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
Platinum
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
Former DARPA official and Google executive Dr. Kaigham Gabriel believes sensor companies think too much like suppliers and need to bring their products closer to the consumer.
One way to keep a Formula One racing team moving at breakneck speed in the pit and at the test facility is to bring CAD drawings of the racing vehicleís parts down to the test facility and even out to the track.
Most of us would just as soon step on a cockroach rather than study it, but thatís just what researchers at UC Berkeley did in the pursuit of building small, nimble robots suitable for disaster-recovery and search-and-rescue missions.
Engineers at Festo were inspired by how a caterpillar builds its cocoon when designing its new 3D Cocooner printer.
Design engineers need to prepare for a future in which their electronic products will use not just one or two, but possibly many user interfaces that involve touch, vision, gestures, and even eye movements.
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.
SEMESTERS: 1  |  2  |  3  |  4  |  5  |  6 |  7 | 8 | 9


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 June 28-30:
Sponsored by Proto Labs
Learn More   |   Login   |   Archived Classes
Twitter Feed
Design News Twitter Feed
Like Us on Facebook

Technology Marketplace

Copyright © 2016 UBM Canon, A UBM company, All rights reserved. Privacy Policy | Terms of Service