Designing efficient residue arithmetic based VLSI correlators

The most important reason for the lack of commercial residue arithmetic (RA) based systems is not the "slow" and area consuming reverse conversion, but the absence of research that explores the system-level trade-offs of such arithmetic in actual VLSI implementations. Such system-level issues are-choice of the moduli set, effect of moduli imbalance on resulting VLSI implementation, choice of the reverse and forward convertors, use of lookup versus computation for modular operations, system characteristics that indicate RA suitability and finally, typical VLSI area and performance figures. This paper explains these concerns by presenting novel RA architectures for VLSI correlators employed in radioastronomy and ultrasonic blood flow measurement. A state-of-the-art, high performance (80-100 MHz), RA-based correlator ASIC was successfully fabricated as a result of this research.