Surface-acoustic-wave devices for communications

Surface-wave components have demonstrated performance capabilities in the VHF/UHF range which are available with no other filtering technique. The major advantages of the filters are their small size, high reliability, low cost, high Q, good reproducibility, temperature stability, wide dynamic range, and linear phase response, as well as special characteristics relevant to specific applications. Surface-acousticwave (SAW) devices are used for bandpass filtering [1], matched filtering for radar pulse compression [2], [3] or spread-spectrum signal processing [4], delay lines [5], and frequency control elements [3], [6]. Within the context of communication systems´ applications, this paper reviews the state of the art for SAW components from high-performance fixed-tuned devices to tunable or programmable filters. Major technological advances discussed include unidirectional SAW filters [7] which eliminate bidirectionality loss and simultaneously suppress in-band spurious responses to achieve an insertion loss below 1 dB with a 0.04-dB peak-to-peak ripple. A novel surface-wave sub-system [8] which offers revolutionary signal processing functions through transform processing is also described.