D-Link DWL-1800 user manual RF Power Level, Attenuation

RF Power Level

RF power level at either the transmitter output or the receiver input is expressed in Watts. It can also be expressed in dBm. The relation between dBm and Watts can be expressed as follows:

PdBm = 10 x Log Pmw

For example: 1 Watt = 1000 mW; PdBm = 10 x Log 1000 = 30 dBm 100 mW; PdBm = 10 x Log 100 = 20 dBm

For link budget calculations, the dBm convention is more convenient than the Watts convention.

Attenuation

Attenuation (fading) of an RF signal is defined as follows:

Figure 28: Attenuation of an RF signal

Pin is the incident power level before attenuation

Pout is the output power level after attenuation

Attenuation is expressed in dB as follows: PdB = -10 x Log (Pout/Pin)

For example: If, due to attenuation, half the power is lost (Pout /Pin = 1/2),

attenuation in dB is -10 x Log (1/2) = 3dB

Path Loss

Loss of power of an RF signal traveling (propagating) through space. It is expressed in dB. Path loss depends on:

??The distance between transmitting and receiving antennas

??Line of sight clearance between the receiving and transmitting antennas

??Antenna height

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