Characteristics Mode Analysis of a Unit-Cell and A 3×3 Finite Metasurface Design for IoT Applications in the mm-wave Band

This paper presents a characteristic mode analysis of a novel metasurface (MTS) for the applications related to the Internet of Things (IoT) at millimeter-wave (mm-wave) band. The CMA is utilized to investigate different modes within the unit-cell design of the proposed metasurface. Through comprehensive analysis, two orthogonal TM modes exhibiting a broadside radiation pattern were identified. These modes were then simultaneously excited on a single substrate using straightforward coplanar waveguide (CPW) magnetic dipoles, resulting in circular polarization (CP). Additionally, it has been shown that the sense of polarization can be easily reconfigured, enabling the realization of a multiple-input-multiple-output (MIMO) antenna implemented with polarization diversity. Mode analysis of the unite cell design is performed followed by a $3 \times 3$ implementation of the metasurface (MTS). A number of modes and their radiation pattern of the unit-cell and the MTS are analyzed using CMA. The two orthogonal modes with broadside radiation and modal significance (MS) close to unity are then excited using a coplanar waveguide feeding on a single substrate. The numerical analysis of the design exhibits wide impedance bandwidth from 23 GHz to 30 GHz. The 3 dB axial ratio (AR) of the proposed antenna is from 25.3 GHz to 30 GHz with the peak gain of 7.4 dBic in the broadside direction.