Wideband Differentially Fed Dual-Polarized Planar Antenna and Its Array With High Common-Mode Suppression

Abstract

A differentially fed dual-polarized planar antenna with a wide bandwidth and high common-mode (CM) suppression is presented in this paper. The antenna is composed of four folded dipoles that are connected to each other via the coplanar striplines. Two integrated baluns are utilized to excite the folded dipoles simultaneously to realize ±45° linear polarizations. Owing to the loaded shorting stubs, the impedance matching is improved and the operational bandwidth is broadened. Under differential-mode (DM) excitation, the antenna has a superior unidirectional radiation over a wide bandwidth. Under CM excitation, the antenna achieves a high level of CM suppression performance due to the proposed feeding structure. Measured results exhibit that the antenna gains a wide −15 dB differential impedance bandwidth of 51.1% (1.66–2.80 GHz) and a high port isolation of 38 dB between the differential ports. Moreover, the CM reflection coefficient is larger than −1.32 dB within the DM passband, which indicates that the high CM suppression is attained. To further validate the design concept, a $1\times4$ antenna array is fabricated and measured to demonstrate the superior performances of wide bandwidth, high port isolation, high CM rejection, and good unidirectional radiation.