Additive Manufacturing of X-Band Waveguide Pressure Window Printed With Low-Loss Polymers

This article explores the design and fabrication of dielectric-based pressure windows using additive manufacturing methods. Pressure windows are required to isolate different media in a waveguide transmission line or to protect the waveguides from the external environment. At times, it can be used to contain a pressurized waveguide section for high power handling. Currently, pressure windows have a limit to their pressure holding capability, where one of the factors is the choice of material. A commonly used dielectric known as polytetrafluoroethylene, or known as PTFE, is known for its low loss tangent, but it is not mechanically rigid enough to withstand high pressure. A promising 3-D printable polymer with a low loss tangent on the order of PTFE and high mechanical strength was utilized. This polymer, known as cyclic olefin copolymer (COC), was processed by hobbyist-grade 3-D printers to lower the cost of fabrication of high-performance radio frequency (RF) devices. With this, a tapered pyramidal design was 3-D printed and demonstrated to withstand 10 bars of pressure while keeping the insertion loss low at 0.2 dB over a bandwidth of 8.4–11.5 GHz. As such, polymer 3-D printing shows good promise as a low-cost fabrication method for dielectric-loaded waveguide devices.