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(0) (lambda(0) is one free-space wavelength at the center frequency). Simulated results show that the impedance BW (vertical bar S-11 vertical bar < -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 x 2 arrays. Subsequently, two 4 x 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 x 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 x 4 array occupies only a size of 3.32 lambda(0) x 3.28 lambda(0) x 0.087 lambda(0).