Research On Radar Signature Extraction From Target With Micro-motions

Since micro-Doppler phenomenon is observed in radar target detection, micro-motion, as one of significant target characteristics with promising applications in radar target feature extraction and recognition, incur increasing attentions and research interests. In usual cases, a radar target may have small vibrations or rotations or other high-order motions in addition to mass translation, which is called micro-motion. The backscatter of a target with micro-motions contains fine micro-Doppler features, which enables us to determine some unique properties of the target.The intent of this dissertation is to investigate radar signature extraction from targets with micro-motions. In the introduction, there are brief reviews and comments of the research background as well as the present situation of the subject, and then the main contributions of the dissertation are introduced, in which the innovations of the whole dissertation are particularly pointed out.In this dissertation, firstly, there is a summary of radar signatures of targets with micro-motions, including basic concepts, classifications and typical examples. Then the meaning and the category of micro-motions are generalized. Also, radar signatures of targets with micro-motions are expounded with extended descriptions, which include micro-Doppler feature, RCS modulation feature and unique high resolution feature. Mathematics and computation technique involved in micro-Doppler and Doppler spectrum are examined, which brings about the introduction of a new concept—micro-Doppler rate. Radar features are investigated for three typical targets with micro-motions, i.e., maneuvering point-scattering target, rotating line-shaped target and precessing cone-shaped target. In addition, unique high range resolution feature is also studied for targets with micro-motions, including the center of micro-motion, the amplitude of micro-motion and the frequency of micro-motion.Low-resolution radar feature extraction is investigated for targets with micro-motions. Both time-frequency transform and FFT are used to analyze micro-Doppler signal due to its time-varying property. With time-frequency filter and Doppler filter, micro-Doppler-based approaches are proposed for parameter estimation of typical targets with micro-motions, which include acceleration motion, three-order motion, sinusoidal vibration, uniform rotation and tumbling motion. Besides, several approaches based on Doppler spectrum are also developed for parameter estimation of typical targets with micro-motions, which include maneuvering point-scattering target, rotating line-shaped target and precessing cone-shaped target. Target micro-motion resolution is examined and a micro-Doppler-based technique is proposed for resolving acceleration, vibration and rotation. Then B-distribution for resolving multiple targets with micro-motions is investigated by virtue of the introduction of a new concept—Multitarget Micro-Doppler.In addition to Low-resolution radar feature, radar imaging is explored for targets with micro-motions. First, there are discussions on the established comprehensive mathematics model of synthesizing high range resolution profile (HRRP) of targets with micro-motions, which include a refined and generalized target model, signal model and motion model. Then with the theory of DFT, Doppler Effect is detailed, and the distortion of synthetic range profile is examined by the theory of Norm, which give us a new mathematics implication and a new signal processing interpretation. As a typical example, Stepped Chirp waveform is used to examine Doppler Effect with some specific numerical simulations, which bring some interesting conclusions about phase shift and the distortion. Synthesizing range profile is investigated for rigid targets with micro-motions. A new waveform and corresponding technique, which are respectively referred to as Phase Cancellation waveform and Phase Cancellation processing, are proposed to reconstruct range profile of a rigid target with micro-motions. Synthesizing range profile is also investigated for a non-rigid target with micro-motions. A new waveform and corresponding technique, which are respectively referred to as Phase Matching waveform and Phase Matching processing, are proposed to reconstruct range profile of a non-rigid target with micro-motions. Phase matching waveform is in fact an adaptive step-down-frequency waveform. The ISAR imaging is primarily examined for targets with micro-motions. Discrete ISAR model is established for targets with micro-motions, and then Phase matching processing is used to generate ISAR image of targets with micro-motions.There are specific applications researches of radar feature extraction from air targets and space targets with micro-motions. Firstly,micro-motions of a helicopter is analyzed, and then radar feature extraction from rotating blades is investigated, including micro-Doppler and Doppler spectrum. Symmetry and power distribution feature of Doppler spectrum are analyzed, which provide a new probable means of air-target identification. The theory of Blind number is researched for dealing with the uncertainty of radar feature of helicopter. Then based on the theory of Blind number, the width of Doppler spectrum is used to estimate rotation parameters. Secondly, micro-motions are analyzed for ballistic missile target, and then radar feature extraction is investigated for ballistic missile target with micro-motions. RCS modulation induced by precession is investigated, and then with RCS modulation, an approach of precession parameter estimation is proposed. Last, micro-motion resolution is explored for ballistic missile target. Micro-Doppler-based motion resolution technique is proposed for resolving vibration and coning motion.The dissertation is concluded with current trends and future outlook in the subject. In particular, some significant and valuable problems are pointed out for further research.