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Communications Systems Analysis Using Hardware and Software-Based Vector Signal Analyzers

by Thad B. Welch

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Two Administrative Items“What Does a New Engineer Face at Work” … UMBC needs a speakerCelebration of the Section’s Centennial

28 February at BWI Marriott$30/personRSVP no later than 20 February

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Trend in Complexity

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Modulation Schemes

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Time and Frequency Domains

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A Few Modulation Schemes

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Constellation Diagrams

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Polar or Rectangular?

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Conversion

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The Effect of Modulation

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BPSK and 8-PSK

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Increasing Spectral Efficiency

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Constellations Aren’t Unique

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Some Higher OrderModulation Schemes

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Spectral Efficiency Results

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Basic Transmitter

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Detailed Transmitter

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Basic Receiver

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Detailed Receiver

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Eye-Pattern and theConstellation Diagram

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Demonstration 1

Rectangular Pulsed 16-QAMTrajectory diagramEye-pattern

Coupled markers

Spectrum

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Pulse Shaping

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Spectral Containment

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Effects of Pulse Shaping

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Symbol Sampling

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Pulse Shaped Eye-Patterns

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Demonstration 2

Pulse shaped 16-QAM Effect of changing the roll-off factor

Trajectory diagramEye-pattern

Coupled markers

Spectrum

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Let’s Enter the 90’sEye patterns, constellation diagrams, and trajectory diagrams have been around for a long timeError vector magnitude (EVM) is a relatively new measurement that provides additional insight into channel and transmitter impairmentsEVM measurements require new, or at least different, hardware/software

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Error Vector Magnitude (EVM)

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Interpretation of EVM

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EVM w/ Symbol Rate Error

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EVM Spectrum withan In-band Interferer

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The Root Raise-Cosine System

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Demonstration 3 (16-QAM)winDSK6 … with the CommDSK feature

NoiseQuad skewGain imbalanceIn-band interferenceFrequency errorSymbol rate error

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Questions?