A comparison of superconductive and surface-acoustic-wave signal processing

A number of superconductive analog signal-processing devices with functions analogous to those of surface-acoustic-wave(SAW) devices have been demonstrated, including filters, resonators, pulse compressors, convolvers, and correlators. Most of these devices utilize the extremely low microwave surface resistance of superconducting thin films to obtain highly compact yet low-loss electromagnetic delay lines, and some incorporate tunnel junctions for nonlinear functions. The design and fabrication of such superconductive devices are discussed, and they are compared to SAW devices in terms of bandwidth, delay, transduction loss, and interface requirements. Two examples with particularly strong analogy to SAW devices are presented: (1) chirp filters for pulse compression and spectral analysis; and (2) high-Q resonators for use in low-phase-noise oscillators. The prospects for devices operating in liquid nitrogen are explored