With fast development of mobile communication technology, the increasingly complex communicating environment and the crowded spectrum have raised stringent requirements on the RF front-end performance. In this paper, the influence of human body on the communication performance is analyzed. In particular, it is shown that the antenna input impedance faces huge variation in the frame of body-centric devices. Consequently, automatic impedance matching appears to be crucial to improve the performance withstand the inconstant environment. The investigation of key tunable components of RF MEMS is therefore presented. A variable capacitor with symmetric balanced structure is designed to achieve a large capacitance tuning ratio and a remarkable linearity of the C-V response. The proposed RF MEMS variable capacitor was modeled and simulated. The results show a linearity factor of 99.82% in C-V response and a large tuning ratio of 480% in a low actuation voltage range from 0V to 16.3V.