Compact Band-Notched UWB Filter Using Parallel Resonators With a Dielectric Overlay

This letter presents compact band-notched ultra-wideband (UWB) filters with independently controlled responses within the lower and upper portions of the UWB frequency band. The proposed filter consists of dual parallel resonators with common feeding structures as well as a dielectric overlay. One resonator is designed to resonate within the lower portion of the UWB band and the other within the upper portion. The coupling strengths within lower and upper UWB portions can be independently adjusted and the corresponding responses can be individually controlled. A notch band is generated by the inter-digital coupling structure without extra circuits. Two transmission zeros are generated close to the passband edges. For demonstration, two UWB filters are implemented and the results are presented.