Slot-fed Dual-Port Patch Antenna for Compact Harmonic Transponders

This paper presents a slot-fed dual-ports rectangular patch antenna suitable for harmonic transponders to be employed in logistics. The antenna is fed with two orthogonal H-slot apertures. The two sides of the patch have their first resonance at ${f}_{0}$ and ${2f}_{0}$, respectively. The developed multi-layer layout is optimized to obtain a compact two-piece tag, where the microstrip circuit components (frequency doubler, microcontrollers, sensors and so forth) and the H-slot apertures can be realized on a thin laminate (possibly a flexible substrate) which can be stuck in the interior of a parcel, while the patch can be easily realized at the exterior of a parcel. A proof-of-concept prototype has been realized using standard laminates in the frequency range 1.22-2.44 GHz. The obtained results confirm the theory, and open the door to a new class of harmonic tags for logistics applications.