Surface acoustic wave (SAW) device coverage includes delay lines and filters operating at selected frequencies in the range from about 10 MHz to 11 GHz; modeling with single-crystal piezoelectrics and layered structures; resonators and low-loss filters; comb filters and multiplexers; antenna duplexers; harmonic devices; chirp filters for pulse compression; coding with fixed and programmable transversal filters; Barker and quadraphase coding; adaptive filters; acoustic and acoustoelectric convolvers and correlators for radar, spread spectrum, and packet radio; acoustooptic processors for Bragg modulation and spectrum analysis; real-time Fourier-transform and cepstrum processors for radar and sonar; compressive receivers; Nyquist filters for microwave digital radio; clock-recovery filters for fiber communications; fixed-, tunable-, and multimode oscillators and frequency synthesizers; acoustic charge transport (ACT); and other SAW devices for signal processing on gallium arsenide. Shallow bulk acoustic wave (SBAW) device applications include gigahertz delay lines, surface-transverse-wave resonators employing energy-trapping gratings and oscillators with enhanced performance and capability. >

Applications of surface acoustic and shallow bulk acoustic wave devices

For the first time waveguides for surface acoustic waves (SAW) have been fabricated by exchanging Li+ ions with protons on Y‐cut LiNbO3 substrates. Different waveguiding structures were investigated. The influence of the proton source dilution, the annealing or the Ti prediffusion on the SAW velocity, and the parameters of the SAW waveguides have been studied.

Proton exchanged waveguides for surface acoustic waves on LiNbO3

Abstmct-High performance has been achieved in SAW convolvers using diffraction-corrected multistrip beam compressors. However, two different levels of metalization are required for optimum performance. A significant simplification of device fabrication was achieved with the design of convolvers using small-aperture chirp transducers, which require only one metalization layer. A design procedure is described that makes the transducers focusing to minimize diffraction loss. Experimental results are presented, which show that performance of this new design surpasses conventional designs in several respects. I. INTRODUCTION M ONOLITHIC acoustic surface wave convolvers on YZ-LiNb03 combine high-speed signal processing capability with ruggedness, small size, and relatively low cost of the device-thanks to the simplicity of its construction. However, the intrinsic nonlinearity of the substrate material polarization, which is used to generate the mixing product of the two input signals, is low and limits the efficiency of the device. High efficiency is crucial to achieve high dynamic range and economize input power. Since the introduction of beamwidth compression [l] to boost device efficiency, the elastic convolver has been developed to high performance in several laboratories [2], [3], [4] by optimization of its various components. The aim of such optimization was to increase the device efficiency by eliminating sources of loss in the acoustic path and providing good match at all electrical ports, while tailoring the device characteristics to minimize signal distortion and suppress spurious signals [5]. This means that the convolution efficiency vs. frequency should be reasonably flat and smooth in magnitude and linear in phase over the desired bandwidth. Notably reflections of acoustic waves in the device have to be suppressed to avoid selfconvolution of one input signal. The distributed output signal has to be collected from the integrating electrode in such a way as to avoid electromagnetic propagation loss or destructive interference of various signal components due to long-line effects. By these considerations one arrives at a standard design scheme as shown in Fig. 1. Interdigital transducers, which convert the input signals, typically are unapodized to avoid

Small-Aperture Focusing Chirp Transducers vs. Diffraction-Compensated Beam Compressors in Elastic SAW Convolvers

A spurious signal in the response of surface acoustic wave (SAW) elastic convolvers due to the mutual interaction of the fundamental and the second higher order mode of 5A-waveguides has been discovered using a novel high-resolution method to determine convohrer plate uniformity from a frequency domain measurement.

Cross Convolution of Acoustic Waveguide Modes in Elastic Convolvers Measured in the Frequency Domain

Degenerate elastic convdvers using surface acoustic waves are investigated. A center frequency of 800 MHz was used because it offers the potential for extremely wide instantaneous bandwidths. An efficiency, Fexternal, of -78 dBm and time-bandwidth product of 190 on Y Z lithium niobate is reported. This efficiency is an 18-dB improve ment over earlier devices.

http://ieeexplore.ieee.org/iel5/10326/32854/01539393.pdf

UHF Elastic Convolver with lmproved Efficiency

Multimoding effects have been experimentally observed in thin-fdm aluminum waveguides on lithium niobate using a laser probe. When the waveguide is used as a convolver, these effects add dispersion and may adversely effect efficiency and minimum achievable time

R.D. Colvin

Papers

Multimoding in SAW Convolver Waveguides