Millimeterwave LTCC wafer probe-to-stripline transition using transverse inductive slots

A broadband 50Ω CPW-to-stripline transition is presented which is capable of operation up to 70 GHz. This vertical transition into stripline (SL) is fabricated in DuPont 9K7 low-temperature co-fired ceramic (LTCC). It employs inductive slots in the upper SL ground plane and a circular aperture in the lower SL ground plane to tune for best return loss at 60 GHz. It is designed for wafer probing an LTCC module containing an embedded stripline. This vertically compact transition occupies only two layers of nominal 5 mil thick tape. It is also compact in the longitudinal direction, occupying less than 30 mils of longitudinal length. Both simulated and measured s parameter results are shown for back-to-back transitions up to 110 GHz. Measured insertion loss for a single transition is about 0.30 dB near 60 GHz and about 0.40 dB up to 100 GHz.