Please, How can I minimization a complex function of multiple variables ?

Regards everyone

I have a doubt about minimization of complex function of multiple variables. So, I show in details the problem, in order to understand completely.

This is the objective function that I need minimization:

 Sum_Erros  = |real(S11measured - S11calculated) |^2 + | imaginary(S11measured - S11calculated) |^2 + 
|real(S21measured - S21calculated) |^2 + | imaginary(S21measured - S21calculated) |^2

I have S parameters generated by measurement or simulation and I have S parameters generated by calculate. The S parameters calculated were generated using first estmative de permittivity ( e' ; e") and permeability ( u'; u") of Nicolson Ross Weir algorithm.

The objective is: From first estimative of epsilon ( e' ; e") and mi( u' ; u'') , to find the values of epsilon and mi which minimize the sum of erro, making it near to zero.

The function objective of Sum of errors is very complex. I put the esqueme of equations to get S parameters S11 and S21 from estimative values of epsilon and mi . The process went maked for 1100 points of frequency.

Someone help in this work ?

I searched a lot about it, but unfortunately I don't get aplicate in my case. Thank very much

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