Research On Target Detection Method Of Random Frequency Array

The resolution is one of the most important criterions to measure the performance of radar imaging antenna aperture,unable to distinguish targets within the same beam coverage.According to the Rayleigh criterion,the method of improving the azimuth resolution is to increase the antenna aperture and the frequency of the transmitted signal.However,the expansion of the antenna aperture will cause the increase of the antennas' size and weight,which brings great difficulty to the design and application of the antenna.SAR and ISAR can get high lateral resolution,but are dependent on the relative motion between radar and target,this condition limits the application.Therefore,it is necessary to explore a kind of high resolution imaging which can realize the static condition.A method for high resolution imaging of a random frequency array radar system is studied in this thesis.From the theoretical analysis,we can break through the limitation of antenna aperture and construct more independent observation functions through the design of two dimensional random radiation field,This way not only can be obtained within the beam target resolution information,but also improve the resolution greatly.The variation of the difference in the radiation field is the key to the construction of two dimensional random radiation field.It can not only determines the imaging resolution in the subsequent correlated process,but also is the basis for the design of radiation source.The main work of this thesis is as follows:First of all,the thesis studies the model of the target correlation imaging system of random radiation field,and analyzes the two key points of the system model: Firstly,in order to ensure the performance of random radiation field,how to optimize the emitter array and the emission signal.Secondly,in order to obtain the high resolution image,how to choose the appropriate sparse recovery algorithm to reconstruct the target scene.Then,it introduces the geometric model of random frequency array radar and derives the signal model of random frequency array radar from the angle of mathematical analysis in detail.Finally,the influence of the two factors of the radiation source diameter and the number of the radiation source array on the randomness of the space-time radiation field is analyzed.The computer simulation is carried out by using the compressed sensing algorithm.Secondly,this thesis introduces the principle of the traditional methods of compressed sensing and fractional order norm and implements the radar super-resolution threedimensional imaging through computer simulation experiment.According to the imaging performance,the results show that the proposed method is more effective and robust than the traditional compressed sensing method.Then,the influence of multi frequency random radar array on super-resolution imaging is analyzed,such as array amplitude error,phase error and signal to noise ratio.It is proved that the robust sparse reconstruction method is very important for radar super-resolution imaging through computer simulation experiment.Finally,the future research direction is put forward.One of the key factors that influence the performance of the random radar array super-resolution imaging is the performance of the space-time random radiation field.At present,the design of space-time random radiation field is still in the research stage,and it is necessary to establish a sound knowledge theory system.In the case of large scenes,how to find a more robust sparse reconstruction algorithm for real-time fast imaging is still a subject to be studied.