Abstract
Design of two different slot-coupled vertical microstrip-microstrip transitions for ultrawideband (UWB) multilayer microwave circuits are introduced. Transitions consist of two stacked substrates with common ground in the middle and two microstrip-feed-lines connected to microstrip patches on the top and bottom. The proposed transitions use broadside coupling between microstrip patches at the top and the bottom layers via a rectangular-shaped slot in the common ground plane (midlayer). The proposed patch shapes are trapezoidal and butterfly shapes, which are capable of achieving broadband characteristics for UWB operation. Extensive parametric studies are performed to address the effect of varying the transition parameters on the coupling value and the operational frequency bandwidth. The simulated results using two simulation programs with two different numerical techniques show that the proposed transitions have low transmission coefficient (less than 1.2 dB) and a high reflection coefficient (better than 16 dB) over the 3.1-10.6 GHz frequency range. Two transition prototypes are fabricated and then tested experimentally using Agilent E8364B PNA Network Analyzer. Experimental results agree well with the simulated ones. (C) 2015 Wiley Periodicals, Inc.