Design and Realization of a Broadband Multi-Beam 1×2 Array Antenna Based on 2×2 Butler Matrix for 2.45 GHz RFID Reader Applications

Abstract

This paper presents design and analysis of a beam switchable [Formula: see text] array patch antenna fed by a [Formula: see text] Butler matrix based hybrid coupler for 2.45[Formula: see text]GHz radio frequency identification (RFID) reader applications in the ISM band. The proposed beam switchable array antenna arrangement consists of two identical patch elements, a pleated quarter-wavelength impedance transformer (PQWIT), and a hybrid coupler. The concept of PQWIT has been utilized to reduce the overall implementation area of the patch elements. The overall area of the patch element is miniaturized by 50% due to the implementation of PQWIT. This miniaturized antenna is used as a radiating element for designing a beam switchable [Formula: see text] array antenna fed by a hybrid coupler. The proposed antenna prototype has been fabricated on a 1.56[Formula: see text]mm thick Rogers RT/duroid 5880 substrate with a physical area of [Formula: see text][Formula: see text]mm2. The simulation and measured results exhibit good agreements. The designed antenna offers a broad bandwidth of 844[Formula: see text]MHz (1.956–2.80[Formula: see text]GHz), peak gain of 8.86 dB, peak radiation efficiency of 99.52% and has two switchable beams in the directions [Formula: see text] and [Formula: see text]. The suggested switched beam array antenna is suitable for RFID reader applications at 2.45[Formula: see text]GHz for tracking of moving objects.