W-Band Bandpass Filter Using Rectangular Microcoaxial Structure

This letter presents a second-order and a third-order W -band bandpass filter (BPF) based on rectangular microcoaxial structures. Rectangular microcoaxial line has the advantages of low dielectric and radiation loss, small size, and easy integration, which is conducive to the design of passive devices. The resonant unit based on rectangular microcoaxial structure consists of a metal cavity, a rectangular metal block suspended inside, and a grounded cylinder. It is used to design two Chebyshev filters. In order to facilitate the interconnection with other devices, ports of the filter are added with rectangular coaxial line to coplanar waveguide (CPW) transitions. The center frequencies of two filters are 93.3 and 94.3 GHz, respectively. Finally, the two filters are fabricated and measured to verify the design method. The minimum insertion loss in passband is 1.3 and 1.5 dB. Good agreements between the simulated and measured results are achieved.