Impedance Matching Designs and Measurements of End-Launched Connectors Used in Multilayer Printed Circuit Boards

This paper presents the impedance matching designs with measurement verifications for end-launched connectors used in multilayer printed circuit boards (PCBs). The multilayer PCBs lead to thinner thicknesses of all layers, making narrower widths of the transmission lines (TLs) to satisfy the 50 Ω requirement of the TL characteristic impedance. However, the center pin diameter of end-launched connectors cannot be shrunk as well, then the associated soldering pads become too wide causing impedance mismatched problems. The launched area of the PCB can be modified by blanking the layer-2 ground plane with proper transitions to the complete ground plane to improve the impedance matching, thereby the same soldering pad design with the center pin of the end-launched connector is maintained. To verify the proposed approach, the original and improved designs of the PCB end-launched connector layouts using grounded coplanar waveguides (GCPWs) with solder masks are fabricated and measured with the multiline Thru-Reflect-Line (TRL) calibration to extract the reflection/transmission coefficients of the end-launched transitions, with comparisons of the simulation data for GCPW lines with connectors in two end-launched area designs, from 0.1 GHz to 10 GHz.