HTSC current controlled devices for microwave applications

The very low microwave resistance of superconducting thin films in superconducting state in combination with possibility to change the state with a bias current to a much higher resistance normal state (S-N transition) permits the realisation of bias controlled microwave devices. Such devices may have an extremely good characteristics: low insertion loss, low noise level, short time of response to the control signal, and a rather large dynamic range. The following microstrip devices are discussed: low-pass filter and switch. The devices are characterised by a successful combination of parameters.