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J. Electromagn. Eng. Sci > Volume 9(3); 2009 > Article
Journal of the Korean Institute of Electromagnetic and Science 2009;9(3):146-151.
DOI: https://doi.org/10.5515/JKIEES.2009.9.3.146   
Low-Loss Broadband Planar Balun with CPW-to-Slotline Transition for UHF Applications
Young-Pyo Hong, Jong-Gwan Yook
Dept. of Electrical and Electronic Engineering, Yonsei University
This paper presents a low-loss broadband balun that uses a coplanar waveguide-to-slotline field transformation. It operates over a very wide frequency range and is of compact size since it does not depend on a resonant structure. To analyse imbalance, the coplanar wavelength(CPW) input ground is connected to the CPW output ground through various capacitors to introduce common-mode impedances. As the common-mode impedance increased the imbalance became significantly higher at the higher-frequency band compared with the lower-frequency band. The bias-circuit approach is used to improve the operation bandwidth of the lower-frequency band. The measured results show a passband of 200 MHz to 2 GHz, an insertion loss of less than 0.75 dB, and a size of $20{times}14;mm$. The amplitude imbalance is approximately 0.3 dB and the phase imbalance is less than $6^{circ}$ over the entire operational range.
Key words: Balun, Broadband, Coplanar-waveguide, Low loss, Planar


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