , wherein determining the estimated observed probe signal comprises:
weighting the probe signal according to the estimate of the observation channel reference.
5. The method of claim 1 , further comprising:
generating a residual error signal, wherein the residual error signal comprises the difference between a weighted portion of the source signal and the estimate of the signal of interest.
6. The method of claim 5 , wherein the weighted portion of the source signal is generated according to least mean squares, recursive lease squares, or sample matrix inversion.
7. The method of claim 5 , wherein the cancel signal is further determined based upon the residual error signal.
8. An apparatus for multichannel simultaneous transmit and receive, comprising:
a plurality of transmit channels, wherein each of the transmit channels comprises an observation channel estimator and an adaptive canceller; and
a plurality of probes each configured to introduce a probe signal to a respective transmit channel;
wherein each observation channel is configured to determine an estimated probe signal;
wherein each adaptive canceller is configured to generate a cancel signal based upon the estimated probe signal.
9. The apparatus of claim 8 , wherein each transmit channel is coupled to an observation receiver configured to measure a transmit signal emitted by the respective transmit channel.
10. The apparatus of claim 8 , wherein each observation channel is further configured to determine the estimated probe signal based upon the measured transmit signal.
11. The apparatus of claim 8 , further comprising a residual signal canceller configured to generate a residual error signal based upon a source signal and an estimated signal of interest.
12. The apparatus of claim 11 , wherein each cancel signal is further generated according to the residual error signal.
13. The apparatus of claim 8 , wherein each cancel signal generated by the plurality of transmit channels is summed at a node.
14. The apparatus of claim 13 , wherein the summed cancel signal is subtracted from a receive signal to generate an estimated signal of interest.
15. The apparatus of claim 8 , wherein a first of the plurality of transmit channels is configured to subtract the cancel signal generated by the first transmit channel from a receive signal to generate a partial error signal.
16. The apparatus of claim 15 , wherein a second of the plurality of transmit channels is configured to subtract the cancel signal generated by the second transmit channel from the partial error signal to generate an estimated signal of interest.
17. The apparatus of claim 8 , wherein the plurality of transmit channels are within an antenna array.