Dual-Band Filtering Power Divider With High Selectivity and Good Isolation

Abstract

A novel microstrip dual-band filtering power divider (FPD) is presented in this letter. By introducing a proper coupling topology between the quarter-wavelength ( $\lambda $ /4) short-ended microstrip line and two multi-mode resonators, the dual-band FPD is constructed. Meanwhile, good isolation of this FPD is attained by installing an isolation resistor between the resonators. Additionally, two $3\lambda $ /4 open-ended stubs are attached in the output coupled lines to improve its frequency selectivity and obtain a wide upper stopband. For validation, a prototype FPD operating at 1.57 and 2.89 GHz is designed, fabricated and measured. Both the simulated and measured results are in good agreement. Results indicate that the proposed FPD exhibits not only a sharp frequency selectivity and good harmonic suppression with the help of the six inherent transmission zeros, but also better than 21 dB isolation within the entire dual operation bands.