Compact Wide‐Stopband QMSIW‐Based BPF for X‐Band Applications

ABSTRACT A novel and compact two‐pole quarter mode substrate integrated waveguide (QMSIW) based bandpass filter with ultra‐wide stopband characteristics (rejection level > 20 dB, up to 4.05 f 0 , where f 0 is the center frequency of the bandpass filter) is designed and developed in this paper. The designed second‐order filter comprises of two circular QMSIW cavity resonators. The filter is designed using the dominant TM 010 mode of the circular SIW cavity. The TM 010 modes of cavities are coupled through the arc‐shaped slot etched in the middle layer. To verify the present design methodology, a second‐order bandpass filter is fabricated and its characteristics are measured. The designed bandpass filter shows outstanding performance in terms of good fractional bandwidth of 14.45%, lower insertion loss of 2 dB and wider stopband behavior (rejection better than 20 dB up to 4.05 f 0 ) in a given footprint. The experimental results of the filter matches well the EM‐simulated ones.