Transition Circuit Boards

Circuit boards were needed to bring the signal from the SMA connectors to the QMMIC. These circuits have microstrip at one end to solder to the SMA pin, and CPW at the other end to wire bond to the QMMIC chip. They were fabricated on 0.010" Duroid to roughly match the thickness and dielectric constant the QMMIC chip. Ground plane spacings for 50 Ohm CPW were calculated for center conductor widths ranging from the QMMIC CPW value to that of 50 Ohm microstrip. These values were used to lay out the transition circuit board. Via holes bring the ground current up to the top plane. The EM simulator Momentum predicted reflections below -34 dB in the 4 to 8 GHz band for the transitions.

Microstrip to CPW Transition