Broadband dielectric loaded parallel coupled microstrip quadrature coupler

Abstract

ABSTRACTIn this article, a wideband dielectric loaded coupled line microstrip 90° hybrid coupler is proposed. The effect of changing the effective dielectric constant of substrate by dielectric loading is capitalized to tune the even‐ and odd‐mode velocities of coupled line to achieve wideband performance. Two different designs are perturbed by dielectric loading to achieve minimum amplitude and phase imbalance with good isolation. The simulated and measured results exhibit a coupling of 3 ± 0.7 dB across the band 3.5–10 GHz. The return loss and isolation are found to be better than 15 dB with 3° phase imbalance over the ultrawideband band. The designed coupler has compact size with a dimension of 30 × 20 mm2. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:1694–1697, 2014