Active Filter: Bessel
(3st order, 18 dB/octave, Highpass)

C=4.7n-10nF
Ra=1.0474/(2*pi*Fc*C)
Rb=2.0008/(2*pi*Fc*C)
Rc=1.3228/(2*pi*Fc*C)

Units: Rx [Ohm], C [F], Fc [Hz]