“…However, the microstrip antenna has obvious disadvantages of narrow bandwidth and large aperture size due to the inherent high Q-value characteristic. 1 To alleviate this problem, many approaches have been proposed, such as adopting aperture-coupled feed 2 or L-probe feed, 3,4 loading fractal structure 5,6 and so on. Nevertheless, while increasing the impedance bandwidth, other properties deteriorated, such as large gain fluctuations, high cross-polarization level, and large size.…”