Broadband Dual Circularly Polarized Dielectric Resonator Antenna for Ambient Electromagnetic Energy Harvesting

For the application of ambient electromagnetic energy harvesting, it is important to collect as much electromagnetic energy as possible in broadband and with arbitrary polarizations. Meanwhile, the antenna should also have high receiving efficiency in order to effectively convert the collected energy into radio frequency current. To meet this requirement, a novel broadband dual circularly polarized (CP) dielectric resonator antenna (DRA) with high receiving efficiency is proposed. The characteristic mode analysis (CMA) is applied to analyze the proposed DRA to reveal the intrinsic behavior of the DR, so that proper mode excitations can be guided. It is found that broadband CP radiation is achieved by exciting two pairs of orthogonal degeneration modes. By choosing a broadband feeding structure, a broadband DRA can be obtained. When different ports are excited, left-hand CP (LHCP) or right-hand CP (RHCP) field can be generated. Measurements show that the antenna has a 3 dB axial-ratio (AR) bandwidth of 43.5%. The impedance bandwidth is wide enough to cover the whole AR bandwidth. The receiving efficiency of the proposed antenna is about 85% within most of the operating frequency range. With these appealing features, the proposed DRA is an excellent candidate for ambient electromagnetic energy harvesting.