We present a new micromechanical tunable capacitor using parallel interconnection of digital actuators with different unit displacements, capable to accomplish a high-precision tuning in practical RF communication. We design, fabricate, and test this digital-to-analog tunable capacitor with 4-bit digital actuators with driving voltage of 25V. The present digital-to-analog tunable capacitor shows the measured capacitance varies from 2.384pF at (0000) to 4.197pF at (1111) digital actuation mode, corresponding to the tuning range of 76.1% at 1GHz. The device's Q is measured to be 24 at (0000) mode at 1GHz. The digital-to-analog tunable capacitor shows the capacitance precision of 7.42±5.48fF, satisfying the required capacitance precision for practical RF tuning. We experimentally verify that the RF performance of the digital-to-analog tunable capacitor using parallel-interconnected digital actuators, while achieving the high-precision capacitance immune to actuation noise.
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