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1. chinaXiv:201703.00300 [pdf]

Design of X/Ku dual-band dual-linear polarization reflectarray using double parallel dipole elements

Xue, Fei; Wang, Hongjian; Yi, Min
Subjects: Geosciences >> Space Physics

Two single-layer X/Ku dual-band dual-polarization reflectarray antennas of different sizes with double parallel dipole elements are presented. Elements of the two bands are set to two orthogonal linear polarizations and placed in interlaced grid. The proposed reflectarrays operate in two frequency-bands within X-band centered at 10 GHz and Ku-band centered at 13.58 GHz. The smaller size reflectarray with elements arranged in a 13 ?13 grid for X-band and in a 12 ?12 grid for Ku-band is designed and simulated first. Based on the excellent dual-band performance of the small size reflectarray, then a larger size prototype has been designed, manufactured and measured. Measured results demonstrate the maximum gain of 28.54 dB with 50.93% aperture efficiency at 10 GHz and 31.06 dB with 51.34% aperture efficiency at 13.58 GHz, which show desirable dual-band dual-polarization radiation performance.

submitted time 2017-03-10 Hits3187Downloads829 Comment 0

2. chinaXiv:201703.00295 [pdf]

A broadband reflectarray using patch with slot ring on ground plane elements

Xue, Fei; Wang, Hongjian; Yi, Min; Dong, Xingchao
Subjects: Geosciences >> Space Physics

A broadband center-fed reflectarray antenna is presented in this paper. Patch with slot ring on ground plane elements are used for bandwidth improvement. It is shown that quasi-linear phase responses with broad frequency band can be achieved by such a phasing element. An 11?1 elements reflectarray is designed and simulated. The results show that the simulated gain is 23.92 dB at the center frequency of 13.58 GHz with 3-dB bandwidth of 52%, which demonstrate significant broadband operation compared with that of conventional reflectarray.

submitted time 2017-03-10 Hits1959Downloads845 Comment 0

3. chinaXiv:201703.00293 [pdf]

A new broadband reflectarray antenna using novel single-layer elements

Xue, Fei; Wang, Hongjian; Yi, Min
Subjects: Geosciences >> Space Physics

A novel single-layer reflectarray element for broadband use is proposed. Ansoft HFSS is used to analyze the reflection phase for the element. By varying the element size, a slow slope of the reflection phase curve with the phase range over 600° is achieved. A center-fed 121-element reflectarray antenna is designed using the proposed elements and a linearly polarized pyramidal horn antenna is used as the feed of the reflectarray. The simulated results show that the gain of 24.42dB at the center frequency of 13.58GHz with 3-dB gain bandwidth of 36.8% (from 11.08?16.08GHz), demonstrating a wideband performance compared to the conventional designs.

submitted time 2017-03-10 Hits1341Downloads695 Comment 0

4. chinaXiv:201703.00290 [pdf]

Deconvolution method for resolution enhancement of Dual-Frequency Polarized Scatterometer

Liu, Liling; Dong, Xiaolong; Zhu, Jintai; Zhu, Di
Subjects: Geosciences >> Space Physics

Dual-Frequency Polarized Scatterometer (DFPSCAT) is a new system utilizing Doppler beam sharpening (DBS) technology for azimuthal resolution enhancement. Considering the DBS technology is inapplicable for the middle areas of the swath, a theoretical framework of deconvolution signal processing is proposed to improve resolution. A deconvolution method of the nonlocally centralized sparse representation (NCSR) is adopted to verify its feasibility, and simulation results show that the deconvolution method have obviously better resolution enhancement and higher recovery accuracy than these of the classical scatterometer image reconstruction (SIR) method. ?2016 IEEE.

submitted time 2017-03-10 Hits2442Downloads885 Comment 0

5. chinaXiv:201703.00289 [pdf]

Estimating the sea state bias of HY-2A radar altimeter by using a three-dimentional nonparametric model

Jiang, Maofei; Xu, Ke; Liu, Yalong; Wang, Lei
Subjects: Geosciences >> Space Physics

The sea state bias (SSB) has become the dominant source of error in satellite altimetry. The operational SSB correction models are two-dimensional (2-D) nonparametric models based on the wind speed (U) and the significant wave height (SWH) that can be directly measured by the altimeters. This paper estimates the sea state bias of HY-2A radar altimeter using a three-dimensional (3-D) nonparametric model based on SWH from HY-2A interim geophysical dataset records (IGDR), U and the mean wave period (MWP) from the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis project ERA-Interim. The 3-D SSB estimates can increase the explained variance by 1.72 cm2, or 1.31 cm RMS relative to the traditional 2-D SSB estimates based on U and SWH. ?2016 IEEE.

submitted time 2017-03-10 Hits2045Downloads814 Comment 0

6. chinaXiv:201703.00286 [pdf]

Temperature and humidity profiles retrieving over land using clear sky measurements of microwave humidity-temperature sounder on Chinese FY-3C satellite

He, Qiurui; Wang, Zhenzhan; He, Jieying
Subjects: Geosciences >> Space Physics

An one-dimensional variational retrieval system was developed to retrieve the clear sky atmospheric temperature and humidity profiles over land using the measurements of microwave humidity-temperature sounder (MWHTS) on Chinese FY-3C satellite. The system parameters are configured by analyzing the MWHTS channel properties and the climate condition over land. The retrieval results are evaluated by root mean square error (rmse) with respect to European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis data. The validated results show that the maximum root mean square error of temperature and humidity are 2.59K and 11.87%, respectively. The retrieval results, compared with National Centers for Environmental Prediction (NCEP) 6 hour forecast profiles, show that the background profiles can affect the accuracy of retrieval profiles and FY-3C/MWHTS measurements can improve forecast precision of humidity. ?2016 IEEE.

submitted time 2017-03-10 Hits4133Downloads842 Comment 0

7. chinaXiv:201703.00252 [pdf]

AN UNFOCUSED SAR APPROACH TO IMPROVE AZIMUTH RESOLUTION OF DUAL-FREQUENCY POLARIZED SCATTEROMETER(DFPSCAT)

Gang Wang; Xiaolong Dong; Qingliu Bao; Di Zhu; Xingou Xu
Subjects: Geosciences >> Space Physics

For the spaceborne scanning pencil-beam scatterometer, the azimuth resolution is low that could not meet the demands. Based on the motion of platform and the scanning rules of the spaceborne scatterometer, this paper takes an unfocused SAR approach to improve the Azimuth Resolution.

submitted time 2017-03-10 Hits900Downloads515 Comment 0

8. chinaXiv:201605.00289 [pdf]

AN UNFOCUSED SAR DESIGN TO IMPROVE AZIMUTH RESOLUTION OF DUALFREQUENCY FULL-POLARIZED SCATTEROMETER

Wang, Gang; Dong, Xiaolong; Bao, Qingliu; Zhu, Di; Xu, Xingou
Subjects: Geosciences >> Space Physics

In order to satisfy a high resolution for the measurement of snow water equivalent, we use the system of using the dual frequency(X-band 9.6GHz and Ku-band 17GHz) and full polarization. This paper discusses the various system options(scanning pencil-beam, high PRF, high SNR) and tradeoffs considered for improving the azimuth resolution of scatterometer are required.

submitted time 2016-05-03 Hits1583Downloads950 Comment 0

9. chinaXiv:201605.00284 [pdf]

THE ALTIMETER PRECISION COMPARISON BETWEEN SAR MODE AND CONVENTIONAL MODE THROUGH AIRBORNE EXPERIMENT

Xu, Ke; Liu, Peng; Shi, Lingwei; Wang, Lei; Yu, Xiufen
Subjects: Geosciences >> Space Physics

Compared with conventional radar altimeter (CRA), synthetic aperture radar altimeter (SARAL) is a new generation radar altimeter and has better height precision and spatial resolution. As using synthetic aperture technique, SARAL data processing is very different from CRA. To verify the performance and the processing algorithm, an airborne experimental system of SARAL is developed. The experimental system was installed in Y-12 aircraft, and a lot of data was obtained in the October 2014. The echo signal with SAR mode and conventional mode are obtained at the same time, so the standard deviations of the two modes are compared. The results indicate that the height precision of SARAL is improved about 1 times. The significant wave height value extracted from the SARAL waveform is very close to that of the buoy deployed at the experiment area.

submitted time 2016-05-03 Hits926Downloads588 Comment 0

10. chinaXiv:201605.00278 [pdf]

THE LATEST ASSESSMENT FOR THE REPROCESSED GDR PRODUCT OF HY-2A ALTIMETER

Liu, Yalong; Xu, Ke; Zhang, Youguang; Wang, Lei; Xu, Xiyu; Chen, Hua
Subjects: Geosciences >> Space Physics

This paper is aimed to assess the accuracy of HY-2A altimetry system. To further improve the accuracy and performance of HY-2A observed SSHs, several new treatments including 4 parameters maximum likelihood estimation (MLE4) retracking for Ku and C band, non-parameter sea state bias (NPSSB) model, and reprocessed dual-frequency altimeter ionospheric correction are included. The evaluation from dual-crossover comparison of the fully reprocessed level-2 sensor geophysical dataset records (SGDRs) data suggests that the algorithm and model improvements mentioned above give rise to remarkable promotion to the accuracy of the forthcoming version GDRs. In this study we conclude that the standard deviation of 5.79 cm is achieved from crossover comparison between HY-2A and Jason-2 sea surface height (SSHs), suggesting a promising situation of HY-2A altimetry datasets.

submitted time 2016-05-03 Hits1316Downloads655 Comment 0

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