Design And Error Analysis Of K-Band Microwave Radiometer

Microwave radiometer is a passive remote sensing atmospheric detection device.The ground-based microwave radiometer detects the brightness temperature of multiple bands.Meteorological factors such as atmospheric temperature,humidity and liquid water content were obtained by inversion.During the comparative observation of the existing commercial ground-based microwave radiometers,it was found that the detection results of different manufacturers are very different and the same model and different equipment also have significant differences.This brings great difficulties to the application of microwave radiometer data.It is necessary to improve the design of the radiometer or eliminate the source of the error of the radiometer to obtain a stable and standardized instrument.The error comes from the structure of the radiometer itself and its inversion algorithm.It designs and simulates the devices at all levels in the K-band receiver system of the radiometer,and performs power spectrum simulation on the whole under certain environmental conditions.The results show that the receiver has the greatest influence on the brightness temperature inversion is the frequency selection characteristics of the intermediate frequency amplifier and the intermediate frequency filter before the amplifier.When the bandwidth of the input power spectrum of the intermediate frequency amplifier is close to the detection power spectrum bandwidth,it will cause a W-shaped deformed power spectrum.The second is the gain unevenness of the device,and the least is the impedance mismatch between the devices.Impedance mismatch is the source of differences between different devices of the same model.In the antenna system,the low antenna efficiency will cause the nonlinearity of the bright temperature inversion,and the temperature change of the feed will have a greater impact on the inversion result.The development direction of microwave radiometers will inevitably be higher integration and imaging,and the RF structure is monolithically integrated using MMIC technology.The imaging methods are divided into focal plane imaging and scanning imaging,and the development of radiometer architecture is divided into direct detection architecture and spectrum analysis architecture.