A tri-band Wilkinson power divider using extended T-shaped stubs

This paper presents a tri-band Wilkinson power divider. The proposed structure is derived from the conventional Wilkinson power divider by replacing the quarter-wavelength branch lines with the extended T-shaped short or open stubs. The first and the third operating frequencies of the proposed power divider can be flexibly controlled, while the second frequency is equal to the mean value of the other two frequencies. Both the power dividers using the extended T-shaped short and open stub structures are designed based on the derived equations and the frequency response characteristics are discussed. For verification, a short stub based tri-band Wilkinson power divider operating at 1.3, 3.0 and 4.7 GHz is fabricated and measured. The measurements are in good agreement with the simulations. The measured bandwidths of -20 dB isolation are 1.22-1.42 GHz, 2.92-3.18 GHz and 4.66-4.86 GHz, respectively. Over these three operating bandwidths, the measured return losses are better than -15 dB at all three ports.