Design of Bandpass Filtering Out-of-phase Power Divider Based on Branch-line Structure

A new bandpass filtering power divider with out-of-phase output characteristics is proposed in this paper based on the modified branch line structure. On the one hand, by loading shorting pins and stubs in the traditional branch-line structure, transmission zeros can be introduced outside the passband, thereby significantly improving DC suppression and achieving good frequency selectivity. On the other hand, the port-to-port isolation and matching condition can be well achieved by loading a grounded resistor at the symmetry plane of the branch-line structure. To further verification, a power divider has been fabricated and measured with three ports. The measured results are in good agreement with the simulated ones. The designed power divider has an operating frequency of 2.0 GHz, a 3 dB fractional bandwidth (FBW) of 28%, a magnitude difference of 0 ±0.32 dB, and a phase difference of 180° ± 3.3°. The results show that the proposed power divider has good filtering responses, excellent out-of-band suppression levels, anti-phase differences, and port isolation.