A Single-Notch Ultra-Wideband Bandpass Filter Based on Bow-Tie Cells

This paper presents a highly efficient ultra-wideband (UWB) bandpass filter using coplanar waveguide (CPW) technology. The design employs bow-tie cells to achieve four transmission poles and one transmission zero. A step impedance resonator is introduced for further performance enhancement, and it contributes an additional transmission zero at low frequencies and optimizes the stopband. A T-shaped short-circuit stub is used to create a trap frequency band with deep attenuation, effectively blocking the ITU8.0 frequency band centered at 8.2 GHz. The proposed filter features a passband range from 3.7 GHz to 9.6 GHz, an insertion loss less than 0.8 dB, and a return loss greater than 20 dB. Additionally, the filter exhibits high selectivity, with a 30 dB skirt factor of 0.88 and a wide stopband up to 17.7 GHz, where S 21 is below −20 dB.