Radiometer Development of an Agile Digital Detector for RFI Detection and Mitigation on Spaceborne Radiometers

A new type of microwave radiometer detector has been developed that is capable of identifying high and low levels of Radio Frequency Interference (RFI) and of reducing or eliminating its effect on the measured brightness temperatures. The Agile Digital Detector (ADD) digitizes its pre-detection radiometer signal, performs digital sub band filtering, and then measures the first four moments of the signal’s probability density function for each sub band. The second central moment reproduces the square law output of a conventional analog detector. Algorithms that utilize higher order moments are used to detect the presence of RFI. The ADD can discriminate between RFI and natural thermal emission signals using higher order moments of the signal. After detection, the ADD then uses spectral filtering methods to selectively remove the RFI. ADD performance has been experimentally verified in controlled laboratory tests and in a series of ground based and airborne field campaigns. High level RFI is easily identified and removed. Very low level RFI contamination, with power levels as low as the radiometric measurement uncertainty of the radiometer, is also reliably detected and removed. ADD can also be used as a form of RFI ground truth to evaluate the performance of standard RFI algorithms that are based on conventional measurements of the 2 moment only. An algorithm has been developed to detect the presence of RFI with the Aquarius Radiometer. ADD is used to evaluate its performance.