Interesting. Several years ago I designed a resonate, near field wireless charging platform and used a simple X5R capacitor; the nonlinearity of the X5R dielec

Interesting. Several years ago I designed a resonate, near field wireless charging platform and used a simple X5R capacitor; the nonlinearity of the X5R dielectric to provide regulation. As the distance increased, the resonant frequency and Q increased, increasing the potential across the X5R, which decreases the capacitance, changing the resonant frequency. Though I can’t remember if I placed the X5R in series or shunt. Though it mainly helped with regulation depending on current draw of the receiver, it did provide some range increase.