A Dual-Polarized Differential-Fed Low-Profile Patch Antenna With Improved Bandwidth and Gain Selectivity

In this communication, a new design of dual-polarized (DP) differential-fed low-profile microstrip patch antenna (MPA) with improved bandwidth and gain selectivity is presented. To form the characteristics of DP radiation, both patch mode (
$\text {TM}^{\text {patch}}_{{{\smash{11}}}}$
) and substrate integrated waveguide (SIW) cavity mode (
$\text {TM}^{\text {SIW}}_{{{\smash{11}}}}$
) are initially investigated and combined in a common patch radiator. Afterward, four arc slots are analyzed and applied as extra radiators for further expansion of bandwidth, together with a cross slot arranged for the stability of gain. As such, design procedures of the new antenna composed of a circular patch radiator with a cross slot, a circular SIW cavity, and four arc slot radiators are completed. Besides, aiming for a more compact size by integration of component functions, a feeding network based on Schiffman phase shifter is designed. Furthermore, to realize improved gain selectivity, the feeding network is loaded with extra short-ended stepped-impedance resonators (SIRs), thus controllable transmission zeros (TZs) are introduced. Ultimately, the proposed MPA with feeding network is fabricated and measured for validation. Experimental results indicate that the presented demonstrator exhibits a wide bandwidth of 20.2% (3.13–3.83 GHz, covering the n79 frequency band designated for the 5G new radio (NR) technology), a 35-dB polarization isolation, a maximum realized gain of 9.5 dBi, a cross-polarization level less than −23 dB, with a low profile of
$0.046\lambda _{0}$
.