Modeling and characterization of non-ideal effects in high-performance RF MEMS tuners
The emerging standards for the next-generation wireless communication system demand for multi-band RF front-ends. Reconfigurable RF devices based on MEMS technology have emerged with the potential to significantly reduce the system complexity and cost. Robust operation of RF MEMS tuners under the non-ideal effects due to fabrication uncertainties and environmental variations is critical in achieving reliable RF MEMS reconfigurable devices. Therefore, it is essential to model and characterize these non-ideal effects, and further to alleviate these non-ideal effects by design optimization. In this dissertation, the effects of non-perfect anchor support, residual stress, and temperature sensibility of MEMS tuners have been studied. The anchor supports of MEMS beams, which are widely used as tunable components, are often far from the ideally assumed built-in or step-up conditions. An equation-based nonlinear model for inclined supports in non-flat fixed-fixed beams has been developed and validated by experimental results. Residual stress developed during the fabrication presents the major challenges in developing reliable MEMS tuners. An efficient extraction method for in-plane residual stress has been proposed using a single beam test structure. This method has been demonstrated by wafer-scale measurements of electrostatically actuated beams. The statistic and spatial distribution of extracted residual stresses on a quarter wafer is presented, and the accuracy of this method is evaluated by uncertainty analysis. With the awareness the residual stress effects, the design optimization has been conducted for designing stress-tolerant micro-corrugated diaphragm tuners used in tunable cavity resonators/filters. Furthermore, the temperature sensitivity issue results from the mismatch of material properties between the structure material and substrate has been discussed and a thermally-stable RF MEMS tuner based on a nonuniform micro corrugated diaphragm has been proposed and experimentally validated over a wide temperature variation.
Peroulis, Purdue University.
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