Design of High-Selectivity Asymmetric Three-Way Equal Wideband Filtering Power Divider

Abstract

An asymmetric three-way equal wideband filtering power divider with high selectivity is presented in this paper. The proposed three-way filtering power divider is an asymmetric structure which is composed of two different $\lambda $ /4 transformers, a pair of short-ended parallel coupled lines, an open-ended parallel coupled line, and a three-line parallel coupled line. Based on 2:1 unequal Wilkinson power divider, an equal three-way power divider is obtained with energy subdivided by three-line parallel coupled line. Subsequently, a Wilkinson power divider with the wideband filtering response is realized by adding a pair of short-ended parallel coupled lines that can provide multiple transmission zeros and poles. Presented with an equivalent circuit, the design procedure for asymmetric three-way equal filtering power divider is developed. Moreover, the reasons for and associated measures of large magnitude imbalance are also analytically developed. The measured results show that the proposed filtering power divider has more than 57.3% 1-dB fractional bandwidth, less than 0.4 dB insertion losses, better than 19.5 dB return loss, and more than 14.9 dB isolation from direct current to 3.3 GHz.