Digital filter-decimator-tuner

1. A digital filter-decimator-tuner configured to receive a complex digitally sampled signal input x k and output a complex digital USB signal yu k and a complex digital LSB signal yl k , comprises:

an upper sideband (USB) processing path coupled to receive x k and output yu k based on a tuned USB complex signal, the USB processing path including a first USB finite impulse response (FIR) filter configured to receive the x k signal and output a filtered USB signal, a decimator configured to decimate the filtered USB signal and output a filtered decimated complex USB signal, a USB tuner configured to receive the filtered decimated complex USB signal and a USB tuning signal and to output the tuned USB complex signal; and

a lower sideband (LSB) processing path coupled to receive x k and output yl k based on a tuned LSB complex signal the LSB processing path including a first LSB FIR filter configured to receive the x k signal and output a filtered LSB signal, a decimator configured to decimate the filtered LSB signal and output a filtered decimated complex LSB signal, a LSB tuner configured to receive the filtered decimated complex LSB signal and a LSB tuning signal and to output the tuned LSB complex signal.

2. The apparatus of claim 1 , further comprising:

a USB equalization filter configured to receive the tuned USB complex signal and output yu k ; and

a LSB equalization filter configured to receive the tuned LSB complex signal and output yl k .

3. The apparatus of claim 2 , wherein the USB equalization filter and the LSB equalization filter are of order m, where m is an integer greater than or equal to one.

4. The apparatus of claim 3 , wherein m=3.

5. The apparatus of claim 1 , wherein the USB FIR filter and the LSB FIR filter are of order n, where n is an integer greater than or equal to one.

6. The apparatus of claim 5 , wherein n=9.

7. The apparatus of claim 1 , wherein the USB tuner and the LSB tuner are implemented with multipliers.

8. The apparatus of claim 1 , wherein the digital filter-decimator-tuner has a sampling rate Fs, the center frequency of the filtered USB signal is +Fs/8, and the center frequency of the filtered LSB signal is −Fs/8.

9. The apparatus of claim 1 , wherein the USB decimator and the USB decimator both decimate by a factor of two.

10. The apparatus of claim 1 , wherein the USB tuning signal is u k =e −j2πk/4 u k =e −j2πk/4 and the LSB tuning signal is u′ k =e +j2πk/4 wherein k is an integer greater than or equal to zero.

11. The apparatus of claim 1 , wherein the USB FIR filter and LSB FIR filter are implemented as a symmetric filter.

12. The apparatus of claim 1 , wherein the USB FIR filter and the LSB FIR filter are implemented as a single filter simultaneously processing USB and LSB signals and producing USB and LSB output signals by partial sums manipulation.

13. The apparatus of claim 1 , further comprising a second USB FIR filter disposed before the USB tuner and the USB decimator and a second LSB FIR filter disposed before the LSB tuner and the LSB decimator.

14. A digital filter-decimator-tuner configured to receive a complex digitally sampled signal input x k and output a complex digital USB signal y uk and a complex digital LSB signal y lk , comprises:

an upper sideband (USB) and a lower sideband (LSB) processing path coupled to receive the input x k signal and output y uk and y lk , the USB and LSB processing path including a finite impulse response (FIR) filter configured to receive the input x k signal and output a filtered USB signal and a filtered LSB signal,

a USB decimator configured to decimate the filtered USB signal and to output a filtered decimated complex USB signal,

a LSB decimator configured to decimate the filtered LSB signal and output a filtered decimated complex LSB signal,

a USB tuner configured to receive the filtered decimated complex USB signal and a USB tuning signal and output a tuned USB complex signal,

a LSB tuner configured to receive the filtered decimated complex LSB signal and a LSB tuning signal and output a tuned LSB complex signal,

a USB equalization filter configured to receive the tuned USB complex signal, and to output y uk , and a LSB equalization filter configured to receive the tuned LSB complex signal, and output y lk .

15. The apparatus of claim 14 , wherein the USB tuner and the LSB tuner include multipliers.

16. The apparatus of claim 14 , wherein the digital filter-decimator-tuner has a sampling rate Fs, the center frequency of the filtered USB signal is +Fs/8, and the center frequency of the filtered LSB signal is −Fs/8.

17. The apparatus of claim 14 , wherein the decimator is configured to decimate by a factor of two.

18. The apparatus of claim 14 , wherein the USB tuning signal is u k =e −j2πk/4 and the LSB tuning signal is u′ k =e +j2πk/4 wherein k is an integer greater than or equal to zero.

19. The apparatus of claim 14 , wherein the FIR filter is configured as a 9-point digital filter.

20. The apparatus of claim 14 , wherein the USB equalization filter is configured as a 3-point digital filter and the LSB equalization filter is configured as a 3-point digital filter.

21. A method for digitally filtering, decimating and tuning a complex digitally sampled input signal x k to output a complex digital upper sideband (USB) signal yu k , the method comprising:

using a finite impulse response filter to filter the input signal x k , and output a first USB intermediate filtered signal;

using a decimator to decimate the first USB intermediate filtered signal and output a second USB intermediate signal;

using a USB tuner configured to receive as inputs the second USB intermediate signal and a USB tuning signal and output a third USB intermediate signal;

outputting yu k in response to the third USB intermediate signal.

22. The method of claim 21 , wherein said outputting yu k includes using a USB equalization filter to equalize the third USB intermediate signal.

23. The method of claim 22 , wherein using the USB tuner includes multiplying the inputs to the tuner to form the output of the tuner.