Very compact IF CDMA filter on GaPO/sub 4/

In the first part of this paper, SAW properties of GaPO/sub 4/ are investigated as a function of cut angles and propagation angle. It is found that singly rotated GaPO/sub 4/ is already very promising. Therefore, SAW propagation characteristics such as velocity, coupling coefficient, reflection coefficient, power flow angle, and first and second order temperature coefficients are presented as a function of propagation angle /spl psi/ and cut angle /spl theta/. Experimental results are presented for two singly rotated cuts. They show good agreement with theoretical results when using a proper set of material constants. The second part of this paper is dedicated to the design and realization of an 85 MHz IF CDMA filter. Low velocity allows for a significant reduction in chip size. Using an advanced SPUDT structure, it was possible to prototype a 85 MHz filter in a 7/spl times/5 mm/sup 2/ SMT package. Performances of the filter are similar to specifications of up-to-date filters on ST-Quartz.