Miniaturized filtering equal/unequal Wilkinson power dividers

In this paper, two miniaturized Wilkinson power dividers with equal and unequal power division ratios capable of suppressing spurious harmonics over a wide frequency range are presented. First, an asymmetric high-low impedance resonator with coupled open-stubs and folded structure is employed to design the equal power divider. Then, how connecting an inductor in series with the introduced resonator can lead to affecting the transmission coefficient of the power divider branch and achieving an unbalanced power division ratio at output ports, is analytically clarified. In the third step, a combination of the resonator with folded structure and the inductor is utilized to design an unequal 2:1 divider. To validate the performed analysis, two equal and unequal Wilkinson power dividers at 900 MHz are fabricated and measured. Regarding S31, both dividers can suppress the 4th to 13th spurious frequencies and with respect to S21 of the unequal case, the 2nd-harmonic to 14th-harmonic are omitted. The occupied areas of the equal and unequal structures are 7.35 mm x 18.9 mm and 7.5 mm x 17.9 mm, respectively, which indicate almost 84 % size reduction in each case.