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Two layer LTCC substrate integrated to rectangular waveguide transition and its application for millimeter‐wave LTCC characterization

In this letter, a new practical approach for designing a millimeter‐wave transition at 76.5 GHz from substrate integrated waveguide (SIW) line on two low temperature cofired ceramics (LTCC) layers to a rectangular waveguide is proposed. To the best of our knowledge, this is the first feasible planar solution to couple a top‐layer SIW exclusively. A very small probe is cut in both layers and inserted into a milled clearance in the metallic waveguide. Shrinkage tolerance is addressed in particular in our design procedure. In addition, multiple back‐to‐back transitions are milled into one fixture and applied to obtain the actual LTCC loss tangent and permittivity. The latter undergoes a strong dispersion. Fabricated circuits are optically analyzed and exhibit a higher shrinkage than expected. Simulation and measurement results show good performances in terms of reflection and transmission. With these features, the proposed solution is able to handle electrically large substrates of around 12λg. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2675–2679, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27167