Parameter Estimation Of Multi-component LFM Signal Based On S Transform

Linear frequency modulation(LFM)signal is a kind of non-stationary signal widely used in electronic countermeasure,underwater acoustic detection,seismic exploration,mechanical fault detection and other fields.The parameter estimation of LFM signal can describe the relationship between its frequency and time,as so to obtain the target's related information for research and analysis.However,in practical applications,LFM signal does not exist in the form of one component.Therefore,the research on parameter estimation of multi-component LFM signal has more practical significance.Time-frequency analysis is one of the most important methods for LFM signal processing,and the S-transform is a flexible and widely used time-frequency analysis method,which has been a research focus in related fields for more than ten years.Based on the S-transform,this paper improves the performance of the S-transform by combining with other methods,and applies it to estimate the parameters of LFM signal.The main contents of this paper are as follows:1)The definition and properties of the S-transform are studied in detail.The S-transform is linear and completely reversible,so it has the advantage of not being affected by cross terms when processing multi-component LFM signal.Meanwhile,the Gauss window function of the S-transform makes it have variable time and frequency resolution.As a result,the S-transform is flexible to process signals.2)The S-transform has poor time-frequency concentration,which leads to a large amount of blurring energy in the time-frequency distribution of LFM signal.Moreover,the result of the parameter estimation will be seriously affected.To solve this problem,the Synchroextracting S Transform(SEST)has been deduced by combining the S-transform with the Synchroextracting Transform,which greatly improves the time-frequency concentration of the original S-transform.Then most of the blurring energy in the time-frequency plane is removed by SEST,which makes LFM signal much closer to linear representation in the time-frequency plane.Finally,the Hough transform is introduced to extract the parameters of the straight line in the time-frequency plane,and the parameters of LFM signal can be estimated by coordinate transformation.3)When the components of the multi-component LFM signal overlap in the time-frequency plane,the time-frequency coefficients obtained by the SEST have great errors at the intersection.The solution of this problem are as follows.First of all,the time-frequency distribution of multi-component LFM signal with relatively high time-frequency concentration is obtained by using the Generalized S-transform.Then the time-frequency ridge of each LFM component is obtained by alternately using the time-frequency ridge extraction method and the intrinsic chirp component decomposition method.Furthermore,the ridge path regrouping method is used to reduce the errors of the instantaneous frequency at the intersection.Finally,the Hough transform is also introduced to extract the parameters of the straight lines in the time-frequency plane,and the parameters can be estimated by coordinate transformation.