Improvements to the modelling of radiowave propagation at millimetre wavelengths. In-depth studies are reported on resonance phenomena in the scattering of spherical ice particles, extinction and backscattering properties of clouds and on the absorption and dispersion spectra of atmospheric gases.

摘要

Various physical mechanisms that affect radiowave propagation at millimetreudwavelengths are considered. Current modelling weaknesses are highlighted and newudimproved models or more appropriate modelling approaches are suggested.udInterference and resonance phenomena in the scattering of spherical ice and waterudparticles are reviewed. The long standing problem of the numerous resonancesudobserved in the scattering diagrams of dielectric spheres is answered.udThe spatial structure and the physical characteristics of non-precipitable ice and waterudclouds are reviewed. Extinction and back scattering calculations for a wide variety ofudcloud models over the entire millimetre frequency spectrum are given. Multipleudscattering and the effects of super-large drops in clouds are also dealt with. Theudpotential of a spaceborne instrument in deducing information about the verticaludstructure of various cloud types is examined. Attenuation and reflectivity profilesudresulting from various cloud types are calculated for a nadir pointing fixed beamudmillimetre wave radar operating at 94 GHz.udThe physics and application of the equation of radiative transfer to millimetre waveudpropagation in the earth's atmosphere are given and also is the solution of thisudequation for a typical millimetre wave remote sensing application. The theory ofudgaseous absorption at millimetre wavelengths is presented and an improved modellingudapproach is proposed for the calculation of the absorption and dispersion spectra ofudatmospheric gases. The effects of trace gases on communication systems operating atudhigh altitudes are for the first time reported.udFinally the use of the 60 GHz oxygen absorption band for top-side air trafficudcontrol/navigation and broadband transmission purposes is studied.