Apodization, or spatial overlap weighting, is a common tap weighting technique for Surface Acoustic Wave filter transducers. The two most common apodization strategies are beam centered and slant centered overlap weighting. Two lesser known apodization geometries are beam spread overlap weighting and generalized distance weighting.
A wide variety of SAW transducer weighting techniques are described. Analysis is focussed on the four apodization geometries listed above. An efficient track based modelling system is developed in order to accurately solve for the acoustic radiation profiles, apodization loss and frequency dependent acoustic conductance. This modelling system becomes the foundation for a set of apodized transducer simulation routines named “STRUCTURECARD.” These routines may be used in conjunction with SAWCAD to generate complete filter response simulations based on the impulse response model and the electrical network responses.
Computer simulations are carried out on filters whose transducers are weighted by the four apodization techniques described above. Transducer geometries are compared on the basis of these simulations for both an Eigen window filter and a low shape factor filter with time sidelobes. It is shown that the two less popular apodization geometrics exhibit more favorable apodization loss characteristics. These transducers function more like amplitude weighted transducers than the beam and slant centered overlap transducers. Some apodized transducer filter responses are predicted to have less passband ripple than their amplitude weighted counterparts.
Master of Science (M.S.)
College of Engineering
Length of Campus-only Access
Masters Thesis (Open Access)
Vigil, Armando J., "Comparison of Apozidalion Geometrics for Bidirectional Surface Acoustic Wave Transducers Based on Efficient Track Modelling" (1986). Retrospective Theses and Dissertations. 4969.