Superconducting single flux quantum circuits using the residue number system
Qing Ke
Superconducting single flux quantum (SFQ) circuits are promising for digital signal processing systems. However, conventional binary arithmetic does not take full advantage of the fundamental properties of SFQ circuits. The residue number system (RNS) is intrinsically more compatible with single flux quantum circuits, and provides the advantage of modularity, parallelism, carry-free structure, simple multiplication and fault tolerance.
We designed a one-decimal-digit adder to demonstrate this new technology. The exclusive use of simple and robust Josephson shift registers creates large margins, simple circuit architecture and high throughput. These attributes are important for state-of-the-art superconducting technology, and are especially crucial for high temperature superconducting digital circuits. We designed, simulated and extensively optimized a mod 5 adder and its subcells. We laid out the circuits and had them fabricated. We tested the low speed functionality of these circuits using a manual test setup and a LabVIEW automated test setup. All the subcell experimental results show decent operation margins and good consistency with the simulation results, and demonstration of the entire mod 5 adder should be straightforward.
An SFQ RNS 8-bit multiplier is proposed. Comparing to superconducting binary bit-serial and bit-parallel 8-bit multipliers, it shows an advantage in design simplicity, operation margins, error rate and throughput, along with its unique feature of simple fault tolerance.
We thus believe that RNS, rather than binary, could be the natural language for superconducting digital electronics, especially in the application of digital signal processors.
•Oct 3, 1996•5 citations