Compact Integrated Feeding Network for Excitation of Dual-Circular Polarization in Series-Fed Antenna Lattice

A novel approach for realization of a feeding network allowing for achieving dual-circular polarization in the slot-coupled microstrip antenna lattice has been proposed. The presented feeding network is an eight-port composed of four 3\mathchar"702DdB/90
^°
directional couplers, and when appropriately integrated with the four-port series-fed antenna lattice ensures a full symmetry of the antenna layout and produces simultaneously right-handed and left-handed circular polarization. The proposed low-profile, low-cost solution can be easily integrated with the antenna lattice, and it allows for reduction of the introduced dissipation losses comparing to the known solutions, i.e., external feeding networks such as Butler matrices or power combiner/divider networks connected via coaxial cables. The proposed concept has been examined by measurements of the manufactured feeding network integrated with the previously developed antenna lattice operating at 5.4 GHz.