A compact low-loss Ka-band filter using 3-dimensional micromachined integrated coax

This paper presents a novel low-loss (1.74 dB) 3-pole Butterworth distributed filter operating in the Ka-band with a center frequency of 29 GHz. The filter has a compact 6 mm square footprint and is designed using 3-dimensional (3D) micromachined integrated coax. The integrated coax transmission lines are made of forty-one nickel layers and fabricated using a selective electrochemical metal deposition process (EFAB™). Full-wave simulations of the filter using Ansoft HFSS show very good agreement on insertion loss compared with measured results. Using the EFAB™, we have been able to produce low-loss, all-metal, completely shielded transmission lines with small bend radii and no inter-line coupling.