Design of highly selective ultra-wideband (UWB) bandpass filter using step impedance resonator and parallel coupled lines

In this paper, a compact highly selective UWB bandpass filter is designed. The detailed analysis is provided for the design procedure where, Chebyshev type filtering response is extracted using even-odd mode analysis. The presented UWB bandpass filter consists of two 90^o parallel coupled lines attached to a 270^o step impedance resonator (SIR). In this configuration, six transmission poles are achieved in the passband. The step impedance resonator provides compactness as well as suppression of spurious resonance at high-frequency side. To validate the proposed design, a microstrip based fabrication is done on Roger Duroid 5880. The simulated and measured results are well correlated.