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

This paper describes a useful design technique to achieve a nonlinear phase SAW filter using slanted finger interdigital transducers (SFITs) or tapered interdigital transducers which are suitable for wide-band filters in intermediate frequency stages. A required nonlinear phase response in the passband can be obtained by changing center-to-center distances between input and output SFITs along an axis perpendicular to the SAW propagation axis. The design is based on a building-block approach in the frequency domain. A nonlinear phase SAW filter with a center frequency of 70 MHz and a fractional bandwidth of about 10% is demonstrated on x-cut 112.2/spl deg/ y-propagating LiTaO/sub 3/. Because the substrate has a power flow angle of 1.55 degrees, the SFIT pattern is tilted along that angle. Good agreement between theoretical and experimental results is obtained.

Design technique for nonlinear phase SAW filters using slanted finger interdigital transducers

Design Technique for Nonlinear Phase SAW Filters Using Slanted Finger

This paper reviews the evolution of SAW transducer technology for communication systems. Applications of TV sets, radar, satellite communications, mobile phones and a wealth of others have driven a diversity of transducer embodiments. Some of the diverse sets of transducers include: bidirectional, multi-phase unidirectional, single phase unidirectional, chirped, coded, slanted, resonant and others. Scientists and engineers continually push the limits on materials, device design and manufacturing, leading to lower loss, broader bandwidths, smaller size and lower cost devices. Connections between past military requirements, commercial communication systems current consumer applications have driven the transducer technology in varied directions culminating in today's diverse, application specific devices. This paper takes an historical view of the SAW transducer's diverse embodiments, practical implementations, and innovative problem solutions, through the eyes of the IEEE Ultrasonics, Ferroelectrics, and Frequency Control (UFFC) society publications.

Evolution of the SAW transducer for communication systems

For pt.I see ibid vol.39, no.1, pp.61-72 (1992). Physical effects causing distortions of the transfer function of a broadband (36% fractional bandwidth) spectrum shaping filter for digital radio with 16 quadrature amplitude modulation (QAM) are analyzed separately and connected with the modular two-dimensional (2-D) model described in Part I, demonstrating the importance of every single effect. A compensation of the second-order effects is performed, yielding an agreement between simulation and measurement in amplitude and phase of more than +or-0.1 dB and +or-1 degrees all over the passband. The stopband is also predicted with high accuracy. >

Modular two-dimensional analysis of SAW filters. II. Analysis and compensation results

Apodization is the most common- ly used weighting technique for defining the impulse response of SAW filters. This work presents the results and compares the parameters of six of the most commonly used transducer apodization geometries. Parameters are presented for the six apodization implementations of a low shape factor filter design example. The parame- ters compared are apodization loss, frequency dependent transducer acoustic conductance and susceptance, transducer group delay and filter passband response. Fast and efficient track modeling ap- proaches are presented. The results show the importance of anticipating the effects of structure geometry when designing apodized low loss SAW filters. Results of the modeling are verified for the case of a low shape factor slant centered apodized transducer SAW filter.

A.J. Vigil

Papers

A Study of the Effects of Apodized Structure Geometries on SAW Filter Parameters