Spectrum Analyzer-Based Phase Measurement for Near-Field EMI Scanning

Often, electromagnetic interference (EMI) scanning applications require phase and magnitude information for the creation of equivalent radiation models and far-field predictions. Magnitude information can be obtained using a spectrum analyzer (SA), which is relatively inexpensive compared to phase resolving instruments such as vector network analyzers (VNAs) and oscilloscopes at tens of GHz. This paper introduces and optimizes a cost-effective SA-based phase measurement method and compares the results to a VNA and oscilloscope-based methods for EMI signal sources. The measured-phase distribution obtained from the three different instruments is additionally compared with the simulated phase determined from full-wave simulation. The three measurement methods are compared based on the type of signal spectrum to be measured, such as single or multiple frequencies, signals requiring low-resolution bandwidth measurements, or transient signal events. The SA-based phase measurement technique is designed to operate from 5 to 12 GHz. However, the system frequency bandwidth is limited only by the frequency bandwidth of the individual RF components used in the SA measurement system