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 = 2·√(L · Zin · Zout) / (L−1) R1 = Zin · A − R2 R3 = Zout · A − R2