High selectivity seventh‐order wideband bandpass filter using coupled lines and open/shorted stubs

Abstract

A compact seventh‐order wideband bandpass filter (BPF) with sharp roll‐off skirts using coupled lines and open stubs (OSs)/shorted stubs (SSs) is proposed. Seven transmission poles in the passband and four deep transmission zeros from 0 to 2 f 0 ( f 0 denotes centre frequency of the passband) can be realised with the help of half‐wavelength OSs and quarter‐wavelength SSs. For demonstration, a wideband BPF prototype is designed, fabricated with a measured 3‐dB fractional bandwidth of 78% (1.22–2.77 GHz) and transition band roll‐off rates of over 175 dB/GHz. Good agreement between the simulations and measurements validates the design method.