Radar Orthogonal Waveform Design And Performance Analysis

Compared with the Phased-Array Radar, MIMO radar has many advantages. There are multiple transmit array elements in MIMO radar. The transmitted waveform of each array element is orthogonal with each other. These waveforms will not form a beam in space and can cover the space effectively and widely. For MIMO radar, the orthogonal waveform design is a premise to ensure that the radar resolution, system accuracy and other properties. The current design approach of MIMO radar orthogonal waveform focuses on obtaining orthogonal waveform through the intelligent algorithm. However, there are many shortcomings in optimization methods, such as time-consuming, real poor, inefficient and limited signal libraries.Chaotic signal gets attention because of its sensitivity to initial conditions, noise-like characteristics, sharp autocorrelation function, thumbtack-type ambiguity function and good distance-measurement precision, etc. Chaos signal is a kind of pseudo random signal. Compared with random signal, the chaos signal is easy to control. And compared with optimization algorithm, waveform design based on chaotic signal is more flexible and its time-consuming is shorter. This thesis is mainly based on chaotic signal to design MIMO radar orthogonal waveform, and the main research works are as follows:1. Based on basic principles of MIMO radar, an in-depth analysis is conducted for orthogonal waveforms of MIMO radar. Four common chaotic maps are studied, which are tent, logistic, bernulli and quadratic. Besides, simulation analysis of their six characteristics are given, i.e. time-domain waveform, bifurcation diagram, ergodicity, phase space characteristics, correlation and power spectral characteristics.2. Three chaotic modulation signals have been explored, i.e. chaotic discrete frequency coded radar signal, chaotic phase-coded radar signal and chaotic amplitude modulated radar signal. And the formation mechanism of three modulated signals are studied emphatically. Then the performances of three chaotic modulation signals have been analyzed, and the comparisons of the autocorrelation property, cross-correlation property and power spectrum have been made for the tent, logistic, bernulli and quadratic modulated signals. Research results show that chaotic modulated radar signal has good autocorrelation and cross-correlation properties, and its power spectrum is relatively flat.3. The main innovation of this thesis is analyzing the principle of complex chaotic sequence and making tent and logistic sequence as the original sequence to form the composite sequence. Then joint amplitude-phase modulation radar waveform and joint frequency-phase modulation radar waveform based on composite sequence are researched. Besides, the correlation, power spectrum and ambiguity function are simulated respectively. Compared with joint amplitude-phase modulation signal based on tent sequence or logistic sequence, joint amplitude-phase modulation signal based on composite sequence has obvious advantages above these three aspects. Joint frequencyphase modulation signal has a slight advantage and inherites the advantage of a flat power spectrum from joint frequency-phase modulation signal based on tent sequence. In the end, the Low Probability of Interception(LPI) has been explored by taking joint frequency-phase modulation signal based on composite sequence for instance. Simulation results show that chaotic modulation signal has a good low interception performance.