A novel butterfly‐shaped multilayer backward microstrip hybrid coupler for ultrawideband applications

Abstract

AbstractIn this letter, the numerical analysis and design of aperture‐coupled backward microstrip hybrid coupler for ultrawideband (UWB) multilayer microwave circuits are introduced. The proposed coupler is composed of two microstrip patches located on two stacked substrate layers. This coupler uses a broadside coupling via a rectangular‐shaped slot in the common ground plane (mid‐layer). To achieve broadband characteristics for UWB operation, butterfly‐shaped patches are used. The numerically simulated results using two simulation programs with two different numerical techniques show that the proposed coupler have good insertion losses (both through S21 and coupled S31) variation (less than ±2 dB) and high return loss S11 (greater than 14 dB) with acceptable isolation S41 (about 14 dB) over most of the 3.1–10.6‐GHz frequency band. A 3dB/90°‐backward hybrid coupler prototype is fabricated and then tested experimentally using Agilent E8364B PNA Network Analyzer. Experimental results agree well with the simulated ones. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2231–2237, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27092