Compact ultra-wide bandpass filter with good out-of-band performance

An ultra-wideband (UWB) microstrip Alter with good out-of-band performance is designed and demonstrated. The filter design is based on a circuit model for an optimum short-circuited stub transmission-line filter whose unit elements or connecting lines are non-redundant. Substituting the connecting lines by the lowpass filter using stepped impedance hairpin resonator (SIHR), the undesired spurious bands can be efficiently suppressed, and the designed filter length is reduced. According to the different requirements, the broadband bandpass and lowpass filter can be independently designed and modified, which makes the filter more convenient and easily implemented.