Demonstration of an electrically small antenna array for UHF direction-of-arrival estimation

Direction-of-arrival (DoA) estimation of incoming electromagnetic signals can play a critical role in surveillance, sensing, and cognitive radio applications. Typical DoA antenna arrays use an aperture measuring several wavelengths across to ensure reliable measurement of phase information. For a UHF application, such an array would need to be a few meters across-too large for a portable array. This work demonstrates a practical DoA array composed of antennas with diverse radiation patterns which is combined with an algorithm which relies primarily on amplitude information rather than phase information. This approach yields a much smaller array with similar direction-finding capabilities to larger ones. A calibration procedure captures the antenna responses, including the parasitic effects of the closely spaced antennas. The calibrated array and direction-finding algorithm then achieves measured accuracy with resolution of six degrees with no front-to-back or quadrant ambiguities.