Research On Improvements Of Microwave Radiometer’s Stability

Stability plays a vital role in measuring microwave radiometer s performances. Thisthesis is based on simplifying hardware complexity of radiometer s system. According todigital compensation theory, the research purpose is mainly about how to restrain thesystem gain s ups and downs and noise fluctuations of radiometer. Experiments are doneto test the improved millimeter-wave digital compensatory radiometer system by themeans of measuring the radiometer system s stability.At first， found on analyzing bad influences to the output signal caused byradiometer s gain and noise fluctuations, an advanced software compensatory algorithmare deduced and validated, from the point of mathematical view, for eliminating the gainand noise fluctuations. With the help of the error correction on compensation theory, theimproved compensatory method can make beneficial additions to stability performance ofthe radiometer s system.Secondly, a new type of low-frequency synchronous detection circuit has beendesigned, which compounds circuitry functions of square-wave oscillator, operationalamplifier, switch controller and voltage converter, aiming at reforming the stability and thecapability of Dicke microwave radiometer hardware circuitry. After the improvementshave been taken, the modulation performance of the radiometer s detector is good enoughto meet the demand of highly integrated circuit module.Experiments are last-mentioned. According to the functions of microwave radiometersystem, a single-chip circuitry of measurement and control has been used to accomplishthe digital compensation through programming software modules. Meanwhile, in order tomeet the test requirements, a kind of PC control communication software has beenadopted for recording the data of radiometer s measurement and calculation, which makesit easier to complete the experiment of measuring the stability. By further analyzing theexperimental data, it is concluded that the improved digital compensatory method canstabilize the radiometer s output signal, with less fluctuations of the system s gain andnoise, and make the long-term stability of radiometer s performance much better.