Design of a <i>W</i>-Band SIW Bandpass Filter Using Perturbative Singlet

In this letter, a perturbative singlet based on substrate integrated waveguide (SIW) is proposed, and a W-band SIW bandpass filter (BPF) with high selectivity can be achieved based on this singlet with perturbative characteristics. To control the position of the transmission zero (TZ) of this singlet, four via holes are specially introduced inside the singlet. By changing the position of the via holes, the pseudo-TE102 mode is controlled with little effect on the TE301 mode, then the control of the TZ is realized. Based on the SIW perturbative singlet mentioned above, two filters are designed and fabricated with a center frequency of 93 GHz and a 3-dB fractional bandwidth of about 2%, with TZs around 90 and 96 GHz, respectively.