Design of broadband patch antenna with enhanced gain by using defected ground artificial magnetic conductor

A microstrip line fed patch antenna is designed at 4.56 GHz on FR4 substrate having a bandwidth of 5.26%. To achieve broadband characteristic, interconnected rectangular slots are incorporated in the ground surface of the antenna. As a result, the antenna resonates from 3.96 GHz to 5.1 GHz showing an increase in bandwidth of the antenna from 5.26% to 25.17%. To achieve higher gain in the entire bandwidth, an artificial magnetic conductor (AMC) surface is introduced at a certain distance below the slotted ground of the antenna. The AMC comprises of grounded periodic rectangular patches on FR4 substrate. This increases directivity of the antenna which in turn enhances gain. But, gain does not increase in the entire bandwidth. So, the ground of the AMC is made defected by introducing two rectangular slotted loops. Hence, directivity of the antenna increases throughout its bandwidth which also increases gain. Radiation patterns of the proposed structure are stable in the entire bandwidth with considerably low cross polarization level. The proposed structure is fabricated and measured results are in good agreement with simulated results.