Jon Titus
User Rank
The math behind frequency aliasing
Jon Titus   4/6/2012 11:07:52 AM
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.

User Rank
Re: Who uses this?
Shelly   4/6/2012 10:03:31 AM
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.

User Rank
using filters and the Nyquist-Shannon theorem
vimalkumarp   4/6/2012 1:08:01 AM

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
Another Keeper!
Nancy Golden   4/5/2012 7:55:00 PM

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
Use of anti-alias filters...
Jon Titus   4/5/2012 12:27:00 PM
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
Who uses this?
Rob Spiegel   4/5/2012 11:21:29 AM
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
Designers of electronic interfaces will need to be prepared to incorporate haptics in next generation products, an expert will tell attendees at the upcoming Designer of Things Conference in San Jose.
According to a Randstad Engineering compilation of salary studies, engineering salaries are increasing beyond inflation, with employers paying to keep potential suitors away from their employees.
The company says it anticipates high-definition video for home security and other uses will be the next mature technology integrated into the IoT domain, hence the introduction of its MatrixCam devkit.
Siemens and Georgia Institute of Technology are partnering to address limitations in the current additive manufacturing design-to-production chain in an applied research project as part of the federally backed America Makes program.
Most of the new 3D printers and 3D printing technologies in this crop are breaking some boundaries, whether it's build volume-per-dollar ratios, multimaterials printing techniques, or new materials types.
Design News Webinar Series
11/10/2015 11:00 a.m. California / 2:00 p.m. New York
10/29/2015 11:00 a.m. California / 2:00 p.m. New York
10/20/2015 8:00 a.m. California / 11:00 a.m. New York
12/2/2015 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.
Jul 6 - 10, Building Raspberry Pi Controllers with Python
SEMESTERS: 1  |  2  |  3  |  4  |  5  |  6 |  7

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 © 2015 UBM Canon, A UBM company, All rights reserved. Privacy Policy | Terms of Service