Compact and high performance UWB band-pass filter based on parallel coupled line

A compact and high performance ultra-wideband (UWB) band-pass filter (BPF) based on two strength coupling quarter-wavelength coupled-lines, which were often served as feedlines between the port and resonator, has been designed and fabricated. Firstly, the desired high coupling factor is achieved by using three-line coupled structure and ground plane aperture technology. Then, the two transmission zeros are generated at the two sides of the wideband to improve the selectivity of this filter by the loading stepped-impedance resonator stubs(SIRs). Finally, the proposed filter is validated through both simulated and measured results and good agreement is obtained.