Design of an RSFQ asynchronous pipelined kogge-stone adder and developing custom compound gates

Since the invention of computers, arithmetic and logic operations using digital circuits have been one of the leading problems in processor design. This problem forced designers to develop specialized logic circuits for faster and efficient calculations, namely adder and multiplier circuits. Nowadays straight forward usage of conventional Complementary Metal Oxide Semiconductor (CMOS) logic circuits, have encountered a fundamental obstacle in terms of power consumption. One of the major alternatives to this technology, Rapid Single Flux Quantum (RSFQ), presents the advantage of higher operation speed while ensuring very low power consumption. In the last 20 years, different circuits have been designed via RSFQ technology with faster operation speed and a third order of magnitude lower power consumption compared to CMOS technology. However, RSFQ is a relatively new technology therefore, there is not many commercially available design and routing tools for the circuit level design and the entire routing have to be done manually. In this study, a custom, wave pipelined, 8 bit Kogge Stone Adder circuit and a custom compound logic gate similar to Full Adder, is designed. It is noteworthy to mention that all wiring and logic block designs are made manually and component parameters of the designed compound gate are optimized using Particle Swarm Optimization tool. Besides, timing analyses are made to the whole circuit by using Statistical Timing Analysis Tool for SFQ Cells (STATS) to improve jitter and timing of the whole circuit. Finally, an 8 bit Kogge-Stone Adder circuit is designed with a 25GHz target working frequency which also utilizes 6581 Josephson Junctions.