Boonton 4540 Peak Power Meter Quick Start - Manual (Page 32)

4540 Power Meter
Quick Start Guide
PN: 98406000A © Copyright 2008 Boonton Page 32
STATISTICAL MODE
Certain signals are completely random and
provide no event that can serve as a trigger
for measurements. CDMA or OFDM are
common examples. Such signal
“randomness” places a challenge to
measurements but the Statistical Mode of the
4540 offers an easy solution.
Statistical Mode is only available
when a peak power sensor is
connected to the 4540. It is the best
choice for analyzing “noise-like”
signals that are modulated in a
random,
non periodic fashion.
Statistical mode yields information
about the probability of occurrence
of various power levels without
regard for when those power levels
occurred. Many digitally modulated
spread-spectrum formats use a
bandwidth coding techniques or
many individual modulated carriers
to distribute a source’s digital information over a wide bandwidth, and temporally
spread the data for improved robustness against interference. When these
techniques are used, it is difficult to predict when peak signal levels will occur.
Analysis of millions of data points gathered during a sustained measurement of
several seconds or more can yield the statistical probabilities of each signal level
with a high degree of confidence. Statistical Mode is best of the following types of
measurements:
• Moderate signal level (above about -40dBm except when modulation is
“off”).
• “Noise-like” digitally modulated signals such as CDMA (and all its
extensions) or OFDM when probability information is helpful in analyzing
the signal.
• Any signal with random, infrequent peaks, when you need to know just
how infrequent those peaks are.