DOA Estimation Of Time-modulated Array Based On Compression Sensing

Antennas play an important role in modern wireless communications and radar systems.With the rapid development of wireless technology such as communication and radar,all kinds of electronic systems require demanding for antenna systems.Thus,“time” is introduced as a new design freedom into the conventional antenna design,replacing or partially replacing the control of the amplitude and phase by controlling the antenna working time.At the same time,due to the introduction of “time” freedom,there are many unique radiation characteristics in time-modulated array,which could meet the antenna requirements of high-performance and low-cost.Direction of arrival(DOA)estimation is a fundamental problem in array signal processing,and it is also one of the most important tasks in radar and sonar.DOA estimation based on conventional arrays has been studied extensively and deeply,but few research on DOA estimation based on time-modulated arrays has been done.Therefore,the following research work on the DOA estimation of time-modulated arrays has been carried out in this thesis:Firstly,the DOA estimation of the conventional array antenna is introduced,including the basic principle of the conventional array signal,the DOA estimation method based on the MUSIC algorithm,the forward and backward spatial smoothing algorithm,and the improved MUSIC algorithm and the compression sensing algorithm.Through simulations,a series of comparative results have been achieved.The estimation performance of the compressed sensing algorithm is better than that of the conventional DOA estimation algorithm,which lays a theoretical foundation for the subsequent research.Secondly,the DOA estimation method of time-modulated arrays based on MUSIC algorithm is introduced.The time sequences and the distance between the elements are optimized by using the artificial bee colony-differential evolution algorithm.Furthermore,by making full use of the sideband radiations,the suitable time-modulated array pattern synthesis algorithm has been realized.The simulation results show that under the circumstances of small number of snapshots,low signal-to-noise ratio,closely spaced sources,and with correlated signals,the performance of DOA estimation algorithm based on MUSIC in time-modulated array is degraded.Then,the DOA estimation for time-modulated uniform linear array based on compression sensing is studied.The sparse recovery problem is constructed based on the sideband signal reception model of the time-modulated uniform linear array.In the construction process,the over-complete matrix is constructed by the uniform meshing of the spatial domain,and then the direction of the arrival is obtained by the optimization problem of the sparse signal ?1-norm.The simulation results verify the feasibility and effectiveness of the compression sensing in the DOA estimation of the time-modulated array.The performance of the DOA estimation based on CS in time-modulated array is much better than that of the traditional estimation algorithm,especially under the circumstances of small number of snapshots,low signal-to-noise ratio,closely spaced sources,and with correlated signals.Finally,in order to reduce the error to obtain more sparse results,the weighted constraint is used in the model of the optimization problem of the ?1-norm.It can be seen from the simulation results that the weighting algorithm can remove the pseudo peak and has higher resolution compared with other calculation methods.And then the idea is introduced into the time-modulated non-uniform linear array.The simulation results show that the algorithm is also applicable to the DOA estimation of the four-dimensional non-uniform linear arrays.