A Compact Sequential-Phase Feed Using Uniform Transmission Lines for Circularly Polarized Sequential-Rotation Arrays

A compact sequential-phase (SP) feed for circularly polarized sequential-rotation (SR) arrays is presented. Unlike traditional SP feed using multiple segments for impedance transformations, the presented SP feed employs only a single-stage transition where the transmission line width is uniform, making the whole SP feed very compact and neat in layout. The radial design of SP-feed lines to antenna elements may further facilitate the optimization work in adjusting the element spacing. Two miniature square SP feeds of the sizes λ_g/4 and 3 λ_g/8 are given and compared. Experimental prototypes were built and verified with measured results. The proposed compact SP feed can be extended to 2^N × 2^N feeding networks, and is very suitable for large-scale printed CP arrays.