Minimizing bandwidth in down-conversion of multiple RF channels

摘要

A method and system is disclosed for simultaneously down-converting multiple selected signals, such as RF signals, into adjacent ranges in an intermediate frequency band so that the total resulting bandwidth, and thus the sampling rate required to digitize the signal, is minimized. A first signal is down-converted into a range starting at a lowest selected frequency in the IF band. The next signal is down-converted, into a range higher than, but near or adjacent to, the down-converted range of the first signal, and so on. A guard band may be left between the signals if desired. In this way, the selected signals occupy the minimum bandwidth required. When the selection of signals to be down-converted is changed, the frequency ranges are dynamically adjusted so that the signals being down-converted always occupy the lowest ranges of the IF band.

主权项

1. A computer implemented method of concurrently down-converting channels of information from an input signal in a first frequency band to a second frequency band, comprising:
receiving in a processor a selection of a plurality of channels in the input signal to be down-converted; determining by the processor a plurality of frequency ranges nearby to one another and starting at a lowest frequency of the second frequency band, each frequency range having a bandwidth corresponding to one of the plurality of channels; receiving in the processor a first selected transfer function and a second selected transfer function, the first selected transfer function for down-converting a first one of the plurality of channels to a first one of the plurality of frequency ranges which is the lowest frequency range in the second frequency band, and the second selected transfer function for down-converting a second one of the plurality of channels to a second one of the plurality of frequency ranges which is the next lowest frequency range in the second frequency band; determining by the processor a first plurality of sets of scaling factors representing the first transfer function and a second plurality of sets of scaling factors representing the second transfer function; receiving a sequential series of samples of the input signal from an array of sampling circuits for sampling the input signal in response to a timing signal, the array configured such that the sampling circuits create samples of the input signal in a time-delayed sequence at an interval, and wherein each individual sampling circuit operates at a rate of the interval between samples times the number of sampling circuits; successively multiplying in the processor each of the samples of the input signal by the first plurality of sets of scaling factors by rotating between each of the first plurality of sets of scaling factors, each multiplication resulting in a first set of interim outputs; successively multiplying in the processor each of the samples of the input signal by the second plurality of sets of scaling factors by rotating between each of the second plurality of sets of scaling factors, each multiplication resulting in a second set of interim outputs; summing in the processor the first set of interim outputs to create a first output signal in the first one of the plurality of frequency ranges in the second frequency band; and summing in the processor the second set of interim outputs to create a second output signal in a second one of the plurality of frequency ranges in the second frequency band.