Wideband microwave low noise amplifiers based on biSQUID SQIFs

We designed, fabricated, and measured broadband low-noise amplifiers based on Superconducting Quantum Interference Filters (SQIFs) for variety of applications ranging from superconducting quantum bits readout to satellite communication receivers. Our microwave amplifiers (Microwave SQAs) are based on 1-, 5-, 10-, 20-cell serial biSQUID SQIF arrays. The RF input is applied via a 50 Ohm coplanar waveguide connected to a superconducting line coupled to each biSQUID cell and integrated with input/output planar capacitors to define and tune up signal frequency bandwidth. The RF output comes out from the central common line via a balanced output circuit matching to a 50 Ohm output coplanar waveguide. The same circuit is used for symmetrical dc biasing of an array. Microwave SQA samples were fabricated on 5 mm × 5 mm chips using standard HYPRES niobium 4.5 kA/cm² fabrication process. The results of experimental evaluation of our Microwave SQAs based on SQIF serial arrays with different number of biSQUID cells are compared. We have demonstrated a power gain up to 20 dB from 8 to 11 GHz.