Technology On Design And Implementation Of Multi-Mode Radar Waveform System

In order to adapt to the complicated external electromagnetic environment and various natural environment, multi-mode radar becomes an inevitable trend of radar technology development, which employs various task modes to complete the different detective tasks. The design and implementation of radar waveform system is the key technique of multi-mode radar system, and it is also the basis of changeful modes in multi-mode radar. However, there are obvious differences in many aspects from waveforms among different modes of multi-mode radar, such as transceiver system, system bandwidth, signal processing, data management, etc. Therefore, in the missile-borne and satellite-borne applications whose resources are strictly limited, it is a critical issue for the multi-mode radar to design and select the waveform parameters to ensure the compatibility of system transceiver and signal processing among different waveform modes in different applications. Under this background, taking the application of re-entry multi-mode radar detector on the air formation target detection for example, the technology on design and implementation of multi-mode radar waveform system are studied in this dissertation. The results of the researches mainly involve:In the first chapter, firstly, the development trend and the significant research value of multi-mode radar are expatiated from the view of military demands and civil applications. Secondly, a comprehensive survey of existing techniques and its tendency is presented, including detection, wideband high resolution, low probability of interception, cognitive ability, and waveform implementation technology. Thirdly, the characteristics of the mission requirement from the distant to the near in this scenario are analyzed. Under this background, the task modes of radar detector are divided into the long range mode and the short range mode in this dissertation. Finally, the pulse train stepped frequency signal and the modulated nonlinear stepped frequency signal are selected as the waveforms of these two modes, respectively. The significant issues in the research process and the solutions are also presented.Aiming at the long range mode, chapter 2 focuses on the methods of waveform design in the high pulse repetition frequency (HPRF) pulse train stepped frequency signal. Firstly, the principles of anti-eclipsing and multi-target identification are introduced, and the design of waveform parameters is divided into two parts, i.e. the coherent pulse train design and the PRF sets design. In the first part, from the view of the detection capability of single pulse, an analyzing method of the realizability of waveform and the receiving mode is proposed based on the duty ratio factor, and a universal method of waveform design on coherent pulse train signal is also brought forward. In the second part, the theoretical relationship between the precision of range measurement and the true probability of ambiguity-resolving is formulated by taking the Coincidence Algorithm (CA) for example. In consideration of characteristics in this application, a method of PRF sets design under the uncertain priori range information is proposed. At last, taking this application for example, the design methods and principles proposed in this chapter are verified by the simulation experiments. The results show the validity of waveform design method.Aiming at the short range mode, chapter 3 focuses on the methods of waveform design in the modulated nonlinear stepped frequency signal. Firstly, the big sidelobes and grating lobes in the range of modulated stepped frequency signal after matching receiving are analyzed theoretically, and a comprehensive summary of this problem and its solutions is presented. Secondly, aiming at this problem, a novel analytic design method of the modulated nonlinear stepped frequency signal is proposed based on the principles of stochastic approximation. The rationale and design flow of this method are introduced in detail. Finally, taking this application for example, the waveform design methods are verified by the simulation experiments. The results show the performance on sidelobes and grating lobes suppression of the proposed method in this chapter is much better than the traditional methods, and it is easy to design and realize.In the fourth chapter, the method of circuit design and implementation on multi-wave system generation and management is explored. Firstly, the constraint conditions are analyzed from the view of implementability as well as in consideration of Direct Digital Synthesize(DDS) technology, and it provides that different implementations have effects on the performance indices of the waveform. A scheme appropriate to the application in this dissertation is given. Secondly, aiming at the problems of high speed digital circuit design, a synthetic simulation method is proposed based on the multi-processors architecture in the waveform management system. Practical results in engineering show that the proposed method improves the performance of system and increases the success rate of design significantly. Finally, the pivotal performance indices of the waveform are tested, and the experiment results of high resolution range profile (HRRP) and inverse synthetic aperture radar (ISAR) imaging in darkroom show the validity of waveform system in this dissertation.