A Fully Symmetrical Uni-Planar Microstrip Line Comparator Network for Monopulse Antenna

In this letter, a fully symmetrical uni-planar comparator network is proposed for monopulse antenna feeding. To break through the fundamental limitation of a conventional 180° coupler (crossing between input and output ports and amplitude imbalance), a novel symmetric ports coupler is designed by cascading two identical 90° couplers with two-phase delay lines, where the total phase delay of two lines is 180°. To realize in planar structure, a zero-phase delay planar crossover is designed to resolve signal crossing between two stage couplers in a comparator network. To verify our design concept, a prototype monopulse array operating at 5.7 GHz is designed, fabricated, and measured, and results are aligned well with simulation and theory.