High-Gain, Endfire Electrically Small Antenna Based on Near-Field Resonant Parasitic Fan Strips

Abstract

This work presents a high-gain endfire electrically small antenna (ESA) based on the near-field resonant parasitic (NFRP) technology. The proposed antenna is evolved from an initial Huygens antenna, and its gain is significantly improved by loading NFRP fan-shaped strips around the initial antenna within an electrically small size ( ka < 1). The NFRP fan strips are validated to improve the gain from two aspects: First, they provide multiple equivalent dipoles with desired amplitudes and phases, which contributes to the gain enhancement; Secondly, the fan shape of NFRP strips makes the induced current distributed along an arc path, and can enhance the concentration of radiated energy to further increase the gain. Besides the gain issue, the NFRP structure also helps achieve the good 50 Ω matching of the ESA. The proposed antenna is fabricated and measured, and the results show that the prototype operates within 840 MHz to 846 MHz with a maximum realized gain (RG) of 6.3 dBi under the standard 50 Ω port excitation. The overall size is π × 0.148 ² × 0.0014 λ ₀ ³ , and ka is 0.94.