Investigation of Resonant Frequencies of High Impedance Surface Structures

A number of approaches can be used to design the high impedance surface (HIS) structure. The most commonly used approach is the full wave numerical simulator due to its accuracy and flexibility. So far, majority of the conventional simulation models proposed by researchers can only predict either the resonant frequency and reflection phase angle or the beginning of the band gap location of the HIS structure, but not both. The aim of this paper is to develop a simulation model that can overcome this limitation. To achieve this, a 3x3 cells simulation model is introduced. To demonstrate the capabilities of this simulation model, a test HIS structure designed to resonate at 5 GHz is created and simulated using our proposed simulation model. The obtained actual and additional resonant frequencies are 5 GHz and 3.655 GHz respectively. The value of the additional resonant frequency obtained from the test HIS structure is compared to the value of the beginning of the band gap frequency obtained from the dispersion diagram of the same HIS structure. Close agreement is observed. Empirical equations for the additional resonant frequency are successfully derived based on the behaviour of the current distribution along the surface of the HIS structure. To validate the proposed equations, additional resonant frequency values obtained from our derived equation are compared with that obtained from our proposed simulation model. A good agreement is observed.