Bird Technologies VPM3 - Manual (Page 45)

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Chapter 5 Statistical Power Mode
Most modern wireless communication systems employ complex modulation
and channel access methods like orthogonal frequency division multiplexing
(OFDM), or code division multiple access (CDMA). These methods use a combi-
nation of amplitude and phase modulation to create symbol based multichannel
or multicarrier systems that result in pseudorandom or noise-like power enve-
lopes. The consequence is that modulation parameters such as AM depth or FM
modulation index are not useful. Indeed, the peak-to-average power ratio of
the modulated carrier is a complex function of the data stream content rather
than just amplitude, and as such is not constant with time. Since digitally modu-
lated signals often appear noise-like it makes sense to use statistical analysis in
order to characterize them.
RF Power meters that provide measurements based upon statistical methods
have been available for use in laboratory environments for more than ten years.
The most significant advantage is that they are capable of making meaningful
power measurements of signals incorporating complex modulation methods. In
essence, provide meaningful measurements independent of the modulation
method used in the system.
The Bird Statistical Power Meter is a rugged, portable power sensor that is well
suited for use in the field by less sophisticated users than those that would typi-
cally be found in a laboratory setting.