Muscle-Inspired Micromechanical Digital-to-Analog Variable Capacitors Using Parallel Digital Actuator Array

We present a high-precision digital-to-analog (DA) variable capacitor, inspired from the structure and principle of biological muscle actuators. The present DA variable capacitor composed of parallel-interconnected digital actuators performs high-precision capacitance adjustment, while achieving high Q due to low-loss interconnection structure. We design, fabricate, and characterize the DA variable capacitor using 4-bit digital actuators with the operation voltage of 25V. In experimental study, the DA variable capacitor changes the capacitance from 2.268 to 3.973pF (0.5GHz), 2.384 to 4.197pF (1.0GHz), and 2.773 to 4.826pF (2.5GHz); thus, achieving the capacitance tuning range of 75.2%, 76.1%, and 74.0%, respectively. The capacitance precision of the DA variable capacitor is measured as 6.16plusmn4.24fF (0.5GHz), 7.42plusmn5.48fF (1.0GHz), and 9.56plusmn5.63fF (2.5GHz), resulting in 10 times improvement of the precision (>100fF) in the conventional analog variable capacitors. The Q factor of the DA variable capacitor is measured as 34plusmn8 (0.5GHz), 18plusmn5 (1.0GHz), and 4plusmn1 (2.5GHz). We experimentally verify the high-precision tuning capability of the muscle-inspired micromechanical DA variable capacitor with high Q for RF communication applications.