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 μm, 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.