Bandwidth-Enhanced, Electrically Small, Planar, Endfire-Radiating Huygens Dipole Antenna

A bandwidth-enhanced, electrically small, planar, endfire-radiating Huygens dipole antenna (HDA) is presented. The near-field resonant parasitic (NFRP) grid-shaped dipole and two concentric interdigitated capacitor (IDC) loaded loops enable broad electric and magnetic dipole responses, respectively. Benefiting from the additional capacitance introduced by the dual-loop design, the magnetic dipole response is achieved at a lower frequency. The consequent balanced, resonant responses of the electric and magnetic NFRP elements yield a wideband and electrically small HDA with endfire-radiating performance characteristics. The fabricated prototype exhibited measured results that closely agree with their simulated values. Being an electrically small, ka = 0.91, system, it had an 8.79% fractional bandwidth, and a 4.7 dBi peak realized gain. Furthermore, the antenna achieved unidirectional radiation patterns and maintained high radiation efficiency (RE), RE > 81%, within its entire operational bandwidth.