An Efficient and Reliable Circuit Model for the Shielding Effectiveness Prediction of an Enclosure With an Aperture

An equivalent circuit model is developed to efficiently and accurately calculate the shielding effectiveness of an enclosure with an aperture. This model employs the concept of quasi-stationary admittance of diaphragms inside a rectangular waveguide and their equivalent circuits. The aperture is represented by a combination of a capacitive diaphragm, an inductive diaphragm, and step discontinuities inside a rectangular waveguide. This new model outperforms the existing circuit models in the following ways. First, it is more accurate compared to Robinson´s model when the aperture is placed centrally (in height and width) in the front face of the enclosure. Second, it can deal with the aperture with arbitrary length-width ratio and arbitrary position. Third, it still works when the length of the aperture corresponds to an integer multiple of wavelength of free space radiation. While in such case the traditional circuit models are found to fail that the SE is erroneously predicted to be infinite. The proposed model provides a high degree of accuracy with a low computational burden, as compared with more complex numerical methods. In all the examples, the accuracy of the results is validated by results of transmission line modeling method and measurements if possible.