Circularly Polarized Antenna Array Using Filtering Phase Shifting Theory

A new circularly polarized (CP) array using the filtering phase shifting theory is designed. First, a phase-designable filter is designed by adjusting the position of the transmission zero (TZ) of the doublet topology filter. Next, a phase-designable 3 rd -order filtering antenna element can be obtained by using a stub-loaded resonator (SLR) as the physical structure of the doublet topology, and the patch is treated as the last resonating mode. Then, two 3 rd -order filtering antenna elements with 90 phase difference are designed. Finally, by using the slot-coupled feed structure, four elements with phases of 0 , 90 , 180 , 270 are rotated sequentially to form a circularly polarized array. The measured results show that the impedance bandwidth is 8.1% (5.07-5.5 GHz) the axial ratio (AR) bandwidth is 6.7% (5.05-5.4 GHz) the maximum CP realized gain is 10.5 dBic and the good filtering function is implanted.