A Measurement Setup for Quantification of Electromagnetic Interference in Metallic Casings

In this paper, a test setup is proposed for quantification of electromagnetic interference (EMI) in an enclosure of digital systems. Small probes at the casing walls are used to measure the internal fields and derive network parameters for the typical coupling between internal components. It is shown that the setup is viable for estimating EMI between enclosed components in a frequency range from 10 MHz to 6 GHz. Measurement results from the proposed setup are in excellent agreement with those of analytical and numerical methods. A statistical approach is introduced to evaluate the measurement results from a twelve-port vector network analyzer at high frequencies above the first resonance. Using this approach, typical components in digital systems are analyzed and simplified geometrical models are given. These models allow full-wave simulations of realistic setups with feasible computation times. A good model-to-hardware correlation between simulation and measurement results over the whole frequency range is achieved. It is demonstrated that the proposed measurement and evaluation approach of the fabricated cavity shows the same characteristic behavior of a real office workstation with internal components.