Design And Calibration Method Of EMI Electromagnetic Probe

In a complex electromagnetic environment,electronic products must not only ensure stable operation without interference,but also ensure that their near-field and far-field radiation does not cause interference to other devices.With the popularization of 5G and the development of 6G technology,the operating frequency of electronic equipment has been greatly increased,making the size of circuit boards,packages and even chips comparable to the wavelength of the main frequency or its harmonics,thus becoming an unknown antenna,electromagnetic interference problems are getting worse.For this reason,strict electromagnetic compatibility access standards for electronic products(IEC 61000,FCC part15,CISPR22,etc.)are stipulated at home and abroad.In order to ensure that electronic products pass standard inspections and save time for rectification,in recent years,electromagnetic interference diagnosis systems based on near-field scanning have become an indispensable method in the industry.Electric and magnetic field probes are key components of the system,which directly affects its testing.Precision and efficiency.This article focuses on the actual needs of near-field diagnosis of well-known domestic communication manufacturers,and does the following work on the equivalent circuit,structural design and calibration method of electric and magnetic probes:First,based on the magnetic dipole and parallel plate capacitance models,the working principles and equivalent circuits of shielded magnetic field probes and electric field probes are systematically studied.In particular,the influence of the magnetic field on the electric field probe and the influence of the electric field on the magnetic field probe are analyzed.The equivalent source of the field to be measured is added to the equivalent circuit of the traditional probe to shield the non-to-be-measured probe during the design process of the electric and magnetic probe.The measuring field provides a theoretical basis.Second,designed and processed two two-component magnetic field probes with different spatial resolutions.The probe can measure two magnetic field components H_x and H_y that are perpendicular to each other at the same time,which solves the problems of long test time and large mechanical positioning errors of the existing commercial single-component probes.Design the windings of the probe detection part to make the sensitivity of the probe H_x and H_y output ends equal;design two probe transmission parts with equal electrical lengths to ensure that the phases of the output H_x and H_y are consistent,and use the CPW structure and shielding vias to suppress the two signals Crosstalk between.Finally,the probe was processed and its high isolation was verified.The sensitivity of the probe is not lower than that of the single-component probe of American commercial API company,and the test time is reduced by half.Third,a low-cost,high-frequency,horizontal component electric field probe is designed based on a four-layer PCB board,and the working frequency band is 14 GHz-40 GHz.The detection part of the probe is designed by using the PCB sidewall metallization;in order to suppress the common mode noise of the electric field probe,the differential line wiring is used,and the balun chip is used to perform differential mode output on the signal on the differential line.Finally the probe was processed and tested.Fourth,a new type of electric and magnetic probe calibration method based on dual calibration factors is designed.According to the calibration principle of dual calibration factor,the dual calibration factor test methods based on differential microstrip line and single-ended microstrip line are designed respectively.Through simulation and testing,the feasibility and accuracy of the proposed method are verified.This calibration method can comprehensively measure the coupling of the probe to the field to be measured and the degree of suppression of the field to be measured,and it makes up for the defect that the current IEC 61967-6 standard ignores the interference of the field to be measured on the probe output.