An Accurate and Simple Design of High Impedance Surface Structure Using an Enhanced Effective Medium Method

The effective medium method is by far the most commonly used method in designing mushroom-like high impedance surface (HIS) structures. This is mainly due to its simplicity and flexibility, however it has some drawbacks such as its accuracy. If it is used directly to design a HIS structure without applying proper rules and limits, this can cause an inaccuracy to the design. As a result, further tuning and modifying will be required. These processes are usually done by using simulation tools based on numerical methods such as the finite element method (FEM) which might take enormous amount of time and computational resources. The aim of this paper is to investigate the possibilities of improving the conventional effective medium method to offer simplicity, speed and accuracy. This is done by setting a parametric study to obtain a required set of rules and limits that will be used prior to applying the method. A test structure has been designed and created to validate the method. A close agreement between the values of reflection phase angle (-90 to 90 degree) and surface impedance from 4 to 8 GHz is obtained by using this proposed improved method and numerical simulation.