Waveform Design And Signal Delay Of Continuous-Chaos Frequency-Modulating Radar

Continuous-Chaos Frequency-Modulating Signal (CCFMS) radar, which uses continuous chaotic signal to realize frequency modulation, belongs to categories of frequency-modulating radars. The CCFMS radar transmits chaotic signals and hence has some excellent characteristics such as simple generation, small realization cost, low probability of intercept, good anti-jamming and electromagnetic compatibility. CCFMS has flat power spectrum and can avoid frequency hopping, time clock synchronization and parameters adjusting in discrete frequency modulation design. Compared with traditional chaotic signals, CCFMS provides the peak to average power ratio (PAPR) with ideal value 2, which can take full advantage of the efficiency of transmitter.This dissertation mainly discusses the waveform design and signal delay of CCFMS radar with chaotic dynamics theory. Main results are concluded as follows:(1) Performance analyses of CCFMSThe mathematical expression of CCFMS is given. The auto-correlation function and root-mean-square (RMS) bandwidth of CCFMS are derived in theory. The results show that autocorrelation function of CCFMS has excellent sidelobe suppression performance. Its RMS bandwidth is proportional to frequency modulation index and RMS of chaotic signal. The performance of CCFMS is further confirmed with typical chaos. It is found that CCFMS has high time peak to sidelobe ratio, flat power spectrum, almost thumbtack ambiguity function and PAPR equal to that of sinusoidal signal.The performance of CCFMS radar against noise and frequency shift jamming is analyzed. Compared with LFMS radar, CCFMS radar has obvious anti-jamming advantages with signal-to-interference ratio improvement factor increased by about 5.5 dB, and does not generates false range targets.(2) Waveform design of CCFMS radarDynamical design theory of CCFMS is proposed, in which CCFMS is generated by nonlinearly coupling continuous chaotic signals with a sinusoidal oscillator. A concrete design implementation is given by taking Colpitts circuits as an example. CCFMS is confirmed to be chaotic by attractor reconstruction and Lyapunov exponents.Direct and iterative designs of CCFMS cognitive waveform with fine spectrum control are given. Depending on the target power spectrum characteristics, this method can generate CCFMS waveforms, whose output-power spectrum varies with the external environment, hence the CCFMS radar has active learning ability.(3) Studies on filtered synchronization and impulsive filtered synchronization methods of chaotic systemsFiltered synchronization method of chaotic systems without original drive signal is studied. This method only transmits the filtered signal, and restores lost information by filtering using response system variables. Low pass and Band pass filtered synchronization performances are discussed respectively. Simulation results show the method can transmit only 50～80% efficient bandwidth energy to achieve synchronization of chaotic systems.Conditional Lyapunov exponent (CLE) based impulse synchronization and impulsive filtered synchronization methods of chaotic systems are proposed. Based on the developed CLE calculation of impulsive synchronization, the method breaks through the restrictions in traditional impulsive synchronization theory and the obtained synchronization interval is closer to the actual synchronization interval. Meanwhile the proposed method can determine synchronization stability and estimate synchronization interval of impulsive filtered synchronization. The simulation results confirm correctness and feasibility of the method.(4) Signal delay of CCFMS radarFiltered synchronization and impulsive filtered synchronization based on signal delay technique of the general chaotic signal are proposed to realize broadband chaotic signal delay using narrowband delay techniques. Filtered synchronization based delay technique gives the smallest filter bandwidth to realize synchronization and impulsive synchronization based delay technique gives the relationship between filter bandwidth and the smallest sampling frequency.Based on generation principle of CCFMS, narrowband delay of CCFMS is studied. Response system of dynamical model of CCFMS is constructed, and synchronization impact on delay performance is discussed. This narrowband delay technique can reduce amplitude-phase uniformity, the insert loss and the cost of delay equipment. Simulation results show this technique can save the delay bandwidth by 65%.