Superconducting tunable multipole bandpass filter with in-situ trim

In this Phase I SBIR project, HYPRES proposes to demonstrate a tunable lumped-element superconducting bandpass filter for transmit/receive isolation applications, using Josephson circuits for in situ trim and control. Such a filter will provide insertion loss below 1 dB and 60 dB out-of-band rejection in a filter which can be tuned over the range 500 MHz - 2 GHz. The project will take advantage of the ability to fabricate precision capacitive and inductive filter elements with very small physical dimensions using the HYPRES NB process, reducing costs and imposing only modest cooling requirements while increasing fabrication yield over filters designed for high-temperature superconducting (HTS) materials. After feasibility is shown, the project will culminate with the design of a digitally controlled bandpass filter which is fully tunable over the range 2 MHz - 2 GHz by a control circuit interfaced to a room-temperature interface control bus. In Phase II, HYPRES proposes to build and test a prototype of that filter circuit with control interface bus.