Two new microstrip tri-mode modified ring resonators (Resonator A and Resonator B) are presented and discussed through mode analysis method. The characteristic difference between these two resonators is that the center frequency of the tri-mode Resonator B is still the same as that of traditional dual-mode ring resonator, while the center frequency of Resonator A will be shifted up compared with that of traditional ring resonator. Based on these two novel resonators, two bandpass filter examples are designed, fabricated and measured. The simulations and measurements are in good agreement which validate the design ideas.
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