Microstrip Antenna With Electrically Large Property Based on Metamaterial Inclusions

Microstrip antenna with electrically large property (ELP) is discussed and designed in this paper. The modal wave equation for the microstrip resonant cavity is analyzed and the fundamental resonant mode (TM100 mode) of the cavity is discussed by considering the boundary conditions. As an example, effective media parameters of one I-shaped resonant metamaterial is extracted from the S-parameters and the ELP is achieved for the antenna in the band of ε > 0 and μ <; 0. The results show that the resonant frequency of the planar microstrip-line-slot feed antenna is increased about 4.6 times by loading with metamaterial in-between the feeding part and radiating part of the planar antenna without deteriorating the directional radiation pattern. One prototype is fabricated and the measured result shows that the resonant frequency for the ELP antenna is centered at about 30 GHz which confirm the theory analysis. The proposed method is a good option to design millimeter wave and terahertz wave antennas and devices in the future.