The ‘sys1’ and ‘sys2’ transfer functions are actually improper, wince with a denominator of 1, they are infinite differentiators.
As such, they have no corner frequencies.
To get the frequencies at any points in the frequency response that you want, use freqresp and interp1 — sys1 = tf(num1,den1)
sys1 =
s + 1
Continuous-time transfer function.
sys1_dB6_radfreq = interp1(mag2db(abs(H1)),w, 6)
sys1_dB6_radfreq = 1.7266
sys2 = tf(num2, den2)
sys2 =
s^2 + 2 s + 1
Continuous-time transfer function.
[H2,wout2] = freqresp(sys2,w);
sys2_dB6_radfreq = interp1(mag2db(abs(H2)),w, 6)
sys2_dB6_radfreq = 0.9976
It is also possible to calculate where the phase reaches a certain value, however it may be necessary to restrict ‘w’ to a monotonically-increasing or -decreasing part of the spectrum in order to avoid problems with non-unique values.
.
