I have no idea what would be necessary for LTSPice to export in Cartesian coordiantes, however to convert them to Cartesian in MATLAB is straightforward, by extracting the real and imag components of the ‘Rsp’ vector as the ‘Real’ and ‘Imag’ vectors (this also identifies the system, since I had that code ready to go) —
filename = 'https://www.mathworks.com/matlabcentral/answers/uploaded_files/844455/Draft3.txt';
T1 = readtable(filename, 'VariableNamingRule','preserve')
V2c = cellfun(@(x)sscanf(x, '%f\t%f'), T1.Var1, 'Unif',0);
V2m = [cell2mat(V2c')' T1.Var2]
T2 = table('Size',[size(T1.Var1,1) 3],'VariableTypes',{'double','double','double'}, 'VariableNames',{'FreqHz','MagndB','PhasDg'});
T2.FreqHz = V2m(:,1);
T2.MagndB = V2m(:,2);
T2.PhasDg = V2m(:,3)
D = table2array(T2)
Mag = db2mag(T2.MagndB); % Absolute MAgnitude (Not Decibels)
Phs = deg2rad(T2.PhasDg); % Radian Phase Angle
Rsp = Mag.*exp(1j*Phs)
Real = real(Rsp) % REAL Part Of Complex Response Vector
Imag = imag(Rsp) % IMAG Part Of Complex Response Vector
Sizes = [size(T2.FreqHz); size(Rsp)]
sysfr = idfrd(Rsp,T2.FreqHz,0,'FrequencyUnit','Hz') % Create System Response Data Object
sys_ss = ssest(sysfr, 3) % State Space Realisation
figure
compare(sysfr, sys_ss)
sys_tf = tfest(sysfr, 2, 2) % Transfer Function Realisation
figure
compare(sysfr, sys_tf)
figure
pzmap(sys_ss)
grid on
format long E
Poles = pole(sys_ss)
Zeros = zero(sys_ss)
figure
subplot(2,1,1)
semilogx(D(:,1), D(:,2))
title('Amplitude (dB)')
grid
subplot(2,1,2)
semilogx(D(:,1), D(:,3))
title('Phase (°)')
grid
xlabel('Frequency')
EDIT — (26 Dec 2021 at 13:24)
Corrected name provided to readtable, and provided subsequent correct parsing of the resulting table.
With those changes, my code runs without error and produces the correct results.
.
