Z_in desired input impedance in Ω

Z_out desired output impedance in Ω

a attenuation in dB

L = 10 ^a/10 (the loss)

A = (L + 1)/(L − 1)

Tee attenuator

R2 = 2*√ (L * Z_in * Z_out )/(L − 1)

R1 = Z_in * A − R2

R3 = Z_out * A − R2