Atmospheric Millimeter-wave Radiation Characteristics And Applied Research

This paper is emphasized on the study of atmospheric millimeter-wave radiation characteristics and applications.Oxygen and water vapor Liebe absorption model and atmospheric Millimetre-Wave Propagation Model (MPM) are derived. The sky brightness temperature is simulated at millimeter-wave band and measured with a W-band radiometer. Radiometer calibration method based on the atmospheric transport model is studied.Firstly, three common forms of atmospheric absorption lines function and the Liebe absorption spectra mode are discussed in detail. Absorption spectra is divided into local line absorption and contimuum absorption in this mode,the absorption spectra of oxygen is made up of 44-line absorption and non-resonant absorption, absorption spectra of water vapor is made up of 29-line absorption and the far wing absorption. Absorption spectrum curve of oxygen and water vapor are simulated in the millimeter-wave band, and the absorption rate data of oxygen are calculated at 50-70GHz band.Secondly, the atmospheric millimeter wave propagation model (MPM) is studied in this paper, which is complex refractivity model.MPM calculation methods of atmospheric attenuation rate and the sky brightness temperature are derived under different weather conditions.The line spectrum of oxygen and water vapor, non-resonant spectrum of dry air and water vapor continuum absorption spectrum are mainly considered in clear air;suspended water droplets refractivity founded on clear air is added due to cloud conditions;and refractivity of rain effected by point rainfall rates is added based on the cloud conditions under rain conditions.With calculated attenuation rate of different weather conditions, sky brightness temperature data are obtained respectively under different angles at 3mm band, 5mm band and 8mm band. Implicit regularity is revealed due to comparative analysis.The feasibility of MPM is verified on account of the measured sky temperature data of clear air.Finally, the tipping angle calibration is studied for a W-band K-factor millimeter wave radiometer based on the ground, and a W-band K-factor radiometer calibration process is discussed. Sky brightness temperature is measured at W-band and data are processed and analysed in view of this calibration method.