Julian Adolfo Maravilla1, Karthik Gopalan1, Ana Claudia Arias1, and Michael Lustig1
1EECS, UC Berkeley, Berkeley, CA, United States
1EECS, UC Berkeley, Berkeley, CA, United States
The Flexible Tunable Capacitor is a small, high Q variable capacitor designed for tuning flexible and thermoformed coils. By exploiting series and parallel combinations of parallel plate capacitors, a wide tuning range with small step sizes is achievable in a small non-mechanical structure.
Figure 1: Flexible Tunable Capacitor schematic and PCB layout with detailed features, a) The basic schematic consists of capacitors $$$C_s$$$ and $$$C_p$$$ in parallel. $$$C_s$$$ is generated by a series combination of $$$C_{sa}$$$ and $$$C_{sb}$$$. All three variable capacitors are arrays of parallel plate capacitors connected in parallel. b) The top and bottom layers of the flex PCB. The exposed traces can be cut to reduce the capacitance of $$$C_{sa}$$$, $$$C_{sb}$$$, and $$$C_{p}$$$.
Figure 2: RF Simulation Results, a) Simulation setup, impedance measured across frequency (100 MHz to 400 MHz). b) CAD model used for RF Simulations. c) Simulated Capacitance compared to ideal calculations. The variable capacitance ranges from 0.5 pF to 7 pF. d) Step size variation across total capacitance (RF Simulation). Maximum step size 0.25 pF (0.225 pF in ideal calculations).
