HW#3 Reference: How to Use MATLAB to Draw Bode Diagrams
MATLAB codes for your reference (Using computer Lab in E213 or E215):
Example: Given a Low-pass RC filter with R = 1 k, C = 0.1 F, draw a bode diagram of the system.
Solution: To use MATLAB to draw the Bode diagram, you need to write out the filter’s transfer
function first. For the RC filter, the transfer function is:
Vout
1
0 j  1


Vin
j RC  1 0.0001 j  1
In MATLAB window, type in the following comments based on the above Transfer Function:
» NUM=[0 1];
» DEN=[.0001 1];
» SYS=TF(NUM,DEN);
» bode(SYS)
» grid;
» grid;
% if numerator is (0j +1)
% if denominator is (0.0001j+1)
% define the transfer function
% draw bode plot
% put grid in the magnitude plot by click the plot first
% put grid in the phase angle plot by click the plot first
Then you will get the bode plot as follows:
You can use the similar codes to draw a High-pass filter response by using the corresponding HP filter
Transfer function.
Dr. Winncy Du, E310F, MAE Dept., SJSU, Tel.:408-924-3866,E-mail: winncy.du@.sjsu.edu
Course Web: www.engr.sjsu.edu/wdu/ME106Spring2010