Design of Wilkinson Power Dividers with SITL Compensated Microstrip Bandpass Filters

This paper presents a simple technique for improving performances of a conventional Wilkinson power divider. The technique is achieved by replacing bulky quarter-wave transmission lines with stepped impedance transmission lines (SITL) compensated coupled lines. With the internal function of bandpass filter integrated with the proposed coupled lines, the spurious response at 2nd harmonics frequencies that normally exists in the conventional divider is considerably reduced. Simulated and measured results at 2.1 GHz operating frequency of the proposed and conventional Wilkinson power divider were compared. The proposed divider achieves -3.8 dB insertion loss (S21,S31) and more than 25 dB return loss (S11,S22,S33) across 10% fractional bandwidth. Based on this measurement, the proposed circuit achieves more than 34.5 dB suppression at the 2nd harmonic frequency.