MATLAB Answers

How to get the -3dB Frequency value for a semilog plot ?

5 views (last 30 days)
GEOFFREY LECOQ on 17 Mar 2021
Answered: Pavan Guntha on 23 Mar 2021
I try to add a line on my graph on -3dB for my Bode Graph, i use a table for store all of my data like Frequency, Gain, Ouput voltage, Input voltage. I already make the semi-log plot but i don't know how get the value.
First of all i try to make a line and find the intersection but i don't understand how i can't use it.
I think i need to make an linear regression of my table to solve the equation "f(x)=-3", i'm not sure.
Thanks !

Answers (1)

Pavan Guntha
Pavan Guntha on 23 Mar 2021
You may have to first find the index at which the gain is -3 dB (i.e., in Classeurl.g). Then the frequency can be found by calculating the value of Classeurl.f at that index. The following code illustrates the idea:
index = Classeurl.g == -3;
f_3dB = Classeurl.f(index);
% To plot a vertical line at -3 dB frequency:
hold on
hold off
You may refer to the documentation of xline for changing the properties as per your requirement.




Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!