Electronically controlled 2 by 1 arrayed beam forming antenna for UHF RFID reader

In this paper, a 2 by 1 array antenna for beam forming based on a feeding network composed of 2 low temperature cofired ceramic (LTCC) hybrid coupler, a 90 degree delay line and 4 Single-pole double-throw (SPDT) switch with 50 Ω termination is proposed. By combining these elements, the feeding network can operate as many kinds of power dividers such as Wilkinson power divider, quadrature hybrid coupler and ring hybrid coupler depending on the switching condition. This feeding network can make different kinds of the phase difference between the divided signals which leads to different direction of beams of the antenna. The antenna used for the array is the quadrifilar spiral antenna (QSA) which can radiate right hand circular polarization (RHCP) beam. The measured results show that the proposed antenna has 5 directional beams of 2.5°, 25°, -25°, 40° and -42.5°.