A Research Of Sidelobe Suppression In Time Modulated Antenna Array

With the popularity of antenna array in military and civil areas, increasingly importance has been attached to the anti-jamming of antenna array. As the major measure of interference suppression, sidelobe suppression has been the focus of specialist in the field. Various solutions have been explored for the sidelobe suppression of antenna array for years. But most of them are not doing very well with ultralow sidelobe and limited to uniform array. In this thesis, the previous work on uniform array is further optimized and applied to thinned array. Details are as follows:1. This thesis puts forward a new algorithm called scale factor and crossover rate dynamic change differential evolution(FCRDC-DE) algorithm to make up the disadvantages such as excessive number of iterations, slow speed of convergence and local minimal in traditional differential evolution(DE) algorithm. This algorithm optimizes the control parameters of traditional DE algorithm through the hill climbing algorithm which makes sidelobe level about 6dB lower under same beamwidth and convergence rate nearly twice as before.2. This thesis introduces the time modulation and applies it to thinned array to solve the problem of high amplitude dynamic-range ratios. The basic idea of time modulation is to turn off some of elements in antenna array in a certain time sequence, so that equivalent amplitude weighting can be achieved when averaged over time. The optimization on the switch-on time and position of elements with the FCRDC-DE algorithm has a better performance in sidelobe suppression and 3dB lower in sideband level than traditional DE algorithm.3. The sideband problem in the time modulated array is discussed in detail and a novel time modulated scheme called sub-sectional optimized time steps(SOTS) is introduced for thinned array. In view of masses of optimized parameters and difficulties of convergence in the SOTS, this thesis proposes an improved approach names variable sub-sectional optimized time steps(VSOTS) which makes the number of time steps of each element dynamic change. The numerical results show that a 5dB lower sideband level can be synthesized with this approach than the traditional method.