Excitation of circularly polarized wave via single-feed metasurface-integrated compact antenna for internet of things

A compact circularly polarized (CP) quasi-omnidirectional antenna is introduced for internet of things (IoT). The structure consists of two components implemented on FR-4 substrates, and separated by an air gap: one printed with a rectangular patch fed through a matching network, and another with a metasurface and a ground plane. Two different methods for impedance matching are employed. An equivalent circuit model of the antenna is developed to facilitate the analysis. The design procedure, operating principle, and experimental validation of the antenna are described. The optimized antenna occupies 0.3λ ×0.1λ footprint and 0.04λ height at 16 GHz and exhibits the impedance bandwidth of ∼2 GHz, axial ratio of <3 dB, realized gain of ∼6 dBi, and efficiency of ∼80%.