Research On Design And Disposal Of Step Frequency Waveform For Radar

Signal processing of step frequency waveform is discussed in this paper. Focusing on signal design and processing , low sidelobe implementation is studied.For signal design, methods are discussed under given spectrum, such as equal area division method, adaptive signal design method based on gradient and method based on genetic algorithms. Equal area division is based on the non-linear frequency waveform design. The combination of frequencies depends on the selected form of window function. Therefore, it is not the optimal one. And the sidelobe is uneven. Adaptive method uses the error gradient of the max sidelobe to adjust each frquency in order to distribute sidelobe even. But due to the gradient algorithm, unperfect initial selection will lead to local minima. Genetic algorithm is the use of its advantage for solving combinatorial optimization problems to achieve the frequencies of the signal. Through discreting the given spectrum, optimal frequencies could be achieved. But as the use of discreting, the solution usually converge to the vicinity of the optimal one. So inited by genetic algorithm and adjusted by gradient algorithm, the best availabele solution could be achieved.For signal processing, as in some cases, low sidelobe can not be achieved by signal design. It can be done only by processing method. So sidelobe suppression method is discussed in this paper. A variety of ways could be used for sidelobe suppression. This paper focuses on the filter design method for suppression. Method is proposed based on second order cone programming(SOCP) for sidelobe suppression filter design. Constant gain can be achieved by this method.Two-dimensional treatment of range-speed is an important processing process. So in addition to range sidelobe suppresion, speed extracted of step frequency waveform is also discussed. Two commonly used method for speed is frequency domain interpolation and direct speed alignment. Target speed processing can also use the interpolation and extrapolation algorithm to get high resolution processing, such as the use of CG model for speed super-resolution.In the two-dimensional processing of step frequency wavform, because of the coupling of range and speed, this paper analyzes the coupling phase cased by speed after speed disposal. And then phase compensation method is discussed. After this, range disposal can be put out: matched filtering and sidelobe suppression. So the two-dimensional processing is finished.