EMC Design Of Portable Equipment Based On PXIe And Modular Components

With the development of information technology,the demand of electromagnetic measurement for portable equipment in complex electronic information system is increasing day by day.Portable equipment with its characteristics of modularization,bus,integration,can be more convenient,fast,efficient to achieve the established measurement task requirements.At the same time,the electromagnetic environment faced by portable devices is becoming more and more complex,and the potential electromagnetic interference and electromagnetic hazards are also increasing.The electromagnetic compatibility problem in this scenario is increasingly prominent,which needs to be paid more attention to.In the interior of portable equipment,the electromagnetic radiation effect of PCB board and card components is an important component of the electromagnetic environment in the case.The analysis and study of portable equipment board level and its related equipment-level electromagnetic characteristics and EMC characteristics is one of the necessary prerequisites for in-depth EMC design.In this thesis,the electromagnetic compatibility of a portable device was studied and improved.The structural characteristics of the microstrip line and the physical law between the transmission signal characteristics and the radiation intensity characteristics of the microstrip line were studied in detail,and the radiation characteristics of the PCB clock line were analyzed by numerical simulation.By combining the PCB radiation equivalent model with the simplified chassis model,the electromagnetic environment,electromagnetic leakage and radiation of PCB in the equipment chassis were analyzed,and the actual wiring on the board and the equipment structure were pre-designed for electromagnetic compatibility according to the relevant EMC standards.The main research work of this paper is as follows:1.The near/far field radiation characteristics of printed circuit board were studied,and an improved EMC design method was proposed.Firstly,the radiation characteristics of the radiation sources inside the equipment were studied to evaluate the overall electromagnetic environment inside the case.The microstrip line of printed circuit board was the core part of connecting components and transmitting signals in the equipment,and its radiation determines the electromagnetic environment in the equipment to a large extent.The microstrip structure characteristics of printed circuit board and the influence of transmission signal characteristics on the radiation characteristics were studied and analyzed,and the radiation conditions of the actual printed circuit board in the far and near fields were calculated.2.Studied the radiation equivalence of printed circuit board and the joint analysis method with portable device structure.The electromagnetic modeling of the equipment case was carried out,and the model of the shielding case was simplified according to the perturbation theory,so as to give consideration to the effectiveness and analysis efficiency.The PCB with complex circuit structure was regarded as a black box,and the near field radiation intensity data of PCB was extracted for system equivalence.The equivalent near-field radiation source was placed inside the simplified case model instead of PCB,and the internal field strength distribution,electromagnetic leakage and mutual influence among PCB of portable equipment were simulated and analyzed.3.According to the electromagnetic interference and leakage studied in 2,EMC design improvement of portable equipment was carried out,and external electromagnetic interference was analyzed and protected.According to the actual situation of the integration of multiple PCB board CARDS in the portable equipment box,the coupling between PCB can be reduced and the electromagnetic leakage can be reduced by setting shielding protection,so as to improve the electromagnetic compatibility of the equipment.The influence of external interference source on internal equipment was calculated,the frequency point and frequency band of the weak electromagnetic protection of the box were analyzed through the calculation of shielding efficiency,and the design approach of relevant protection measures was explored according to the relevant EMC standards.