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
FPGAs are the glue logic in today's systems, but what they glue together are a variety of diverse sub-systems with different interface requirements.
Enterprising Tesla Model S owner Steve Sasman seems to have figured out a way of recouping some of the cost on his car by renting the trunk out on AirBnB, the room/house rental website.
Everyone has had the experience of trying to scrape the last of the peanut butter or mayonnaise from the bottom of a glass jar without getting your hand sticky. Inventor Ron Jidmar thinks he has a solution to all of that nonsense with a flexible jar design that can be squeezed with one hand to lift contents from the bottom to the top of a jar or container, leaving the other hand free to scoop the contents out cleanly.
Made by Monkeys highlights products that somehow slipped by the QC cops.
2014 was big dark year for cyber attacks. Here's the month-by-month blow-by-blow breakdown.
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
2/25/2015 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.
Jan 26 - 30, IPv6 for Micros – Hands-On
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.
Last Archived Class
Sponsored by Stratasys
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