Wideband Microstrip to 3-D-Printed Air-Filled Waveguide Transition Using a Radiation Probe

In this letter, a novel wideband microstrip to additively fabricated waveguide transition is presented. The proposed design takes advantage of the flexibility of 3-D printing to realize a highly integrated transition from the microstrip line on a printed circuit board (PCB) to an air-filled waveguide using an additively manufactured radiating probe. The idea is experimentally verified by the realization of an exemplary transition working within the X-band at $f_{0} =10.5$ GHz. The measured performance of the back-to-back transition proves its usefulness and possibility of utilization in highly integrated PCB-waveguide circuits. A PolyJet printing technology with copper electroplating was used in combination with PCB on microwave grade laminate. A bandwidth of $f_{H}/f_{L} =1.8$ was obtained with the impedance match better than 9.5 dB and in-band insertion loss per transition below 1.1 dB.