W -band quasi-elliptical waveguide filter with cross-coupling and source–load coupling
A high-performance waveguide bandpass filter operating at W-band is presented. This folded fourth-order filter with quasi-elliptic response is developed by introducing cross-coupling and source–load coupling, while maintaining a compact construction for simple computer numerical control (CNC) milling process. The filter fabricated within aluminium block shows an insertion loss of about 1.2 dB in a 3 dB fractional bandwidth of 5.5% from 90.1 to 95.2 GHz, which are very close to the simulated results in the full W-band.