| Characteristic of radar terrain return is very important for R&D of spacebrone/ airbrone radar, remote sensing equipment, and radar altimeter. Scattering coefficient measurement is the most important way to retrieve the characteristic, and the development of the equipment of scattering coefficient measurement, scatterometer, is one of the key techniques of the measurement.An S band radar scatterometer and its implement have been introduced in this dissertation. The scatterometer is designed to work at near vertical incidence with truck mounted. It is a LFMCW system with separated transmit and receive antennas. The post mixer signal of radar return is directly digitalized after amplified and filtered, and then acquiesced and stored in computer by a data acquiescing card. Using the spectrum of the stored post mixer signal, radar parameter and geometric information, scattering coefficient of the target could be calcluted.Calibration is the core different of scatterometer from normal radar, and directly decides the precision of the measurement. The ordinary calibration procedure has been summed up, and a specified calibration procedure for the LFMCW scatterometer has been designed in the dissertation. Two metal balls with known RCS were used in the extern calibration experiment. According the experiment result, the system works properly and has excellent performance. Otherwise, PGA gains and rang measurement also have been calibrated using radar delay line and corner reflector at indoor and outdoor experiment.Finally, scattering coefficient of the crown of big tree was measured with the LFMCW scatterometer, and the data were analyzed. The dissertation also discussed some problems of scattering coefficient measurement with near vertical incidence.In conclusion, the two aspects of following work have been done in the dissertation:First, the development of the scattering coefficient measure equipment. Including:According the measure method designed the whole system and specified its parameters.Designed and implemented the RF front and IF module of the system. Developed post mixer signal acquisition and storage software at PC platform. Second, calibration and measurement method, including:Developed a specified calibration procedure for the equipment. With indoor and outdoor experiment PGA gains and rang measurement have been calibrated, and also absolute calibration have been done with two metal balls.Measured and analyzed scattering coefficient of the crown of big tree. Some problems of scattering coefficient measurement with near vertical incidence were discussed in the end of the dissertation. |
