The 3rd Edition of Digital Filters for Everyone is now available on Amazon. It will take a few days before all of the features are populated, but it can be ordered now.
The 3rd Edition e-book is in work and should be available in a few weeks.
As with the 2nd Edition, the 3rd omits nothing from the previous editions. There is a new chapter on two-dimensional (2D) filters, and a section of pseudo code to facilitate software implementation. Thank you to some reviewers for pointing out that deficiency.
Besides those major elements, the entire book has been edited yet again in an effort to make it as clear and easy to use as possible.
Friday, March 27, 2015
Monday, October 27, 2014
Upcoming Filter Webinar
I will be teaching a filter webinar through PDHengineer.com on December 30. The six hour course can be taken all together or either half can be take separately. Join me if you can!
Thursday, July 17, 2014
DFFE is #1!
Thanks to all of you, Digital Filters for Everyone is currently number 1 in signal processing books on Amazon. I am touched and honored. Thank you!
Wednesday, February 12, 2014
Slide and Divide
Am I the only one who didn't know the slide and divide method?
If you've read my book, or the digital filter courses in this blog, you know that I know a thing or two about math in general, and polynomials in particular. But I hadn't heard of "Slide and Divide" until last week. The excellent math teacher at one of the places where I volunteer as a tutor, e-mailed me to Google on it and learn how to do it. I did, and have now been able to help several of her students with it.
You could also Google it, but I'll show it here for those who haven't seen it. To begin with, let's make an example that we know will be factorable:
(3x + 2)(5x - 4) = 15x^2 -2x -8. (Did I do that right?)
The first thing we do is replace c (the -8 in this case) with the product of a and c = -8 x 15 = -120.
Now, we write a new polynomial: x^2 -2x -120. Note that it is NOT equivalent to the one we're trying to factor. It's just a new polynomial that will help us with our job. So let's factor it. It's easier since a = 1.
(x + 10)(x - 12)
Now, we have to divide the roots by the 15 by which we multiplied c above. (Repeat caveat about equivalence.)
(x + 10/15)(x - 12/15) = (x + 2/3)(x - 4/5)
Now, in the case of fractional roots such as these, we multiply each factor by its root's denominator: 3(x + 2/3) and 5(x-4/5). (Repeat caveat about equivalence.)
Finally, we simplify those: (3x + 2)(5x - 4)
Ordinarily we could FOIL it back out to check, but there's no need since we started with the same factors above.
Pretty slick right? The fact that it violates equivalence along the way was bothersome at first, but that's really just an accounting problem. One keeps track of what's equivalent and not, and uses the rest as intermediate calculations. In the end it's easy to demonstrate that the result is correct.
If you've read my book, or the digital filter courses in this blog, you know that I know a thing or two about math in general, and polynomials in particular. But I hadn't heard of "Slide and Divide" until last week. The excellent math teacher at one of the places where I volunteer as a tutor, e-mailed me to Google on it and learn how to do it. I did, and have now been able to help several of her students with it.
You could also Google it, but I'll show it here for those who haven't seen it. To begin with, let's make an example that we know will be factorable:
(3x + 2)(5x - 4) = 15x^2 -2x -8. (Did I do that right?)
The first thing we do is replace c (the -8 in this case) with the product of a and c = -8 x 15 = -120.
Now, we write a new polynomial: x^2 -2x -120. Note that it is NOT equivalent to the one we're trying to factor. It's just a new polynomial that will help us with our job. So let's factor it. It's easier since a = 1.
(x + 10)(x - 12)
Now, we have to divide the roots by the 15 by which we multiplied c above. (Repeat caveat about equivalence.)
(x + 10/15)(x - 12/15) = (x + 2/3)(x - 4/5)
Now, in the case of fractional roots such as these, we multiply each factor by its root's denominator: 3(x + 2/3) and 5(x-4/5). (Repeat caveat about equivalence.)
Finally, we simplify those: (3x + 2)(5x - 4)
Ordinarily we could FOIL it back out to check, but there's no need since we started with the same factors above.
Pretty slick right? The fact that it violates equivalence along the way was bothersome at first, but that's really just an accounting problem. One keeps track of what's equivalent and not, and uses the rest as intermediate calculations. In the end it's easy to demonstrate that the result is correct.
Sunday, February 9, 2014
Amazon's Top 100
Amazon recently published a list of 100 books to read before you die. I checked, and Digital Filters for Everyone wasn't on it. Could that be right? Hey, get Amazon on the phone...
Surely we're 101, and didn't quite make the cut? Well, not quite. Surprising though it may seem to those of us who do, there are people in the world who will never bother to design a digital filter. It seems like such a waste.
But I am grateful to my loyal followers who have made Digital Filters for Everyone a top seller within its category. I am humbled by your support.
Surely we're 101, and didn't quite make the cut? Well, not quite. Surprising though it may seem to those of us who do, there are people in the world who will never bother to design a digital filter. It seems like such a waste.
But I am grateful to my loyal followers who have made Digital Filters for Everyone a top seller within its category. I am humbled by your support.
Sunday, September 29, 2013
Errata for Digital Filters for Everyone
Thanks to an attentive reader who found a bug that had been in my First Edition and the 1st Printing of my Second Edition. Note that I missed one spot when correcting, so the bottom of page 19 in the 2nd Printing of the Second Edition still has one mistake. Third Printing of Second Edition, which is what you'll get if you order now (and for the past couple weeks) has all known issues resolved. (Second edition ebook came out only after this was resolved.)
I am less concerned about minor bugs that don't much affect understanding, though I'll continue to try to clean those up too. However, since this particular issue could leave you scratching your head, I'm posting the correction here too. Most of you don't need a new book, you just need to see the correct presentation.
Let me know if you have questions.
(The second half of the slide above is from the bottom of page 19 in the current edition. The 1-alpha part was backwards still in the 2nd Printing of the Second Edition. The other errors, however, were corrected in that printing.)
I am less concerned about minor bugs that don't much affect understanding, though I'll continue to try to clean those up too. However, since this particular issue could leave you scratching your head, I'm posting the correction here too. Most of you don't need a new book, you just need to see the correct presentation.
Let me know if you have questions.
(The second half of the slide above is from the bottom of page 19 in the current edition. The 1-alpha part was backwards still in the 2nd Printing of the Second Edition. The other errors, however, were corrected in that printing.)
Saturday, July 20, 2013
Upcoming Filter Course: Orlando
I'll be teaching a day long filter seminar at this conference on Wednesday October 9th.
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