Single flux quantum circuits using the residue number system

We have designed and developed superconducting single flux quantum (SFQ) digital signal processing circuits using the residue number system (RNS). RNS arithmetic is a complete alternative to binary arithmetic for performing digital computations, which appears to have many advantages for SFQ circuits. We present a scheme for performing all RNS arithmetic functions using Josephson shift registers alone, and suggest that this Is advantageous for high-temperature superconductor computational circuits. We have designed a one-decimal-digit adder, realized with Nb-based superconducting circuitry. Its most complex component, the mod5 adder, has been simulated to show perfect functionality and subcell simulated margins are compared with the experimental results.<>