Digital transponder with real signal channelizer and synthesizer

1. A digital transponder comprising:

(a) an analog to digital converter configured to receive a real analog wideband multi-carrier signal and generate a real digital wideband multi-carrier signal from the real analog wideband multi-carrier signal, the real analog wideband multi-carrier signal comprising M channels, M being an integer greater than or equal to one;

(b) a channelizer configured to channelize the real digital wideband multi-carrier signal into 2M channelized digital signals, the 2M channelized digital signals comprising M pairs of channelized digital signals, each pair of channelized digital signals comprising a primary channelized digital signal and a secondary channelized digital signal, the secondary channelized digital signal being an image of the primary channelized digital signal;

(c) a switch matrix and signal construction module configured to generate a plurality of intermediate signals from only the primary channelized digital signals, the plurality of intermediate signals comprising pairs of intermediate signals, each pair comprising a primary intermediate signal and a secondary intermediate signal, the secondary intermediate signal being an image of the primary intermediate signal;

(d) at least one synthesizer, the at least one synthesizer configured to combine at least one pair of intermediate signals to generate a real digital output signal; and

(e) at least one digital to analog converter, the at least one digital to analog converter configured to convert the real digital output signal to an analog output signal.

2. The digital transponder of claim 1 , wherein each secondary intermediate signal is equal in amplitude and is anti-phase with the corresponding primary intermediate signal.

3. The digital transponder of claim 1 , wherein the channelizer is a polyphase FFT filter bank channelizer.

4. The digital transponder of claim 3 , wherein the channelizer is a 2M-point polyphase FFT filter bank channelizer.

5. The digital transponder of claim 1 , wherein the at least one synthesizer is a polyphase IFFT filter bank synthesizer.

6. The digital transponder of claim 5 , wherein

the digital output signal comprises N channels, N being an integer greater than or equal to one; and

the at least one synthesizer is a 2N-point polyphase IFFT filter bank synthesizer.

7. The digital transponder of claim 1 , wherein the switch matrix and signal construction module comprises:

at least one switch matrix configured to receive the primary channelized digital signals, select at least one primary channelized digital signal, and output the at least one selected signal as a desired channel signal; and

at least one signal construction module configured to receive the desired channel signal and generate the plurality of intermediate signals based on the desired channel signal.

8. The digital transponder of claim 7 , wherein

the switch matrix and signal construction module further comprises a digital control signal; and

the at least one switch matrix selects the at least one primary channelized signal based on the digital control signal.

9. The digital transponder of claim 8 , wherein

the real digital output signal comprises at least one of the M channels of the real digital wideband multi-carrier signal; and

the digital control signal dictates the at least one of the M channels.

10. The digital transponder of claim 8 , wherein

the analog output signal is at an intermediate frequency; and

the digital control signal dictates the intermediate frequency of the analog output signal.

11. The digital transponder of claim 7 , wherein at least one pair of intermediate signals comprise NIL signals.

12. The digital transponder of claim 11 , wherein the transponder is a bandwidth tunable filter.

13. A method of converting an input wideband multi-carrier signal into at least one analog output wideband multi-carrier signal, the method comprising:

(a) receiving the input wideband multi-carrier signal, the input wideband signal being a real analog signal and comprising M channels, M being an integer greater than or equal to one;

(b) digitizing the input wideband multi-carrier signal to produce a real digital input wideband multi-carrier signal;

(c) channelizing the real digital wideband multi-carrier signal into 2M separate channelized digital signals, the 2M channelized digital signals comprising M pairs of channelized digital signals, each pair of channelized digital signals comprising a primary channelized digital signal and a secondary channelized digital signal, the secondary channelized digital signal being an image of the primary channelized digital signal;

(d) generating a plurality of intermediate signals from only the primary channelized digital signals, the plurality of intermediate signals comprising pairs of intermediate signals, each pair comprising a primary intermediate signal and a secondary intermediate signal, the secondary intermediate signal being an image of the primary intermediate signal;

(e) synthesizing at least one pair of intermediate signals to generate at least one real digital output signal; and

(f) converting the at least one real digital output signal to the at least one real analog output signal.

14. The method of claim 13 , wherein the channelization is performed by a polyphase FFT filter bank channelizer.

15. The method of claim 14 , wherein the channelization is performed by a 2M-point polyphase FFT filter bank channelizer.

16. The method of claim 13 , wherein the synthesization is performed by at least one polyphase IFFT filter bank synthesizer.

17. The method of claim 13 , wherein the synthesization is performed by at least one 2N-point polyphase IFFT filter bank synthesizer where the at least one digital output signal comprises N channels and N is an integer greater than or equal to one.

18. The method of claim 13 , wherein the secondary intermediate signal is equal in amplitude and anti-phase with the primary intermediate signal.

19. The method of claim 13 , wherein the plurality of intermediate signals are generated in accordance with a digital control signal.

20. The method of claim 19 , wherein:

the at least one analog output signal comprises at least one of the M channels; and

the digital control signal dictates which of the M channels the at least one analog output signals comprises.

21. The method of claim 19 , wherein:

the at least one analog output signal is centered at an intermediate frequency; and

the digital control signal dictates the intermediate frequency of the at least one analog output signal.

22. A digital transponder system comprising:

a first transponder comprising:

a first analog to digital converter configured to receive a first real analog wideband multi-carrier signal and generate a first real digital wideband multi-carrier signal from the first real analog wideband multi-carrier signal, the real analog wideband multi-carrier signal comprising K channels, K being an integer greater than or equal to one; and

a first channelizer configured to channelize the first real digital wideband multi-carrier signal into 2K first channelized digital signals, the 2K first channelized digital signals comprising K pairs of first channelized digital signals, each pair of first channelized digital signals comprising a first primary channelized digital signal and a first secondary channelized digital signal, the first secondary channelized digital signal being an image of the first primary channelized digital signal; and

a second transponder interconnected with the first transponder so that the second transponder receives at least a portion of the first primary channelized signals, the second transponder comprising;

a second analog to digital converter configured to receive a second real analog wideband multi-carrier signal and generate a second real digital wideband multi-carrier signal from the second real analog wideband multi-carrier signal, the second real analog wideband multi-carrier signal comprising M channels, M being an integer greater than or equal to one;

a second channelizer configured to channelize the second real digital wideband multi-carrier signal into 2M second channelized digital signals, the 2M second channelized digital signals comprising M pairs of second channelized digital signals, each pair of second channelized digital signals comprising a second primary channelized digital signal and a second secondary channelized digital signal, the second secondary channelized digital signal being an image of the second primary channelized digital signal;

a switch matrix and signal construction module configured to generate a plurality of intermediate signals from only the portion of the first primary channelized digital signals and the second primary channelized digital signals, the plurality of intermediate signals comprising pairs of intermediate signals, each pair comprising a primary intermediate signal and a secondary intermediate signal, the secondary intermediate signal being an image of the primary intermediate signal;

at least one synthesizer, the at least one synthesizer configured to combine at least one pair of intermediate signals to generate a real digital output signal; and

at least one digital to analog converter, the at least one digital to analog converter configured to convert the real digital output signal to an analog output signal.