Experimental investigation of a dual mode antenna using characteristic mode analysis with enhanced directivity for GSM/5G applications.

In this article, a dual-mode, dual-polarized antenna designed using characteristic mode analysis (CMA) is described. An elliptical-shaped patch radiator is chosen with double slits on its minor axis. This design is based on mode separation from the circular patch into the elliptical patch. The suggested antenna geometry has a footprint of 60 mm × 60 mm × 1.6 mm. To design and fabricate the antenna, an FR-4 substrate with a relative permittivity of 4.3 is used, along with copper sheets 0.035 mm thick for the ground plane and the radiating plane. The circular patch has the resonating mode at 1.8 GHz, whereas the elliptical radiator gives different resonant modes at 1.8 GHz and 3.5 GHz. An orthogonal mode is excited with a 50-Ω coaxial feed line at 3.5 GHz by applying a full-wave approach. The antenna gives a -10dB bandwidth of 51 MHz (1.77-1.82 GHz) centered at 1.8 GHz and a bandwidth of 210 MHz (3.37-3.58 GHz) centered at 3.5 GHz. The working principle is explained through modal analysis and characteristic angles. This dual-band antenna covers a 1.8 GHz GSM band with horizontal polarization and a 3.5 GHz 5G service with vertical polarization. Peak gain attained with these bands is 5.9 dBi and 7.1 dBi, respectively. A CST full-wave simulator is used for the simulations. As a result of the antenna, radiation is stable and enhanced. Compared to measured results, simulation results are close to reality. The characteristic mode analysis (CMA) provides an in-depth look into different operating modes on the antenna in contrast with the conventional method, which relies on the simulated current distribution to verify functionality.