Theory and Experiment of Two-Section Two-Resistor Wilkinson Power Divider With Two Arbitrary Frequency Bands

In this paper, a novel design theory of two-section two-resistor Wilkinson power divider (WPD) is introduced. By selecting two different physical lengths of two-section transmission lines (TLs), two arbitrary frequency band WPD can be achieved. Compared with the former work, the designable frequency ratio range u can be extremely extended from 1 < u < 3 to 1 < u < \infty , general design equations for characteristic impedances, physical lengths, absorption resistors, and frequency ratio ranges are newly derived and proved from even- and odd-mode analysis. Because of no capacitors or inductors, the proposed WPD can be used for high-frequency applications. Spurious band of S_{21} appears between two passbands under the condition of two different physical lengths; therefore, a \Pi -type dual-band transformer is newly introduced to replace single TL for spurious band suppression. We proved that \Pi -type structure could effectively suppress spurious band of S_{11} , maintain two arbitrary frequency passband of S_{21} , and provide an extra isolation band of S_{32} at center frequency. Finally, three proposed WPD examples with \Pi -type structure are selected with different frequency ratios, where frequency ratio u = 4 in Example A, u = 6 in Example B, and u = 20 in Example C are designed and fabricated in the experiment. Measured results show good agreement with the theoretical results.