Broadband Direction Finding via Beam Scanning with a Frequency-Invariant Beam for Detecting High-Speed Platforms

This paper proposes a frequency-invariant beam (FIB)-based beam-scanning algorithm for determining the direction of signals from high-speed platforms. In broadband beam scanning, the beam width narrows as the frequency increases, which increases the number of beams required to provide a given beam coverage and increases detection time. To overcome this limitation, we employ an FIB algorithm that maintains a constant beam width, thus enabling rapid direction finding with fewer beams. In addition, we analyzed the performance of FIB-based beam-scanning with respect to beam-pattern characteristics. For validation, a 16×1 array antenna operating in the 3:1 broadband range was designed. FIBs were generated from the measured active element patterns (AEPs), and their direction-finding performance was evaluated. Within ±45°, the proposed method achieves an RMSE ≤6° using five beams, thereby demonstrating the effectiveness of fast, FIB steering for direction finding and jamming.