Superconducting cryogenic front end receivers

High temperature superconducting planar filters combined with cooled low noise amplifiers form low noise receivers with very sharp skirts and very low IL. These receivers when installed in cellular telephone base stations fill coverage gaps, provide reduced adjacent band interference and better capacity utilization, extend super speed to more users and the decrease number of drop out and blocked calls. There are more than 4000 cryogenic front end (CRFE) receivers working commercially around the world. This paper presents an historical review of the field and basic properties and designs of CRFE receivers.