Active Filter: Bessel
(4th order, 24 dB/octave, Highpass)

C=4.7n-10nF
Ra=1.3701/(2*pi*Fc*C)
Rb=1.4929/(2*pi*Fc*C)
Rc=0.9952/(2*pi*Fc*C)
Rd=2.5830/(2*pi*Fc*C)

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