Electrically-small, low-profile, dual-linear and circularly polarized huygens dipole antennas with broadside radiation patterns

Electrically-small, low-profile, broadside-radiating Huygens dipole antennas are reported that have high radiation efficiencies and are either dual-linear (LP) or circularly (CP) polarized. The Huygens behavior, i.e., a high front-to-back ratio, is realized by exciting two complementary electric and magnetic dipole radiators, simultaneously having the same amplitude and phase. To achieve this design, we modified the electrically-small near-field resonant parasitic (NFRP) Egyptian axe dipole (EAD) antenna to act as the electric radiator and the capacitively loaded loop (CLL) NFRP antenna to act as the magnetic radiator. By organically combining the crossed EAD and CLL NFRP elements together with proper excitations by a pair of driven dipole elements, the resulting electrically small antenna generates broadside Huygens radiation patterns with either dual-LP or CP characteristics. They have ka = 0.87; are low-profile, ∼0.04λ exhibit good radiation performance with 4.54 dBi LP and 4.58 dBic CP peak realized gains; have > 20 dB front-to-back ratios; and have > 93.9% radiation efficiencies at their resonant frequencies. These antenna systems are quite suitable for narrow bandwidth applications including, e.g., wireless power transfer (WPT) to charge batteries in wireless sensors, unmanned aerial vehicles (UAVs), and other compact portable devices.