Frequency agile MEMS patch antenna for reconfigurable RF front-ends

A new micromachined electro-thermally driven more mechanically stable compact frequency tunable microstrip patch antenna is demonstrated in this paper. The antenna structure employs the idea of introducing an adjustable air gap between suspended antenna patch and fixed ground plane. The patch of the antenna is a 3×3mm² golden layer and is deposited over a 3mm×3mm×4μm bulk micromachined silicon membrane which is connected to the silicon chip through electro-thermal micro-actuators and meandered springs. These actuators are employed to precisely adjust the air gap height by voltage levels compatible with CMOS circuitries. Downward deflection produced by micro-actuators deflects the suspended silicon membrane downward toward the fixed ground plane. This deflection reduces the air gap height and consequently, operating frequency of the antenna. To enhance mechanical stability of the antenna structure against environmentally induced mechanical perturbations such as vibrations and shocks, embedded slits and slots are created on the antenna patch and suspended silicon membrane to decrease effective mass of the suspended structure. The up-state operating frequency of the antenna is 15.12GHz which continuously can be lowered to 14.62GHz. A tuning range of 500MHz is achieved by a CMOS compatible actuation voltage of 1.25V. The RF performance of the antenna and its mechanical behavior is investigated by FEM analysis and satisfactory results are obtained.