# “fred harris rule of thumb”:

I would like to cite "fred harris rule of thumb" for estimating filter order. Is there a book or paper where I can find this rule of thumb? Thanks a bunch.

• i know about fred harris, but i have never heard of a *"fred harris rule of thumb". i gotta few rules of thumb, too. but i don't think any are published. – robert bristow-johnson Jan 11 '18 at 7:29
• It was also mentioned in this answer. You could ask Dan for a reference (by leaving a comment under his answer). – Matt L. Jan 11 '18 at 8:01

You can find the formula for (at least) one "Harris method" or "Harris approximation" in Multirate Signal Processing for Communication Systems, Fredric J. Harris, 2004, page 216, equation (8.16), with details in Chapter 3. F. Harris calls it "harris approximation" (without capital for the name), namely:

$$N = \frac{f_{SMPL}}{\Delta f}\frac{Atten(dB)}{22}$$

Also in Digital Communications with Emphasis on Data Modems: Theory, Analysis, Richard W. Middlestead, page 752, equation B.39.

Former questions might provide you with additional insights and references:

• Yes, fred usually writes his name as "fred harris" without capitals. You can tell by the capitals that it's not him writing it. :-) – Peter K. Mar 17 at 17:12

Scanned below is the fred harris' "Rule of Thumb" which included the filter taps as well as his other "rules".

This is from DSP World ICSPAT Class Notes DSP World Workshops, Orlando, Florida, November 1-4, 1999. That course along with other similar presentations and courses by fred harris have significantly influenced my views and thinking of signal processing, and likely contributed to how much I've been interested in it ever since.

(Pardon my scribbles)

• Nice!!! Are they online? – Peter K. Mar 18 at 0:43
• No I don't think so, but you could likely ask fred directly – Dan Boschen Mar 18 at 0:47