Novel ultra-wideband bandpass filter with embedded notch-band structure

Compact ultra-wideband bandpass filter using square-ring resonator with two symmetrical stubs is presented in this paper. A quarter-wavelength resonator is embedded into the square-ring resonator to realize notch-band performance, where the notch-band frequency can be conveniently adjusted by changing the parameters of the embedded resonator, and the attenuation level as well as notch-band bandwidth could be determined by the coupling between the embedded resonator and the square-ring resonator. Two ultra-wideband bandpass filters are simulated, fabricated and measured. The measured results are well agreed with the simulated responses.