The Research On Radiation Emission Measurement Of Large Size Electrical Equipment

With the development of information technology,more and more spectrum resources in space are occupied.In order to ensure that all kinds of electronic equipment not interfere each other in the complex electromagnetic environment and operate normally,it is necessary to test the radiation emission of them.However,for large size electrical equipment or systems,it is difficult to find a suitable indoor site for radiation emission test because of the limitation of volume and power.If the test is carried out in the outdoor environment,it is easily affected by the various electromagnetic energy in the space.In this thesis,a device which can measure the radiation emission in the natural environment was proposed.It can not only achieve real-time measurement,but also reduce the background noise by physical means,thus improving the accuracy of test results.Firstly,this thesis analyzed the existing radiation emission test sites and the radiation emission test methods in outdoor environment.Then the thesis pointed out that these sites and methods are not applicable for the test of the radiation emission of large size equipment.Next,based on the theory of wave propagation and the basic principle of shielding,an incomplete shielding device was proposed to test the radiation emission for the large size equipment.Next,the test device was modeled and simulated with the electromagnetic simulation software HFSS.(1)First,the case without absorbing material was simulated.The plane wave was set at the opening of the case,and its propagation direction was perpendicular to the opening surface of the box.At that time,the standing wave appeared in the shielding case.Then the wave absorbing material was laid on the five sides of the case,and the simulation was done again.At that time the standing wave in the case was obviously weakened.Through those two simulations,the absorption effect of the absorbing material to the electromagnetic wave was verified.(2)The EUT was placed on the opening surface of the case.The plane wave was set in the rear of the EUT,and its propagation direction was perpendicular to the case.The distance between the EUT and the shielding case was changed to record the attenuation of the ambient noise at each distance.The simulation results were compared and analyzed,and the optimum distance between the EUT and the incomplete shielding case was selected.(3)The distance between the EUT and the box kept fixed,and the position of the incident signal was moved from the opening of the case to the rear of the case with a certain step.The different attenuation effects of the shielding case on the electromagnetic wave were recorded when the wave propagated from different positions.Through the analysis of the simulation results,the regular patterns were summarized.Finally,according to the simulation model and the simulation results,the incomplete shielding case was tested.First,when there was no absorbing material in the case,the standing wave was recorded.Then the absorbing material was laid on the inner wall of the case,and the test was carried out again.At that time,the standing wave in the case was disappeared,thereby the simulation results were verified.Next,the EUT was placed on the opening surface of the case,and the position of the transmitting antenna was moved from the opening of the case to the rear of the case with a certain step.The intensity of the electric field received by the receiving antenna in the case were recorded when the transmitting antenna was in different positions.Through the above tests,it was proved that the incomplete shielding case can achieve a good attenuation effect on the noise propagated from different directions.