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A Study on the Fabrication and the Impedance Matching of SPUDT Type SAW Filter  

You Il-Hyun (세명대학교 컴퓨터 응용 과학과)
Publication Information
Journal of the Korea Institute of Information and Communication Engineering / v.9, no.3, 2005 , pp. 602-608 More about this Journal
Abstract
We have studied to obtain the SAW filter for the Single Phase Unidirectional Transduce. (SPUDT), was formed on the Langasite substrate and was evaporated by Aluminum-Copper alloy and then we performed computer-simulated by simulator. We can fabricate that the block weighted type IDT as an input transducer of the filter and the withdrawal weighted type IDT as an output transducer of the filter from the results of our computer-simulations. Also, we have performed to obtain the properly conditions about impedance matching of the SAW filter for SPUDT. We have employed that the number of pairs of the input and output IDT are 50 pairs and the thickness and the width of reflector are 5000A and $3.6{\mu}m$, respectively. And the width of IDT' fingers is $2.4{\mu}m$, and the space between IDT' finger and reflector is $2.0{\mu}m$. Frequency response of the fabricated SAW filter has the property that the center frequency is about 190MHz and bandwidth at the 3dB is probably 7.7MHz after when we have matched impedance. Also, we could obtain that ripple characteristics is less than 0.4dB and standing wave ratio is probably 1.5 after when we have matched impedance.
Keywords
Single Phase Unidirectional Transducer; SPUDT; Slanted finger; Tapered Transducer; Interdigital Transducer : IDT; Weighting;
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