Research On Pattern Synthesis Of Time-modulated Array Based On Sequential Second-order Cone Programming Algorithm

Time-modulated antenna arrays have the advantage of flexible beam scanning,which can help to realize the multi-beam and ultra-low sidelobe pattern.Therefore,they have been widely used in the fields of radar,wireless communication and navigation.Time-modulated antenna arrays can obtain a low sidelobe pattern under the constraint of a low amplitude dynamic range ratio through periodically modulated RF switches,which breaks through the bottleneck of the traditional antenna array design.By using sequential second-order cone algorithm,this paper explores several key problems in depth,including optimizing the sparse array with shaped-patterns which are reconfigurable,the sidelobe and sideband suppression of time-modulated array antennas and random errors.The major work and innovations are as follows:(1)A sparse array pattern reconstruction algorithm based on a sequential second-order cone programming is proposed,which realizes the synthesis of multiple shaped patterns with a single array structure and the minimum number of array elements.By minimizing the number of working elements,the proposed algorithm selects certain antennas in an array to satisfy the prescribed arbitrary main lobe width,response ripple,nulling,and side lobe level.The array can achieve multiple shaped patterns by changing the excitation coefficients.The simulation results of linear and sparse array show that the algorithm can achieve the desired beam paterrn with fewer array elements under the same array aperture.(2)A sequential second-order cone programming algorithm is proposed for the efficient synthesis of time-modulated antenna arrays,which achieves low sidelobe and low sideband patterns with a low amplitude dynamic range ratio,and speeds up the convergence time.Based on the Pulse Shifting(PS)model,the pattern synthesis problem is divided into two steps: sidelobe suppression and sideband suppression.The sidelobe suppression can be directly realized by convex optimization algorithm.The sideband suppression is a multi-dimensional nonlinear optimization problem,hence using intelligent algorithms such as particle swarm optimization(PSO)takes long time.In order to solve this problem,a relaxed convex optimization algorithm is considered.On this basis,a sequential second-order cone programming algorithm based on Taylor series expansion is proposed to optimize the switch-on time sequence and excitation coefficients.Simulation results show that the algorithm takes less time and achieves lower sideband level than other algorithms such as PSO.(3)A robust low sidelobe pattern synthesis algorithm against array element position disturbance is proposed.The relationship between position disturbance and steering vector error is deduced and robust second-order cone programming algorithm for low side lobe pattern is proposed.Various simulation experiments are conducted to discuss the performance of the algorithm.In addition,this paper also analyzes the switch time error of the time modulation.Simulation results demonstrate that the trapezoidal pulse waveform generated by the switch-on time error can suppress the high frequency sideband.