Power Distribution Plane Cavity Resonance and Radiated Emissions
Power distribution plane cavity resonances create high impedance peaks that drive edge fringing fields, forcing radiated emissions beyond CISPR 32 limits.
Two Port VNA Measurement
Network Characterization
A high frequency characterization method determines the transmission and reflection coefficients of a device under test by applying a calibrated signal to its ports. This technique, known as a two port vna measurement, evaluates the scattering parameters of transmission lines, power distribution networks or passive components. It measures both the magnitude and phase of the reflected and transmitted waves across a wide frequency range.
The method is bounded by the calibration plane established during the initial setup of the vector network analyzer.
Impedance Extraction
The acquisition of all four scattering parameters allows the extraction of the complex impedance of the network or transmission line under test. This capability is used to measure the ultra-low impedance of power distribution networks to ensure power integrity under dynamic load conditions. By measuring the signal transmission between two ports, engineers can cancel out the contact resistance and inductance of the test probes.
This technique provides accurate impedance measurements down to the milliohm level, which is necessary for verifying the performance of modern multi-layer printed circuit boards.
Calibration Process
Accuracy is achieved by executing a formal calibration such as the short-open-load-thru method before conducting the measurement. This step mathematically removes the systematic errors introduced by the test cables and adapters.