Research On Methods Of MIMO Radar Waveform Design Based On Chaotic Signals

MIMO radar as a new radar system changes the work way of the traditionalradar. MIMO radar transmitting orthogonal signals to detect the targets all over thespace has the features of better resolution, anti-interception and anti-jamming, whichhas become a hot research field in recent years. The orthogonal signals direct impactthe function of MIMO radar. Thus orthogonal waveform design of MIMO radar isan important aspect of technology.Currently the methods of orthogonal waveform design for MIMO radar aresetting up cost functions to find the orthogonal signals by the optimization algorithm.The optimization algorithm owns the disadvantage of inefficiency. The performanceof the signals got by the optimization algorithm will be changed with change of thetransmit signal array elements and code length of MIMO radar. Chaotic signals as aclass of pseudo-random signals own good randomness, sensitivity of initial value,the ergodicity, orthogonality and other characteristics. In this thesis, we fully use theadvantages of this series of chaotic signals to design the orthogonal waveform ofMIMO radar.For the characteristics of orthogonality of MIMO radar’s transmission, we usethe chaotic signals to design the waveform of MIMO radar. The main work andcontributes are as follows:1. Firstly, for the characteristics of orthogonality of MIMO radar’s transmission,we scientifically elaborate the criterion of orthogonality and ambiguity for thewaveform design of MIMO radar.2. Secondly, this thesis uses the method of using chaotic signals to continuouslymodulate the amplitudes of the carrier waves in a high frequency for design thewaveform of MIMO radar. The complex envelopes of MIMO radar signals are stillchaotic signals, which have the broadband spectral properties, orthogonality andother characteristics of chaotic signals. Performance of the radar signal is mainly determined by the chaotic signals. With taking advantages of the chaotic signalsensitivity to initial conditions and the orthogonality of the different kinds of chaoticsignals, we can get a large capacity of orthogonal signals.3. Thirdly, this thesis uses the method of using chaotic signals to continuouslymodulate the frequency of the carrier wave in a high frequency for design thewaveform of MIMO radar. By using normalized chaotic signal frequency tomodulate continuously the frequencies of carrier signals, the frequencies of theMIMO radar signals are random various within the bandwidth. This method differsfrom the chaotic sequences of discrete frequencies waveform design based on codedsignals, and do not need to integerize and sort the sequence of chaotic signals, whichhave better randomness. The method of continuous FM based on chaotic signalsbelongs to the method of phase spectrum modulation. The orthogonal signals got bythe method are a kind of pulse-compressed signals having nonlinear phase, whichhave a great time-bandwidth product and good ambiguity.4. Finally, this thesis uses the chaotic sequence to design MIMO radar signals.The waveform of phase coded based on the chaotic sequences takes the place of thewaveform of coded based on pseudorandom sequence, solving the problem of thelength and higher ASP of pseudorandom sequence. Meanwhile, this thesis uses theimproved method of binary-phase coding and researches an improved method basedon two chaotic signals. MIMO radar transmits different orthogonal signals in thedifferent periods through the improved method. The signals produced by theimproved method have low probability of intercept and better stealth.