| Title |
Miniaturized Design of a Narrow Bandpass Filter using Quarter-wavelength Short Stubs with Staircase-structure Transmission-line |
| DOI |
https://doi.org/10.5573/ieie.2025.62.8.114 |
| Keywords |
Bandpass filter (BPF); Staircase-structure transmission line; Quarter-wavelength short stub; Size reduction; Harmonic suppression |
| Abstract |
This paper proposes a compact structure for a narrowband bandpass filter (BPF) using a λg/4 short-circuited stub, realized with a staircase-structure transmission line (TL). By applying the staircase-structured TL instead of a conventional λg/4 transmission line, the overall length of the stub bandpass filter is successfully reduced by more than 39%. At a center frequency of 5.8 GHz with a 10% fractional bandwidth, the measured insertion loss and return loss are 1.85 dB and 16.9 dB, respectively. The measured second harmonic is suppressed to 15.3 dB (S21) at 16.6 GHz, demonstrating excellent performance. The total measured size of the proposed stub bandpass filter is 20.0 × 11.1 mm². |