Multifunctional Scatterometer System for Measuring Physical Oceanographic Parameters Using Range-Doppler FMCW Radar
A multifunctional scatterometer system and optimized radar signal processing for simultaneous observation of various physical oceanographic parameters are described in this paper. Existing observation methods with microwave remote sensing techniques generally use several separate systems such as sca...
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| Format: | Article |
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MDPI AG
2022-04-01
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| Series: | Sensors |
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| Online Access: | https://www.mdpi.com/1424-8220/22/8/2890 |
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| author | Ji-Hwan Hwang Duk-jin Kim Ki-Mook Kang |
| author_facet | Ji-Hwan Hwang Duk-jin Kim Ki-Mook Kang |
| author_sort | Ji-Hwan Hwang |
| collection | DOAJ |
| description | A multifunctional scatterometer system and optimized radar signal processing for simultaneous observation of various physical oceanographic parameters are described in this paper. Existing observation methods with microwave remote sensing techniques generally use several separate systems such as scatterometer, altimeter, and Doppler radar for sea surface monitoring, which are inefficient in system operation and cross-analysis of each observation data. To improve this point, we integrated separate measurement functions into a single observation system by adding a measurement function of Doppler frequency to the existing system. So it enables to simultaneously measure the range and polarimetric responses of backscattering as well as movements of the sea surface. Here, the simultaneous measurement function of Doppler frequency was implemented by sampling an FMCW (frequency modulated continuous wave) radar signal as 2D raw data consisting of fast- and slow-time samples, i.e., the range and backscattering of radar target signals are analyzed from the fast-time samples while the Doppler frequency by the radar target’s movement extracts from the slow-time samples. Through the Fourier transformed-based range-Doppler signal process, distance (<i>R</i>), backscattering (<i>σ°</i>), and Doppler frequency (<i>f<sub>D</sub></i>) are sequentially extracted from the 2D raw data, and a correlation to the physical oceanographic parameters is analyzed. Operability of the proposed system was examed through total 3 times of field campaigns from June 2017 to August 2020 and the observation data retrieved by the radar measurement data (<i>R</i>, <i>σ°</i>, <i>f<sub>D</sub></i>) was also cross-analyzed with in-situ data: e.g., tide, significant wave height, and wind speed and direction. Differences in the comparative results as an observational accuracy are as follows. Tidal level (Root Mean Square Error 0.169 m (<i>R</i>)), significant wave height (RMSE 0.127 m <i>(R)</i>, 0.362 m (<i>σ</i>°)), wind speed (RMSE 1.880 m/s (<i>f<sub>D</sub></i>), 2.094 m/s (<i>σ</i>°)) and direction (18.84° (<i>f<sub>D</sub></i>)). |
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| institution | Directory Open Access Journal |
| issn | 1424-8220 |
| language | English |
| last_indexed | 2024-03-09T10:30:17Z |
| publishDate | 2022-04-01 |
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| spelling | doaj.art-9203fedb8ea44d15ab88ebf9e434f2dc2023-12-01T21:22:46ZengMDPI AGSensors1424-82202022-04-01228289010.3390/s22082890Multifunctional Scatterometer System for Measuring Physical Oceanographic Parameters Using Range-Doppler FMCW RadarJi-Hwan Hwang0Duk-jin Kim1Ki-Mook Kang2Research Institute of Basic Sciences, Seoul National University, Seoul 88026, KoreaSchool of Earth and Environmental Science, Seoul National University, Seoul 88026, KoreaWater Resources Satellite Research Center, K-Water Research Institute, Daejeon 34045, KoreaA multifunctional scatterometer system and optimized radar signal processing for simultaneous observation of various physical oceanographic parameters are described in this paper. Existing observation methods with microwave remote sensing techniques generally use several separate systems such as scatterometer, altimeter, and Doppler radar for sea surface monitoring, which are inefficient in system operation and cross-analysis of each observation data. To improve this point, we integrated separate measurement functions into a single observation system by adding a measurement function of Doppler frequency to the existing system. So it enables to simultaneously measure the range and polarimetric responses of backscattering as well as movements of the sea surface. Here, the simultaneous measurement function of Doppler frequency was implemented by sampling an FMCW (frequency modulated continuous wave) radar signal as 2D raw data consisting of fast- and slow-time samples, i.e., the range and backscattering of radar target signals are analyzed from the fast-time samples while the Doppler frequency by the radar target’s movement extracts from the slow-time samples. Through the Fourier transformed-based range-Doppler signal process, distance (<i>R</i>), backscattering (<i>σ°</i>), and Doppler frequency (<i>f<sub>D</sub></i>) are sequentially extracted from the 2D raw data, and a correlation to the physical oceanographic parameters is analyzed. Operability of the proposed system was examed through total 3 times of field campaigns from June 2017 to August 2020 and the observation data retrieved by the radar measurement data (<i>R</i>, <i>σ°</i>, <i>f<sub>D</sub></i>) was also cross-analyzed with in-situ data: e.g., tide, significant wave height, and wind speed and direction. Differences in the comparative results as an observational accuracy are as follows. Tidal level (Root Mean Square Error 0.169 m (<i>R</i>)), significant wave height (RMSE 0.127 m <i>(R)</i>, 0.362 m (<i>σ</i>°)), wind speed (RMSE 1.880 m/s (<i>f<sub>D</sub></i>), 2.094 m/s (<i>σ</i>°)) and direction (18.84° (<i>f<sub>D</sub></i>)).https://www.mdpi.com/1424-8220/22/8/2890multifunctional scatterometerFMCW radarrange-doppler processocean observation |
| spellingShingle | Ji-Hwan Hwang Duk-jin Kim Ki-Mook Kang Multifunctional Scatterometer System for Measuring Physical Oceanographic Parameters Using Range-Doppler FMCW Radar Sensors multifunctional scatterometer FMCW radar range-doppler process ocean observation |
| title | Multifunctional Scatterometer System for Measuring Physical Oceanographic Parameters Using Range-Doppler FMCW Radar |
| title_full | Multifunctional Scatterometer System for Measuring Physical Oceanographic Parameters Using Range-Doppler FMCW Radar |
| title_fullStr | Multifunctional Scatterometer System for Measuring Physical Oceanographic Parameters Using Range-Doppler FMCW Radar |
| title_full_unstemmed | Multifunctional Scatterometer System for Measuring Physical Oceanographic Parameters Using Range-Doppler FMCW Radar |
| title_short | Multifunctional Scatterometer System for Measuring Physical Oceanographic Parameters Using Range-Doppler FMCW Radar |
| title_sort | multifunctional scatterometer system for measuring physical oceanographic parameters using range doppler fmcw radar |
| topic | multifunctional scatterometer FMCW radar range-doppler process ocean observation |
| url | https://www.mdpi.com/1424-8220/22/8/2890 |
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