I can't find solution with solve fuction
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sohyeon jung
le 11 Déc 2018
Commenté : madhan ravi
le 11 Déc 2018
Literally I can't find the solution with my code, which use 'solve' function to find solution of two equation.
The sol struct is filled with x(which is nowhere in my code) with this error message.
"Unable to convert expression into double array."
The code is below!
Is it because the equation itself is too complex?
How can I do for this?
S21_dB = -3.4964;
S21_deg = 2.1936;
syms er tanL positive;
assume(er, 'real');
assumeAlso(tanL, 'real');
assumeAlso(er<20 );
assumeAlso(tanL < 0.1 );
c = 3*10^8 ;
d = 731 *(10^-6);
f= 75*10^9;
lam = c./f;
w= 2*pi*f;
u_0 = 4*pi*(10^-7);
e_0 = 8.8541*(10^-12);
ec = er.*(1-1i*tanL);
z_0 = sqrt(u_0/(e_0));
z_d = sqrt(u_0/(e_0.*ec));
r = ((2*pi)/lam)*sqrt(ec);
S21_M = ((z_d+z_0).^2 - (z_d-z_0).^2)./((exp(1i.*r.*d).*(z_d+z_0).^2)- (exp(-1i*r*d).*(z_d-z_0).^2));
S21dB_M = real(20*log10(S21_M));
S21deg_M = real(angle(S21_M));
eqn1 = S21_dB- S21dB_M == 0;
eqn2 = S21_deg- S21deg_M == 0;
sol = solve([eqn1 eqn2],[er tanL],'ReturnConditions',true);
eps = double(sol.er);
losst = double(sol.tanL);
sol.er
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madhan ravi
le 11 Déc 2018
Modifié(e) : madhan ravi
le 11 Déc 2018
You are solving system of non-linear equations so use fsolve()
S21_dB = -3.4964;
S21_deg = 2.1936;
syms er tanL real;
assumeAlso(er<20 );
assumeAlso(tanL < 0.1 );
c = 3*10^8 ;
d = 731 *(10^-6);
f= 75*10^9;
lam = c./f;
w= 2*pi*f;
u_0 = 4*pi*(10^-7);
e_0 = 8.8541*(10^-12);
ec = er.*(1-1i*tanL);
z_0 = sqrt(u_0/(e_0));
z_d = sqrt(u_0/(e_0.*ec));
r = ((2*pi)/lam)*sqrt(ec);
S21_M = ((z_d+z_0).^2 - (z_d-z_0).^2)./((exp(1i.*r.*d).*(z_d+z_0).^2)- (exp(-1i*r*d).*(z_d-z_0).^2));
S21dB_M = real(20*log10(S21_M));
S21deg_M = real(angle(S21_M));
[tanL,er]=fsolve(@rootss,[10,10])
function eqn=rootss(x)
tanL=x(1);
er=x(2);
eqn=[20*real(log((((-777820666600722137088/(5480422450918343*er*(- 1 + tanL*1i)))^(1/2) - 6627542629724307/17592186044416)^2 - ((-777820666600722137088/(5480422450918343*er*(- 1 + tanL*1i)))^(1/2) + 6627542629724307/17592186044416)^2)/(exp(-(pi*(-er*(- 1 + tanL*1i))^(1/2)*842785619867605125i)/2305843009213693952)*((-777820666600722137088/(5480422450918343*er*(- 1 + tanL*1i)))^(1/2) - 6627542629724307/17592186044416)^2 - exp((pi*(-er*(- 1 + tanL*1i))^(1/2)*842785619867605125i)/2305843009213693952)*((-777820666600722137088/(5480422450918343*er*(- 1 + tanL*1i)))^(1/2) + 6627542629724307/17592186044416)^2))/log(10));
angle((((-777820666600722137088/(5480422450918343*er*(- 1 + tanL*1i)))^(1/2) - 6627542629724307/17592186044416)^2 - ((-777820666600722137088/(5480422450918343*er*(- 1 + tanL*1i)))^(1/2) + 6627542629724307/17592186044416)^2)/(exp(-(pi*(-er*(- 1 + tanL*1i))^(1/2)*842785619867605125i)/2305843009213693952)*((-777820666600722137088/(5480422450918343*er*(- 1 + tanL*1i)))^(1/2) - 6627542629724307/17592186044416)^2 - exp((pi*(-er*(- 1 + tanL*1i))^(1/2)*842785619867605125i)/2305843009213693952)*((-777820666600722137088/(5480422450918343*er*(- 1 + tanL*1i)))^(1/2) + 6627542629724307/17592186044416)^2))];
end
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