I. Introduction
A microstrip patch antenna has been extensively applied in modern wireless communication and radar systems due to its merits of low fabrication cost, low profile, and easy integration with circuits [1]. But the bandwidth of the patch antenna is narrow, given its high -factor. The enhancement of bandwidth attracts considerable research interests because the demand for wide bandwidth grows rapidly. Increasing antenna profile is useful to decrease the -factor of patch. However, the feeding network needs to be carefully designed to excite the potential bandwidth as wide as possible. Complex feeding techniques, such as aperture coupling [2], [3], proximity probe coupling [4], [5], and meandering probe feeding [6], [7], have been well researched. But the size of these feeding networks is large. The complexity will further increase if balanced or multiple-Port feeding is required.