Abstract: A novel ridge substrate integrated waveguide using LTCC technology to microstrip transition is presented in this paper. The design ideas of the conventional ridge-waveguide to microstrip transition are applied to achieve the SIW based on LTCC technology to Rogers5880 substrate microstrip transition. And it realizes broadband transition. According to the simulated results, its return loss S11 is less than-15dB and insertion loss is better than 0.2dB, over the specified frequency range from 25.2GHz to 40 GHz.