Multichannel signal modulator for use in broadcast satellite applications

1. A multichannel signal modulator for use in the digital generation of a unitary multichannel signal at a selected bandwidth from a plurality of source signals, said multichannel signal modulator being a device comprising:

a plurality of signal inputs each comprising a device connection for reception of a separate source signal from a signal source;

a signal assembly system, comprising:

modulation means, namely a plurality of modulator circuits corresponding to the plurality of source signals and each operatively connected to one of the plurality of signal inputs for the modulation of the corresponding source signal, wherein following modulation by the plurality of modulator circuits the plurality of source signals is a plurality of modulated signals;

source upsampling means, namely a plurality of source upsamplers corresponding and operatively connected to each of the plurality of modulator circuits and each capable of upsampling the related modulated signal to an upsampled signal at at least one selectable sample rate shared with each of the other of the plurality of source upsamplers, whereby in operation upon selection of a selected common sample rate from the available selectable sample rates selected to allow representation of each of the plurality of source signals in the ultimately completed unitary multichannel signal at the selected bandwidth, each source upsampler will yield an upsampled signal at the selected common sample rate;

frequency mixing means, namely a frequency mixer operatively connected to the source upsampling means to receive and combine the plurality of upsampled signals into a unitary signal; and

final upsampling means, namely a final upsampler operatively connected to the frequency mixer for the upsampling of the unitary signal into a unitary multichannel signal at the selected bandwidth; and

a signal output for output of said unitary multichannel signal from the signal assembly system at the selected bandwidth;

wherein in operation the signal assembly system will:

modulate each source signal received via its corresponding modulator circuit into a modulated signal;

select a selected common sample rate for use by the source upsamplers from the at least one available selectable sample rate;

upsample each modulated signal at the selected common sample rate into an upsampled signal, via the source upsampler corresponding to the corresponding modulator circuit;

using the frequency mixer, mix the plurality of upsampled signals into a unitary signal; and

format the unitary signal into the desired final unitary multichannel signal at the selected bandwidth using the final upsampler for output via the signal output, wherein the final unitary multichannel signal contains a representation of all of the source signals by virtue of the selection and application of the appropriate selected common sample rate.

2. The multichannel signal modulator of claim 1 , further comprising a digital-to-analog converter between the final upsampler and the signal output, where in operation of the multichannel signal modulator the multichannel signal will be converted from its digital creation format to an analog format for further processing or transmission.

3. The multichannel signal modulator of claim 1 , wherein the plurality of source signals are at different frequencies.

4. The multichannel signal modulator of claim 1 wherein the modulation of the plurality of modulator circuits, in respect of each source signal, comprises at least one of:

grooming the source signal;

application of forward error correction to the source signal;

modulation of the source signal;

pulse shaping of the source signal; or

amplitude control of the source signal.

5. The multichannel signal modulator of claim 1 further comprising a timing control circuit operatively connected to the plurality of modulator circuits, to synchronize the modulation of the plurality of source signals.

6. The multichannel signal modulator of claim 1 wherein the source upsampler comprises a plurality of source upsampling circuits corresponding to the plurality of modulated signals, each source upsampling circuit for upsampling of an individual modulated signal from the modulation means.

7. The multichannel signal modulator of claim 1 wherein the frequency mixer comprises at least one mixing circuit operable to place the plurality of upsampled signals relative to each other in the unitary signal.

8. The multichannel signal modulator of claim 7 wherein the at least one mixing circuit is a plurality of mixing circuits corresponding to the plurality of upsampled signals.

9. The multichannel signal modulator of claim 8 wherein the frequency mixer further comprises a signal adder for summing the outputs of the plurality of mixing circuits into the unitary signal.

10. The multichannel signal modulator of claim 8 , wherein each of the plurality of mixing circuits further comprises a numerically controlled oscillator.

11. The multichannel signal modulator of claim 1 further comprising signal transmission means, namely a signal transmitter for the transmission of the multichannel signal at the selected bandwidth to a receiver.

12. The multichannel signal modulator of claim 11 , wherein the signal transmitter amplifies the multichannel signal before transmission to the receiver.

13. The multichannel signal modulator of claim 11 wherein the signal transmitter shifts the multichannel signal to a final output frequency before transmission to the receiver.

14. The multichannel signal modulator of claim 1 wherein the source upsampler and the frequency mixer comprise a channelizer.

15. The multichannel signal modulator of claim 14 , wherein the channelizer comprises a Fast Fourier Transform (FFT) channelizer.