Wide Stopband Bandpass Filter Implemented With Spur Stepped Impedance Resonator and Substrate Integrated Coaxial Line Technology

A novel wide stopband bandpass filter implemented with spur stepped impedance resonator (SSIR) and substrate integrated coaxial line (SICL) technology is proposed in this letter. SSIR possesses capabilities of both suppressing and staggering spurs without complicated fine-tuning, and SICL is very suitable for wide stopband applications. A prototype with compact size is fabricated, and the measured results exhibit extended stopband up to 8.76 f
₀
with a rejection better than 40 dB (except for a little 36.5 dB burr in 7.06 f
₀
), or 9.36 f
₀
with rejection better than 30 dB.