Low-Pass Filters in Standard Rectangular Waveguide Using 3D Printed Dielectric Inserts

A new approach to using dielectric 3D printing in realizing low-pass filters in waveguide is demonstrated. Cascaded stepped-impedance sections are printed and inserted into conventional WR42 off-the-shelf waveguide, with the resulting filters implementing a pass-band or 18 - 20 GHz and a stop-band of 22 - 27 GHz. Using a commonly available SLA printer and resin, maximum insertion loss of 4.3 and 5.6 dB is achieved across the band of interest for the C-first and L-first filters, respectively, with both featuring more than 30 dB attenuation across the stop-band. The effect of support structures on isolation is demonstrated