Uncertainty of Radiometer Calibration Loads and Its Impact on Radiometric Measurements

Abstract

<div> We present an uncertainty analysis of radiometer calibration.</div> <div> The procedure can be used to determine the uncertainty</div> <div> in the nominal brightness temperature of the unknown scene. A</div> <div> total power radiometer requires frequent calibration with known</div> <div> reference loads that are connected to the radiometer. Our analysis</div> <div> includes uncertainties from the radiometer calibration loads and</div> <div> from the connecting network (CN) that is required to multiplex</div> <div> calibration loads and scene to the radiometer input. We show the</div> <div> design and analysis of three calibration loads and how their uncertainties</div> <div> propagate from load terminals to the radiometer calibration</div> <div> plane and to the scene. All three loads, including a cryogenic</div> <div> load, are simple, inexpensive, and show great stability and</div> <div> accuracy. We give an uncertainty calculation example for our three</div> <div> calibration loads and for the CN. We validate our model and the</div> <div> long-term stability of the loads through measurements. The analysis</div> <div> is done at 52 GHz, but the analysis and the construction of the</div> <div> loads are generic and easily scalable to other frequencies.</div>