HOME  |  NEWS  |  BLOGS  |  MESSAGES  |  FEATURES  |  VIDEOS  |  WEBINARS  |  INDUSTRIES  |  FOCUS ON FUNDAMENTALS
  |  REGISTER  |  LOGIN  |  HELP
Comments
View Comments: Newest First|Oldest First|Threaded View
Rob Spiegel
User Rank
Blogger
Re: Why the filter?
Rob Spiegel   9/17/2012 4:01:45 PM
NO RATINGS
That makes sense, Jon. I look forward to seeing your upcoming columns on this subject.

Jon Titus
User Rank
Blogger
Re: Why the filter?
Jon Titus   9/17/2012 3:31:47 PM
NO RATINGS
Correct, Rob.  You want a steep filter roll off and a response that doesn't attenuate the signals you want.  Stay tuned...

Rob Spiegel
User Rank
Blogger
Re: Why the filter?
Rob Spiegel   9/17/2012 2:05:45 PM
NO RATINGS
I take it the filter has to be fairly sophisticated, Jon, in order to avoid filtering out the data you're actually seeking.

Jon Titus
User Rank
Blogger
Re: Why the filter?
Jon Titus   9/17/2012 12:08:25 PM
NO RATINGS
Correct, Rob.  Information at higher frequencies (or outside the bandwidth of interest) can interfere with sampled data if not removed with a filter beforehand.

Rob Spiegel
User Rank
Blogger
Re: Why the filter?
Rob Spiegel   9/17/2012 10:06:48 AM
NO RATINGS
Thanks Jon. So I take it the quality of the data is compromised without the filter. I look forward to seeing the upcoming columns.

alexp
User Rank
Iron
Re: Why the filter
alexp   9/13/2012 10:57:16 AM
NO RATINGS
Hello Rob and All,

IF there are signals with frequency content above the  Nyquist frequency ( half the sample rate ), AND analog anti-aliasing filtering is not used prior to Analog to Digital Conversion, the signals will appear as signals between DC and the Nyquist frequency ...  AND once digitized, the aliased signals cannot be separated nor recognized as being invalid - can be a Major issue.

 From my experience anti-alias filtering is usually a compromise and typically you set the sample rate higher than the desired max needed frequency to allow some  roll-off without significantly compromising the data of interest.

 Modern ADC systems typically sample at their max rate and use  anti-alias filters set  appropriately high... the data is then Digitally low pass filtered and Decimated to create lower effective sample rates with no analog anti-aliasing filter artifacts...

 Alex

mrdon
User Rank
Gold
Re: Why the filter?
mrdon   9/12/2012 11:01:22 PM
NO RATINGS
Hi Jon,  As always, great technical article. I'll definitely be waiting for the additional articles on Anti-Alias Filters so I can share this information with my Integrated Circuits class at ITT Tech Institute. Keep the tech articles coming!

Jon Titus
User Rank
Blogger
Re: Why the filter?
Jon Titus   9/12/2012 1:55:02 PM
NO RATINGS
Hi, Rob.  You can get some unusual results because signals at higher frequencies alias, or fold, into the bandwidth over which you want to make measurements. The alising arises from the sampling of signals at discrete time intervals.  Upcoming columns get into more details and explain how to use aliasing to "shift" signals to lower "frequencies" on purpose.  Stay tuned. --Jon

Rob Spiegel
User Rank
Blogger
Why the filter
Rob Spiegel   9/12/2012 1:33:39 PM
NO RATINGS
Jon, how much of a problem do you run into if you don't use a filter?



Partner Zone
Latest Analysis
Researchers in Canada have developed a chin strap that harvests energy from chewing and can potentially power a digital earplug that can provide both protection and communication capabilities.
In case you haven't heard, the deadline to enter the 2014 Golden Mousetrap Awards is coming up fast Oct. 28! Have you entered yet?
Made by Monkeys highlights products that somehow slipped by the QC cops.
A Tokyo company, Miraisens Inc., has unveiled a device that allows users to move virtual 3D objects around and "feel" them via a vibration sensor. The device has many applications within the gaming, medical, and 3D-printing industries.
In the last few years, use of CFD in building design has increased manifolds. Computational fluid dynamics is effective in analyzing the flow and thermal properties of air within spaces. It can be used in buildings to find the best measures for comfortable temperature at low energy use.
More:Blogs|News
Design News Webinar Series
9/25/2014 11:00 a.m. California / 2:00 p.m. New York
9/10/2014 11:00 a.m. California / 2:00 p.m. New York
7/23/2014 11:00 a.m. California / 2:00 p.m. New York
7/17/2014 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.
Oct 20 - 24, How to Design & Build an Embedded Web Server: An Embedded TCP/IP Tutorial
SEMESTERS: 1  |  2  |  3  |  4  |  5  |  6


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 Class: October 1 - 30
Sponsored by Gates Corporation
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