A Triple-Band Bandpass Filter Based on Triple-Mode Metal Block Resonators

This letter presents a design methodology for triple-band bandpass filters. A triple-mode resonator comprising two metal blocks is proposed to configure the topology. Compared with the traditional triple-band cavity filters, the most noteworthy attribute of the proposed resonator is the ability to independently tune the resonance and coupling of one of the three modes, making the design procedure simple and fast. In addition, the use of metal blocks can further reduce the size of the filter. To verify the proposed design method, a third-order triple-band filter with an identical bandwidth is designed, fabricated, and measured. The measured results are in good agreement with the simulations.