Font Size: a A A

Study On Theory And Method Of Chirp Signal Time-delay Estimation In Noise Environments

Posted on:2009-10-17Degree:MasterType:Thesis
Country:ChinaCandidate:C L ShaoFull Text:PDF
GTID:2178360242481449Subject:Pattern Recognition and Intelligent Systems
Abstract/Summary:PDF Full Text Request
Chirp signal (linear frequency modulated signal,LFM) is a very important signal in signal processing. It is widely used in many systems, e.g., communication,radar,sonar,seismography,geology exploration and medical imaging. The research on chirp signal is important for signal processing theory and its practical applications.The correlation function of chirp signal contains time variable , the chirp signal is nonstationary signal.Scholars have developed many theories and methods of chirp signal in recent years. However, most of existing chirp parameter estimation approaches are restricted by assumptions of white Gaussian noise,high computational cost and ideal signal models. To deal with these questions, time-varying cross-four-order cumulant and four-order cross wavelet cumulant are proposed in this paper, Multi-path time delay estimation,time delay and doppler stretch estimation of chirp signal are studied. The main research work can be generalized as: t1. Multi-path time-delay estimation of chirp signal based on time-varying cross-four-order cumulant.Most of existing chirp frequency parameter estimation methods are based on white Gaussian noise assumption. This assumption is in favor of theory analysis and processing, but noise is often more complicated in practice. So these approaches are no longer suitable. In this paper time-varying cross-four-order cumulant techniqu is proposed. The time-varying cross-four-order cumulant can suppress correlated Gaussian noise and all kinds of uncorrelated noise. The special time-varying cross-four-order cumulant of chirp signal derived by the analysis of chirp structure is time independent. In this paper four subspace decomposition methods are presented which are MUSIC, SVD-MN, ESPRIT and GEESE. To reduce the aliasing ambiguities in multi-path time delay estimation, an unambiguous technique based on multi-frequency sampling theory is presented.Simulation results show that the four algorithms can realize high accurate and high reliable frequency time-delay estimation of multi-path chirp signal in mixed noise environment. 2. Joint multi-path time delay and doppler stretch estimation of chirp signal based on time-varying cross- fout-order cumulant.Joint multi-path time delay and doppler stretch estimation should be used when relative motion of objects cannot be ignored. In this paper a time-varying four-order cumulant is presented to estimate echo frequency and doppler stretch factor. Then, the echo frequency and factor are used to reconstruct a reference signal, and joint multi-path time delay and doppler stretch estimation is estimated through four subspace decomposition methods which are MUSIC, SVD-MN, ESPRIT and GEESE based on time-varying cross-four-order cumulant.Simulation results show that these joint estimation algorithms can suppress Gaussian colored noise and their computational loads are smaller than most nonstationary joint estimation approaches.3. Joint time delay and doppler stretch estimation of chirp signal based on four-order cross wavelet cumulant.Wideband cross ambiguity function can work well on joint time-delay and doppler stretch estimation in Gaussian white noise environment. higher-order cumulant has the good capability of suppressing Gaussian noise.In this section, four-order cross wavelet cumulant is used.The result of joint time delay and doppler stretch estimation can be gained through two dimensions researching of maximum module value of wide band cross ambiguity function based on four-order cross wavelet cumulant. This algorithm has some prominent virtues such as Gaussian noise suppression ability, high estimation accuracy compared with Wide band cross ambiguity function algorithm.
Keywords/Search Tags:chirp signal, cumulant, time delay estimation, doppler stretch, wavelet, ambiguity function
PDF Full Text Request
Related items