Custom Search
Over 9,000 pages indexed!
Your Host
Click here to read about RF CafeKirt
Blattenberger

... single-handedly
redefining what an
engineering website should be.

View the YouTube RF Cafe Intro Video Carpe Diem!
(Seize the Day!)

5CCG (5th MOB):
My USAF radar shop

Hobby & Fun

Airplanes and Rockets:
My personal hobby website

Equine Kingdom:
My daughter Sally's horse riding business website - lots of info

Doggy Dynasty:
My son-in-law's dog training business

•−•  ••−•    −•−•  •−  ••−•  •
RF Cafe Morse Code >Hear It<
Job Board
About RF Cafe©
RF Cafe E-Mail
Product & Service
Directory
Engineering
Jobs
Personally Selected
Manufacturers
Employers Only
(no recruiters)

Butterworth Filter Prototype Element Values

Visit the Anatech Electronics websiteButterworth poles lie along a circle and are spaced at equal angular distances around a circle. It is designed to have a frequency response which is as flat as mathematically possible in the passband, and is often referred to as a 'maximally flat magnitude' filter. Prototype value real and imaginary pole locations (ω=1 at the 3 dB cutoff point) for Butterworth filters are presented in the table below.

The Butterworth type filter was first described by the British engineer Stephen Butterworth in his paper "On the Theory of Filter Amplifiers", Wireless Engineer (also called Experimental Wireless and the Wireless Engineer), vol. 7, 1930, pp. 536-541.

The table below lists prototype element values for the normalized lowpass function, which assumes a cutoff frequency of 1 rad/sec and source and load impedances of 1 Ω. Either an input capacitor (top reference line in table) or an input inductor (bottom line in table) can be used.

Convert Butterworth prototype values to other cutoff frequencies, impedances, and to highpass, bandpass or bandstop using the equations here.

See my online Butterworth filter calculators and plotters here.

Complex poles are here.

RF Cafe - Prototype filter schematic - capacitor input           RF Cafe - Prototype filter schematic - inductor input

                                         Capacitor Input                                           Inductor Input

OrderC1L2C3L4C5L6C7L8C9L10
12.000         
21.414211.41421        
31.000002.000001.00000       
40.765371.847761.847760.76537      
50.618031.618032.000001.618030.61803     
60.517641.414211.931851.931851.414210.51764    
70.445041.246981.801942.000001.801941.246980.44504   
80.390181.111141.662941.961571.961571.662941.111140.39018  
90.347301.000001.532091.879382.000001.879381.532091.000000.34730 
100.312870.907981.414211.782011.975381.975381.782011.414210.907980.31287
 L1C2L3C4L5C6L7C8L9C10


RF Cafe Software

RF Cascade Workbook
RF Cascade Workbook is a very extensive system cascaded component Excel workbook that includes the standard Gain, NF, IP2, IP3, Psat calculations, input & output VSWR, noise BW, min/max tolerance, DC power cauculations, graphing of all RF parameters, and has a graphical block diagram tool. An extensive User's Guide is also included. - Only $35.
RF system analysis including
frequency conversion & filters

Smith Chart™ for Excel
Smith Chart™ for Visio
RF & EE Symbols Word
RF Stencils for Visio

A Disruptive Web Presence

Custom Search
Over 9,000 pages indexed!
Read About RF Cafe
Webmaster: Kirt Blattenberger
KB3UON

Product & Service Directory
Personally Selected Manufacturers

RF Cafe T-Shirts & Mugs
Calculator Workbook
RF Workbench
Please Support My Advertisers