Small hybrid rat-race coupler

Abstract

A broadband and compact size rat-race hybrid using multilayer technology is done in this project. It has some benefits over the conventional rat-race hybrid. Firstly, the size is reduced. The conventional rat-race hybrid is composed of three λ/4 sections and one 3λ/4 section. Its total circumference is 1.5 wavelengths. By contrast, making use of the multilayer technology, the broadband compact rat-race hybrid occupies only about 33% of the conventional one. Besides the size consideration, the performance is definitely taken into a deep consideration. The theory of the broadband rat-race hybrid and the factors relating to the performance are studied. Meanwhile, throughout the simulation and measurement process, desirable features can be identified Furthermore, it integrates one double-sided parallel-strip line (DSPSL) port and three microstrip line ports. Base on its extraordinary characteristic, this rat-race can facilitate circuit implementation. In this project, the broadband rat-race hybrid is combined with a passive antenna element on the same substrate. It is so-called active integrated antenna (AIA). The work done in the project covers passive and active elements, the former is comprehensively examined in Chapter 3 and the latter is described in Chapters 4 and 5.