Design of Quasi-Absorptive Ultra-Wideband Bandpass Filter Based on Stub Resonator

In this paper, a design method for quasi- absorptive ultra-wideband (UWB) bandpass filter (BPF) that can achieve quasi-reflectionless at both ports is proposed. The absorptive UWB BPF consists of a reflective UWB BPF and two resistively terminated bandstop filters (BSF), which are connected on both ports of the reflective UWB BPF. Within the passband, the BSF sections are considered as open circuit due to their high input impedance, allowing energy transmission through the reflective BPF. In the stopband, the input impedance of the BSF sections match the source impedance, resulting in the absorption of energy reflected by the reflective BPF. To demonstrate the design, an absorptive UWB BPF are designed and simulated.