Decibels and Radars

Converting dBW to dBm and Vice Versa

dBm measures power relative to 1 milliwatt, while dBW measures power relative to 1 watt.

So to convert between the two, you have these equations:

dBm = dBW + 30
or
dBW = dBm - 30

Converting Radar Power in Watts to Decibels

dBW = 10 x log10(PowerWatts)

dBW: Transmitter power output in decibels.
PowerWatts: Transmitter power output in watts.

EXAMPLE: What is the dBW of a 1 megawatt radar?

10 x log10(1,000,000) = 60 dB

Converting Radar Power in Decibels to Watts

PowerWatts = 10(Decibels/10)

PowerWatts: Transmitter power output in watts.
Decibels: Transmitter power output in decibels.

EXAMPLE: What is the power in watts of a 100 dBw radar?

10(100/10) = 10,000,000,000 watts.

Converting Radar Cross Section in Square Meters to Decibels

dBsm = 10 x log10(RCS/1m2)

dBsm: Radar Cross Section of target in decibels.
RCS: Radar Cross Section of target in square meters.

EXAMPLE: What is the dBsm of a stealth fighter with a RCS of 0.01 m2?

10 x log10(0.01/1m2) = -20 dBsm

Converting Radar Cross Section in Decibels to Square Meters

RCS = 10(Decibels/10)

RCS: Radar Cross Section of target in square meters.
Decibels: Radar Cross Section of target in decibels.

EXAMPLE: What is the RCS in square meters of an aircraft with a RCS of 5 dB?

10(5/10) = 3.16 m2

Converting Antenna Gain into Decibels Relative to Isotropic (dBi)

dBi = 10 x log10(Gain/1)