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

Abstract

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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\circ}$</tex-math> </inline-formula> coupler (crossing between input and output ports and amplitude imbalance), a novel symmetric ports coupler is designed by cascading two identical 90 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\circ}$</tex-math> </inline-formula> couplers with two-phase delay lines, where the total phase delay of two lines is 180 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\circ}$</tex-math> </inline-formula> . 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.