RF micromachined varactors with wide tuning range

Polysilicon surface micromachined varactors using two- and three-plate structures with 1.5:1 and 1.87:1 tuning ranges, respectively, are presented. The tuning ranges are near-theoretical limits and can be obtained within 4.4 V control voltage. The two-plate varactor has a nominal capacitance of 2.05 pF and a Q-factor of 20 at 1 GHz.