5991-4317EN Understanding and Applying Probability of Intercept In Real-Time Spectrum Analysis- Appl part of Agilent 5991-4317EN Understanding and Applying Probability of Intercept In Real-Time Spectrum Analysis- Appl 5991-4317EN Understanding and Applying Probability of Intercept In Real-Time Spectrum Analysis- Appl, Agilent 5991-4317EN Understanding and Applying Probability of Intercept In Real-Time Spectrum Analysis- Application Note c20140815 [17].pdf text manual preview

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Keysight Technologies
Understanding and Applying Probability of
Intercept in Real-time Spectrum Analysis

Application Note
Introduction

As today's wireless signals become more complex, the process of analyzing and understanding those
signals becomes more difficult. Examples include signals that have some combination of highly agile carrier
frequencies, digital modulation, time-division multiplexing and burst shapes. In addition, more devices and
systems are using the same frequency bands. As a result, it's becoming increasingly difficult to identify and
characterize interference and signal errors, especially when they come from transient signals.

When chasing an elusive signal, several attributes are important: when it occurs, how long it lasts, where
it occurs within the spectrum, and how large or small it is. Determining these attributes requires a signal
analyzer capable of performing real-time spectrum analysis (RTSA), real-time data capture, or both. Real-
time spectrum analysis is crucial for detecting, observing and identifying transient signals. Real-time data
capture enables detailed post-processing analysis, including demodulation.

The first step is detecting the transient signal, and the main question in RTSA is, "Which signals can I
see?" The key specification is probability of intercept (POI), which is actually a statistical property (see
the sidebar on page 2). In the specifications for a signal analyzer, POI is often expressed as the minimum
duration of a signal that can be observed with 100 percent probability--and accurately measured--if that
signal is a specific amount above the instrument's noise floor. As an example, a Keysight Technologies, Inc.
PXA X-Series signal analyzer equipped with 160-MHz analysis bandwidth and real-time spectrum analyzer
capability (both are optional) can detect a signal as short as 5