Abstract:
Baluns are ubiquitous element in numerous applications such as RF/Microwave components and systems, TV receivers, and modern era telecommunication networks. These are primarily used with push-pull amplifiers, balanced mixers, and in driving the antennas. There have been several reported techniques for balun but it has been always challenging to design balun architectures with wideband and multi-frequency operations. Though, there are multiple reports on wideband and dual-band baluns, there is only one report, that too employing several compensation techniques with complex defected ground structure (DGS), which shows effective operation at three arbitrary frequencies. In this thesis, therefore, a high frequency wideband balun with a very simple and intuitive impedance matching procedure is presented. Furthermore, a design scheme to provide isolation between the output ports across the whole bandwidth is also presented. The broadband balun, although, is extremely useful but may not be able to meet the requirements of evolutions in wireless standards. Keeping this in perspective, a new structure for a passive tri-band balun, operating at three arbitrary frequencies is presented. The tri-band balun is symmetric and enables simple even- and odd-mode analysis to obtain the simplified design equations. The exciting aspect of this design is the presence of free variables which can be chosen independently to facilitate the design. All the design schemes presented in this thesis have been validated through prototypes developed on microstrip boards.
