Low-Profile Triple-Element Antenna for UWB Indoor Localization in Handheld Devices

This letter presents a low-profile, triple-element ultrawideband (UWB) antenna designed for angle of arrival estimation in both azimuth and elevation across UWB channels 8–14 (7.2 GHz to 10.2 GHz). Fabricated on thin polyimide (PI) substrates with a total thickness under 150 $\mu$m, it is suitable for compact Internet of Things devices, including handhelds for indoor localization. Fully enclosed striplines with radiating slots replace conventional half-open microstrip lines, enhancing impedance bandwidth and radiation performance. Each element includes a coplanar waveguide connected via a buried via. Decoupling ground structures and neutral lines reduce mutual coupling and improve bandwidth. A prototype using two flexible PI-based copper laminates was fabricated and measured in an anechoic chamber. Elements 1, 2, and 3 exhibit unidirectional patterns. With its compact size and diverse patterns, the antenna supports efficient indoor UWB positioning.