研究目的
To investigate the dependence of the backscattering coefficient on the soil moisture and vegetation properties on the ground over a wide frequency range (1 – 10 GHz) for at least a full annual cycle.
研究成果
The scatterometer setup and calibration procedure have been successfully described, with the measured radar cross section of a dihedral reflector matching the theoretical model for 3 – 10 GHz after calibration. Future steps include analyzing the first measurements and comparing them to in-situ measurements of soil moisture and vegetation changes.
研究不足
The temperature-induced systematic error in the radar return and the applicability limits of the theoretical models at lower frequencies (1-3 GHz) due to the wavelength approaching the physical dimensions of the calibration standards.
1：Experimental Design and Method Selection:
The scatterometer setup includes a vector network analyzer (VNA), two dual polarization broadband gain horn antennas, and four phase stable coax cables. The VNA measures the full polarimetric backscattering coefficient over a wide frequency range.
2：Sample Selection and Data Sources:
The study area is located near Maqu, a city in the northeastern part of the Tibetan Plateau, with the dominant land cover being alpine meadow.
3：List of Experimental Equipment and Materials:
VNA type PNA-L 5232A, dual polarization broadband gain horn antennas type BBHX9120LF, and phase stable coax cables type Succoflex SF104PEA.
4：Experimental Procedures and Operational Workflow:
The scatterometer was calibrated using metal calibration standards (a sphere, a rectangular plate, and a dihedral reflector) to derive the backscattering coefficient.
5：Data Analysis Methods:
The backscattering coefficient is derived by accounting for the frequency-dependent antenna radiation pattern and the site geometry, with fading dealt with by using frequency agility techniques.
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