SLM Waveguide Attenuation

January 31, 2017



One of the first questions I am often asked about Optisys’ printed waveguide parts is how the insertion loss compares with equivalent brazed or machined parts.  Although we’ve tested equivalent parts in the past with promising results, those proprietary designs could not be shared.  Further, as complex assemblies, there were other issues that obscured the insertion loss.  To answer the insertion loss question, Optisys printed straight WR42 waveguide and tested against machined and COTS (Commercial Off The Shelf) waveguide pieces.  The formal test results and analysis have been submitted to the 2017 IEEE International Microwave Symposium (IMS).  To be included in the conference, submissions must be exclusive to IMS or published elsewhere until after the conference.  Before the conference though, we can summarize our testing and results.


We tested 6 dimensionally identical pieces of WR42 – 2 COTS, 2 SLM printed and 2 machined from aluminum (with the seam along the upper H-plane corner).  Straight WR42 waveguide was selected for the test for the following reasons:


1.  Straight waveguide is simple.

2.  K-Band is of significant interest for satellite communications.

3.  Eliminates SLM specific advantages, like

a. Reduced path length with geometry optimization

b. Elimination of internal connections

c. Elimination of assembly errors

d. Internal features to enhance performance


Testing consisted of measuring S21 over the frequency range of 18.0 – 26.5 GHz.  In addition to measuring individual pieces of waveguide, assemblies were measured and the relative insertion loss used to calculate the loss of individual parts.  Preliminary results can be seen in this Optisys white paper available on the downloads page  – and additional plots and analysis are included in the submitted paper.  The primary conclusions are that:


1.  The printed waveguide insertion loss is comparable to machined aluminum.

2.  There is less variability between the printed waveguides than the machined.


For the complete paper and test results, watch for our submission to 2017 IMS titled “Selective Laser Melting Aluminum Waveguide Attenuation at K-Band.”  See you in Honolulu in June.



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