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.

This paper presents design and analysis of a beam switchable 1 × 2 array patch antenna fed by a 2 × 2 Butler matrix based hybrid coupler for 2.45 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 1 × 2 array antenna fed by a hybrid coupler. The proposed antenna prototype has been fabricated on a 1.56 mm thick Rogers RT/duroid 5880 substrate with a physical area of 1 1 2 × 1 0 0 mm2. The simulation and measured results exhibit good agreements. The designed antenna offers a broad bandwidth of 844 MHz (1.956–2.80 GHz), peak gain of 8.86 dB, peak radiation efficiency of 99.52% and has two switchable beams in the directions − 3 0 ∘ and + 3 0 ∘ . The suggested switched beam array antenna is suitable for RFID reader applications at 2.45 GHz for tracking of moving objects. [ABSTRACT FROM AUTHOR]