Study On Microwave Scattering And Propagation Of Terain And Sea And Their Applications To Radar And Remote Sensing

Microwave scattering and propagation characteristics of terrain and sea surfaces are paid more attention in the design and performance analysis of radar and remote sensing. These problems are studied and some applications are discussed as follows: The first ground-based multi-band polarization microwave scatterometer, the first L- band single-channel HH polarization airborne radar and the first L-band multi-channel VV polarization airborne radar are developed in China to meet the needs for the theory study and applications. The specifications of system, calibration, measurement and analysis methods are introduced. Many tests have been made on the ground and in the air with these measurement systems and provide this paper and other research subjects with a lot of valuable data. The calibration of scatterometer and radar system is a key problem to the precision and reliability for the determination of scattering coefficient from experiment data. The absolute calibration techniques of scatterometer and airborne clutter radar are analyzed by using passive and active calibrators. The data precision is within 2.0dB or 2.5dB by means of error modification. The measurement methods of scattering coefficient in time and frequency domain are studied. Four kinds of terrain clutter and some models are analyzed. The scattering characteristics of sea surfaces are observed with long-term, multi-state, multi-band, multi-polarization, and multi-angle using the same one scatterometer for the first time. The obtained data are processed and compared with Rayleigh distribution, Log-normal distribution, Rice distribution, Weilbull distribution and K distribution. The general relation between clutter and the parameters of radar and sea states is obtained. Multi-course and multi-sortie airborne clutter measurement of many kinds of typical terrain and southeast sea area in China has been carried out. The statistical characteristics for different kinds of terrain and sea clutter are given and the model parameters are extracted. The Kirchhoff approximation based on fractal model and Gaussian model (Gaussian or exponent correlation) are analyzed and compared with constant y model, exponent model and experiment data. The data and results derived are more important to the choice of flight-test area of our AEW radar and to the test of airborne radar performance. Combined the Split-step Fourier transform of parabola equation (PE) with non-linear dynamic model of space-time 2D fractal terrain and sea surfaces, statistical relationships between propagation factors and fractal parameters are calculated and analyzed considering the exponent model of atmospheric refractive index. The results show that the field can vary as high as 20dB. The variation becomes stronger and shows some III fractal characters for longer transmitter-receiver distance and altitude difference. The production and evolvement of terrain and sea scattering may be explained from non-linear chaos and the geometry may be described with fractal. The chaos and fractal characteristics are analyzed using the data measured by scatterometer and airborne radar. Lyapunov index, correlation dimension, spectral dimension, fractal or multi-fractal parameters are calculated. It is pointed out for the first time that the clutters also show chaos and fracta~ character at larger grazing angles, multi-band, cross-polarization and in the conditions of airborne measurement, but their characters may be different. This is important to t...