Connector interconnections to transmission lines for 40 Gb/s broadband applications

The electrical performance of Sub-Miniature Coaxial Connector (SMCC) interconnections to transmission lines was investigated in a frequency range up to 50 GHz. A family of test coupons was built to evaluate the following design parameters of SMCC connector interfaces: transmission line structures, solder pad shapes and structures, SMCC connector structures and grounding of the SMCC housing. Electromagnetic 3D full-wave solver (HFSS) was used not only to elucidate the main design factors affecting the electrical performance of the interconnection but also to compare between model results and measured S-parameters. Low-loss SMCC interconnections to well designed Grounded Co-Planar Waveguide (GCPW) and microstrip transmission lines were achieved without significant resonances up to a frequency range of 50 GHz. Grounding between the SMCC connector housing and bottom ground plane of the transmission line was found to be the most critical factor for electrical loss. Transmission line design and connector structure details were also found to have a significant impact on performance.