De-Embedded S-Parameters to Characterize Surface Mount RF Components
The explosive growth of wireless, hand-held devices requires circuit designs that utilize surface-mount components, such as amplifiers, filters, and mixers. These components require accurate characterization so that they can be rapidly integrated into designs that employ high component density and multi-layered printed circuit boards (PCBs).
When measuring a surface-mount device, a test fixture is required to transition the test equipment's coaxial connectors to the non-coaxial environment of the device under test. The equipment is often calibrated outside the test fixture and the uncharacterized fixture introduces a large measurement uncertainty to the device performance. Through proper modeling of the test fixture, a mathematical calculation can be performed to remove the effects of this transition from the measurement. This fixture "de-embedding" procedure can produce very accurate measurements of the non-coaxial device under test, without complex fixturing and non-coaxial calibration standards.
This paper provides the RF engineer with a brief tutorial of the types of de-embedding and calibration procedures available for measuring and characterizing surface mount devices. It describes the mathematical process of S-parameter de-embedding using a series of two-port networks that represent the test fixture and measured data.