Adaptive Waveform Design For Cognitive Radar

Cognitive radar, a new kind of intelligence radar, breaks the receiver–launchopen-loop mode of the traditional radar. It makes full use of the environmentalresources which makes the radar system have better estimation and detectionperformance. Cognitive radar has become the research focus of the radar system inrecent years. Cognitive radar mainly introduces the closed-loop system. It makes fulluse of the environment and the information of the target to design and launch thereal-time waveform, which improves the detection efficiency and the estimationperformance of the system.Currently, the methods of cognitive radar waveform design are based on SNRcriterion and mutual information criterion. However, the influences of the clutter inradar transmitted waveform are not considered and the optimization algorithms ofwaveform design are mostly based on the Lagrange multiplier algorithm in thesemethods. If the Lagrange multiplier is introduced in the optimization algorithm whenthe radar transmitted waveform is designed, the program has to search for it firstly,which leads to a large amount of calculation. Under the background of clutter, thewaveform design method based on Lagrange multiplier algorithm and the waveformdesign method based on the maximum energy distribution are researched in this paper.There is no need to search for the Lagrange multiplier in the waveform design methodbased on the maximum energy distribution, which makes the algorithm simple andhave better practicability.For the adaptive waveform design of the cognitive radar, the main contents inthis paper are as follows:Firstly, the optimal waveform design method of the cognitive radar based onmutual information criterion under the background of clutter is researched in thispaper. The mutual information formula between transmitted waveform and the targetis given. The Lagrange multiplier algorithm and the maximum energy distribution algorithm are respectively used to optimize the waveform. Then the optimalwaveform of the cognitive radar based on mutual information criterion can beobtained. With this method the mutual information between the goals and the echo ismaximized and the estimation performance of the radar system can be greatlyimproved.Secondly, the optimal waveform design method of the cognitive radar based onSINR criterion under the background of clutter is introduced in this paper. Theformula between the transmitted waveform and SINR of the system is given. TheLagrange multiplier algorithm and the maximum energy distribution algorithm arerespectively used to optimize the waveform. Then the optimal waveform of thecognitive radar can be obtained based on SINR criterion. With this method the SINRof the system is maximized and the detection efficiency of the radar system can begreatly improved.Thirdly, to solve the problem that the SINR of the actual radar system must meeta certain threshold value, this paper makes research on the cognitive radar waveformdesign method of the maximum mutual information under the condition of limitedSINR and the energy. This method regards SINR and energy as the constraintconditions and regards the mutual information between the target and the echo as theobjective function. Then the model of the cognitive radar optimal waveform based onmutual information criterion can be established. The sequence quadratic programmingoptimization algorithm is used to solve the optimization model. The optimalwaveform obtained by this method has better practicability.Finally, to solve the problem that the radar transmitting signal is usually a timedomain signal in the actual radar system, but the adaptive waveforms of the cognitiveradar designed before are all based on the form of the amplitude energy spectrum,which lacks the phase information, the time domain waveform synthesis algorithm toconvert the designed optimal waveform to the time domain waveform is used in thispaper. With the method of the signal sequential detection, the model of the cognitiveradar target detection is established and the optimal waveform on the target detectionis completed. Compared with linear frequency modulation signal launched by the traditional radar, the optimal cognitive radar waveform designed in this paper hasbetter detection performance.