A Planar Dual-Band Coupled-Line Balun With Impedance Transformation and High Isolation

作者：Wu, Yongle^*; Yao, Lidan; Zhang, Weiwei; Wang, Weimin; Liu, Yuanan

来源：IEEE Access, 2016, 4: 9689-9701.

DOI：10.1109/ACCESS.2016.2640187

• Coupled-line balun
• dual band
• impedance transformation
• high isolation

This paper proposes a novel planar dual-band coupled-line balun with impedance transformation and high isolation. Closed-form design equations are obtained based on the classical even-odd mode equivalent approach. For convenience of designing and synthesizing such a novel dual-band balun, the practical ranges of the frequency ratio, terminated impedances, and two free variables are provided under the conventional microstrip fabrication constraints. By adopting four coupled-line sections, six transmission-line stubs, and an isolation resistor, a microstrip prototype balun working at 1.0/2.6 GHz is designed, fabricated, and measured. There is a good agreement between the simulated and measured results. The wide bandwidths of 290 MHz from 0.83 to 1.12 GHz and 270 MHz from 2.44 to 2.71 GHz are obtained with the measured return losses (vertical bar S-11 vertical bar, vertical bar S-22 vertical bar, vertical bar S-33 vertical bar) and the isolation (vertical bar S-23 vertical bar) better than 10 dB, which effectively confirm the proposed theoretical predictions.

• 出版日期2016
• 单位北京邮电大学