HOME  |  NEWS  |  BLOGS  |  MESSAGES  |  FEATURES  |  VIDEOS  |  WEBINARS  |  INDUSTRIES  |  FOCUS ON FUNDAMENTALS
  |  REGISTER  |  LOGIN  |  HELP
Jon Titus
User Rank
Blogger
The math behind frequency aliasing
Jon Titus   4/6/2012 11:07:52 AM
NO RATINGS
The next column explains the math (with a few equations) behind the frequency aliasing. Engineers often understand the concept of aliasing, but the math provides details.

Shelly
User Rank
Iron
Re: Who uses this?
Shelly   4/6/2012 10:03:31 AM
NO RATINGS
We use them a lot in vibration testing/measurement.  If you consider the sampling rate of a sine wave, and the apparent measured frequency of high frequency signals measured too slowly, Nyquist is a good place to start, but we typically acquire data at much higher speeds than 2X our filter cutoff frequency.

vimalkumarp
User Rank
Gold
using filters and the Nyquist-Shannon theorem
vimalkumarp   4/6/2012 1:08:01 AM
NO RATINGS

Execellent  explanation on using filters and the Nyquist-Shannon theorem  . This will be of great use to every engineer as Nyquist-Shannon theorem was and is  realy the backbone of communication engineering. Thanks   Jon!


Nancy Golden
User Rank
Platinum
Another Keeper!
Nancy Golden   4/5/2012 7:55:00 PM
NO RATINGS

Very nice explanation on using filters and the Nyquist-Shannon theorem  -  something every test engineer needs to keep in mind when determining their sampling rate. Thanks for another great article, Jon!

Jon Titus
User Rank
Blogger
Use of anti-alias filters...
Jon Titus   4/5/2012 12:27:00 PM
NO RATINGS
I recommend using an anti-alias filter whenever you must measure anuthing more than a DC, or near-DC signal. Some companies include them in data-acquisition equipment or on analog-to-digital-converter (ADC) boards, and some don't, so it pays to ask. If a board or system includes a filter or filters, find out how much control you have over it and get a plot of frequency vs. attenuation (a Bode plot) and a plot that shows phase vs. frequency. I didn't get into phase changes in this column, but people should know that filters change phase relationships of signals, too.  Those changes could affect measurements when you must correlate signals in the time domain.

Engineers can build their own anti-alias filters, but I don't recommend that course unless they have filter-design experience and plan to build a lot of them. Commercial filters are the way to go in almost all situations.

Rob Spiegel
User Rank
Blogger
Who uses this?
Rob Spiegel   4/5/2012 11:21:29 AM
NO RATINGS
Interesting article, Jon. Are these filters widely used these days? And who is using them? Is this mostly for large, advanced organizations or is it more more widely deployed?



Partner Zone
Latest Analysis
A bold, gold, open-air coupe may not be the ticket to automotive nirvana for every consumer, but Lexus’ LF-C2 concept car certainly turned heads at the recent Los Angeles Auto Show. What’s more, it may provide a glimpse of the luxury automaker’s future.
Perhaps you didn't know that there are a variety of classes, both live and archived, offered via the Design News Continuing Education Center (CEC) sponsored by Digi-Key? The best part – they are free!
Engineer comic Don McMillan explains the fun engineers have with team-building exercises. Can you relate?
The complexity of diesel engines means optimizing their performance requires a large amount of experimentation. Computational fluid dynamics (CFD) is a very useful and intuitive tool in this, and cold flow analysis using CFD is an ideal approach to study the flow characteristics without going into the details of chemical reactions occurring during the combustion.
The damage to Sony from the cyber attack seems to have been heightened by failure to follow two basic security rules.
More:Blogs|News
Design News Webinar Series
12/11/2014 8:00 a.m. California / 11:00 a.m. New York
12/10/2014 8:00 a.m. California / 11:00 a.m. New York
11/19/2014 11:00 a.m. California / 2:00 p.m. New York
11/6/2014 11:00 a.m. California / 2:00 p.m. New York
Quick Poll
The Continuing Education Center offers engineers an entirely new way to get the education they need to formulate next-generation solutions.
Jan 12 - 16, Programmable Logic - How do they do that?
SEMESTERS: 1  |  2  |  3  |  4  |  5  |  67


Focus on Fundamentals consists of 45-minute on-line classes that cover a host of technologies. You learn without leaving the comfort of your desk. All classes are taught by subject-matter experts and all are archived. So if you can't attend live, attend at your convenience.
Learn More   |   Login   |   Archived Classes
Twitter Feed
Design News Twitter Feed
Like Us on Facebook

Sponsored Content

Technology Marketplace

Copyright © 2014 UBM Canon, A UBM company, All rights reserved. Privacy Policy | Terms of Service