Optimised Hot-Via Transition with 20 dB Return Loss for MMIC Packaging from DC to 110 GHz

A hot-via transition from a monolithic microwave integrated circuit (MMIC) to a printed circuit board (PCB) has been developed with a measured back-to-back insertion loss less than 0.88 dB and return loss higher than 20 dB from dc to 110 GHz. Two techniques are proposed to extend the maximum operating frequency of the microstrip to grounded coplanar waveguide (GCPW) transition. An oversized microstrip line is used on the MMIC to increase capacitance, and a critical return path via in the PCB is positioned near the edge of the hot-via gap to lower inductance. Both techniques improve the maximum operating frequency to 110 GHz for a transition with return loss better than 20 dB and insertion loss of 0.39 dB. To the authors' best knowledge, this MMIC packaging technique demonstrates the highest bandwidth achieved for a dc connected hot-via transition with less than 1 dB back-to-back insertion loss.