Effective transduction weighting (ETW) method for SPUDT

With unidirectional reflections distributed among the transducer, transduction efficiencies of cells in a SPUDT are not equal. So classical source strength function is not suitable for SPUDT design, because they will cause the distortion of the spectrum and phase near the center frequency of the transducer. In this paper a novel weighting method, Effective Transduction Weighting (ETW) for SPUDT are presented that could remedy the drawbacks of classical weighting functions well. Both theoretical and experimental results shows ETW method is able to improve the filter characters and the design flexibility. For an simulation example, the SPUDT filter made up of 380 DART cells with ETW processed Hamming and Sinc weighting on ST-X cut quartz, the shape factor (-40 dB: -3 dB) is 1.8:1, and the shapes of spectrum are symmetry with the center frequency (200 MHz), including sidelobes and ripples in passband