Design and application of a mobile miniature current probe for analysing the cause of EMI noise in IC circuits

This study is based on International Electrotechnical Commission (IEC) 61967-4 standards for measuring electromagnetic emissions and interferences at the chip level. Conventional measurement methods using fixed SMA connectors were replaced with an improved radio frequency current probe featuring semi-rigid coaxial cables, making it capable of taking mobile measurements, enhancing the flexibility and convenient probing usage. To effectively assess the practical value of the improved probe, the authors have referred to the standard designs provided in IEC 61967-1 to manufacture a four-layer digital circuit board that controls the screen of an on-board navigational screen for automobiles. Circuit board electromagnetic interference (EMI) noise frequency and level readings from the improved probe were also compared with three other measurement methods, namely magnetic field probes available in the market, TEM cells, and the 10-m far-field measurement method. The results demonstrated the capability of the improved probe to effectively identify sources of noise at the chip-level during the IC design phases, helping with root cause analysis and allowing EMI noises experienced by the product to be solved promptly during the process of electromagnetic compatibility design optimisation and analysis.