Mixed-Signal High-Voltage CMOS Control Circuit For RF MEMS Varactors

To make MEMS varactors more robust and reliable, a closed-loop control circuit was designed to sense the varactor capacitance and tune the MEMS bias in real time to adjust the capacitance to the desired value within 1 fF and in 200 $\mu$s. The designed circuit was successfully implemented in a standard RF CMOS technology despite the challenge for handling high voltage at high speed and for suppressing the substrate-coupled noise. The fabricated chip was tested to function according to the design simulation and to be capable of switching 150 V repeatedly.