MRC antenna diversity for FM IBOC digital signals

1. A method for processing a radio signal comprising:

receiving a signal on two antennas;

demodulating the signal using first and second independent signal paths that are synchronized by symbol number;

maximum ratio combining branch metrics from the two receiver paths; and

using the combined branch metrics to produce an output, wherein a first one of the first and second independent signal paths to reach Subframe Lock coordinates operations for maximum ratio combining the branch metrics and downstream operations.

2. The method of claim 1 , wherein the first and second signal paths adjust the magnitudes of the first and second branch metrics in response to a signal-to-noise ratio of the signal in the first and second signal paths.

3. The method of claim 1 , wherein the maximum ratio combining step sums corresponding, synchronized branch metrics from the first and second independent signal paths.

4. The method of claim 1 , wherein when one of the signal paths has no branch metrics available, the branch metrics of that signal path are zeroed.

5. A method for processing a radio signal comprising:

receiving a signal on two antennas;

demodulating the signal using first and second independent signal paths that are synchronized by symbol number;

maximum ratio combining branch metrics from the two receiver paths; and

using the combined branch metrics to produce an output, wherein the first and second independent signal paths each include a demodulator and only one of the demodulators at a time changes its state.

6. The method of claim 5 , wherein transitions between states is initiated either by a reacquisition or a Subframe Lock.

7. The method of claim 5 , wherein each of the demodulators can be in only one of two modes, SYNC or DECODE.

8. The method of claim 7 , wherein the SYNC mode is entered by a reacquisition, and the DECODE mode is entered by a Subframe Lock.

9. A receiver comprising:

first and second inputs configured to receive a signal on two antennas; and

first and second demodulators for demodulating the signal in first and second independent signal paths that are synchronized by symbol number; and

circuitry for maximum ratio combining branch metrics from the two signal paths, and using the combined metrics to produce an output, wherein a first one of the first and second independent signal paths to reach Subframe Lock coordinates operations for maximum ratio combining the branch metrics, and downstream operations.

10. The receiver of claim 9 , wherein the first and second signal paths adjust the magnitudes of the first and second branch metrics in response to a signal-to-noise ratio of the signal in the first and second signal paths.

11. The receiver of claim 9 , wherein the maximum ratio combining sums corresponding, synchronized branch metrics from the first and second independent signal paths.

12. The receiver of claim 9 , wherein when one of the signal paths has no branch metrics available, the branch metrics of that signal path are zeroed.

13. A receiver comprising:

first and second inputs configured to receive a signal on two antennas; and

first and second demodulators for demodulating the signal in first and second independent signal paths that are synchronized by symbol number; and

circuitry for maximum ratio combining branch metrics from the two signal paths, and using the combined metrics to produce an output, wherein only one of the demodulators at a time changes its state.

14. The receiver of claim 13 , wherein transitions between states is initiated either by a reacquisition or a Subframe Lock.

15. The receiver of claim 13 , wherein each of the demodulators can be in only one of two modes, SYNC or DECODE.

16. The receiver of claim 15 , wherein the SYNC mode is entered by a reacquisition, and the DECODE mode is entered by a Subframe Lock.