Modeling SIS junction arrays for APEX band 3 (385-500 GHz)

Paper in proceeding, 2010

Abstract- A methodology for the modeling of superconductinginsulator- superconducting (SIS) junction arrays will be presented and compared with measured results. In many cases, junction arrays (either in parallel or series) are treated as a single equivalent junction. The APEX Band 3 (385-500 GHz) receiver design has been implemented with two junctions connected in parallel via a section of inductive microstrip line. In this case, it is desirable to separately model each junction as the pumping between junctions is no longer symmetrical across the entire band. Since the performance of the SIS junction depends on its terminating network, a complicated interaction occurs when another junction is part of the embedding impedance and, therefore, there remain aspects of its performance that are difficult to analyse. A simplified model, demonstrated with MATLAB, will be given and compared with a more complete model implemented using a common circuit simulator, Agilent ADS. In both cases, each junction is represented by a quasi 5-port network determined using the quantum theory of mixing. The model is then used to predict the performance of the APEX Band 3 mixer and compared with measured results.