Design and optimization of coax-to-microstrip transition and through-hole signal via on multilayer printed circuit boards

The design of coax-to-microstrip transition and signal via through a multilayer printed circuited board (PCB) is presented. Extensive design and parameterization study was performed using HFSS, a commercial finite element tool from Ansoft. The coax-to-microstrip transition and the signal via were individually optimized and subsequently cascaded. Various test cases were fabricated and experimentally characterized. Return loss and insertion loss for an optimized back-to-back coax-to- microstrip transition was better than 20 dB and 1.5 dB respectively up to 12 GHz. Additionally, the return loss for two coax-to-microstrip transition and two signals via was better than 12 dB up to 12 GHz. Good correlation between measured and simulated data is obtained.