Wide stopband out-of-phase filtering power divider using double-sided parallel-strip line

This Letter presents a novel out-of-phase filtering power divider (FPD) with a very wide stopband by using double-sided parallel-strip line (DSPSL) and through ground via (TGV). The DSPSL structure facilitates the out-of-phase outputs of the FPD. The TGV and two compleximpedance terminations connected to the common input port are employed to achieve the isolation. By choosing proper feeding coupling region and the loading resistors at the centre of the resonators, the second, third and fourth harmonics are suppressed. For verification, a prototype FPD operating at 1.85 GHz (f0) with 5.2% bandwidth is designed, fabricated and measured. The experimental results show that the isolation between the output ports is better than 24 dB across the passband, and the 28 dB rejection band is extended to 4.6f0.