| Waveform design based on constraint optimization theory can achieve flexible and extensive waveform applications,allowing radars to gain more degrees of freedom and improve detection performance.Phase-coded waveform has a large compression ratio,which is a kind of pulse compression signal with a large time width and a large bandwidth.However,for moving targets,this waveform has Doppler sensitivity.This will seriously affect the radar’s target positioning,range and speed resolution,ranging and speed measurement accuracy,etc..At the same time,this problem also restricts the application range of the waveform.Multiple-input multiple-output(MIMO)radar has the capability of flexible waveform diversity,which can provide more system degrees of freedom,and has significant advantages in resolution,parameter identification and other aspects.However,the superiority of MIMO radar waveform is reduced when it is affected by clutter or interference,so it is difficult to achieve a joint design of the transmit and receive beamforming for multi-tasking while ensuring detection performance.Meanwhile,the solution to the problem model is often difficult.In view of the above problems,based on the constraint optimization theory,this thesis studies the design problem of phase-coded waveform with high Doppler tolerance in monostatic radar and the joint optimization problem of transmitting and receiving beamforming with multi-task requirements in MIMO radar.The main research work is as follows:(1)To tackle the problem of Doppler sensitivity of phase-coded waveform in radar systems,a method for designing transmit waveform with Doppler tolerance under constant modulus(CM)constraint is considered.In this method,the variance between the ideal local ambiguity function(LAF)and the real one is used as the objective function to establish the minimization problem.To solve the non-convex quartic problem,a template matching sequence optimization(TMSO)algorithm is proposed.By introducing an auxiliary variable and problem transformation,the solution to the original problem can finally be obtained,involving two alternately iterative subproblems with closed-form solutions.Numerical experiments show that the waveform designed by the proposed method not only has high Doppler tolerance,but also has a certain performance of low probability of interception(LPI).In addition,the execution efficiency of the algorithm is at least two orders of magnitude faster than that of the reference algorithms,which has a significant advantage.(2)To tackle the problem of the joint design of the transmit beamforming vector and the receive beamforming vector in MIMO radar system,the signal-to-interference plusnoise-ratio(SINR)is used as the figure of merit in the background of signal dependent interference.This design is pursued studying a maximization SINR with multiple constraints on the similarity conic,power and energy,and can ensure a good transmit beampattern to a certain extent.To solve the proposed optimization problem,the transmit beamforming vector and the receive beamforming vector are combined based on some mathematical manipulations so that they can be updated simultaneously,bypassing the traditional transmit and receive(T-R)iterations and initialization.The numerical simulations show that the proposed method achieves a flexible trade-off between the two metrics of maximizing SINR and a good transmit beampattern.Compared with the traditional T-R iterative method,the proposed method achieves better performance,and its running time is at least 200 seconds faster. |
