Compact wide‐stopband bandpass filter using FSIW‐patch triple‐mode resonator.

In this study, the compact third‐order filter with wide stopband is proposed, and it is based on the folded substrate integrated waveguide (FSIW)‐patch resonator. The embedded semicircular patch with two etched slots is integrated into the closed dual‐mode FSIW, so the miniaturized single‐cavity triple‐mode resonator with electromagnetic (EM) shielding and high quality can be achieved. In addition, the slots can reduce transverse electricity (TE)101 and TE201 on FSIW, while the other higher‐order modes of FSIW remain unchanged, then the wide stopband can be realized, and the stopband can be further widened by designing the feeding position to suppress higher‐order modes. Then, this filter based on hybrid FSIW modes has compact size, wide stopband, and good EM shielding. Finally, a prototype with 3‐dB fractional bandwidth of 8.4% is designed at 5.87 GHz (f0), and its insertion loss is only 1.16 dB. The upper‐stopband attenuation is better than 23 dB extended to 3.08f0. It occupies only 0.18λg2, where λg is the guided wavelength at f0. [ABSTRACT FROM AUTHOR]