Design Of A Novel Wideband Microstrip Balun

Balun(balanced to unbalanced transformer, Balun) is the abbreviation of the balanced to unbalanced transformer and has already been widely used in many fields such as balanced mixers, frequency multipliers, push-pull amplifiers and antenna feed networks. In an antenna system, a balun will transform an unbalanced feeding signal to a balanced one. With the development of the modern communication technology, antennas are required to work in a wider and wider frequency band, which lead to baluns are also required to have wider and wider bandwidth. Owe to its advantages of wideband and easy to be fabricated, the microstrip balun becomes a hot research topic currently. In this paper, a kind of new wideband microstrip balun is presented and analyzed.The new wideband microstrip balun proposed in this paper is the first balun that adopts two transmission lines, Coplanar Waveguide Ground (CPWG) and Coupled Strip Line (CSL). It can be fabricated on a substrate with low dielectric constant and possesses several advantages, e.g. low-cost, compacted and easy to be fabricated.A proposed balun, which transforms a 50Ω. unbalanced input to the 50Ω balanced output, is designed, fabricated and tested. Results of a numerical simulation based on Finite Element Method (FEM) and a measurement using a network analyzer show the balun has a quite promising ultra-wideband...