find frequency in specified phase

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arash rad 2021-6-14

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链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/856255-find-frequency-in-specified-phase

have a system and i want to calculate bandwidth of DRGA element in 180 degree how can i write this code

i wrote a little i dont know how to continue

clc
clear all 
close all 
s = tf('s')
G = [((-1.986)*(1-((0.71*s)/2)))/((1+((0.71*s)/2))*(66.67*s+1)) (5.24*(1-((60*s)/2)))/((1+((60*s)/2))*(400*s+1)) (5.984*(1-((2.24*s)/2)))/((1+((2.24*s)/2))*(14.29*s+1)) ;...
    (0.0204*(1-((4.199*s)/2)))/((1+((4.199*s)/2))*(5*s+1)) (-0.33*(1-((1.883*s)/2)))/((1+((1.883*s)/2))*(3.904*s+1)) (2.38*(1-((1.143*s)/2)))/((1+((1.143*s)/2))*(10*s+1)) ;...
    (0.374*(1-((7.75*s)/2)))/((1+((7.75*s)/2))*(22.22*s+1)) (-11.3*(1-((14.78*s)/2)))/((1+((14.78*s)/2))*(35.66*s+1)) (-9.881*(1-((1.59*s)/2)))/(1+((1.59*s))*(11.35*s+1))]
G0 = dcgain(G);
G_hat = inv(G0);
DRGA = G.*(inv(G))';
[mag,phase] = bode(DRGA)
for i=1:length(G)
    for j=1:length(G)
        Bandwidth(i,j)=bandwidth(G(i,j));? %%how to calculate frequency here for 180 deg
    end
end
E=G0.*Bandwidth;
ERGA=E.*(inv(E))';
E = G0.*Bandwidth;
ERGA = E.*(inv(E))'