•−•  ••−•    −•−•  •−  ••−•  •
RF Cafe Morse Code >Hear It<

Job Board

About RF Cafe™

Sitemap

RF Cafe Software

RF Cascade Worbook
 RF Cascade Workbook 2005 - RF Cafe
Calculator Workbook
RF Workbench
Smith Chart™ for Visio
Smith Chart™ for Excel
RF & EE Symbols Word
RF Stencils for Visio

Your RF Cafe
Progenitor & Webmaster

Click here to read about RF CafeKirt Blattenberger
BSEE
KB3UON
EIEIO

Carpe Diem!
(Seize the Day!)

5th MOB:
My USAF radar shop

Airplanes and Rockets:
My personal hobby website

Equine Kingdom:
My daughter Sally's horse riding website

Fixed Pi and Tee Attenuators - Equations

Fixed attenuators can be designed to have either equal or unequal impedances and to provide any amount of attenuation (theoretically) equal to or greater than the configuration's minimum attenuation - depending on the ratio of Z1/Z2. Attenuators with equal terminations have a minimum attenuation of 0 dB. Unequal terminations place a lower limit on the attenuation.

k = power in / power out:

Attenuator k-min equation - RF Cafe, or in decibels

Attenuator k-min equation (dB) - RF Cafe 

An online attenuator calculator is provided below.

Unbalanced Tee (T) Attenuator

These equations apply to the two forms of Tee attenuators at the left.

"T" Attenuator R1 Equation - RF Cafe

"T" Attenuator R2 Equation - RF Cafe

"T" Attenuator R3 Equation - RF Cafe

If  Z1 = Z2, then:

"T" Attenuator (Z1 = Z2) R1 & R2 Equation - RF Cafe

"T" Attenuator (Z1 = Z2) R3 Equation - RF Cafe

Unbalanced T Attenuator - RF Cafe
Balanced Tee (T) Attenuator
Balanced T Attenuator - RF Cafe
Unbalanced Pi (π) Attenuator

These equations apply to the two forms of Pi attenuators at the left.

"Pi" Attenuator R1 Equation - RF Cafe

"Pi" Attenuator R2 Equation - RF Cafe

"Pi" Attenuator R3 Equation - RF Cafe

If  Z1 = Z2, then:

"Pi" Attenuator (Z1 = Z2) R1 & R2 Equation - RF Cafe

"Pi" Attenuator (Z1 = Z2) R3 Equation - RF Cafe

Unbalanced Pi Attenuator - RF Cafe
Balanced Pi (π) Attenuator
Balanced Pi Attenuator - RF Cafe

Note: Only enter values in the yellow cells or risk overwriting formulas!

An RF Cafe visitor wrote to say that he thought the above equations might be in error when unequal source and load termination resistances are used. The image below shows the mathematical steps that prove the equations are correct. It uses a source resistance of 50 ohms and a load resistance of 100 ohms, with an attenuation of 10 dB. Resistor values for both the "T" and ""Pi" attenuators were determined using the attenuator calculator on RF Cafe (which uses these equations). 

Attenuators with unequal terminations - RF Cafe

Try Using SEARCH to Find What You Need.  >10,000 Pages Indexed on RF Cafe !

Copyright 1996 - 2016
Webmaster:  Kirt Blattenberger, BSEE - KB3UON
Family Websites:  Airplanes and Rockets | Equine Kingdom

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