| Particular research effort has been directed to Micro- Electro-Mechanical System (MEMS) varactors because of their desirable characteristics including high tuning ranges, high quality factors, and virtually nonexistent current losses.;Although numerous MEMS varactors have been manufactured fruitfully in many processes, the modeling and characterization of these varactors were primitive and several design aspects were ignored. As such, this dissertation dedicated its attention to the analysis and design of MEMS varactors.;The analytical part of the dissertation studied the effects of etching holes and residual stress on the ideal capacitance calculation method in MEMS parallel plate varactors. It was found that the etching holes do not significantly affect the capacitance or the tuning range of MEMS varactors, regardless of their presence in one or two plates, perforation configuration, number, shape, or size. On the other hand, the initial warping of a suspended plate caused by residual stress was found to cause a discrepancy between theoretical and measured capacitance results ranging from 15% to 80%. Hence, holding the residual stress responsible for this discrepancy, haphazardly, irrespective of suspension configuration, as mostly exercised in the literature, is unjustified. The latter statement is especially true remembering that some reported measured results are thrice as much their theoretical counterparts.;Following the analytical study, the developmental part proposed two novel MEMS variable capacitance device (VCD) structures capable of providing a predetermined, customizable, tuning range. Further, a MEMS varactor based on the zipping motion was presented. Both the VCD and zipping varactor utilized the silicon substrate to emulate the role of the bottom plate. Theoretical analysis and simulations were carried out and verified with measurements. The VCD structures provided theoretical tuning ranges from 4.9 to 35 and from 3.4 to 26 respectively. The first VCD obtained, selectively, distinct tuning ranges of 3, 3.4, and 4.4 at 1 GHz, while the other had mediocre performance. Measurements of a first version of the zipping varactor provided a tuning range, quality factor, and actuation voltage of 4.5, 16.4, and 55 V respectively, while another version had a tuning range, quality factor, and actuation voltage of 4.2, 17, and 55 V respectively. |
