Research On Timr-frequency Analysis Method For Fretting Target Feature Extraction

With the continuous improvement of the guidance system,the false target and the bait can exhibit almost the same characteristics as the real target,including the motion trajectory,the radar cross-sectional area,the surface material and the geometric features,etc.,so that the identification of non-cooperative objects becomes more and more The more difficult it is,the radar signal processing is transformed from a single function such as scale measurement to a target fine structure and motion feature measurement.It is impossible to extract the useful identification information for the structural information or geometry of the target extracted from the radar echo signal.It is necessary to use the unique micro-motion characteristics of the target(including the small vibrations such as vibration,rotation,roll and swing of the target).The modulation of the radar signal is gradually taken into account,and the modulation signal is used to extract the micro-Doppler characteristic parameters,thereby inverting the target information.We know that target fretting exhibits phase modulation and frequency modulation in radar echoes.This modulation phenomenon appears in the time domain as having a certain sideband of the signal,which is called the micro-Doppler frequency.Through a certain time-frequency analysis method,the relationship between the frequency and time of the fretting target is reflected on the time-frequency map,and then the time-frequency plane is analyzed and processed to extract and separate the instantaneous frequency of the target,and use these instantaneous frequencies or The shape,structure,posture,surface material electromagnetic parameters,stress state,etc.of the target can be reversed.In this thesis,the current research status of the precession and nutation parameters of the micro-motion target at different angles is firstly described.Then,according to the motion characteristics of the single motion mode of the fretting target,the composite motion state combined with the single motion state is analyzed.And the movement characteristics of the nutation.The corresponding radar echo model is established for different motion situations,and the theoretical expression of micro-Doppler signal is given.Then,for the time-frequency analysis methods commonly used at present,the non-stationary signal is taken as an example for simulation analysis.The advantages and disadvantages of different time-frequency analysis methods and their application range are obtained.Based on this,an improved CTD instantaneous frequency extraction method is proposed.The effectiveness,practicability and stability of the improvedmethod are verified by simulation experiments.Finally,the practical application of improved CTD instantaneous frequency extraction method in multi-objective micro-Doppler feature extraction in mid-ballistic segment and micro-motion feature information extraction in networked radar is explored.