a is attenuation in dB Zin is desired input impedance in Ω Zout is desired output impedance in Ω
L = 10a/20 A = (L+1) / (L−1) R2 = (L−1) / 2·√(Zin · Zout / L) R1 = 1 / (A/Zin − 1/R2) R3 = 1 / (A/Zout − 1/R2)