A Compact, Low-Cost, Ultrawideband Direction-Finding System: Techniques Suitable for Small-Aperture Designs

A review of different direction-finding (DF) systems and the design of a compact, very low-cost ultrawideband (UWB) DF system are presented. The proposed system uses a compact, reconfigurable switched-beam antenna with a height of 0.089 and a diameter of 0.25 λ
₀
. The antenna can generate 11 figure-eight-shaped radiation patterns in the 460- to 1,550-MHz band, which can be electronically rotated in the azimuth plane. This allows for using a single-channel, amplitude-only receiver to perform DF. Commercially available single-pole, six-throw switches and a two-way 180°-power splitter are used to feed the antenna and perform the beam selection. The DF system is controlled using a low-cost, microcontroller unit (MCU) connected to a computer, which is also used for data collection and processing. The angle of arrival (AoA) of the signal is determined using the maximum likelihood estimation (MLE) method. The UWB DF system was fabricated and characterized in an outdoor field. For a signal-to-noise ratio (SNR) of 36 dB, the AoA bias is <;1.5° with a <;0.8°-error of estimation over all of the azimuth angles across the whole operation band. For SNRs > 5 dB, a better than 5°-AoA estimation accuracy is obtained over all of the azimuth angles and the entire band of operation.