Large FoV Direction-Finding System Based on A Small-Aperture Phase Mode Antenna and Its Applications on UAVs

Unmanned aerial vehicles (UAVs), serving as small mobile platforms, are well-suited for emitter detection and localization tasks in dynamic environments. However, implementing large antenna array apertures on the compact platform of UAVs is impractical. This paper presents a small-aperture phase mode antenna (PMA) direction-finding (DF) system for UAV applications. Initially, a small-aperture, high port-isolation dual-port PMA is introduced. Through miniaturization and decoupling, a conventional slot antenna pair is transformed into the final dual-port PMA. The dual-port PMA features a compact aperture of 0.4λ × 0.47λ (where λ is the wavelength at 2 GHz), with port isolation reaching up to 40 dB. Next, we investigate the integration of the dual-port PMA with a novel amplitude-only DF (AODF) method, termed the single PMA multiple patterns amplitude comparison (SPMAMP-AC) method. This method utilizes multiple patterns to construct a DF function cluster, providing higher DF accuracy over a broader field of view (FoV) compared to the traditional AODF method. The measured results indicate maximum DF errors of 2.4°, 4.3°, 4.9°, and 7.9° for FoVs of 60° (θ ε[-30°, 30°]), 140° (θ ε[-70°, 70°), 160° (θ ε[-80°, 80°), and 180° (θ ε[-90°, 90°) in the yoz plane, respectively.