Experts at the U.S. Naval Research Laboratory have created and tested 3D-printed antennas and arrays to advance radar technology and enable new applications for the U.S. Navy. The lightweight and rapid production of 3D-printed parts make it an attractive alternative to traditional manufacturing that often requires expensive materials and specialized equipment. 3D printing is a way to produce rapid prototypes and get through multiple design iterations very quickly, with minimal cost.
Radar systems perform critical functions for the Navy and remain an important part of maritime navigation and national defense. Parts for antennas and arrays, which are multiple connected antennas working together as one, may unexpectedly break or wear out requiring replacement. Traditionally, parts are ordered or intricately machined out of metal, sometimes taking weeks to produce. 3D-printed radar parts, such as a cylindrical array, which provide 360-degree visibility, can be produced within hours versus several days using traditional methods due to the reduced machining and assembly time.
In addition to the production benefits, the relatively low cost of 3D printing materials enable researchers to test multiple versions of parts at minimal overhead. The perfected prototypes can then be machined using traditional methods. Once a prototype is successfully produced, whether 3D printed or traditionally manufactured, it must undergo rigorous testing before it is used operationally. In early 2019, Anna Stumme submitted a paper comparing 3D-printed parts against traditionally manufactured parts at the Antenna Applications Symposium. She won the student paper contest for her research.
New applications
Stumme and her colleagues are investigating how weight-and-size-constrained applications, such as unmanned aerial vehicles or small ships, can benefit from 3D-printed parts. Many of the 3D prototypes are printed using lightweight nylon in NRL’s Laboratory for Autonomous Systems Research facility. Once the part is printed, it undergoes a process called electroplating.
During the electroplating process, a thin coat of metal is applied to the printed part. Electroplating provides a conductive surface for the device to radiate as intended; something that isn’t feasible with plastic alone. The result is a lightweight prototype that can then be evaluated for a variety of attributes, such as surface roughness - a major factor in the functionality of antenna elements.
Stumme collaborates with NRL materials scientists from across NRL, who perform critical surface roughness characterization. Surface roughness characterization provides an assessment of the coating on an antenna, and the impact toughness has on its performance.
Surface roughness is important for waveguides and antennas because it can cause scattering losses and result in a less efficient antenna. Antennas radiate and receive waves. So if a wave runs along a rough surface it is distorted and the energy may not go where it wanted to go.
Nick Charipar and his team, part of NRL’s Material Science & Technology Division, prototype 3D printed parts for the NRL’s Radar Division. Once the part is created, researchers investigate how the material features impact the functionality of the radar. Each 3D printer has unique characteristics that may alter product performance. If researchers can figure out the optimal parameters for specific 3D printed parts, Stumme and her colleagues agree ships could become self-reliant for those critical parts anywhere in the world.
Next steps
Despite current COVID-19 restrictions, research at NRL continues to thrive from a distance. Later this year, Stumme and her colleagues plan to demonstrate new prototype cylindrical array apertures for an X-band surveillance radar demonstration in a laboratory setting. The X-band surveillance radar is designed to search the area surrounding a particular platform, such as a ship. They are exploring integrating cylindrical arrays into the masts of smaller vessels using microwave photonics and optical fibers.
Cylindrical arrays are advantageous because they provide full 360-degree visibility. Optical fibers are valuable because they can allow for long separations between the antenna itself and where the processing is conducted.
Using optical fibers reduces the number of components required on a Navy ship’s mast, further reducing heat and weight constraints. The demonstration will include testing traditionally manufactured and 3D printed versions of the array to compare performance. Stumme designed both versions.
In 2021, the team is scheduled to perform field testing on the prototype. The demonstration will be in the final year of their four-year effort to make the array more practical to use on smaller platforms and show how to use arrays easily with optical fibers. Funding for the research is provided by NRL base funding.
