Power Attenuator Calculator Ideal and 1% Tolerance Resistor Values

This Attenuator Calculator is probably unlike any you have seen. Not only does it calculate resistor values for both balanced and unbalanced Pi and Tee topologies, but it also calculates the power dissipated by each resistor, and calculates the input and output VSWR when 1% tolerance resistors are used rather than ideal values. Equations and schematics for all four configurations can be seen on the Attenuators page.

Disclaimer: These calculations are believed to be accurate, but you must validate all results for critical applications. RF Cafe's calculators are entirely unique code - not "borrowed" from somebody else's work.

Attenuation (dB):	Source Resistance (Ω):
Load Resistance (Ω):	Source Power:	mW dBm
Resistor values: 1% Tolerance (E96) Ideal

Ideal power ratio k = 2.000 linear power ratio | Ideal attenuation: 3.010 dB | Psource = 30.00 dBm

Unbalanced Pi

Component	Value	Power
R_in shunt	291.4 Ω	0.17156 W
R_series	17.7 Ω	0.24263 W
R_out shunt	291.4 Ω	0.08578 W
P load		26.99 dBm

Match

Parameter	Value
Input VSWR	1.000
Input Return Loss	308.989 dB
Output VSWR	1.000
Output Return Loss	308.989 dB

Actual insertion loss: 3.010 dB

Unbalanced Tee

Component	Value	Power
R_series src	8.6 Ω	0.17156 W
R_series load	8.6 Ω	0.08578 W
R_shunt	141.4 Ω	0.24263 W
P load		26.99 dBm

Match

Parameter	Value
Input VSWR	1.000
Input Return Loss	310.927 dB
Output VSWR	1.000
Output Return Loss	310.927 dB

Actual insertion loss: 3.010 dB

Balanced Pi

Component	Value	Power
R_shunt in	291.4 Ω	0.17156 W
R_series each leg	17.7 Ω total 8.8 Ω per leg	0.24263 W
R_shunt out	291.4 Ω	0.08578 W
P load		26.99 dBm

Match

Parameter	Value
Input VSWR	1.000
Input Return Loss	308.989 dB
Output VSWR	1.000
Output Return Loss	308.989 dB

Actual insertion loss: 3.010 dB

Balanced Tee

Component	Value	Power
R_series src leg	8.6 Ω total 4.3 Ω per leg	0.17156 W
R_series load leg	8.6 Ω total 4.3 Ω per leg	0.08578 W
R_shunt line-line	141.4 Ω	0.24263 W
P load		26.99 dBm

Match

Parameter	Value
Input VSWR	1.000
Input Return Loss	310.927 dB
Output VSWR	1.000
Output Return Loss	310.927 dB

Actual insertion loss: 3.010 dB