The impact of ENR and coaxial calibration in accurate on-wafer noise parameter testing for ultra-low noise devices

A revealing case study is presented to explore the impact of excess noise ratio (ENR) and vector network analyzer (VNA) mechanical coaxial calibration on accurate on-wafer noise parameter testing for ultra-low noise devices. On-wafer noise parameter tests were conducted on a GaAs pHEMT device from 2-50 GHz after calibration with three different noise sources. For each, ENR specified from an external calibration service and also with ENR measured internally using vector corrected noise power measurements with appropriate coaxial calibration kits. Initial results show that significant variation in noise parameters, especially Fmin can result from seemingly subtle differences in ENR values as well as coaxial calibration accuracy. Excellent agreement is demonstrated for noise parameter measurements made with the three different noise sources, after using in-house measured ENR values and eliminating the use of a suspect coaxial calibration kit.