A Low-Profile Broadband Circularly Polarized Pattern Diversity Metasurface-Inspired Antenna
Peicai Gao, Feng Xu
Abstract
A low-profile broadband circularly polarized (CP) pattern diversity metasurface-inspired antenna is proposed, which can realize the diversity of broadside and conical patterns while radiating CP waves. First, based on the theory of characteristic mode analysis (CMA), a metasurface composed of 45 square ring elements arranged in a cross shape is designed. Two sets of four characteristic modes of the proposed metasurface were found, one of which is related to the broadside pattern and the other is related to the conical pattern. In addition, two modes of the same set provide the possibility for CP waves. Then, by investigating the current distribution of these modes, the optimal excitation position of a pair of cross-slot is obtained. Finally, two feeding networks are designed to excite the broadside and conical patterns of the metasurface, respectively. A processed antenna prototype with a low profile of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.05~\lambda _{0}$ </tex-math></inline-formula> (the free-space wavelength at the center frequency) is reported for verifying the design concepts. The measured operating bandwidth of the antenna is 11.6% (4.23–4.75 GHz), which is determined by the operating bandwidth of the two CP patterns. Within this operating bandwidth, the measured peak gains are 4.33 dBic (broadside) and 4.28 dBic (conical), respectively. This antenna is suitable for mobile wireless communication systems because of its broadband CP characteristics.