Design of Compact Wideband Circularly Polarized Hexagon-Shaped Antenna Using Characteristics Mode Analysis

Abstract

The design of an antenna, for its subsequent characterization by means of real sets of measurement, requires a specific modeling that allows a best approximation to the actual construction of the device and true measured values. Like Fourier series expansion, the characteristic mode analysis (CMA) creates a set of orthogonal true current on a conducting material with arbitrary geometry. In this work, a hexagon-shaped wideband circularly polarized (CP) antenna using CMA is presented. The design of the proposed antenna is completed in two stages: first, a hexagon-shaped monopole is designed to achieve circular polarization in the upper frequency band, and subsequently a hexagon-shaped slotted patch is implemented for obtaining circular polarization in the lower frequency band. This procedure helps in achieving the wideband CP antenna. In place of using the conventional method of analyzing simulated surface current distribution to verify CP radiation, CMA is used to understand the different modes of the antenna and their contribution toward CP radiation of antenna. A prototype of the proposed antenna is fabricated with dimensions 0.36λ×0.36λ×0.013λ ( λ corresponds to the wavelength for lowest working frequency) to validate the simulated results. The impedance bandwidth of the proposed antenna is 2.3-7.6 GHz and the 3-dB axial ratio bandwidth (ARBW) of the antenna is 3.4-6.5 GHz. The measured peak gain of the antenna is 4.6 dBic. The proposed antenna exhibits a consistent radiation pattern, and the operating frequency band of the antenna effectively includes the international mobile telecommunication (IMT), industrial, scientific, and medical band (ISM), and WiMAX spectrums.