HOME  |  NEWS  |  BLOGS  |  MESSAGES  |  FEATURES  |  VIDEOS  |  WEBINARS  |  INDUSTRIES  |  FOCUS ON FUNDAMENTALS
User Rank
Blogger
The math behind frequency aliasing
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.

User Rank
Iron
Re: Who uses this?
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.

User Rank
Gold
using filters and the Nyquist-Shannon theorem
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!

User Rank
Platinum
Another Keeper!
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!

User Rank
Blogger
Use of anti-alias filters...
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.

User Rank
Blogger
Who uses this?
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
Clearly, zombies are in this year -- taking over from a decade of vampire dominance in Halloween fashion.
Researchers in China have developed a battery with self-healing electrodes that makes it resistant to cracking, leaking, or just plain breaking.
The IoT will bring us the many positives of AI, evolving our technologies in ways that only a few years ago seemed like science fiction, according to ARM’s buyer.
Days after a massive, distributed denial-of-service attack took down dozens of major websites around the country, ARM Holdings plc is rolling out a pair of new processor architectures aimed at shoring up IoT security.
Dow Chemical and several other companies have launched a program in Omaha, Neb. to divert about 36 tons of plastics from landfills in its first phase, and convert it into energy used for cement production.
More:Blogs|News
Quick Poll
The Continuing Education Center offers engineers an entirely new way to get the education they need to formulate next-generation solutions.
Oct 10 - 14, Embedded System Design Techniques™: Getting Started Developing Professional Embedded Software
SEMESTERS: 1  |  2  |  3  |  4  |  5  |  6 |  7 | 8 | 9 | 10

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.
Next Course September 27-29: