Semiconductor-Tuned High-T Superconductor Filters for Ultrasensitive RF Receivers (SURF): Technology development and evaluation

The DARPA/STO Semiconductor-Tuned High Temperature Superconductor Filters for Ultrasensitive RF Receivers (SURF) Program was initiated for the purpose of detecting small signals in a dense background of radio-frequency (RF) interference. The specifications for these filters include exceptional operational bandwidth, low insertion loss, high out-ofband rejection, and microsecond tuning times, addressing applications beyond those of commercially available switched-tuned bandpass or fixed-notch bandpass filters. The Air Force Research Laboratory lead a team of collaborators including MacAulay-Brown, the University of Dayton Research Institute and the Naval Research Laboratory to technically guided the four SURF contractors, as well as independently characterized the SURF program´s tunable RF receiver subsystem. An engineering level description of the rack mount system with tunable filter bank operating at cryogenic temperatures (77K) will be provided. Detailed test results of the SURF technology operating over two frequency bands (800-1100 MHz and 1500-1850 MHz) with 512 programmed tuned filter states, show out-of-band rejection of at least 80dB, insertion loss below 1dB, and switching times between filter states of one microsecond. Measured test data will be presented. Integration of the SURF technology into innovative receiver architectures for challenging RF defense applications will be discussed.