S-parameter measurements and applications of superconducting flux flow transistors

Microwave two-port S-parameter measurements and modeling were performed on superconducting flux flow transistors. These transistors, based on the magnetic control of flux flow in an array of high-temperature superconducting weak links, can exhibit significant available power gain at microwave frequencies (over 20 dB at 7-10 GHz in some devices). The input impedance is largely inductive, while the output impedance is resistive and inductive. These devices are potentially useful in numerous applications, including matched amplifiers.<>