A Novel Differentially-Fed Dual-Polarized Shared Aperture Antenna Array

This communication proposes a novel dual-polarized shared-aperture antenna array with wide bandwidth (BW) by carefully designing and tightly arranging the elements. The single element comprises four L-probes and four parasitic patches, differentially fed by microstrip lines for each polarization, with a profile of around
$0.073\lambda _{\mathbf {0}}$
(
$\lambda _{\mathbf {0}}$
is one free-space wavelength at the center frequency). Simulated results show that the impedance BW (
$\vert \,\,{S} _{\mathbf {11}}\,\,\vert < -10$
dB) is 35% for both orthogonal polarizations, with a low cross-polarization level and a peak gain up to 9.7 dBi. The shared-aperture property is investigated using two
$1\times $
2 arrays. Subsequently, two
$4\times $
4 dual-polarized arrays with ideal differential feeds are employed to illustrate how the proposed shared-aperture approach can improve the aperture efficiency. Finally, a dual-polarized
$4\times $
4 array prototype with microstrip line feeding networks arranged in different layers is designed, fabricated, and experimentally verified. It presents an overlapped BW of 25.4% from 23 to 29.7 GHz for the two orthogonal polarizations, a peak gain of 19.8 dBi, and an isolation larger than 18 dB. Most of all, the
$4\times $
4 array occupies only a size of
$3.32\lambda _{\mathbf {0}} \times 3.28\lambda _{\mathbf {0}} \times 0.087\lambda _{\mathbf {0}}$
.