Abstract
Dispersive transducers have sharp cut-off and flat wide band frequency characteristics. Moreover phase linear and the very low loss characteristics are obtained by combining down-chirp and up-chirp unidirectional dispersive transducers (DUDIDT and UUDIDT). In this paper, DUDIDT and UUDIDT were investigated using TeO2 thin film gratings with the large impedance ratios. The impedance ratio of r=Ze/Zg (Ze: with shorted thin film and Zg: without open thin film) were investigated using TeO2 thin films. The results showed the large impedance ratio, r=0.96 at the thickness of H/lambda =0.01 on TeO2/128 Y-X LiNbO3. These grating are applied for DUDIDT and UUDIDT. The very low insertion loss of 0.2 dB and flat wide band of 10% and the very sharp cut-off characteristics were theoretically obtained and the experimental results showed the insertion loss of 0.6 dB at 400 MHz. Also we developed new boundary waves and applied to DUDT and UDT filters. Theoretical and experimental results of new boundary waves are described.
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