Design of a Compact Null-Filled Meander-Slot Biconical Antenna for 3-D Direction-Finding Applications
Woo-Jeong Jeon, Jongho Keun, Hosung Choo · IEEE Access · 2026
In this paper, we propose a compact meander-slot biconical antenna with quasi-isotropic radiation characteristics over the S-band for three-dimensional (3-D) direction-finding applications. The proposed antenna consists of conical radiators with meander slots embedded on the surface, a dielectric loading structure for miniaturization, and an SMA connector for feeding. The geometry of the meander-slot is designed using a sigmoid-tapered profile to simultaneously achieve miniaturization and radiation pattern uniformity. For further miniaturization, the dielectric material is loaded inside the conical radiators to selectively lower the resonant frequencies of the higher-order transverse magnetic (TM) modes. To verify the performance, the proposed antenna is fabricated and measured in a full anechoic chamber. The proposed antenna shows a reflection coefficient of less than −10 dB from 2 GHz to 4 GHz and achieves zenith ( $\theta = 0^{\circ }$ ) gains of −3.3 dBi, −1.8 dBi, and −2.9 dBi at 2 GHz, 3 GHz, and 4 GHz, respectively. To evaluate the 3-D direction-finding performance, 3-D ray-tracing simulations are conducted in a realistic propagation environment. The proposed antenna achieves a low direction-of-arrival (DoA) estimation error of less than 5°. These results demonstrate that the proposed antenna provides an effective solution for practical 3-D direction-finding systems requiring compact size and stable quasi-isotropic radiation characteristics.