Compact Wideband Bandpass Filter Using Improved Triple-Mode Resonator with Broad Upper Stopband

摘要

A triple-mode microstrip square ring short stub-loaded stepped impedance resonator (SIR) is proposed for the design of bandpass filters (BPFs). The resonator possesses three resonances over the wide frequency band, which can be employed to implement a BPF with flat response. This kind of the filter is able to control spurious response by changing the structure of the resonator. For validation, a triple-mode BPF with central frequency of 2.55 GHz has been designed, fabricated and measured. Good agreement is observed between measured and simulated results.