Notch UWB Filter Based on Four-mode Resonator

In order to build a bandpass filter for ultra-wideband applications, a new configuration of a four-mode resonator was given in this paper. A stepped impedance resonator loaded with three open stubs serves as the basis for the proposed four-mode resonator's design. The four-mode resonator's resonant properties are investigated using a conventional analytical technique based on odd-/even-mode analysis. The filter has a relative bandwidth of 116% and a passband bandwidth of $3.1 \sim 11.7$ GHz. Asymmetric interdigital coupled lines feed the four-mode resonator to create a controlled notched band. The central frequency of the notch is 6.8 GHz. The filter is 17 mm $\times 5$ mm in size.