Analysis And Research On Signal Integrity Of Transmission Line In Superconducting RSFQ Circuit

Due to the size and performance of traditional complementary metal oxide semiconductor(CMOS)integrated circuits approaching their limits,superconducting rapid single-flux-quantum(RSFQ)circuit has been proposed for high performance processors.There are two fundamental methods used for interconnection of the logic cells in RSFQ circuits: Josephson transmission line(JTL)and superconducting passive transmission line(PTL).Modeling and analysis of these two kinds of interconnects are the key to design of large scale superconducting RSFQ circuits.In this dissertation,JTL and PTL are modeled and analyzed.The main work of this dissertation includes two aspects:To analyze the time-domain response of Josephson transmission line,a method based on Runge-Kutta algorithm is proposed to analyze Josephson transmission line using the resistive-capacitive shunted junction(RCSJ)model.The numerical results obtained by this method agree well with the simulation results from WRspice.To analyze the time-domain response of passive superconducting transmission lines terminated with Josephson junctions,two co-analysis methods are proposed for passive superconducting transmission lines combined with active Josephson junctions.Firstly,a method based on finite-difference time-domain(FDTD)and Newton-Raphson iterative algorithm is proposed to co-analyze single passive superconducting transmission line combined with Josephson junctions.The FDTD numerical method is used to solve the telegraph equations of the single passive transmission line,and the Newton-Raphson iterative algorithm is used to solve the nonlinear boundary conditions at the interfaces between the passive superconducting transmission line and Josephson junctions.Secondly,a method based on FDTD and contractive mapping theorem is proposed to co-analyze multiconductor passive superconducting transmission lines combined with Josephson junctions.The FDTD method is used to solve the multiconductor transmission-line equations of coupled passive transmission lines.Then,according to the contractive mapping theorem,an iteration algorithm is used to solve the nonlinear equations generated by the nonlinear boundaries.In addition,the convergence and stability conditions of the proposed co-analysis methods are also given.The simulation and numerical results show that the proposed co-analysis methods have the same accuracy as WRspice and higher efficiency than WRspice.