Study On DOA And Time Delay Estimation In Wireless Passive Positioning

Directions-of-arrival (DOA) estimation and time delay estimation are important means of wireless passive position technology. They are also important parts of parameters estimation and extraction in modern signal processing and have been widely used in radar, sonar, wireless communication positioning system, radio monitoring, military and other fields. In recent years, DOA estimation of cyclostationary signal has been obtained more and more attention, but most of the current algorithms are based on the second-order cyclic statistics. The performance of these algorithms will degenerate seriously in α-stable distribution noise environments. This desertation mainly studies DOA estimation of cyclostationary signal under impulsive noise environment. On the other hand, as the time delay estimation develops up to now, many excellent methods of the time delay estimation have been proposed. But the problem of narrowband RF signal delay estimation is still a difficult work in wireless location technology, and the existion of intermediate frequency difference (IFD) will affect the accuracy of time delay estimation. So this desertation mainly study the new methods of the time delay estimation based on frequency difference compensation (FDC). The main researches and conclusions are listed as follows:(1) Since DOA estimation of broadband cyclostationary signal based on ULA is a difficult work, by combining the fractional lower order cyclic statistics with SC-SSF algorithm, a spectral correlation signal subspace fitting algorithm (SC-SSF) based on the fractional lower order cyclic correlation is proposed. Then the DOA estimation of broadband cyclostationarity signal in impulsive noise is realized. Furthermore, an extended fractional lower order cyclic MUSIC algorithm is proposed by constructing a new extended data model. The algorithm has higher estimation accuracy. Meanwhile, in order to improve the estimation performance, a novel phase fraction pth-order cyclic correlation by fusing the phase fractional lower order statistics and cyclic statistics is defined. Then a novel extended phase fraction pth-order cyclic MUSIC algorithm (EX-POC-MUSIC) and phase fraction pth-order cyclic Root-MUSIC (EX-POC-RMUSIC) algorithm are proposed. Both algorithms have high-resolution estimation performance.(2) In order to solve the DOA estimation problem of cyclostationary signal based on uniform circular array (UCA) under α-stable distribution environment, after analysing and verifing the phase shift characteristics of the fractional lower order cyclic correlation, we propose a fractional lower order cyclic MUSIC algorithm based on UCA, which can estimate both azimuth and elevation angles accurately even in impulsive noise. Meanwhile, a novel extended cyclic MUSIC algorithm based on UCA is developed in this paper. The algorithm exploits simultaneously the information contained in both cyclic correlation matrix and cyclic conjugate correlation matrix of the extended array data vector, and breaks through the limitation of the classic MUSIC algorithm in which the number of source signal can not be greater than the number of element in the receiving array. The algorithm improves the estimation accuracy of the azimuth and elevation angle, which is a high-resolution DOA estimation algorithm.(3) As the intermediate frequency difference (IFD) impacts the delay estimation, two time delay estimation (TDE) algorithms based on the frequency difference compensation (FDC) are proposed. Since time-delay estimation using the phase spectrum for narrowband radio frequency (RF) signal exists limitations, frequency doubling methods is used to estimate the intermediate frequencier (IF) of both receicved signals, and chirp Z transform (CZT) is applied to increasing the available frequency bins within a limited bandwidth. Then, a phase spectrum TDE method based on FDC is proposed, which can improve the accuracy of TDE. In order to solve the time delay estimation problem of the closely spaced signals, the model of TDE with IFD and the model of MUSIC algorithm are compared, and then an effective time delay estimation method based on FDC for narrowband RF signals is proposed. This method exploits the high-resolution performance of MUSIC algorithm, which improves the performance of TDE.