Surface Acoustic Wave filters for space use
This paper describes the design and development of surface acoustic wave (SAW) filters proposed to be used in the analog mesh-processor payload of GSAT-7 satellite. Four high performance SAW filters with center frequencies in the range of 176 MHz to 183 MHz and band widths in the range of 0.78 MHz to 2.28 MHz are being developed for the payload. Delta-function Model is used in the first order design of these filters followed by the rigorous estimation and compensation of various important second-order effects, namely, Diffraction, Bulk waves and electromagnetic feed through. Further, the effect of inter-electrode capacitance of the filterspsila IDT (Inter Digital Transducer) which contributes to a tilt in the pass band frequency response of the filterspsila has also been explained by using Crossed-field Model. Simulated and measured results at various stages of development of the 176.57 MHz filter are presented. The paper also discusses the qualification plan for these devices, for space use.