W-Band Broadband Waveguide Filter Based on H-Plane Offset Coupling

In this paper, a high-performance waveguide bandpass filter (BPF) operating at W-band is proposed. This fifth-order BPF with a wide fractional bandwidth (FBW) of 20% is realized by adopting strong H-plane offset magnetic coupling, while maintaining a simple and robust structure for the computer numerical control (CNC) milling technology. An extra transmission zero is introduced through the extracted pole method to improve the rejection in the upper out-of-band. The BPF fabricated by aluminum exhibits a low insertion loss of about 0.6 dB in the passband and the 3-dB FBW of 20.2% from 83.6 to 102.3 GHz, which agree well with the simulations. Besides, the effects of tolerance on the filter features are discussed, which indicate that such W-band waveguide filter can be manufactured by the conventional CNC milling technology accurately.