Low-Profile Multiband Circularly Polarized Antenna for Indoor/Outdoor Tracking and Sensing Applications

This article presents a low-profile, small size, multi-functional circularly polarized antenna design for tracking and sensing systems. The antenna resonates in the ultra-high frequency (UHF) (915 MHz), GPS L2 (1.227 GHz), RFID 1.8 GHz, 2.45 GHz, and 3.3 GHz bands. The use of the GPS L2 band makes sensing more secure, precise, and accurate than the GPS L1 band, and RFID bands are used for indoor sensing, whereas GPS L2 is used for outdoor sensing. The proposed antenna is a cross-dipole arrangement, with three dipoles printed on each side of the polyimide substrate, which is extremely flexible and heat-resistant. The primary dipole, consisting of longer metallic patches with semi-arrow-shaped terminations, is designed to cover the UHF and GPS L2 frequency bands. The subsequent dipole consists of inverted mirrored L-shaped radiators that operate in the 1.8 GHz frequency band. The third dipole consists of an L-shaped radiator that operates in the 2.45 GHz and 3.3 GHz frequency bands.