Agilent Technologies Agile or Elusive Signals Using Manual

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Analyze Agile or Elusive Signals Using
Real-Time Measurement and Triggering
Ben Zarlingo, Agilent Technologies Inc.

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This Webcast
Agile & Elusive Signals
Discovering Signals vs. Troubleshooting, Optimizing
Two Case Studies
Dynamic signal environment-ISM band
Radar signal
Choosing & Using Techniques & Tools
Make the most of what you already know & own
Swept spectrum analyzers
Vector signal analyzers/VSA software
Oscilloscopes
Real time analyzers
Using Triggering to Enhance Measurement Effectiveness

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Case Study #1: 2.45 GHz ISM Band
100 MHz Wide
Spread Spectrum Techniques
Lightly Regulated, Signals Not Explicitly Coordinated
WLAN (typically dominant occupant), Bluetooth, Cordless Phones
•And 1 kW+ microwave ovens!
•And almost anything else!
Very Dynamic
•Content not known at any specific point in time
•May be very low occupancy
Lots of Collision Tolerance May Be Needed
Potential “Cliff Effect” at Some Degree of Crowding

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ISM Band View: Swept Spectrum Analysis
Band: 100 MHz
Span: 160 MHz
Dynamics X2 (swept RBW & changing signals) Confuse the View
Peak Hold Detects Signals but Frequency Overlap Obscures
Signals Typically Short Duty Cycle, Total Low Occupancy
POI is Approx. “Low” (useful concept even if not strictly applicable)
Single Sweep
(fast but retrace not as fast)
Peak Hold (short)
Peak Hold (long)

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ISM Band View: Real Time Analyzer
Density or
Histogram Display
Gap-Free Analysis
No Signals Missed
Density Display Shows Signals Inside Signals
Fast, Full Display Update Rate Shows Signal Dynamics
See Unexpected Behavior, Even If Infrequent
Individual Display Updates Combine Thousands of Spectra

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ISM Band View: Real Time Analyzer
Spectrogram Display
Top Trace is Latest or
Selected Spectrum
Same Spectral Data as
Density/Histogram
Individual Spectrogram Line
Represents Many Spectra
(typically thousands)
View into Dynamics, Timing
Acquisition Time Setting Affects Way Spectra are Combined to Form
Display Update
WLAN Signals Active Continuously?
What are Vertical Bars? A Multitone Signal?

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Spectrogram Display
Adjusting Acquisition Time
Shorter Acquisition Time
Determines Amount of Data
Processed for Spectrum or
Spectrogram Trace Update
Each Trace Update &
Spectrogram Line Represents
Fewer Spectra
More Trace Updates/Second, Finer Time Resolution
Spectrogram Covers Shorter Interval
Determines Time Scale of Spectrogram
Use Spectrogram Trace Buffer to Examine Signal Dynamics

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Characteristics of the Real Time Analyzer
Density View
Fast Display Updates, High Data Density
Easily Understand Signal or Event Frequency
Find Very Infrequent Events
Find Unexpected Events, Behavior
Limitations
•Combining traces combines behavior from different times
•Limited flexibility (RBW, span combinations)
•Limited frequency span
•Power spectrum only
•Markers only on combined spectrum or density at a point

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What is “Real Time” Analysis?
Understanding Real Time Analyzers and Real Time Analysis
General Definition of Real Time
•Measurement operations where all signal samples are used in calculating
measurement results of some kind (usually spectrum)
Real Time Bandwidth (RTBW)
•The widest analysis bandwidth where an analyzer can maintain real time
operation
•Duration of maintaining real time operation is not specified; it may
assumed to be short term or long term or unlimited
Current Usage for Signal Analyzers
•A spectrum or FFT analyzer having a signal processing path where most or
all samples, even at wide bandwidths, are used to create a spectral display
or to trigger signal measurement or acquisition (sometimes both)

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Real Time Operation
In Real Time Operation the Analyzer’s Processing (CALC) is
Fast Enough to Keep Up with All Data Samples
CALC Time Includes FFT or Power Spectrum, Averaging, Display
Updates, etc.
However some data
may still be “lost”