Rf Mems Switches Designed For High Performance Uniplanar Microwave And Mm Wave Circuits PDF Download

Small, low power devices for manipulation of high frequency (above 10 GHz) signals are an enabling technology for improved communications and remote sensing equipment. MEMS devices for switching of microwave or millimetre wave signals show promise for applications in areas such as agile radio systems, reconfigurable tuning and matching networks, and phased arrays. The mechanical operating principle of MEMS switches allows these devices to achieve electrical performance (including linearity, isolation, and insertion loss) competitive with or in some cases exceeding that possible with semiconductor technology, in combination with small size and low power consumption. In applications where fast (microsecond) switching times are not required, at frequencies sufficiently high that semiconductor switches are challenging to design or lossy, MEMS technology has excellent potential. The technology of MEMS switches using electrostatic actuation and metal-to-metal or metal-to-dielectric contact has been extensively developed. Unfortunately, practical difficulties such as high actuation voltage, poor reliability, or poor power handling have proven hard to resolve, and the wider adoption of these devices has been delayed. It is therefore worthwhile to develop novel device designs that may be able to comprehensively avoid these issues. The aim of this project was to investigate and validate a concept for a piezoelectric contact-less MEMS switch. The device uses a variable capacitance principle, avoiding the need for contact during switching. Piezoelectric actuation allows high power handling to be achieved with a reasonable (predicted sub 25 V) actuation voltage. A comprehensive model for the mechanical and electrical behaviour of the device was developed. In order to inform the design of a high performance device, the effects of the structure, materials, and applied RF power were considered. Predictions from this model were compared with the results of finite element analysis. Static test structures were designed to validate the electrical performance model and fabricated on glass wafers. S-parameter measurements made on these validation structures were compared with the expected results from the model. Finally, a fabrication process was developed to produce a device in silicon. Additional electrical measurements were carried out on a prototype version of this silicon structure (fabricated without piezoelectric material) to further study the performance of this contact-less RF MEMS switch design.