Research On Grating Lobe Suppression Method Of Distributed Aperture MIMO Radar

Achieving high-precision measurement is one of the important directions in the development of modern radar.The high-precision measurement depends on the resolution of the radar.Increasing the radar aperture can improve the resolution.The number of radars required for the half-wavelength array designed according to the conventional method leads to high costs.The thinned array can greatly reduce the number of array elements.However,a large number of grating lobes will occur when a large-space periodic array is performed.As an emerging radar system,MIMO radar realizes the virtual aperture expansion capability through waveform diversity technology,and improves the angular accuracy,clutter suppression and energy utilization of the radar system.Combine MIMO radar system with thinned array,the distributed aperture MIMO radar can greatly improve the resolution,but the large number of grating lobes generated seriously affect the radar detection performance.It is important to solve the grating lobe problem of distributed aperture MIMO radar.This paper studies the grating lobe problem of distributed aperture MIMO radar.The main work is divided into the following two aspects:The nested array simulates a large array with an aperture expansion and an increase in the number of array elements through the original physical array.The physical structure is relatively simple.It has a closed solution and the degree of freedom of expansion can be calculated.In order to solve the grating lobe problem of distributed aperture MIMO radar in far field,a non-uniform nested MIMO radar model is established.The normalized patterns of the model is derived.We get the distributed aperture MIMO radar arrangement through a series of derivations such as Poisson summation,Stationary phase approximation and Taylor series expansion method.The genetic algorithm is very effective for the research of distributed-aperture MIMO radar,we can use genetic algorithms to solve optimization problems.Compare this algorithm with several existing grating lobe suppression algorithms.Simulation results demonstrate the effectiveness of our algorithm.In the near field situation,when we use the virtual array element technology of MIMO radar,the transmitting array is densely distributed,its resolution is poor but there are no grating lobes and the receiving array is sparse distributed,it has high resolution but there are many grating lobes.Even if the transmitting array and receiving array are properly designed,the patterns are distorted,the Nulls and the grating lobes can not be completely aligned,and the grating lobe can not be completely suppressed.But the same design can be used to get high resolution and less grating lobes in the far field.In order to solve the application problem of MIMO radar array in the near field,we simulate the distortion of the near-field pattern and propose a solution that widening the Nulls of the transmitting pattern through weighting at the receiver.This improves the grating lobe suppression problem of near-field MIMO radar.Simulation results demonstrate the effectiveness of our method.Compared to the original MMO radar pattern,the grating lobes are suppressed.