Novel design for microstrip to stripline transitions for millimeter-wave application in LTCC

This paper presents two transitions between microstrip and stripline in Low Temperature Co-fired Ceramic technology, including a vertical transition and a coplanar transition for millimeter-wave application. These interconnects are simulated and optimized by a three-dimensional electromagnetic field simulator. Simulation results show that the return loss of microstrip to stripline vertical transition is less than −22 dB, and insertion losses are greater than 0.5 dB up to 35 GHz, and greater than 1 dB up to 40 GHz. Similarly, the return loss of the coplanar transition is less than −32 dB and insertion loss is better than 0.5 dB. LTCC test structures were fabricated and the performance of all transitions was successfully validated by scattering parameter measurements up to 40 GHz.