Superconductive digital instantaneous frequency measurement subsystem

A 5-b high-temperature-superconductive digital instantaneous frequency-measurement (DIFM) subsystem has been constructed for the determination of the frequency of unknown signals over a 500-MHz bandwidth, centered on 4 GHz, with a resolution of +or-7.8 MHz. The subsystem contains a cryogenic section with five discriminator modules using superconductive delay lines, GaAs mixers, and power dividers. The subsystem also has a room-temperature GaAs limiting amplifier and a silicon postprocessor. With a single-tone CW (continuous-wave) input between -40 dBm and +10 dBm, the frequency quantization boundaries of the subsystem are, on average, 3.1 MHz from their design values.>