Research On New Ventilation Waveguide Structure With High Electromagnetic Shielding Effectiveness

With the steady development of electronic and information technology,various complex systems,including computer-based control systems,and electronic,electronical and communicational equipments,etc.,are extensively utilized in practical engineering,which have provided many conveniences and benefits for human life but have generated harmful electromagnetic radiation.However,almost all of the equipments are required to be cooled by flow of air in order to ensure their performances.Cutting a cooling hole in the thin wall of shielding cavity without any protective measures may lead to electromagnetic pollution of surroundings and may affect the normal operation of equipments by various coupled ways due to the fact that electromagnetic radiation inside and outside the shielding cavity can pass through the hole.Thus,this thesis focuses on investigating a novel ventilated waveguide structure using electromagnetic wave theory.The main research contents are summarized as follows:(1)Study on electromagnetic field distribution law for the regular waveguide and the proposed waveguide with metal diaphragm.Field distribution characteristics of the regurlar waveguide under the mode transmission area are summarized.Further,we investigate the variation of electromagnetic field structure in the waveguide when inserting a metal diaphragm,and then we obtain the loss law of electromagnetic wave for the waveguide with metal diaphragm by analyzing the difference of field distribution between regular waveguide and the proposed one.After that,electromagnetic field distribution for waveguide at cut-off region and operational principle of cut-off waveguide are studied.(2)Research on the transmission characteristics for the reguar waveguide and the proposed new waveguide.We first analyze the transmission properties of regular waveguide with different shapes at the mode transmission area and cut-off region,and give the similarities and differences of transmission properties at these two regions.Further,we compare the transmission characteristics for the reguar waveguide and the proposed new waveguide at cut-off region.Finally,the electromagnetic simulation software is employed to optimize the new waveguide to improve its transmission performances.(3)Research on passive test of transmission performances for the reguar waveguide and the proposed new waveguide.Straight waveguide is microwave component with two ports,and measuring the Scattering Matrix of Networks between two ports of waveguide can verify the trend consistency of simulation and measurement.The transmission characteristics of the proposed new waveguide is compared with that of the reguar waveguide,and the loss law of electromagnetic energy for the new waveguide is summarized,and finally shielding properties of the new waveguide under cut-off region with regards to electromagnetic wave are obtained by reverse induction.(4)Study on shielding performances of a single waveguide and waveguide window installed in the encloser of electronic equipment.Shielding performances of a single regular waveguide and waveguide window with an array of regular waveguides are first analyzed by empirical formulas,in which field monitoring point is fixed at the geometric center position of the encloser and external plane wave is served as radiation source.After that,shielding performances of a single new waveguide and waveguide window with an array of new waveguides are studies,demonstrating the shielding advantages of the proposed novel waveguide structure.