How to get ztransform from looking into Frequency response graph of Gain and Phase

Good Morning, How we can get ztransform or filter Transfer Function from Frequency response graph of Gain and Phase plots Regards, Hayder

Answer 1

[Star Strider]

You can visually determine the passband (half-power or -6dB points) from the Bode plot. Then use those to design your filter. Adjust the parameters (passband and stopband frequencies and ripples) until your filter looks like the one you have the plot for.

If you have the data in a .fig file, you can extract the 'XData' and 'YData' vectors and use the firls function (or its friends) to do a least-squares approximation of the amplitude characteristics.

In either situation, you will probably have to adjust some of the parameters of the functions you use to design your filter to have it fit the Bode plot you are working from.

[SoftCr]

thank you for your reply

Or can I get the TF if the Kgain,, Timeconst , and pole freq is given for a specific controller (PI-type2= improved PI),thankyou

[Star Strider]

I thought you were referring to filters, not control systems.

If you have the necessary data on your control system, you can certainly do a state space representation of it and calculate its transfer function.