Very Compact IF CDMA Filter on GaP04

In the first part of this paper, SAW properties of GaP04 are investigated as a function of cut angles and propagation angle. It is found that singly rotated GaP04 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 w and cut angle 8. 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 7x5 mm2 SMT package. Performances of the filter are similar to specifications of up-to-date filters on ST-Quartz.