User's Manual

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Section 2 Microwave Path Engineering Basics TRACER 4208 System Manual
Higher levels of fade margin indicate stronger protection against signal fading and a more reliable link. For
most applications, 20 to 30 dB of fade margin should ensure a reliable link.
The following sections further discuss the necessary power calculations and their components.
4. RECEIVER POWER
The viability of a particular microwave path is determined by the power of the transmitted microwave
signal, the transmit and receive antenna gain, distance, and accumulated system losses (such as RF coaxial
cable losses and path loss).
The equation relating received signal power to the other microwave parameters is
P
T
G
T
G
R
λ
2
= ------------------------------
(Watts, W)
P
R
(
4
π )
2
d
2
L
or (in decibel notation)
P
R
= P
T
+ G
T
+ G
R
- L - L
P
(decibels referenced to a Watt, dBW)
where the variables in the equation are defined as
P
R
received power (Watts)
P
T
transmitted power (100 mW (max) for TRACER 4208 - adjustable)
G
T
transmit antenna gain
G
R
receive antenna gain
λ carrier wavelength (meters)
d path distance (meters)
other losses (RF coaxial cable, etc.)
L
P
path loss (dB)
When using decibel notation, all quantities must be individually converted to decibels
prior to performing addition and subtraction.
Figure 1 on page 17 illustrates a wireless link configuration containing all the parameters necessary for the
power budget analysis.
© 2003 ADTRAN, Inc. 612804208L1-1A 16