Study On Waveform Design For Highly Maneuvering Targets Using Polarimetric Radar

Accurate acquisition and utilization of polarization information can effectively improve the performance of target detection,anti-clutter/interference,target imaging and classification recognition.The challenge of the accurate acquisition of polarization information is related to the changing types of the targets.The features of the target have changed from static/slow,centarinty and point target to high dynamic and extened targets.The modulation effect,causing by the motion of the target,brings new error factors for polarization measurements.And the above factors brings new challenge to the waveform design and signal processing of the polarimetric radar.Aiming at the requirement of obtaining precise polarization information of high dynamic target,this paper conducts an in-depth study on the design of orthogonal waveforms based on the simultaneous polarimetric radar system.The main contents of this paper are as follows:Chapter one firstly summarizes the development and research status of the polarization measurement system and points out that the characterics of observed targets are changing.Then the research background and signification of this study is introduced.Focusing on the waveforms design of the simultaneous polarimetric radar,the research status and main problems of the orthogonal phase-coded sequences and the complete complentary sequences are discussed.Finally,the main research topics and structure of this paper are explained.In Chapter two,the evaluation criteria of the waveforms for polarization measurement are proposed.At the same time,the performance of typically orthogonal waveforms are analyzed.For the waveforms design of the simultaneous polarimetric radar,the criteria,such as,peak side-lobe level,isolation and Doppler tolerance,are proposed.These criteria evaluate the performance of the waveforms in terms of the autocorrelation,crosscorrelation and Dopller sensitivity properties.Next,the performance of typical waveforms,such as,up-going and down-going slpoe of linear frequency modulation waveforms,up-going and down-going slpoe of nonlinear frequency modulation waveforms,orthogonal phase-coded sequences and orthogonal discrete frequency coding waveforms,are analyzed in detail.The disadvantages of these waveforms are also proposed.In Chapter three,the design of orthogonal phase-coded sequences with high Doppler tolerance is studied.Firstly,for the design of discrete phase-coded sequences,using the flexible block encoding method and consideing the velocity and acceleration of the target,an optimization model is built.The ovjective function of the model is the sum of the peak sidelobe of the autocorrelation,the peak of the cross-correlation,the sidelobe energy of the autocorrelation and the energy of the cross-correlation.Using the genetic algorithm,the waveforms with good properties can be obtained.Compared with the waveform designed by the method of Deng,the performance of our designed waveform improve about1 ～ 1.5 dB.Then,for the design of continuous phase-coded sequences,combining the practical demand,the minimizaiton of the local sidelobe of the correlation function is considered.A cyclic algorithm based on the gradient of the objective fucntion is proposed.To improve the computational efficiency of the method,the FFT algorithm is used to compute the gradient.Compared with the previous state-of-the-art WeCAN method,the performance improvement is about 25 dB.In Chapter four,the design of complete complentary sequences with high Doppler tolerance is studied.Based on the signal processing of the simultaneous polarimetric radar,the evaluation model of Doppler tolerance is built.Moreover,the optimization of the sequences is transformed to a minimization problem with unconstraint condition.By defining an auxiliary matrix,the FFT algorithm can be used to compute the objective function and the corresponding gradient.Numerical experiments indicate that the designed complete complementary sequences keep good correlation properties under the given Doppler interval.Chapter five summarizes the research and innovation points of the paper and points out the further study topics.