Beamforming and beam steering applied to power 915 MHz RFID systems

Abstract

This article proposes a Digital Beamforming (DBF) architecture aimed at Wireless Power Transfer (WPT) to passive RFID tags, aiming to mitigate the directivity and efficiency limitations of isolated radiating elements. The ability to control the spatial distribution of electromagnetic energy is fundamental for modern WPT systems, and the use of antenna arrays allows for the synthesis of highly directive lobes and electronic beam steering. The study evaluates the performance of the proposed system using an SDR platform to perform digital phase and amplitude manipulation at baseband. The directional beam is used to energize a 915 MHz RFID tag, comparing it with a single element circular polarization from a commercial device. Experimental results demonstrate that the DBF architecture achieved a significant reduction in the tag’s charging time, presenting a 74.8% improvement for normal incidence (frontal alignment) and a 21.3% improvement for oblique incidence at 30° compared to the commercial solution. It is concluded that the DBF system offers a more robust and flexible link for WPT applications, compensating for the loss of spatial power density through precise electronic beam redirection.