User's Manual

Quatech, Inc. Company Confidential
Revision 1.0 100-8026-100G Airborne 802.11b/g Value Radio Databook 25
contributes to the Equivalent Isotropically Radiated Power (EIRP) of the system.
This is part of an overall measurement of the link quality called link margin.
Link Margin provides a measure of all the parts of the RF path that impact the
ability of two systems to communicate. The basic equation looks like this:
EIRP (dB) = TxP + TxA – TxC
Link Margin (dB) = EIRP – FPL + (RxS + RxA – RxC)
Where: TxP = Transmitter output power (dBm)
TxA = Transmitter antenna gain (dBi)
TxC = Transmitter to Antenna coax cable loss (dB)
FPL = Free Path Loss (dB)
RxS = Receiver receive sensitivity (dBm)
RxA = Receiver antenna gain (dBi)
RxC = Receiver to Antenna coax cable loss (dB)
This is a complex subject and requires more information that is presented here,
Quatech does recommend at least looking at the subject and evaluating any
system at a basic level.
It is then possible, with a combination of the above items and an understanding
of the application demands, to achieve a link quality optimized for the application
and host design. It is important to note that this is established with a combination
of hardware selection, design choices and configuration of the radio.