Characteristics mode analysis and excitation of orthogonal modes on a single substrate for wideband IoT applications in the millimeter wave band

This paper presents the design of a circularly polarized millimeter-wave (mm-wave) metasurface (MTS) antenna. The Characteristics Modes Analysis (CMA) is employed to examine various modes within the unit-cell design of the proposed metasurface. Based on a thorough analysis, two orthogonal TM modes with a broadside radiation pattern were identified. These modes were then simultaneously excited on a single substrate using simple coplanar waveguide (CPW) magnetic dipoles resulting in circular polarization (CP). Further, it has been demonstrated that the sense of polarization can be easily reconfigured for realizing multiple-input-multiple-output (MIMO) antenna with polarization diversity. Both the single MTS antenna and the MIMO design are characterized numerically and experimentally. The simulated and measured results show that impedance bandwidth (S11 ≤ - 10 dB) of the antenna is from 25 to 30.8 GHz. The axial ratio (AR) below 3 dB is from 26 to 31 GHz with a stable broadside radiation pattern. The proposed design features a low profile and simple geometry which is extremely appropriate for applications in the mm-wave band.