Tri-band filtering power divider based on multi-mode fork-type resonator for performance enhancement

A new microstrip tri-band filtering power divider (FPD) with favourable filtering and isolation performance based on the tri-mode fork-type resonator is presented in this study. By constructing the coupling scheme between the input transmission line and two pairs of symmetric fork-type resonators, a nice tri-passband filtering power division response can be easily achieved without an additional matching network. Meanwhile, the desired port-to-port isolation is attained by elaborately arranging two resistors between the symmetrical resonators with respect to the central input line. To demonstrate the authors' design concept, one tri-band FPD prototype is implemented with good agreement between the simulation results of the electromagnetic simulation software and the measurement results of the vector network analyser. Results show that the new tri-band FPD exhibits sharp roll-off with five transmission zeros at passband edges, 17.1 dB harmonic suppression up to 4.6 GHz [2.35f₀ (f₀ = 1.95 GHz)], and better than 15.7 dB in-band isolation.