The Design Of The Electromagnetic Probes For Near-Field Diagnosis

With the high-speed,more compact and complicated chips design,the electromagnetic interference(EMI)problems tend to be more severe than before.Electromagnetic near-field scanning technology can quickly analyze and diagnose the EMI problems of high-speed circuits without knowing the structural details of the chips.Therefore,it becomes a hot research topic in recent years,and it also shows a great market value.The electromagnetic probe is the key to the near-field scanning technology.The accuracy of the near-field scanning depends on the probe.High-speed and high-density chips also bring new challenges to the design of electromagnetic probes.This paper focuses on the key issues related to the design of electromagnetic probes:high frequency,high spatial resolution,high sensitivity and multi-components detection.Through theoretical analysis,electromagnetic simulation,fabrication and measurement,high-quality electromagnetic probes are designed and applied in measuring the commercial products.The contributions of this paper includes the following three points:1.High frequency and high spatial resolution magnetic probe.With the increasing working frequency of the circuits,in order to identify the high-frequency radiation source of the electronic device,a high frequency magnetic probe is required to measure the magnetic field up to several tens of gigahertz.At the same time,with the increasing integration density of the electronic device,the spatial resolution of the probe should be in micrometer level.We designed a micron-sized toroidal magnetic probe using a multi-layer printed circuit board(PCB)process.The working frequency of the probe is up to 30 GHz by reducing the parasitic parameters of the probe and optimizing its impedance matching.The test results show that the magnetic probe can measure the magnetic field accurately in a wide frequency band.Due to the low cost of the PCB process,the proposed magnetic probe is a cost-effective design.2.High sensitivity and high spatial resolution magnetic probes.Next,multi-turns structure,impedance optimization and the low-noise amplifiers are used to improve the ability of the high spatial resolution magnetic probe to detect weak signals,which solves the contradiction between the high sensitivity and high spatial resolution of the probe.The design of the probes has been adopted by a company and has been put into production.The sensitivity of the active probe with five loops is increased by 20 dB compared to API commerical probe with the same size.3.Multi-component electromagnetic hybrid probe.Finally,based on the above single-component ring probe structure,we designed a new multi-component electromagnetic hybrid probe.The multi-component probe utilizes a compact and hybrid "loop-wire" structure,which can measure the Hx,Hy,and Ez components simultaneously through an electromagnetic calibration algorithm.It solves the problems of the long testing time caused by multiple scans of the single-component probe and the mechanical positioning error caused by the replacement of the probe.The accuracy and measurement efficiency of the multi-component probe are verified by measuring the near-field distributions of the Z-type microstrip line and the inverted-F antenna.