Assumptions:
source impedance: 50Ω
load impedance: 50Ω
attenuation: 20dB
source terminal voltage = 5
-----------------------------
since the source and load impedance is 50Ω, then the input and output impedances should be also 50Ω
input impedance: 50Ω
output impedance: 50Ω
------------------------------
The voltage attenuation ratio K (Vin/Vout) can be calculated from attenuation value in decibels as follow:
K = 10^(attenuation/20) = 10
-----------------------------
R1 = Z * ((K-1)/(K+1)) = 40.91Ω
R2 = Z * (2K/(K^2-1)) = 10.10Ω
