First metal 3D printed satellite RF filter is flight ready

Airbus Defence and Space has partnered with 3D Systems to produce an industry first, a 3D printed radio frequency (RF) filter tested and validated for use in commercial telecommunications satellites.

The 3D printed RF filter designed by Airbus Defence and Space integrated into the satellite payload. (Photo: Airbus Defence and Space)

Metal RF or waveguide filters have a long history with space communication efforts. The filters allow frequencies from selected channels to pass through and rejecting those from signals outside those channels. High-capacity satellites can have up to 500 RF filters and more than 600 waveguides, many of which are custom-designed to handle specific frequencies.

The 3D Systems ProX DMP 320 3D printer used in the Airbus RF filter project enables manufacturers to consolidate parts, improve functionality with shapes and surfaces not possible to manufacture via traditional means, reduce production time and lower costs for customized designs, and decrease weight while maintaining or improving material strength.

The Airbus Defence and Space project was 3D Systems Leuven’s first foray into RF filters.

The Airbus Defence and Space RF filter project demonstrates the ability of 3D printing to enable new design innovation for aerospace parts that haven’t changed appreciably in decades.

RF filters are traditionally designed based on libraries of standardized elements. Shapes and connections are dictated by typical manufacturing processes such as milling and spark eroding. This means that cavities for RF filters typically need to be machined from two halves bolted together, increasing weight, adding an assembly step to production time, and requires extra quality assessment.

Designing the parts for 3D printing enabled Airbus Defence and Space to explore complex geometries at no additional manufacturing cost.

CST MWS, a standard 3D electromagnetic simulation software tool, was used to design the 3D printed RF filters. The increased manufacturing flexibility enabled by 3D printing led to a design using a depressed super-ellipsoidal cavity. The unique shaping helped to channel RF currents and deliver the required tradeoffs between Q factor—a measure of a waveguide’s efficiency based on energy lost—and rejection of out-of-band signals.

Initially, the different surface topology in 3D printed metal parts was thought to be an issue, but extensive testing by Airbus Defence and Space eliminated those concerns.

Three aluminum samples printed on the ProX DMP 320 using different processing paths were tested by Airbus Defence and Space at its Stevenage facilities. Tests mimicked conditions the parts would face during launch and orbit, including vibration, shock and thermal situations such as temperature extremes and vacuum conditions.

All three samples met or exceeded requirements, with the best performance coming from a filter that was silver-plated via an electrolytic process.