Performance Improvement of NRD Guide / Microstrip Line Transition at 60 GHz

Performance of an NRD guide / microstrip line transition was investigated from the viewpoints of easy fabrication and reliability. At first, unwanted surface waves generating in the dielectric substrate in millimeter wavelengths was suppressed by using a low permittivity dielectric substrate instead of a high permittivity one used in the previously- fabricated microstrip line. Because it was necessary to solder an L-shaped mount made from a metal block together with a ground plane of the microstrip line in die attachment process, performance of the transition had poor reliability due to non-uniform application of the solder. To overcome such difficulty, a new type of NRD guide / microstrip line transition was devised next, and thus the fabrication process and the reproducibility were improved.