3-D-Printing and High-Precision Milling of W-Band Filter Components With Admittance Inverter Sequences
Chad Bartlett, Jens Børnemann, Michael Höft
Abstract
This work presents the design of an additively manufactured W-band bandpass filter and a subtractively manufactured W-band diplexer to demonstrate the use of admittance inverter sequences for the ease of manufacture at millimeter-wave frequencies. Contrary to typical impedance inverters (E-plane and H-plane irises), the use of admittance inverters (E-plane and H-plane stubs) allows for larger dimensions to be specified and ultimately does not impede the general waveguide path. The proposed bandpass filter is designed with all E-plane stubs, while the diplexer is designed with one branch using both E-plane and H-plane stubs as an arbitrary sequence, and the second branch using all H-plane irises. The additively manufactured bandpass filter is fabricated using the most elementary-level stereolithography (SLA)-based methods, demonstrating that a hobbyist-type SLA printer and metallization method can procure exceptional results for millimeter-wave filter designs. The subtractively manufactured diplexer is fabricated using high-precision computer numerical control (CNC) milling to highlight the use of arbitrary inverter sequences in a more complex and robust design profile, while the dispersive transmission zeros that are caused by over-moding of the inverter stubs are used to demonstrate unique isolation characteristics in the upper W-band region. The design concepts, fabrication profiles, simulations, and measurements which are presented in this work highlight a viable option for overcoming miniaturized dimensions in millimeter and submillimeter-wave applications.