Projeto de acopladores híbridos em quadratura modulares e aterramento virtual para aplicações em microondas

Abstract

This work presents the development, optimization, and experimental validation of a fullyplanar quadrature hybrid coupler, developed on FR-4 substrate and designed to operatefrom 2 to 4 GHz. The study started from the reproduction of a reference model andevolved through five methodological stages: initial modeling in F4B-2, transposition ofelectrical lengths to FR-4, substitution of grounding vias with radial stub networks actingas virtual grounds, parametric optimization aiming to minimize losses, maximize isolation,and ensure phase quadrature, and finally, prototype fabrication and characterization.The results demonstrated the technical viability of FR-4 for microwave applicationswhen combined with virtual grounding techniques, presenting impedance matching andisolation lower than -15 dB, as well as phase deviation within ±5◦ in the 2.41 GHz to 5.00GHz range. However, S12 degradation below 2 GHz and fabrication constraints due tothe extreme miniaturization of the tracks were observed. It is concluded that the FR-4substrate combined with radial stubs constitutes an alternative for broadband couplers,recommending geometric adjustments and high-resolution manufacturing techniques toimprove device robustness.