Algorithm To Retrieve Precipitation And Antenna Study From Synthetic Aperture Radar

Not only does precipitation directly affect the ability of human beings to unitilze fresh water resources such as agricultural irrigation, flood control, drought response and fresh water supplies, but also it playes an important role in energy transfer and biogeochemical cycle. Therefore, precise measurement of the precipitation has a great significance on weather forecast, disaster prevention and mitigation, and industrial and agricultural production. There are some strengths like strong penetrating, high-resolution, all-weather and day and night capabilities to X-band synthetic aperture radar(X-SAR). So X-SAR can detect two dimensional distribution of global precipitation, and retrieve more characteristics of precipitation and cloud, and bring the investment benefit of SAR. Hence, it has the theoretical and the practical significance in utilizing X-SAR measuring precipitation. This paper mainly researches principle and retrieval algorithm of precipitation measurement with SAR, and antennas of SAR. The main contents are as follows:First of all, the paper studies the basic principles of precipitation measurement with SAR. Related concepts are also introduced; for instance, the resolution of SAR and the three-dimensional and volume resolution of rainfall measurement with SAR. The paper also provides analyses on scattering and attenuation of precipitation and cloud, and the signal to noise ratio(SNR) and signal to clutter ratio(SCR).Then the paper establishes the normalized radar cross sections(NRCS) model. The NRCS, σSAR, consists of scattering from the surface, σsrf, and scattering by the precipitation, σvol. This paper also studies precipitation spatial distribution models. The 2D precipitation distributions can be decomposed into independent horizontal and vertical distribution function. The paper makes analyses on echo path in each region of precipitation and cloud, and simulates the NRCS values of SAR.And then the paper reviews the model-oriented statistical(MOS) retrieval algorithm. The model-oriented statistical and volterra integration retrieval algorithm(MOSVI) can be presented based on the MOS algorithm. We verify the MOSVI algorithm by simulation. Simulation results show that the proposed algorithm is effective and simple, and can save nearly half of time than MOS. One application of SAR data is also discussed, which retrieves precipitation information of an area of the South China Sea.At last, the paper researches graphene antenna of SAR. In microwave to THz band, electromagnetic properties of graphene are introduced. Graphene has attracted tremendous interest as antenna of spaceborne SAR thanks to its unique thermal, mechanical and electronic properties, namely, negligible quality, excellent mechanical property, thermal stability and tunable electrical conductivity. This paper also designes and simulates ultra-wideband and frequency-reconfigurable graphene-based antennas. The ultra-wideband antenna works at 9.09 GHz, and has achieved a-10 d B impedance bandwidth over 33%. The frequency-reconfigurable antenna works at 9.48 GHz, 9.49 GHz, 9.57 GHz, 9.65 GHz and 9.79 GHz. It has achieved a-10 d B impedance bandwidth over 30% at every resonant frequency.