Design of extensible superconducting multiplexer with modular structure to overcome the limit of wafer size

Abstract In this paper, a new compact superconducting multiplexer with an extensible modular structure is proposed. The multiplexer consists of a common input feeder and multiple bandpass filters. The common feeder is realized by a transmission line with a characteristic impedance of 50 ohms. Compared with the conventional multiplexer, the proposed length of the common feeder is extensible, making it feasible to design a multiplexer consisting of arbitrary number of channels. In addition, the interaction between channel filters can be compensated for by adjusting the parameters of the channel filters. Therefore, no additional compensation circuit will be needed for the proposed multiplexer, leading to a lower volume or smaller size than conventional multiplexers. A six-channel multiplexer is designed and fabricated. Moreover, since there are open circuit points in the common input feeder of the proposed multiplexer, it is possible to divide the whole multiplexer into several individual components along these points. As a result, each component can be fabricated individually before being assembled by bonding gold wires at those open circuit points. Electromagnetic simulation results show that the performance of the proposed wire-bonded multiplexer only changes slightly, when compared to multiplexers that are fabricated on a single HTS wafer. Measurement results show that the proposed method is efficient in designing multiplexers. Therefore, a multiplexer with a large number of channels can be created to overcome the limit of wafer size by assembling individual components that are fabricated on different superconducting substrates.