Electromagnetically coupled coplanar waveguide to stripline transition in LTCC technology

A coplanar waveguide-to-stripline signal transition based on electromagnetic coupling principle is presented in this paper. The signal transition is designed in low temperature co-fired ceramic (LTCC) technology for integration in a 122 GHz radar System-in-Package (SiP) design. Simulation results of the signal transition, in back-to-back configuration, show an operational bandwidth of 114.5 to 132 GHz i.e. 14.2% relative bandwidth. A manufactured prototype of the signal transition was measured in the frequency range of 110 to 170 GHz using coplanar waveguide probes. The measured insertion loss S 21 is < 2 dB from 120.5 to 135 GHz for the single-ended transition. X-ray images of the manufactured prototype are shown to highlight the manufacturing errors. The simulation model is modified on the basis of X-ray analysis and a good agreement between the modified simulation and the measurement result is achieved.