Resumen:
This article presents two rat-race 180 degrees ring hybrid couplers that operate on ultra wide band at the frequency range of 3 to 10 GHz. All pass coplanar strip structure, based on one of the ten canonical coupled line circuits, is proposed for the ?/4 sections [1, 2], and two-metal structure on suspended substrate [3] is used to improve the return-losses of hybrid. Besides the two end-shorted coupled lines for the 3?/4 section, which is already known to broaden the narrowband behaviour of the traditional rat-race ring [4], a three-coupled lines structure [5] was studied as a design alternative. This hybrid could be used in a UWB low cost passive mixer with the advantage of maximizing the available space for the mixing devices and their associated circuitry, leaving free the internal area of the hybrid on the both sizes of the substrate. Consequently, the total size of the complete mixer is minimised and the compactness improved. The low coast approach is remarked by the use of standard FR-4 laminate. (c) 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:909915, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26718
