| The Global Navigation Satellite System(GNSS)was designed to provide global navigation,positioning,and timing services,but it could also be used for remote sensing applications.The technology of employing the reflected signals to monitor the surface of earth is called GNSS-Reflectometry(GNSS-R).And now the GNSS-R technology is widely applied for remote sensing observations such as sea surface height measurement,sea surface wind measurement,sea ice monitoring,and vegetation detection.Compared with traditional remote sensing methods,GNSS-R technology has several advantages including all-weather,low cost,high resolution,and wide coverage.Consequently,the GNSS-R technology is a research hotspot in the field of GNSS.Sea ice is an important component in terms of global climate,and it also has a significant impact on human production practices.Hence,this paper focuses on applying the GNSS-R technology to the field of sea monitoring,and the signal processing software system of a GNSS-R sea ice monitoring instrument is designed,based on DSP+FPGA structure.Firstly,this paper introduces the domestic and foreign research status in regard of GNSS-R equipment development and related experiments in the field of sea ice monitoring.Subsequently,based on basic principles of the GNSS-R,the sea ice reflection model is established,and simulation experiments of reflected signals received by multi-polarized antennas are carried out.Moreover,some advantages about exploiting multi-polarized signals in sea ice detection are also described.A signal processing software system is designed and described in this paper.It is designed based on modular design and divided into two parts: direct processing module and reflection processing module.The direct module is used for the signal acquisition,tracking process and positioning solution,and the reflection module is used to correlate the reflected signal with the local code under multi-level delay to obtain the correlation power curve and store the data for subsequent sea ice inversion.And then functional simulation is conducted.In addition,taking into account the modulation characteristics and conventional processing methods concerned with the Beidou-3 B1 C signals,this paper proposes and implements a B1I-assisted processing method for B1 C reflected signals.Compared with conventional processing methods,this new method reduces the consumption of hardware resources and requires less signal-processing time.Finally,based on all above-mentioned researches and work,a preliminary experiment concerned with the GNSS-R sea ice monitoring instrument is performed through the shore-based platform.The positioning function,reflection correlation power output,and the reception and processing functions of the B1 C reflection signal are validated in this experiment.It proves that the signal processing software system is working well.This new instrument is supposed to correct and plays an important role in subsequent researches and applications. |
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