Characteristics Of Josephson Transmission Line In Superconducting RSFQ Circuits

RSFQ (Rapid-Single-Flux-Quantum) logic family is a new type of technology in superconducting digital circuits, in which the information is carried in the presence or absence of SFQ voltage pulses generated by damped Josephson junctions. Its intrinsic switching time is very short; on the order of a picosecond. Perhaps even more important is the low power dissipation; superconducting circuits dissipate on the order of a microwatt per gate, a thousand times less than CMOS circuits.JTL (Josephson junction transmission line) is & key element of RSFQ, comprising several Josephson junctions connected in parallel by superconducting strips of a relatively low inductance. The comprising of clock distribution network and information transmission between different cells is firmly depended on proper working of JTL. To understand the features of parameters and transmission of JTL, in this dissertation, a complete study is performed through theoretical analysis and numerical simulations, and some features and new phenomenon are founded.(1) Through simulations on JTL with different parameter conditions, the new phenomenon of annihilation and passing through of voltage pulses are founded, and the conditions are obtained at the same time;(2) The JTL ring oscillator is utilized in studying the repulsion effect of pulses on JTL, thus the bounded influence is eliminated, and precision results can obtained. And frequency of RSFQ circuits is limited by this effects;(3) A systemic studies of characteristics of parameters on SFQ transmission are performed, such as transmission time and voltage height. The results that increasing of bias current and shunted resistance and lowing critical current and connected inductance can decrease the transmission time are shown;(4) A new type of circuit, ladder shape multiplayer JTL. structure is provided by author, thus output signal of RSFQ circuits can be amplified before transfer to room temperature electronics system. It has highly gain of amplify relatively and the double peak structure are avoided through decreasing parasitic capacitance.