Modified Vertically Installed Planar Couplers for Ultrabroadband Multisection Quadrature Hybrid

In this letter, we describe a five-section ultrabroadband 1-9GHz microstrip quadrature hybrid (90deg, -3dB coupler), which uses two types of modified vertically installed planar (VIP) couplers and is suitable for conventional printed circuit board realization. The modified VIP couplers provide not only a way to implement tight coupling value with reduced modal phase velocity difference but also a layout flexibility to minimize the discontinuity between sections. An experimental circuit is designed and fabricated with a passband ripple of plusmn0.5dB, a return loss of less than -20dB, and an isolation of better than 20dB over the frequency of 1-9GHz. Very good agreement between the simulated and measured results is obtained