Frequency Response of a SISO System

This example shows how to plot the frequency response and obtain frequency response data for a single-input, single-output (SISO) dynamic system model.

Create a transfer function model and plot its frequency response.

H = tf([10,21],[1,1.4,26]); 
bode(H)

When you can bode without output arguments, it plots the frequency response on the screen. Unless you specify a frequency range to plot, bode automatically chooses a frequency range based on the system dynamics.

Calculate the frequency response between 1 and 13 rad/s.

[mag,phase,w] = bode(H,{1,13});

When you call bode with output arguments, the command returns vectors mag and phase containing the magnitude and phase of the frequency response. The cell array input {1,13} tells bode to calculate the response at a grid of frequencies between 1 and 13 rad/s. bode returns the frequency points in the vector w.