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Design of Surface Acoustic Wave Compressors with Interdigital Transducers
Marija Hribšek Dejan Tošić
An algorithm suitable for the computer aided design of the surface acoustic wave (SAW) compressor with interdigital transducers (IDT) is presented. The geometry of the uniform interdigital transducer is calculated first. Starting from the desired impulse response, the electrode positions and lengths (apodisation) of the dispersive IDT are determined. The last algorithmic step is the design of the matching networks between the IDTs and the load and the generator. The algorithm takes as input the central frequency, bandwidth, delay dispersion, substrate, compressor and electrode type, weighting function, and load and generator resistances. The output results are the electrode positions and geometry, and the element values of the matching networks. The algorithm has been exemplified by a filter design with the central frequency of 60 MHz and dispersion of 1μs, within the 10 MHz bandwidth, fabricated on ST-quartz. The delay characteristic of the fabricated filter is measured and the experimental results satisfy the filter specification verifying the proposed algorithm and software. Key words: SAW element, SAW filter, SAW compressor, expander, design, algorithm.
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