Development of packaged LC-resonator module using RF MEMS technology for linear resonant frequency tuning

Abstract

This thesis suggests a device level solution to acquire a linear frequency tuning with respect to a tuning voltage sweep in an inductor (L) - capacitor (C) resonant system. Since the linearity of the resonant frequency vs. tuning voltage relationship is closely related to the shape of the capacitance (C) - tuning voltage (V) response, the C-V response tunable variable capacitor was suggested and used to realize the linear frequency tuning. The proposed variable capacitor was fabricated using microelectro mechanical system (MEMS) surface micromachining. The capacitance of the fabricated MEMS variable capacitor was normally tuned according to the tuning voltage $(V_{tune})$, and the C-V response shape was changed with respect to the control volt-age $(V_{control})$. When the control voltage increased from zero to 9 V, the C-V response shape changed from a linear to a concave form (i.e. the capacitance decreased fast at low tuning voltage region and slowly at high tuning voltage region). On the other hand, the relationship of the resonant frequency and the tuning voltage changed from concave to an almost linear form (linearity factor was 99.99%) in the same increment of the control voltage. The proposed MEMS variable capacitor’s C-V response tuning capability is vital and amenable to various circuit demands.