Low-Profile Wideband Circularly Polarized Complementary Antenna and Arrays for Millimeter-Wave Communications

Abstract

Low-profile millimeter-wave (mm-Wave) arrays using wideband complementary element combining circularly polarized (CP) electric and magnetic sources are proposed in this article. A pair of centrosymmetric printed <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$ {\Gamma }$ </tex-math></inline-formula> -shaped strips serve as a CP electric source, and a modified narrow slot with two etched centrosymmetric stubs can be treated as a CP magnetic source. The combination of them can provide a wide 3 dB axial ratio (AR) bandwidth. Operating mechanism of the proposed CP radiating element is investigated and provided. Two differently constructed CP arrays, i.e., a sequentially rotated <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4\times4$ </tex-math></inline-formula> CP array and a full-corporate fed <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8\times8$ </tex-math></inline-formula> CP array, are then designed based on the proposed CP radiating element, to confirm the expandability of the proposed CP radiating element. Prototypes of these two arrays were fabricated and measured. According to the measured data, the sequentially rotated fed <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4\times4$ </tex-math></inline-formula> CP array exhibits an impedance bandwidth ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\vert S_{11}\vert &lt; -10$ </tex-math></inline-formula> dB) better than 57.1% (i.e., 25–45 GHz), a 3 dB AR bandwidth better than 31.4% (i.e., 29–40 GHz), and a maximum gain of 16.4 dBic, while the corresponding results for the full-corporate fed <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8\times8$ </tex-math></inline-formula> CP array are 25.8% (i.e., 29–37.5 GHz), 19.1% (i.e., 29.8–36 GHz), and 24.3 dBic. These competitive performances together with merits, such as compact size, low profile, low cost, and direct integration ability, make these two arrays promising candidates for mm-Wave communications.