A Horizontal Gradual Ultra-Low-Reflection Stripline to Grounded Coplanar Waveguide Transition

In this letter, a horizontal gradual low-reflection stripline (SL) to ground coplanar waveguide (GCPW) transition is proposed, which consists of a gradient SL transition with a non-linear gradient slot and a GCPW transition with two extra ground plates. To measure performance of the proposed SL-to-GCPW transition, a back-to-back GCPW-SL-GCPW structure is designed and fabricated under low temperature co-fired ceramic (LTCC) process. Simulation and measurement results agree well. The results show the bandwidth of the proposed transition up to 110GHz. From DC to 67 GHz, the return loss and insertion loss are larger than 15 dB and less than 0.8 dB, respectively.