Fitting a trendline to Bode plot data for a second-order system

[tandoorichicken]

Homework Statement

I have to plot some data for a lab writeup. It's based on the frequency response of fluid catheter-transducer systems. Part of this writeup includes making Bode plots for the gain and phase shift. I know how to plot my data; the problem that I am having is that I want to try to fit a trendline that closely follows the data, but I don't know how to do this.

1) What is the function (as in x/y) for a theoretical Bode plot for a second-order system?
2) Is this the right way to go about this or is there a better way?

Any insight would be much appreciated.

 

[berkeman]

Do you know what the gain and phase shift are for 2nd order lowpass, highpass, bandpass and notch filters? Start by understanding what these four types of filters have for their 2nd order responses, and I think you'll see what your options are.