Analysis and implementation of compact two-section half-wave balun using artificial transmission lines

Abstract

ABSTRACTIn this paper, a compact two-section half-wave balun using artificial transmission lines is proposed. This paper describes design rules that need to be satisfied for a two-section half-wave balun by the even- and odd-mode analysis. According to the design rules, a two-section half-wave balun using microstrip lines is designed and simulated. Then, to reduce dimensions, conventional quarter-wavelength microstrip transmission lines are replaced by artificial transmission lines realized by a series of meandered-line inductors, parallel-plate capactiors, and interdigital capacitors. Additionally, the improved artificial transmission lines with chip capacitors have realized lines with very low characteristic impedance that cannot be easily achieved by conventional transmission lines. Based on these theories, a two-section half-wave balun using artificial transmission lines has been designed and fabricated. The developed balun occupies 25.1 mm × 20.2 mm, which almost equals to 5.0% of this topology of balun adopting conventional microstrip transmission lines. The simulated and measured results demonstrate good agreements between them, which verifies feasibility of the proposed designing method.