3D printing has revolutionized the production of passive waveguide and antenna components. This manufacturing technology enables the combination, for the first time, of low fabrication cost, short fabrication cycles, reduced mass and high performance in a monolithic assembly. If the building material is a metal alloy, the fabricated device is already RF conductive and can withstand demanding environmental conditions such as found in space, naval or airborne applications. 3D printing is now accepted by the aerospace and electronic warfare industry and its use is expected to keep growing in the coming years.
SWISSto12 pioneered the development of metal 3D printed passive components. The company developed a proprietary chemical treatment to reduce the surface roughness of the printed parts. Without this treatment, the surface finish is too rough, which results in high insertion loss. The SWISSto12 process multiplies conductivity by a factor of 3x to 5x, depending on the material selected for the finish. SWISSto12 offers two finishing options: raw aluminum and copper-silver.
KA-BAND DUAL-POLARIZED DIPLEXERS FOR SATCOM
Ka-Band dual-polarized diplexers (DPDs) are five-port waveguide devices used in satellite communications to feed an antenna aperture, typically a feed horn, with two circular polarizations (RHCP and LHCP) and two frequency bands. The uplink is around 30 GHz, the downlink around 20 GHz. A DPD requires precise manufacturing to meet Ka-Band performance requirements, yet the satcom industry is pushing for cost reduction because these systems often target the final user or are integrated in multi-beam arrays in quantities of hundreds. SWISSto12’s 3D printing process simultaneously meets both requirements: performance and cost.
Figure 1 Basic DPD with ports on the bottom (a) and a multi-beam GEO cluster (b).
Figure 2 Measured return loss, in-band isolation and Tx-Rx isolation of four identical DPDs (option 1 in Table 1).
Examples of SWISSto12 DPDs are shown in Figure 1. The DPD consists of two diplexers to combine and separate the two frequency bands and one dual-band septum polarizer for converting linear to circular polarization. Using 3D printing to fabricate these building blocks achieves the required fabrication tolerances and reduced cost. Further cost optimization is possible since the devices can be produced in quantity, up to 50 per printing run. 3D printing of these DPD building blocks enables customization of the interfaces and footprint without significant non-recurring engineering.
SWISSto12 currently offers DPD options for two downlink and uplink bands (see Table 1). Each DPD is available with a square or circular flange, and each has two size options: standard (35 x 35 mm footprint) and compact (22 x 22 mm). Figure 2 shows the return loss, in-band isolation and isolation between transmit (Tx) and receive (Rx) measured at the rectangular ports of four identical samples (option 1 in the table). The performance is comparable to conventionally fabricated DPDs and highly repeatable, since the parts do not require any assembly. Figure 3 shows the cross-polarization discrimination of a DPD with a monolithically integrated antenna. Highlighting this point, other components such as the antenna or a monopulse tracker can be added to the DPD without significantly increasing fabrication cost.
Figure 3 Measured cross-polarization of the DPD with integrated feed horn (option 2 in Table 1).
THE SWISSto12 PROCESS
SWISSto12’s process comprises the following steps:
- 3D printing using selective laser melting followed by thermal cycling for stress relief
- Basic post-processing: cleaning and machining the mechanical interfaces
- Surface treatment: chemical polishing for roughness reduction and plating. SWISSto12 products are always chemically treated for roughness reduction and insertion loss improvement. The basic process provides competitive loss, while the copper-silver finish process provides the lowest possible loss.
- Assembly and RF test. Assembly may include helicoils, sealing or integration into a more complex system. Various tests can be performed, depending on customer requirements.
SWISSto12 products, including DPDs, are currently found on multiple platforms, from large GEO satellites to small CubeSats in space and navy ships on Earth. The 3D fabrication process has been qualified to MIL and GEO standards and complies with the European Cooperation for Space Standardization laser powder bed fusion techniques for space applications, issued in 2021.
SWISSto12 SA
Renens, Switzerland
www.swissto12.com
sales@swissto12.ch