Electronics World articles Popular Electronics articles QST articles Radio & TV News articles Radio-Craft articles Radio-Electronics articles Short Wave Craft articles Wireless World articles Google Search of RF Cafe website Sitemap Electronics Equations Mathematics Equations Equations physics Manufacturers & distributors Engineer Jobs LinkedIn Crosswords Engineering Humor Kirt's Cogitations Engineering Event Calendar RF Engineering Quizzes USAF radar shop Notable Quotes App Notes Calculators Education Engineering Magazines RF Cafe Software,T-Shirts,Coffee Mugs Engineering magazine articles Engineering software Engineering smorgasbord RF Cafe Archives RF Cascade Workbook 2018 RF Stencils for Visio RF & EE Shapes for Word Advertising RF Cafe Homepage Sudoku puzzles Test notes Thank you for visiting RF Cafe!
Innovative Power Products Couplers

Bessel Filter Poles

Order
(N)
Re Part
(-σ)
Im Part
(±jω)
1 1.0000  
2 1.1030 0.6368
3 1.0509
1.3270
1.0025
4 1.3596
0.9877
0.4071
1.2476
5 1.3851
0.9606
1.5069
0.7201
1.4756
6 1.5735
1.3836
0.9318
0.3213
0.9727
1.6640
7 1.6130
1.3797
0.9104
1.6853
0.5896
1.1923
1.8375
8 1.7627
0.8955
1.3780
1.6419
0.2737
2.0044
1.3926
0.8253
9 1.8081
1.6532
1.3683
0.8788
1.8575
0.5126
1.0319
1.5685
2.1509
10 1.9335
0.8684
1.8478
1.6669
1.3649
0.2424
2.2996
0.7295
1.2248
1.7388

Bessel poles lie along a circle similar to the Butterworth filter, but are spaced approximately equal distances apart relative to the real axis rather than at equal angular distances. Prototype value real and imaginary pole locations (ω=1 at the 3dB cutoff point) for Bessel filters are presented in the table below.

4th-order lowpass Bessel filter pole-zero diagram - RF Cafe

This pole-zero diagram shows the location of poles for a 4th-order Bessel lowpass filter.

Bessel filter prototype element values are here.

Bessel function plots can be found here.

Data taken from "Filter Design," by Steve Winder, Newnes Press, 1998. This is a great filter design book, and I recommend you purchase a copy of it.

Related Pages on RF Cafe
- Filter Transfer Functions
- Filter Equivalent Noise Bandwidth
- Filter Prototype Denormalization
- Bessel Filter Poles
- Bessel Filter Prototype Element Values
- Butterworth Lowpass Filter Poles
- Butterworth Filter Prototype Element Values
- Chebyshev Lowpass Filter Poles
- Chebyshev Filter Prototype Element Values
- Monolithic Ceramic Block Combline Bandpass
  Filters Design
- Coupled Microstrip Filters: Simple Methodologies for
  Improved Characteristics
ERZIA (RF amplifiers, wireless, communications) - RF Cafe Rohde & Schwarz FPC1500 Spectrum Analyzer - RF Cafe
Rohde & Schwarz USA (Signal Generator Pocket Guide 2) - RF Cafe
About RF Cafe
Kirt Blattenberger - RF Cafe Webmaster
Copyright: 1996 - 2018
Webmaster:
    Kirt Blattenberger,
    BSEE - KB3UON

RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. The Internet was still largely an unknown entity at the time and not much was available in the form of WYSIWYG ...

All trademarks, copyrights, patents, and other rights of ownership to images and text used on the RF Cafe website are hereby acknowledged.

My Hobby Website:  AirplanesAndRockets.com

spacer