Research On The Optimization Of The Site Setup For CISPR 25 Automotive Components Radiation Emission Test

Various of electronic parts are widely used in the automobile with the rapid development of motor vehicle industry and the popularization of new energy vehicles.Considerable attention has been paid to the electromagnetic compatibility of automobile.The radiation emission test of electronic parts is a kind of near-field measurement and the validation method of test site performance is illustrated in the international standard CISPR 25.However,the“resonance”problem occurs frequently in the radiation emission test due to the complicated near-field electromagnetic environment and the imperfect test setup,which has a significant influence on the evaluation of real radiation characteristics of the equipment under test.To the point that“resonance”at 30 MHz–200 MHz and 200 MHz–1 GHz,a new test setup of radiation emission is proposed based on theoretical analysis,simulation modeling,and experimental verification.Primary contents and innovations are listed as bellows:The near-field measurement of electromagnetic compatibility which is less paid attention to is studied,and the“scattering resonance”in automobile parts radiated emission test is proposed for the first time.Based on the original test site setup elucidated by CISPR 25,a new setup is put forward for the“scattering resonance”problem.The tolerance stipulated in the standard can be reduced from±6 d B to±5 d B creatively if the new layout is used for site performance validation,which makes a substantial improvement to the automobile parts radiated emission measurements.（1）The reference field measurement method and the long wire antenna modeling method used to validate the test site performance are studied.The advantages and disadvantages of this two methods are compared and several important factors that affect the site performance are pointed out.The grounding plane size,the grounding material performance,and the grounding ways can be improved if site validation requirements are not met.（2）The new optimized test site setup is proposed and studied.Firstly,the long line antenna,the test setup,the biconical antenna,and the log periodic antenna are modeled by the full electromagnetic wave simulation software.Then by changing the grounding ways of test bench,the S₂₁and the surface current distribution of different site setup are analyzed separately based on the transmission coefficient analysis theory of the reference site measurement method.When the new setup,which the front edge of test bench is grounded,is apply to test,the trend of S₂₁in the frequency range become more smooth,the surface current does not converge,and the“scattering resonance”is no longer occurs.（3）The accuracy and rationality of the new setup is analyzed.The field strength deviation of the original layout and the new layout with receiving antenna or not is compared separately by means of simulation,which is proved that the deviation of the new layout is smaller,so the radiation emission measurement is more accurate.In terms of the evolution of site setup,it is demonstrated that the electromagnetic environment under the new layout can restore to the real state of vehicle wire harness in the automobile.Then,the miniaturization of the receiving antenna is investigated.Using the VUBA 9117 small biconical antenna can not only reduce the coupling effect with the test bench but also be convenient to use.（4）The new setup was tested by means of the radiation emission test site of the National Institute of Metrology,China.The experimental results showed good agreement with simulation through the analysis of measurement data of the original layout and the new layout,which further substantiates the rationality and practicability of the new setup.To summarize,the new setup which grounding at the front edge of test bench can not only avoid the“scattering resonance”effectively but also improves the accuracy,consistency,and repeatability of the radiation emission measurement of automobile parts.There are 87 pictures,3 tables and 56 references in this paper.