Whitepaper

Spectrum Analyzer Based Phase Measurement for Near-Field EMI Scanning

Published by Amber Precision Instruments

This paper presents a fully automated, cost-effective spectrum analyzer method for phase-resolved near-field EMI scanning operating from 5–12 GHz. Using SP3T switches, phase-shift cables, and a variable attenuator, the system extracts phase from magnitude-only measurements via a Nelder-Mead optimization algorithm. Compared against VNA, oscilloscope, and CST full-wave simulation results over a 5 GHz resonant structure, the SA method achieves ±20° phase accuracy — comparable to the oscilloscope and near the VNA's ±10°. It outperforms the VNA in broadband and low-RBW scenarios, while only the oscilloscope handles transient signals.