volume | PIER Journals

Abstract

High-performance dual-band Doherty power amplifier and non-uniform circularlypolarizedantenna array require impedance-transformingunequal dual-band 90° branch-line couplers forpower dividing and phase shiftingin the feed networks.In this paper, an analytical design methodology of generalized impedance-transforming dual-band branch-line couplers for arbitrary coupling levels is proposed. The coupler features wide range of realizable frequency ratio, multiple ﬂexibleselections of open- or short-circuited and pi- or T-network topologies. For demonstration, four numerical examples with different parameters are presented.Furthermore, two microstrip couplers based on open-circuited pi- and T-network topologies were fabricated and measured.The measured results show good performance at dual 1.8/3.45 GHz bands.Thefractional bandwidthsdefined by the fluctuation of the coupling level and the phase difference less than ±0.5 dB and ±5°are up to 17% and 18%, 18% and 2% for open-circuited pi- and T-network topologies, respectively.

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Dr. Qiang Liu

Dr. Yuan'an Liu

Prof. Yongle Wu

Dr. Jun-Yu Shen

Dr. Shulan Li

Dr. Cuiping Yu

Dr. Ming Su