Experimental study on the performance of dithered single-phase unidirectional transducers (DSPUDT) and their filter applications on ST-quartz and LiTaO/sub 3/ substrate materials

Abstract

In this paper we present experimental results of the different reflection and transduction characteristics for transducers that have sampling rates of 1/3/spl lambda/, 3/8/spl lambda/, 2/5/spl lambda/, 3/7/spl lambda/, 5/12/spl lambda/, and 5/14/spl lambda/. Directivity tests on the different structures built on quartz and LiTaO/sub 3/ were performed and compared. Wide band measurements of all transducers were taken as well. These measurements suggest the possibility of implementing a DSPUDT filter with mixed sampling rates in order to suppress unwanted spurious modes like group and bulk wave modes. As a result, a table with the best combinations of sampling rates for high frequency (above 550 MHz) and low frequency (below 550 MHz) DSPUDT filters on ST-quartz and Y112-LiTaO3 was generated. This table was used to implement a 916.5 MHz filter in ST-QUARTZ, and a 960 MHz and 350 MHz filter on Y112-LiTaO/sub 3/.