CPW to stripline transitions in LTCC for millimeter-wave applications

A novel additional intermediate ground plane structure is proposed in this paper to improve the RF performance of the grounded coplanar waveguide (GCPW) to stripline vertical transition. The ground plane is placed in an inner layer to reduce the distance between the upper and lower grounds, making the approximate impedance of GCPW close to 50 Ω. Meanwhile, with another additional pad in the inner layer, the inductive effect of the transition can be compensated and improvement has been achieved from 55 GHz to 70 GHz. The presented design was simulated and validated by measurements.