High-$Q$ 3 b/4 b RF MEMS Digitally Tunable Capacitors for 0.8–3 GHz Applications

A high-Q digitally tunable capacitor is demonstrated with 3 and 4 b resolutions for 0.8-3 GHz applications. The device shows a tuning range of 1.0-3.75 pF in the 3 b configuration and 1.25-3.80 pF in the 4 b configuration ( ~ 1-4 pF simulated). In addition to digital tuning, 30-530 fF of analog tuning is achieved and allows for precision tuning. The measured Q of the digitally tunable capacitor is >;100 at 1 GHz and >;60 at 2 GHz for all tuning states. A novel circular geometry maintains a high- Q as the capacitance is increased. The device is 2×1.8 mm which is ideal for tunable filters, matching networks and antennas.