Optimal Synthesis of Feeding Network for Implementation of Dolph-Chebyshev Current Distribution on Microstrip Antenna Arrays

A microstrip feeding network (MFN) that implements a Dolph-Chebyshev (D-Ch) current distribution is designed to feed a microstrip antenna array (MAA) operating in B2 LTE band. The study consists of three phases. In the first phase, the elements of MAA are directly excited by equi-phase current sources complying with a D-Ch amplitude distribution to ensure a sidelobe level (SLL) of -20 dB. Then, MAA is optimized for maximum forward gain. Finally, the input impedances of the elements of the optimized MAA and the element spacing are recorded. In the second phase, the MFN is considered to terminate at lumped loads with values equal to the input impedances of the respective elements of the optimized MAA and is then optimized to achieve low standing wave ratio, high power efficiency, and output currents equal to those applied in the first phase by the current sources. All optimizations are performed with an improved particle swarm optimization variant in conjunction with CST. In the third phase, the optimized MFN is attached to MAA and is evaluated with CST. The purpose of this study is to show that it is possible to design an MFN that satisfies multiple requirements, without the knowledge of MAA geometry.