| Frequency diversity array radar(FDA)has more freedom to change the phase and frequency,it can choose to change both the phase and frequency,or can choose to change the frequency only,giving it more flexibility and application scenarios.Due to the small frequency offset between array elements of frequency diversity array radar,the formed pattern is an "S" beam with range angle correlation,this feature is not always meet the actual demand,such as only need to focus the energy in a fixed interval,suppression and target with different distance or angle with interference from different angles,improve target localization accuracy,and so on and so forth,It brings severe challenges to beamforming and interference suppression,so it is of great significance to study the formation of spot beam pattern.By using the method of nonlinear change of array frequency,this paper intends to study the three problems of spot beamformingăinterference suppressionănear field beamforming and target positioning of FDA radar,so as to achieve the maximum response of single beam to any target and effectively suppress interference.The main work is as follows:1.Aiming at the problem of multiple main lobe beams in the received beam of frequency diversity array radar,an iterative local search algorithm(ILS)based on Metropolis criterion is proposed to optimize the frequency offset and array element spacing.In this method,the single base transceiver array model is used,and the iterative local search algorithm is used to find the optimal frequency offset and the optimal spacing between array elements.In the search process,the frequency offset value is received probabilistically according to metropolis criteria to find the global optimal frequency offset value.Compared with simulated annealing algorithm,this method effectively reduces the number of side lobe peak pulses,reduces the range side lobe energy peak,improves the focusing resolution in the angular direction,and forms a beam pattern closer to the regular dot shape.In order to enhance the ability of interference suppression in beamforming,SMI algorithm and LMS algorithm are further applied to frequency diversity array to suppress interference based on the above methods.Simulation results show that the two algorithms not only form the maximum gain of energy at the target point,but also suppress the interference to a certain extent.And SMI algorithm has stronger suppression ability than LMS algorithm.2.Aiming at the problem that the waveform of frequency diversity array radar is spherical wave and the range loss can not be ignored in the near-field emission,a weight for compensating the range loss is proposed,which can make the range loss constant and effectively reduce the error of energy focusing offset.In order to improve the focusing accuracy of near-field energy,the Zigzag frequency offset is proposed,and the multi carrier mixed frequency offset is formed by combining the multi carrier logarithmic frequency offset and the multi carrier square shaped frequency offset.Compared with logarithmic frequency offset and chaotic frequency offset,the Zigzag frequency offset and the multi carrier mixed frequency offset improve the energy convergence performance,especially the range focusing resolution.Among them,the best effect is multi carrier mixed frequency offset.Finally,combined with multi carrier mixed frequency offset,the beam scanning is used to traverse the spatial region to achieve near-field target positioning and improve the positioning accuracy. |
