[Scipy-tickets] [SciPy] #1812: Erratic phase plot for high order filters
SciPy Trac
scipy-tickets@scipy....
Sat Jan 12 20:51:47 CST 2013
#1812: Erratic phase plot for high order filters
------------------------+---------------------------------------------------
Reporter: kitmonisit | Owner: somebody
Type: defect | Status: new
Priority: normal | Milestone: Unscheduled
Component: Other | Version: 0.11.0
Keywords: |
------------------------+---------------------------------------------------
PROBLEM: The phase plot computed from scipy.signal.lit.bode function shows
abrupt changes between -180° and 180°.
I'm using the scipy.signal module to design analog filters. These are the
steps I used to do it (it's also commented in the code):
1. Set up specifications
2. Convert Hz to rad/s (w is "omega")
3. Normalize w from 0 to 1
4. Calculate required filter order and natural frequency
(scipy.signal.buttord)
5. Calculate zeros, poles, and gain (scipy.signal.butter)
6. Create LTI system (scipy.signal.lti)
7. Compute Bode plots (scipy.signal.lti.bode)
8. Convert w back to f and scale appropriately
9. Plot stuff to "plot.pdf"
Attached files are butterworth.py and plot.png
--
Ticket URL: <http://projects.scipy.org/scipy/ticket/1812>
SciPy <http://www.scipy.org>
SciPy is open-source software for mathematics, science, and engineering.
More information about the Scipy-tickets
mailing list