Repeatability Issues for De-Embedding Microstrip Discontinuity S-Parameter Measurements by the TSD Technique

Connection repeatability is a critical issue for millimeter-wave de-embedding. Regardless of the de-embedding scheme, the electrical connections made to standards used for fixture characterization must be repeatable and similar to those made to the device under test. Key repeatability issues related to the measurement of microstrip discontinuities with the "TSD" (thru-short-delay) technique are discussed. These include the repeatability of coax/microstrip connections, microstrip/microstrip interconnects, microstrip line fabrication and substrate mounting, and the electrical characteristics of coax-to-microstrip transitions (launchers). Each of these issues has been explored experimentally and the results are presented for two types of coaxial-to-microstrip test fixtures: one usable from 2 to 18GHz, and the other from 2 to 40GHz.