A Miniaturized Dual-Mode Ring Bandpass Filter

A novel miniaturized dual-mode ring bandpass filter is proposed in this letter. The miniaturization is accomplished by slow-wave synthesized microstrip lines in an asymmetrical form. At the input/output ports, two saw-toothed coupling structures with quarter-wavelength open-circuited stubs are used to provide tight coupling. The miniaturized filter features a very compact size and the in-band responses are comparable to its conventional counterpart. The design methodology, circuit topology, and simulated and measured results are investigated and compared.