$W$ -Band Dual-Band Quasi-Elliptical Waveguide Filter With Flexibly Allocated Frequency and Bandwidth Ratios

A <inline-formula> <tex-math notation="LaTeX">$W$ </tex-math></inline-formula>-band dual-band waveguide bandpass filter with each passband of fourth-order quasi-elliptic response and flexibly allocated frequency and bandwidth ratios is presented by adopting an advanced coupling scheme and introducing easily manufactured electric coupling structures. An experimental prototype centered at 80 and 100 GHz is fabricated by the computer numerical control (CNC) milling technology, and an excellent agreement is achieved between the measurements and simulations. The effects of machining tolerances and surface roughness on filter performance are also discussed, indicating the conventional CNC process can completely meet the accuracy and roughness requirements of such <inline-formula> <tex-math notation="LaTeX">$W$ </tex-math></inline-formula>-band dual-band waveguide filter.

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