Antenna diversity combining for differentially modulated orthogonal frequency division multiplexed (OFDM) signals

1. An apparatus comprising:

a first tuner configured to receive a radio frequency (RF) signal from a first antenna and to process the RF signal to generate a first time-domain quadrature signal;

a second tuner configured to receive the RF signal from a second antenna and to process the RF signal to generate a second time-domain quadrature signal;

a combiner circuit configured to receive the first and second time-domain quadrature signals, the combiner circuit including:

a first path circuit configured to convert the first time-domain quadrature signal to a first frequency-domain signal and to differentially decode the first frequency-domain signal;

a second path circuit configured to convert the second time-domain quadrature signal to a second frequency-domain signal and to differentially decode the second frequency-domain signal; and

a first combiner configured to combine the first and second decoded frequency-domain signals into a combined frequency-domain signal;

a re-encoder coupled to the first combiner to generate an estimated signal based on the combined frequency-domain signal;

a first filter configured to filter the first time-domain quadrature signal based at least in part on the estimated signal;

a second filter configured to filter the second time-domain quadrature signal based at least in part on the estimated signal; and

a second combiner configured to combine the filtered first and second time-domain quadrature signals.

2. The apparatus of claim 1 , wherein the re-encoder comprises a phase integrator configured to integrate a phase between consecutive symbols.

3. The apparatus of claim 2 , further comprising a controller configured to initialize the phase integrator using a phase of a Time-Frequency-Phase-Reference (TFPR) symbol.

4. The apparatus of claim 1 , further comprising:

a first multiplier configured to multiply a conjugate of the first frequency-domain signal with the estimated signal to generate a first channel estimate; and

a second multiplier configured to multiply a conjugate of the second frequency-domain signal with the estimated signal to generate a second channel estimate.

5. The apparatus of claim 4 , further comprising:

a first conversion engine configured to convert the first channel estimate from a frequency-domain to a first time-domain estimate; and

a second conversion engine configured to convert the second channel estimate from a frequency-domain to a second time-domain estimate.

6. The apparatus of claim 5 , wherein the first filter comprises at least one tap configured with the first time-domain estimate, and the second filter comprises at least one tap configured with the second time-domain estimate.

7. The apparatus of claim 1 , further comprising a third tuner configured to receive the combined frequency-domain signal and including a third combiner configured to generate a diversity combined signal via combination of the combined frequency-domain signal with a third frequency-domain signal generated in the third tuner from the RF signal received in the third tuner from a third antenna.

8. The apparatus of claim 7 , wherein the third tuner further comprises a de-mapper configured to de-map the diversity combined signal into a de-mapped frequency-domain signal and to provide the de-mapped frequency-domain signal to a demodulator, the demodulator not including a de-mapper.

9. The apparatus of claim 7 , wherein the third tuner further includes:

a second re-encoder configured to encode the diversity combined signal; and

a conversion engine to convert the encoded diversity combined signal to a diversity time-domain signal.

10. The apparatus of claim 9 , further comprising a cyclic prefix generator configured to generate a cyclic prefix from the diversity time-domain signal and to append the cyclic prefix to the diversity time-domain signal to generate a differential orthogonal frequency division multiplexed (OFDM) time-domain signal to a demodulator.

11. The apparatus of claim 1 , wherein the combiner circuit is integrated in the second tuner, the first tuner and the second tuner each formed on a single semiconductor die.

12. A method comprising:

receiving a radio frequency (RF) signal from a first antenna and generating a first time-domain quadrature signal therefrom;

receiving the RF signal from a second antenna and generating a second time-domain quadrature signal therefrom;

converting the first time-domain quadrature signal to a first frequency-domain signal and converting the second time-domain quadrature signal to a second frequency-domain signal;

differentially decoding the first frequency-domain signal and differentially decoding the second frequency-domain signal;

combining the decoded first frequency-domain signal and the decoded second-frequency domain signal to obtain an estimated signal;

combining the estimated signal with a conjugate of the first frequency-domain signal to obtain a first channel estimate;

combining the estimated signal with a conjugate of the second frequency-domain signal to obtain a second channel estimate;

filtering the first time-domain quadrature signal using the first channel estimate and filtering the second time-domain quadrature signal using the second channel estimate; and

combining the first and second filtered time-domain quadrature signals to generate a diversity time-domain signal.

13. The method of claim 12 , further comprising:

convolving the conjugate of the first frequency-domain signal with the estimated signal to generate the first channel estimate; and

convolving the conjugate of the second frequency-domain signal with the estimated signal to generate the second channel estimate.

14. The method of claim 13 , further comprising:

converting the first channel estimate to a first time-domain estimate; and

converting the second channel estimate to a second time-domain estimate.

15. The method of claim 14 , further comprising configuring at least one tap of a first filter with the first time-domain estimate and configuring at least one tap of a second filter with the second time-domain estimate.

16. The method of claim 12 , further comprising receiving the diversity time-domain signal in a tuner and generating a diversity combined signal via combination of the diversity time-domain signal with a third time-domain signal generated in the tuner from the RF signal received in the tuner from a third antenna.

17. An apparatus comprising:

a first tuner configured to receive a radio frequency (RF) signal from a first antenna, the first tuner including:

a RF front end circuit configured to condition the RF signal;

an analog-to-digital (ADC) converter configured to convert the conditioned RF signal to a digitized signal;

a digital front end circuit configured to generate a first time-domain quadrature signal from the digitized signal; and

a digital signal processor (DSP) coupled to the digital front end circuit, the DSP comprising:

a first path circuit configured to convert the first time-domain quadrature signal to a first frequency-domain signal and to differentially decode the first frequency-domain signal;

a second path circuit configured to convert a second time-domain quadrature signal to a second frequency-domain signal and to differentially decode the second frequency-domain signal, the second time-domain quadrature signal generated by a second tuner from the RF signal received from a second antenna;

a first combiner configured to combine the first and second decoded frequency-domain signals into a combined frequency-domain signal; and

a re-encoder coupled to the first combiner configured to generate an estimated signal based on the combined frequency-domain signal, a first filter configured to filter the first time-domain quadrature signal based at least in part on the estimated signal, a second filter configured to filter the second time-domain quadrature signal based at least in part on the estimated signal, and a second combiner configured to combine the filtered first and second time-domain quadrature signals.