Modeling of microstrip patch antennas with electromagnetic band gap superstrates

Microstrip patch antennas have some limitations such as restricted bandwidth of operation, low gain and a potential decrease in radiation efficiency due to surface wave losses. Electromagnetic bandgap (EBG) crystals can offer a real solution to these problems. In this paper, we have simulated the performance of a microstrip patch antenna with a square high-permittivity EBG crystal with air-columns used both as substrate and superstrate. The EBG-structure was analyzed using our implementation of the Plane Wave Expansion method in MATLAB. The input return loss, radiation pattern and the directivity of the antenna were calculated using the CST Microwave Studio transient solver based on the Finite Integration Technique (FIT). It is shown that the presence of the EBG-superstrate is very efficient for improving the far-field radiation pattern and enhances significantly the directivity of the antenna. The performance of antenna is enhanced when the superstrate is placed half operating-wavelength apart from the patch.