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

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 2f₀ ( f₀ 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. [ABSTRACT FROM AUTHOR]