Analysis of a Novel Singlet and Its Application in THz Bandpass Filter Design

In this paper, a novel singlet based on TE₃₀₁ mode resonant cavity is first introduced and analyzed. By using the mode cancelling between the dominant resonance and the spurious resonance, a transmission zero (TZ) is then produced. Furthermore, the position of TZ can be controlled properly by changing the dimensions of the resonant cavity. Based on the novel singlet, a fifth-order filter centered at 140 GHz with two TZs at 131 and 151 GHz has been presented and fabricated by conventional computer numerical control-metal-milling technology. The measured results are in excellent agreement with the simulated ones with a low insertion loss of 0.52 dB and a 3-dB bandwidth of 13 GHz. A high selectivity with a 40 dB outband rejection at 132 and 149 GHz is achieved.