Wideband Digital Downconverters for Synthetic Instrumentation

In this paper, we introduce a new wideband digital downconverter (WDDC) for synthetic instruments (SIs). DDCs first tune to a signal´s center frequency using a numerically controlled oscillator and mixer and then zoom-in to the bandwidth of interest using sample rate conversion (SRC). The SRC is required to produce continuously variable output sample rates from a fixed input sample rate over a large range. Current implementations accomplish this using a prefilter, an arbitrary factor resampler, and integer decimation filters. In this paper, we simplify the SRC of the WDDC, yielding a reduction in computational cost by a factor of 3 or more.