A novel procedure for characterization of multiport high-speed balanced devices
2006 IEEE International Symposium on Electromagnetic Compatibility, 2006. EMC 2006.
Accurately measuring the frequency response of highspeed differential devices using a VNA can be exceptionally challenging for two reasons. First, instrument test ports and calibration artifacts have coaxial electrical interfaces, while typical devices needing to be measured do not. Second, differential devices generally have some amount of electrical coupling between pair halves (test ports), but all calibration algorithms assume isolation between test ports. Various approaches have been
... ed and employed, but usually with unsatisfactory results. The incompatible interface issue is addressed by using test fixtures. However, the challenge of building and compensating for test fixtures becomes increasingly difficult as industry requires faster data transmission. Ideally, test fixtures are electrically transparent, but since this is not the case in practice, a method of compensating for its effects must be used to be able to obtain accurate measured data on the device of interest. The technique discussed in this paper describes a method of characterizing the test fixture that is simple and highly effective, yet requires a minimal number of assumptions. The method only requires that the input and output fixtures be mirror images, and that they be cascaded to form a THRU standard that can be measured. The THRU standard is connected directly to a traceable coaxial test port of a multiport VNA. Accuracy is extremely good because the traces on the fixture can exactly replicate the DUT test condition, there are no non-coaxial on-board standards, and traceable instrument grade coaxial connecters can be deployed on the fixture.