Subsystem of Phased Array Antennas With Adaptive Beam Steering in the Near-Field RFID Applications

An antenna subsystem is presented for RFID reader applications at 2.45 GHz in the near-zone tag detection. The subsystem is programmable to adaptively steer the radiation beam from one spot to another inside the target zone, and allows the RFID to achieve a better signal reception by changing the beam patterns along the horizontal cut. The created beams have narrow spots, and may potentially reduce the interference by the electromagnetic scattering from the nearby metal structures. An antenna prototype is examined to validate the feasibility.

I. Introduction

An Antenna subsystem is presented for the RFID [1], [2] reader applications at 2.45 GHz in the near-zone tag detection. The potential applications are illustrated by the scenario in Fig. 1, which widely appears in the department stores [3]. Here the products’ tags move on the transportation belt through a detection zone. To reduce the electromagnetic (EM) interferences arising from the nearby metal structures, the near-field focus antennas (NFAs) [4], [5] have been proposed to produce narrow spot beams in the target region. As shown in Fig. 1, the NFAs confine the radiation energy in a small region at the cost of sacrificing the possibility of wide area coverage, which limits their applicable flexibility such as in the example where the width of transportation belt is doubled. Fig. 1.

Scenario of a near-field focus problem for RFID applications.