Analysis And Design Of Rf Mems Switches And Phase Shifters

RF MEMS switches and phase shifters have been shown to provide very low loss, very small capacity and very light ponderance and are easily compatible with other fabrication craft. As a result, it is being paid more and more attention in phased array radar, microwave communication satellite communication and microwave measurement, and so on. All the time, it is the research focus to optimize and compare performances of RF MEMS switches and phase shifters and to choose them according to different application areas. This paper, based on electromagnetics and mechanics theories, analyzes and designs various kinds of switches and phase shifters and make comparisons of performance indexes.Firstly, this paper analyzes circuit models of both serial and shunt switches, derives formula of isolation and insertion loss for different switching states. Traditional T-match circuits are improved and the relevant analytical solution is also derived. Then, mechanical models of both serial and shunt switches are analyzed and the formula of pull-in voltage and time are also derived. The multi-field software ANSYS is introduced to verify and improve the switch performances to get the switch model under actuation voltage of 18V DC.After the theoretical analysis on electromagnetics and mechanics, the paper continues to analyze and optimize 5 kinds of RF MEMS serial and shunt switches and make comparisons of RF performances and fabrication crafts to discover that double-contact serial switches possess good RF performances and simple fabrication, while via-hole shunt switches have better RF performances and complex fabrication. Then, 3 kinds of RF MEMS phase shifters are analyzed and designed. Comparisons are made on size, RF performances and fabrication crafts to discover that distributed phase shifters have poor performances on nearly every aspect, which indicates that it is not compatible to other phase shifters on the same wafer, while switched-line phase shifters have medium RF performances and simple fabrication process and reflection-type phase shifters show excellent RF performances and complex fabrication process. All of these analysis and design will provide instruction for the follow-up actual fabrication.