A Tone-Based Flicker Noise Mitigation Technique for Broadband Digital Microwave Radiometers

High-frequency microwave radiometers with low-noise amplifier (LNA) front-ends commonly suffer from gain instability, or so-called “flicker” noise. This noise has a $1/f$ energy spectrum and hence is also commonly referred to as $1/f$ noise. The effect of this noise on a passive instrument is to degrade its sensitivity and introduce postprocessing calibration errors such as “striping.” In this letter, we present a $1/f$ noise mitigation technique using a combination of single-frequency tone injection and high spectral resolution digital signal detection. This technique can be used in radiometers with sufficient information redundancy so that a limited portion of the detected signal spectrum can be dedicated to noise mitigation. A key requirement of implementing this technique is application specific integrated circuit (ASIC) or field programmable gate array (FPGA)-based spectral decomposition of the radio-frequency energy. A proof-of-concept hardware setup and signal processing steps required to implement such a technique are presented in this letter. Measurements presented here show a reduction up to $87~\%$ in $1/f$ noise energy using this technique and are applicable to airborne and ground-based instruments.