A high-tuning-range MEMS variable capacitor using carrier beams
A microelectromechanical systems (MEMS) variable capacitor having additional carrier beams is proposed. The use of carrier beams makes it possible to obtain an equivalent nonlinear spring constant, which increases the capacitor's tuning range and prevents the top plate from collapsing at a tuning range of 50%. A lumped element model and a continuous model of the proposed variable capacitor are developed. The continuous model is simulated using commercial software. A detailed analysis for the steady state of the capacitor is presented. The tuning range is measured and found to be 410% at 1 GHz with a maximum de bias voltage of 9.2 V. The achievable tuning range exceeds that of the traditional parallel-plate MEMS variable capacitors. The self-resonance frequency is measured and found to exceed 11 GHz. The proposed MEMS variable capacitor is built using the PolyMUMPs process.
variable capacitors rf mems tunable elements varactors