This double plate moveability feature of the capacitor increases the tuning range.
Ebrahim Abbaspour-Sani, Naser Nasirzadeh, G.Dadashzadeh 2006, 'A Novel Structure for MEMS Based Varactors', Sensors & Transducershttp://www.sensorsportal.com/HTML/DIGEST/august_06/P_78.pdf. Retrieved from DOAJ CC BY 4.0 (https://creativecommons.org/licenses/by-sa/4.0/legalcode)