Highly Accurate Radar Cross Section and Transfer Function Measurement of a Digital Calibration Transponder without known Reference - Part II: Uncertainty Estimation and Validation

Abstract

Active Radar Calibrators (ARC), also known as calibration transponders, are often used as reference targets for absolute radiometric calibration of radar systems due to their large Radar Cross Section (RCS). Before such a transponder can be used as a reference target, the hardware itself has to be calibrated. A novel method, called three-transponder-method, was proposed some years ago to allow RCS calibration of digital transponders without using any known RCS target as reference. The first part of this paper refined said technique and presented the measurement setup as well as the results of a comprehensive measurement campaign performed to calibrate a single digital transponder. In this part of the paper, the results are validated and a comprehensive uncertainty analysis is performed to estimate the total RCS uncertainty associated with the presented measurement data. This uncertainty analysis follows the international standard "Guide to the expression of uncertainty in measurement" (GUM) and will derive expressions for all major sources of uncertainty. For the validation, the measurement results will be compared with full-wave electromagnetic simulations of trihedral corner reflectors and show excellent agreement between simulation and measurement.