Broadband Filtering Power Dividers Using Simple Three-Line Coupled Structures

Three-line coupled structure (TLCS) is employed in the design of the filtering power divider (FPD) to achieve a broad fractional bandwidth and good frequency selectivity in this paper. A detailed theoretical analysis of the proposed FPD is presented by using the calculated method of impedance matrix deduction. To validate the design concept, the proposed initial FPD prototype is electromagnetically simulated, whose performance shows good consistency with that of the proposed theoretical calculation. In addition, a simple quasi-lumped impedance transformer is introduced near the input port to further improve the matching status of the FPD. These two above-mentioned FPDs are both designed with center frequencies of 2.42 GHz and 3-dB fractional bandwidths of over 82.6%, the latter one of which is fabricated and tested. Comparisons between the simulated and measured results are presented with good agreement to verify the calculated predictions.