Efficiency enhancement of microstrip patch antenna with defected ground structure

Defected ground structures (DGS) have been developed to improve characteristics of many microwave devices. Although the DGS has advantages in the area of the microwave filter design, microstrip antenna design for different applications such as cross polarization reduction and mutual coupling reduction etc., it can also be used for the antenna size reduction. The etching of a defect in the ground plane is a unique technique for the antenna size reduction. The DGS is easy to be an equivalent LC resonator circuit. The value of the inductance and capacitance depends on the area and size of the defect. By varying the various dimensions of the defect, the desired resonance frequency can be achieved. In this paper the effect of dumbbell shaped DGS, to the size reduction of a microstrip patch antenna is investigated. Then a cavity backed structure is used to increase the efficiency of the microstrip patch antenna, in which the electric walls are placed surrounding the patch. The simulation is carried out with IE3D full wave EM simulator.