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International Journal of Antennas and Propagation
Volume 2015, Article ID 256536, 6 pages
http://dx.doi.org/10.1155/2015/256536
Research Article

Compact Two-Section Half-Wave Balun Based on Planar Artificial Transmission Lines

1School of Electronics and Information Engineering, Sichuan University, Chengdu 610064, China
2School of Optoelectronics Engineering, Chongqing University of Posts and Telecommunications, Chongqing 40065, China

Received 23 September 2014; Accepted 26 November 2014

Academic Editor: Sanming Hu

Copyright © 2015 Changjun Liu et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Artificial transmission lines are realized by a series of meandered-line inductors, parallel-plate capacitors, and interdigital capacitors, which belong to metamaterial transmission lines. An ameliorated artificial transmission line is proposed to realize a low characteristic impedance transmission line. A two-section half-wave balun at 900 MHz is designed, fabricated, and measured in this paper. The compact balun is based on conventional and ameliorated planar artificial transmission lines instead of microstrip transmission lines. The main advantage of the proposed balun is its size reduction, which occupies only about 10% of a conventional one. Measured results match well with theory and simulation. The balun features excellent amplitude and phase balance in microwave power combining and a reasonable bandwidth of the return loss as well.