| With the rapid development of satellite communication, communication satellites are being interfered more and more frequently by ground sources, and the number of these interference events becomes larger and larger, which brings great threat to the normal satellite broadcasting and telecommunications business and may generate immeasurable social impact. In order to deal with radio frequency interference, it is very necessary to determine the position of the interference sources on the ground rapidly, timely and effectively through the interfered satellites. And there is a great significance for the operation of the satellite navigation system maintenance and use.The locating process realization of satellite interference sources usually requires two steps: firstly, estimates the corresponding parameter; secondly, according to the parameters of position, determines the location of the interference sources with some corresponding localization algorithms. The triple stars interference source localization usually uses two adjacent satellites which is interference with a satellite and estimates a pair of TDOA parameters. After two hyperboloids intersecting, we can get the interference sources area on the surface of the earth, so how to estimate the parameters accurately is the key to realize the localization of interference source.Based on triple stars positioning system, this paper deeply studies triple stars TDOA positioning methods in the field of passive location and estimates TDOA mainly from the three aspects which are instantaneity, high precision and practicability. The main works and research results include the following aspects:(1) According to the characteristics of the interference sources location`s high real-time demand, this paper puts forward the “quadratic correlation fast TDOA estimating algorithm”, which is based on the quadratic correlation method. Using the relationship of Fourier transform characteristics between correlation function and power spectral density, fast Fourier transform(FFT), the calculation is simplified and becomes more quickly and accurately. The simulation results on MATLAB show that,compared with generalized cross correlation method under same SNR condition, thenew fast algorithm can estimate the TDOA values more quickly and effectively, which can more effectively improve the real-time quality of satellite interference sources position.(2) In order to meet the requirements of high precision positioning, based on the research of the correlation method above and its problem, the improved algorithms of PHAT weighting and wavelet denoising are proposed. These algorithms usually preprocess the received signals by selecting some window function or the best wavelet functions. In this way, not only reducing the amount of calculation, but also having the effect of main sharpen peak point in the peak detection processing. The simulation results shows that these two algorithms for both stationary signal and non-stationary signal in the condition of low SNR and even weak signals can obtain the high-precision TDOA estimation parameters and the wavelet denoising method is better.(3)The adaptive TDOA estimation algorithm of higher-order cumulantst and minimum mean square is studied when the noise environment is related or metabolic SNR. Based on the fourth-order cumulants, the improved least mean square adaptive TDOA estimation algorithm(FOC-LMSTDE) is proposed. The core of this algorithm is making the adaptive filter divided into two parts, one is used to track the time delay,and the other is used to adjust to the changes of the SNR. Besides, combining the advantage that higher order cumulants is not sensitive to noise, it can not only estimate the TDOA effectively under the condition of low SNR and related noise, but also estimate TDOA accurately in the case of metabolic SNR. The simulation results show that this improved algorithm has adequate feasibility and superiority. |
PDF Full Text Request