Issue solve function using complex numbers

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MGuillaume
MGuillaume 2019-6-23
评论： Star Strider 2019-6-30
Hi all,
I want to solve equation containing complex numbers.
The goal is to find R (Resistance value >0) that gives |Zeq| = 84 Omhs using solve function.
Following Matlab script should return 2 solutions:
solution #1 : close to 24 Ohms
solution #2 : close to 57 Ohms
but when I run the script , solve function returns no solution.
clc
clear
syms R Real;
C=5e-14;L=1.5e-10;Lc=3e-10;Cg=5e-14;Z1=50;Z2=50;
f=50e9;
w=2*pi*f;
Zp=2*1i*Lc*w + (R+1i*w*(L-R^2*C-L^2*C*w^2))/(1+C*((w^2*(R^2*C-2*L)+L^2*C*w^4)));
Yg=1i*Cg*w;
A=1+Yg*Zp;
B=Zp;
CC=Yg*(Yg*Zp+2);
D=A;
DEN=A*Z2+B+CC*Z1*Z2+D*Z1;
S11=(A*Z2+B-CC*Z1*Z2-D*Z1)/DEN;
Zv=84;
Zeq=abs((2*Z1*S11)/(1-S11));
solve(Zv==Zeq,R)
For information , I solved graphically this equation and solution #1 and #2 are found when the target value is |Zeq|=84.
Any suggestions ?

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采纳的回答

Star Strider
Star Strider 2019-6-23
I cannot figure out the reason solve is not solving for those values.
I ended up with this:
Rfcn = matlabFunction(Zeq)
Rr(1) = fzero(@(R)Rfcn(R)-Zv, 1);
Rr(2) = fzero(@(R)Rfcn(R)-Zv, 100)
producing:
Rr =
23.823647889981203 57.458880414574708

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