A simple CAD-based method to develop and evaluate calibration standards

The vector network analyzer (VNA) is one of the tools most commonly used by microwave engineers for component characterization and modeling. It allows the reflection and transmission coefficients to be quickly and efficiently measured. With any VNA measurement, it is important for the engineer to know and understand the error associated with a measurement. A key component of this measurement error comes from the quality of the VNA calibration. In this article, we review the fundamentals of VNA calibration and the 12-term error model. We outline the basic short-open-load-through (SOLT) calibration technique and a simple computer-aided design (CAD)-driven program to aid in the extraction and evaluation of SOLT calibration coefficients. The CAD-driven technique is useful because it allows calibration accuracy to be efficiently evaluated over frequency. It also allows for the systematic evaluation of process variation effects on the accuracy of on-wafer-calibration (OWC).