Net Power

Net Power is defined as Forward Power minus the Reflected Power. This document describes the formula's that should be used to correctly calculate the Net Power.

Given information

Frequency [MHz]	Forward Power [dBm]	Reflected Power [dBm]
201,973	50	30

Question: What is the Net Power?

Answer: 49,95635195 dBm

The calculation

First you calculate the dBm values to linear values.

${\displaystyle 50\$dBm=10^{\frac {50}{10}}\ mW=100\ W}

Formula -1: Logarithmic power value to linear power value

${\displaystyle 30\$dBm=10^{\frac {30}{10}}\ mW=1\ W}

Subtract the linear values

$P_{net}=P_{fwd}[W]-P_{refl}[W]=100[W]-1[W]=99\ W$

Formula -2: Net power calculation from forward and reflected power

Convert the value to dBm again:

${\displaystyle 10*log10(99*1000)\approx 49,95635195\$dBm}

Formula -3: Linear power value to logarithmic power value

Power expressed in milliWatt in dB values.

• 1 mW = 0 dBm

• 2 mW = 3 dBm

• 100 mW = 20 dBm

• 1 W = 30 dBm

• 100 W = 50 dBm