Research On Signal Design And Processing For Orthogonal Waveform MIMO Radar

The term of multiple-input multiple-output (MIMO) radar has recently been introduced by MIT Lincoln Laboratory, Bell Laboratory and New Jersey Institute of Technology. MIMO radar has been extensively studied in recent years and has become a hot topic of theoretical researches and experiments in the field of radar.In the MIMO radar, all transmitting elements generally send different signals, form a low-gain wide-beam in spatial domain; and all receive elements receive echoes independently and then perform synthetic processing and integration. MIMO radar operated with orthogonal waveforms is called orthogonal waveform MIMO radar.Orthogonal waveform MIMO radar has some advantages on target detection, angle measurement capability and low probability of intercept (LPI) compared with the traditional radar. The performance of orthogonal MIMO radars is partly decided by characteristics of waveforms. Hence, orthogonal waveform design becomes a significant research subject and only excellent waveforms can exploit the potential of MIMO radars. In recent years, some orthogonal waveforms for MIMO radars have been derived. These results, whereas to some extent, have some limits on performance.In this dissertation, orthogonal waveforms and corresponding signal processing techniques for MIMO radar are explored. The main contributions are summarized as follows.1 Orthogonal multi-frequency signals design and processing. A general orthogonal multi-frequency signal form is researched, several possible types are listed. Conventional OFDM-LFM and orthogonal polyphase coding are its special cases. Doppler ambiguous resolusion, Doppler integration and high resolution Doppler processing approaches and their performance analyses are presented for multi-frequency signal. In addition, multi-carrier phase coded-amplitude modulation signal is suggested for MIMO radar and corresponding fast pulse compression approach is also presented.2 Orthogonal noise waveforms design. Some generation and optimization methods for noise are presented. In particular, spectrum shaping-based sidelobe mitigation and nonlinear bending function mapping-based crest factor reduction techniques are proposed. Due to the noise nature, optimized noise is suitable for orthogonal waveforms generation. The design results are much better than orthogonal discrete frequency coding waveform and orthogonal polyphase coding.3 Orthogonal chaotic signals design. The relations between chaotic signal and radar performance are analyzed by the help of the sensitivity to initial conditions and system parameters. Specially, parameters'optimation, selection of initial values and design of band width, and pre-filtering are researched. Chaotic radar signals are generated through designing parameters of chaos system for good signal embryos and band width of signals, and utilizing a set of optimizing algorithms.4 Stepped time intervals pulse train (STIPT) waveform design and corresponding processing. The range sidelobes are eliminated through modified correlation algorithm (MCA). Coherent MCA and Manchester code-based non-coherent MCA architectures are presented. Coherent MCA performs fast processing by using FFT and can obtain unambiguous range and Doppler measurements. The non-coherent MCA can be used in simple or conventional noncoherent radar systems.5 Orthogonal STIPT-based waveforms design. Three orthogonal STIPT-based coding methods, frequency divided STIPT coding, stagger interval STIPT coding and random interval STIPT coding, are proposed for orthogonal MIMO radar waveform generation. The design principle and an example are presented to obtain a perfect range sidelobe performance from stagger interval STIPT coding. A simulation is presented to achieve a large number of orthogonal waveforms from random interval STIPT coding. Both the peak of autocorrelation sidelobe level and the peak of cross-correlation level of these resulted waveforms are superior to -30dB.The above proposed orthogonal waveforms can be used in MIMO radar systems; also can be used to bistatic, multistatic or netted radar systems straightly or through minor modifications. The single waveform versions of some orthogonal signals can be used in the conventional monostatic radar to improve the radar performance.