Equalizers for multi-branch receiver
A multi-branch receiver comprises a plurality of signal branches including branch filters to filter respective branch input signals and to produce corresponding branch output signals, a combiner to combine the branch output signals to produce a combined baseband signal, a pre-filter to filter the combined baseband signal to produce a received signal with minimum phase channel characteristics, and an equalizer to generate an estimate of a data sequence contained in the received signal.
1. A multi-branch receiver comprising:
a plurality of signal branches including branch filters to filter respective branch input signals and to produce corresponding branch output signals;
a combiner to combine the branch output signals from said branch filters to produce a combined baseband signal;
a pre-filter to filter the combined baseband signal to produce a received signal with minimum phase channel characteristics; and
an equalizer to generate an estimate of a data sequence contained in the received signal.
2. The multi-branch receiver of claim 1 wherein said plurality of branch input signals comprise two or more diversity signals received by two or more receive antennas.
3. The multi-branch receiver of claim 1 wherein said plurality of branch input signals comprise two or more signals received by a single antenna.
4. The multi-branch receiver of claim 3 wherein said plurality of branch input signals comprise two or more signal sample sequences with different sampling phases.
5. The multi-branch receiver of claim 4 wherein said plurality of branch input signals comprise quadrature and in-phase signals.
6. The multi-branch receiver of claim 1 wherein each branch filter comprises a matched filter matched to the channel impulse response of a corresponding signal branch.
7. The multi-branch receiver of claim 1 wherein said equalizer comprises a maximum likelihood sequence estimation equalizer.
8. The multi-branch receiver of claim 1 wherein said equalizer comprises a decision feedback equalizer.
9. The multi-branch receiver of claim 1 wherein said equalizer comprises a decision feedback sequence estimation equalizer.
10. The multi-branch receiver of claim 1 wherein said equalizer comprises a reduced state sequence estimation equalizer.
11. The multi-branch receiver of claim 1 further comprising a whitening filter preceding said branch filters to whiten noise in said branch input signals.
12. The multi-branch receiver of claim 11 wherein said branch input signals are oversampled signals and wherein said signal branches further comprise a serial-to-parallel converter generate a plurality of branch output signals for each signal branch.
13. A method of receiving signals in a multi-branch receiver, said method comprising:
filtering branch input signals in respective signal branches of the multi-branch receiver to produce branch output signals;
combining the branch output signals to produce a combined baseband signal;
prefiltering the combined baseband signal to provide a received signal with minimum phase channel characteristics; and
equalizing the received signal to provide an estimate of a transmitted data sequence.
14. The method of claim 13 wherein said branch input signals comprise two or more diversity signals received by two or more antennas.
15. The method of claim 13 wherein said plurality of branch input signals comprise two or more signals received by a single antenna.
16. The method of claim 15 wherein said plurality of branch input signals comprise two or more sample sequences with different sampling phases.
17. The method of claim 15 wherein said plurality of branch input signals comprise quadrature and in-phase signals.
18. The method of claim 13 wherein said branch input signals are filtered by matched filters matched to the channel impulse responses of said signal branches.
19. The method of claim 13 wherein said composite baseband signal is equalized by a maximum likelihood sequence estimation equalizer.
20. The method of claim 13 wherein said composite baseband signal is equalized by a decision feedback equalizer.
21. The method of claim 13 wherein said composite baseband signal is equalized by a decision feedback sequence estimation equalizer.
22. The method of claim 13 wherein said composite baseband signal is equalized by a reduced state sequence estimation equalizer.
23. The method of claim 13 further comprising whitening said branch input signals prior to filtering said branch input signals.
24. The method of claim 23 wherein said branch input signals are oversampled signals and further including converting the oversampled branch input signal into a plurality of symbol-spaced sequences.