China Research Institute of Radiowave Propagation CRIRP

Qingdao, China

China Research Institute of Radiowave Propagation CRIRP

Qingdao, China
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Wan J.,China Research Institute of Radiowave Propagation CRIRP | Li Q.,China Research Institute of Radiowave Propagation CRIRP | Li X.,China Research Institute of Radiowave Propagation CRIRP | Zhao P.,China Research Institute of Radiowave Propagation CRIRP | Zhang Y.,China Research Institute of Radiowave Propagation CRIRP
ISAPE 2016 - Proceedings of the 11th International Symposium on Antennas, Propagation and EM Theory | Year: 2016

With the S-band sea clutter data measured by the radar located on a cliff top employed, this work compares the amplitude characteristics of the sea clutter in S-band and X-band (IPIX data). On this basis, the difference of the sea spike properties between the two radar bands is analyzed both in time and frequency domain. The identification method of the sea spike from the sea clutter background uses the spike amplitude, the minimum spike width and the minimum interval between spikes, as three qualitative parameters. Comparing with X-band, the specificity of the sea spikes in S-band is presented. © 2016 IEEE.


Wang R.,Hubei University | Zhou C.,Hubei University | Deng Z.,Hubei University | Deng Z.,China Research Institute of Radiowave Propagation CRIRP | And 2 more authors.
Journal of Atmospheric and Solar-Terrestrial Physics | Year: 2013

A regional model for the ionospheric critical frequency of the F2 layer (f oF 2) over China is developed by neural networks (NNs) trained by the genetic algorithm (GA). In order to avoid the 'local minimum' phenomena in most NN applications, GA is utilized here to optimize the initial weights of NNs. The input parameters used in this GA-NN based f oF 2 prediction model include Beijing time (BJT, GMT+8), day number (day of the year), seasonal information, solar cycle information, magnetic activity, magnetic declination, magnetic dip angle, angle of meridian relative to sub-solar point, solar zenith angle, and geographic coordinates. The f oF 2 datasets employed in this model are obtained from nine ionosonde stations located in China for the time span of 1990-2004 that covers one entire sunspot cycle. The datasets for 1996 and 2000 are selected for validation instead of for training use. Prediction results of GA-NN model, unimproved NN model, and International Reference Ionosphere 2007 (IRI2007) model (from International Radio Consultative Committee (CCIR) coefficient) are compared with the observation data for the year of 1996 and 2000 respectively. The results indicate that GA-NN model is superior to the unimproved NN model and the IRI2007 model for f oF 2 prediction. According to the statistical analysis of average RMSE, the GA-NN method offers an improvement of 4.89% over NN method and an improvement of 27.79% over IRI2007 model. The improvement of accuracy for one single station forecasting is validated with the data from the Wuhan ionosonde station both at 00:00 (BJT) and 12:00 (BJT) in 1996 (solar minimum) and 2000 (solar maximum). © 2012 Elsevier Ltd.


Zhou C.,Hubei University | Wang R.,Hubei University | Lou W.,China Earthquake Administration | Liu J.,China Earthquake Administration | And 4 more authors.
Journal of Geophysical Research: Space Physics | Year: 2013

A real-time mapping model of foF2 in northern China was established using neural networks (NNs). To avoid the local minimum problem associated with traditional NNs, a newly improved genetic algorithm-based NN (GA-NN) was developed using the input parameters of solar activities, geomagnetic activities, neutral winds, seasonal information, and geographical coordinates. The foF2 data were extracted by inversing the oblique ionograms obtained from the oblique ionosondes of the China Ground-based Seismo-ionospheric Monitoring Network every 30 min for the period from August 2009 to December 2011. The data associated with five transmitter stations (Beijing, Changchun, Qingdao, Xinxiang, and Suzhou) and one receiver station in Binzhou were considered the input parameters for the real-time f oF2 mapping model, and the data from the Dalian and Jinyang transmitter stations were used to verify the results. The Jining transmitter station data were used to test the capability of the model. The root-mean-square error and percent deviation were calculated to estimate the performance of the model. The correlation coefficient was used to evaluate the correlation of observed and predicted values. In addition, observations of foF2 from the vertical ionosondes at Beijing, Changchun, Qingdao, and Suzhou stations are compared with the model prediction of f oF2. The results indicate that the developed real-time foF2 mapping model based upon genetic algorithm-based NN is very promising for ionospheric studies. Key PointsA foF2 real-time mapping model is established by using neural networks.RMSE and PD are used to estimate the performance of the model.foF2 of ionosondes are compared with the model prediction. ©2013. American Geophysical Union. All Rights Reserved.


Zhao H.-S.,Xidian University | Xu Z.-W.,China Research Institute of Radiowave Propagation CRIRP | Wu Z.-S.,Xidian University | Wu J.,China Research Institute of Radiowave Propagation CRIRP | And 4 more authors.
Journal of Atmospheric and Solar-Terrestrial Physics | Year: 2013

The computerized ionospheric tomography (CIT) is an under-determined, ill-posed inverse problem. The limited-angle geometry and sparse receivers cause incomplete information in measurements, which limit the precision of the CIT imaging, especially in the vertical dimension. This paper puts forward a new method by combining vertical and oblique sounding data with the total electron content (TEC) retrieved from an assumed tri-band beacon of a planned Chinese satellite for seismological studies transmitting VHF, UHF and L-band frequencies. In this paper the bottomside of the initial profile for the iteration is specified by actual vertical while oblique sounding data and the topside specified by the Chapman layer model. This combined initial deviates from the actual electron density distribution and is smaller than those calculated only from the models. The appropriate initial will ensure that the iterative algorithm is reliable and steady. The numerical simulations show that electron density images reconstructed from only TEC using the three-frequency technique are significantly improved after combining real observation data of the ground-based vertical and oblique sounding. The results shown in this paper throw a new light on the application and potential of the solid network of a satellite beacon and ground-based facilities. © 2013 Elsevier Ltd.


Wang C.,Xidian University | Zhang M.,Xidian University | Xu Z.-W.,China Research Institute of Radiowave Propagation CRIRP | Chen C.,China Research Institute of Radiowave Propagation CRIRP | Sheng D.-S.,China Research Institute of Radiowave Propagation CRIRP
IEEE Transactions on Antennas and Propagation | Year: 2014

This paper discusses the degradation of space-borne synthetic aperture radar (SAR) imaging due to anisotropic ionospheric irregularities. In the case of the oblique incidence and anisotropy of ionospheric irregularities, two types of potential ionospheric effects on SAR imaging are derived from an improved transverse correlation function. First, in the range direction, the image shift due to both multiple scattering and dispersion of irregularities is considered. In addition, pulse broadening due to multiple scattering of the irregularities is also studied, which leads to degradation of the range resolution. Second, in the azimuthal direction, the decorrelation distance is obtained by the second moment of the generalized ambiguity function. Using the range Doppler algorithm (RDA), several degraded point target responses due to the ionospheric irregularities are evaluated. The simulation results show that the adverse effects of ionospheric irregularities on SAR imaging are worsened at lower frequencies and stronger ionospheric fluctuations. © 2014 IEEE.


Li L.,Xidian University | Lin L.-K.,China Research Institute of Radiowave Propagation CRIRP | Wu Z.-S.,Xidian University | Zhao Z.-W.,China Research Institute of Radiowave Propagation CRIRP
IET Microwaves, Antennas and Propagation | Year: 2016

In this study, a method to choose the maximum calculation height and the maximum propagation angle of the split-step troposcatter wide-angle parabolic equation (TWAPE) method is presented. The method is implemented with the height and the scatter angle of the troposcatter common volume. The performance of this method is then demonstrated with a few examples which rely heavily on the choosing of the maximum calculation height and the maximum propagation angle. These examples include the comparison of calculated results of TWAPE for choosing different maximum calculated height and maximum propagation angle at frequencies of 3 and 1 GHz, path lengths of 300 and 500 km, respectively. Finally, the seasonal variation mechanism of the troposcatter propagation loss is discussed based on the seasonal variation of the refractive-index structure parameter. © The Institution of Engineering and Technology 2016.


Li L.,Xidian University | Wu Z.-S.,Xidian University | Lin L.-K.,China Research Institute of Radiowave Propagation CRIRP | Zhang R.,China Research Institute of Radiowave Propagation CRIRP | Zhao Z.-W.,China Research Institute of Radiowave Propagation CRIRP
IEEE Transactions on Antennas and Propagation | Year: 2016

In this article, a novel semiempirical average annual troposcatter transmission loss prediction model is presented. The model is generated by optimizing the correlation coefficients of propagation path conditions utilizing the modern optimization algorithm. The statistical relativities of troposcatter transmission loss as captured by changing frequency, path length, scatter angle, and meteorological condition are each analyzed using the terrestrial trans-horizon propagation loss data banks released by the International Telecommunication Union (ITU). For the percentages of time transmission loss not falling below 50%, the model is combined with the model of anomalous propagation mechanism introduced in the Recommendation ITU-R P.2001. The prediction results of this new troposcatter model are compared with other troposcatter models and with the trans-horizon propagation loss data banks. The comparisons show that the new model has a better estimated accuracy. © 2016 IEEE.


Jin Z.,China Research Institute of Radiowave Propagation CRIRP | Ma Y.,China Research Institute of Radiowave Propagation CRIRP | Wu Y.,China Research Institute of Radiowave Propagation CRIRP
2014 31th URSI General Assembly and Scientific Symposium, URSI GASS 2014 | Year: 2014

We propose a wide area cooperative communication scheme for ionospheric HF links in order to increase communication reliability and throughput under a given range and power. By exploiting multiple radios in a collaborative fashion, we can obtain diversity gains similar to Single Input Multiple Output (SIMO). Based on experimental results, this paper demonstrates the benefits of wide area cooperative communication strategies, and gives correlation function of diversity channels with different distance by measuring channel parameters. © 2014 IEEE.


Zhang R.,China Research Institute of Radiowave Propagation CRIRP | Wang H.,China Research Institute of Radiowave Propagation CRIRP | Zhang L.,China Research Institute of Radiowave Propagation CRIRP
2014 31th URSI General Assembly and Scientific Symposium, URSI GASS 2014 | Year: 2014

Fourier transform methods in a three-dimensional parabolic equation are presented in this paper. Decomposing the double integral to three one-dimensional Fourier transforms, three-dimensional parabolic equation can be computed by means of fast-Fourier transforms. Comparing the results with the two-ray model, the validity of the methods is testified. © 2014 IEEE.


Xu T.,China Research Institute of Radiowave Propagation CRIRP | Wu J.,China Research Institute of Radiowave Propagation CRIRP | Zhao Z.,China Research Institute of Radiowave Propagation CRIRP | Liu Y.,China Research Institute of Radiowave Propagation CRIRP | And 4 more authors.
Natural Hazards and Earth System Science | Year: 2011

The problem of earthquake prediction has stimulated the research for correlation between seismic activity and ionospheric anomaly. Many observations have shown the existence of anomaly of critical frequency of ionospheric F-region, foF2, before earthquake onset. Ionospheric sounding has been conducted routinely for more than 60 years in China by the China Research Institute of Radiowave Propagation (CRIRP), and deveoloped a very powerful ability to observe the ionosphere. In this paper, we briefly describe the anomalous variation of the foF2 before Ms8.0 Wenchuan earthquake (occurred on 12 May 2008 at 14:28 LT; 31.00° N, 103.40° E), which is a sign of the great interest arising in the seismo-ionospheric investigation of Chinese researchers. Furthermore, we introduce the routine work on seismo-ionospheric anomaly by the ground based high-resolution ionospheric observation (GBHIO) network comprising 5 vertical and 20 oblique sounding stations. © 2011 Author(s).

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