Study On Analytical Formulation And Simulation Method About Electromagnetic Compatibility Of Shielding Cavity

In complex electromagnetic environment, Electromagnetic Compatibility(EMC) of electronics becomes more and more prominent. Electronics must pass EMC test before they are produced. Shielding enclosure, which can decrease electromagnetic radiation, is very important for EMC of electronics. Revising structure of shielding enclosure wastes much time and finance after it cannot pass the EMC test. Therefore, analyzing EMC of shielding enclosure and modifying its structure in design process turn out to be of great importance.In this dissertation, many analytical methods analyzing EMC of shielding enclosure are derived, a new numerical simulation method is proposed, and the relationship between EMC of shielding enclosure with its structure parameters is intensively studied. The main topics covered in this dissertation include:1) Based on Generalized Sheet Transition Conditions(GSTC), the analytical formulation for transmission and reflection coefficient of metal sheet with apertures is derived. Moreover, we transform transmission and reflection coefficient into SE, then the analytical method for calculating SE of metal sheet is obtained. We use numeical simulation software to validate the analytical method. The relationship between EMC of metal sheet and its structure parameters is intensively studied by numerical simulation software.2) Robinson’s analytical method can predict SE of shielding enclosure with an aperture quickly and accurately. Although it has been extended many times, it has some limitions. In this dissertation, this analytical method has been extended again. The extended analytical method can deal with apertures at off-axis locations and observation points can be located at arbitrary position. On the other hand, the accuracy of original and extended analytical method decreases when obervation points get close to apertures. The relationship between structure parameters of shielding enclosure and accuracy of analytical method is intensively studied. A prediction method, which can estimate the accuracy of the original and extended analytical formulation, is derived by using data fitting method.3) This dissertation derives an analytical method for resonance frequencies of enclosure with apertures based on perturbation theory. Then, numerical simulation software and measurement are used to validate the accuracy of this new analytical method. Some long slots cannot be studied by the analytical method because of its long size. Therefore, numerical simulation software is used to research the relationship between EMC of shielding enclosure and its structure parameters.4) The full wave simulation method is presented to research electronics with actual PCB. First, we obtain the electromagnetic radiation of actual PCB. Second, we transfer the radiation into the shielding enclosure as interference source. Last, after the simulation calculation, the full wave EMC of the actual electronics can be obtained. Moreover, based on the full wave simulation method, we analyze the relationship between EMC of electronics and their structure parameters.Based on these research contents, the innovative points of this dissertation are as follows:1) Robinson’s analytical method is extended in this dissertation. The original analytical method can only deal with center aperture and observation point. The extended analytical method can cope with SE at off-axis observation points with rectangular apertures positioned anywhere in the front face of the box.2) An anlytical method for calculating resonance frequencies is derived. Resonance frequencies for closed box can be obtained by classical formulas. However, the classical formulas cannot be used to predict resonance frequencies of shielding enclosure with apertures because apertures on enclosure can change resonance frequencies. In this dissertation, based on perturbation theory, the analytical method for calculating resonance frequencies of shielding enclosure with apertures is derived.3) The full wave simulation method is proposed to study EMC of electronics with actual PCB. Scholars often use monopole antenna, dipole antenna and coupled microstrip lines to simulate interference sources. However, these methods cannot simulate interference sources precisely. The full wave simulation method uses actual PCB as the interference source, so it can exactly obtain electromagnetic radiation of the interference source. Therefore, the full wave simulation method is more accurate than other simulation methods.In this dissertation, several analytical methods for shielding enclosures with apertures are derived, and the full wave simulation method for shielding enclosures with actual PCB is proposed. By using these methods, we can study EMC of shielding enclosures before production process, and we also can revise the strcture of shielding enclosure in design process. Moreover, based on the calculation, simulation and measurement in this dissertation, many useful conclusions about the relationship between EMC of shielding enclosure and its structure parameters are obtained. These conclusions can lay a foundation for theoretical EMC analysis of shielding enclosures and give some references to pratical shielding enclosure production.