An SISL All-FR4 Based Dual-Polarized Broadband High-Gain Antenna With Differential Open Feed Line for Millimeter-Wave Applications

A differential-fed dual-polarized antenna based on substrate-integrated suspended line (SISL) technology is proposed for millimeter-wave base stations. The differential feed structure is used to improve the port isolation and cross-polarization discrimination (XPD). It adopts the method of adding coupling patches as the load to improve impedance matching and obtain broadband performance without introducing additional structures, forming a two-unit antenna array to achieve high gain. An equivalent circuit model of the evolving antenna is analyzed. After changing the shape of the patch and adding branches, the bandwidth and gain were further improved. A pair of orthogonal differential open feed lines are utilized to realize dual polarization. The measured results show that the –10 dB bandwidth of the proposed antenna is 66.7% from 20 GHz to 40 GHz, and the 3 dB gain bandwidth is 67.8%. Port isolation is better than 40 dB, and XPD is better than 25 dB. In addition, the peak gain and radiation efficiency reached 8.7 dBi and 85%, respectively. The proposed antenna has the advantages of low cost, wide bandwidth, high gain, low cross polarization, high port isolation, etc.