Very high SFDR interpolation filters for software radio

Software radio liberates several important functions and parameters from a crippling dependence on hardwired characteristics. Examples are the intermediate frequency (IF), the baseband sampling rate, and the choice of the demodulation/detection scheme. By merely downloading the software matched to a particular mode or standard, it allows the desired operation to be achieved. It also permits the use of frequency agile techniques, since the NCO can change the frequency in a single clock cycle. One such key function is the sampling rate conversion. We present a new family of interpolation filters for sample rate conversion, which offer very high SFDR (spur-free dynamic range) values ranging from 90 dB to 170 dB. Called JIF, they are constructed by cascading two or more stages of Hamming-windowed sine pulse filters. In addition to the remarkable SFDRs, these filters also offer excellent passband characteristics so that the need for an additional shaping stage, warranted in some designs, is obviated. Also discussed is a novel platform-based implementation concept. Significant improvement in both performance and design time can thereby be achieved.