BIRD 5012D, Operation Manual

Page: 14 / 46

Wideband Power Sensors
6
Function Descriptions
Figure 1 Average and Peak Envelope Power - Square Wave Signal
Average Power
Average power is a measure of the equivalent “heating” power of a signal, as
measured with a calorimeter. It measures the total RF power in the system, and
does not depend on number of carriers or modulation scheme. The WPS is a
broadband sensor that measures power across its entire frequency range. Its
diodes operate in their ‘square law’ region so that the detector output is directly
proportional to the average power, without any additional error correction.
Average power is the most important measurement of any transmission system
since the average power is normally specified on the operating license. It is also
valuable as a maintenance tool, showing overall system health, and for
calibration.
VSWR
VSWR measures the relation between forward and reflected average power.
The Bird Wideband Power Sensor calculates the VSWR from the Forward and
Reflected Average Power measurements. Rho and Return Loss are also the
same measurement, but in different units:
Rho
Rho
  
P
R
P
F

=
VSWR
VSWR
1

+
1

–
------------ =
Return Loss (dB)
ReturnLoss dB
 
10 P
R
P
F
  
log =