Research On Phaseless Terahertz Coded Aperture Imaging Technology

Phaseless terahertz coded aperture imaging(PL-TCAI)is a new radar imaging technology proposed in recent years.Based on the terahertz coded aperture imaging(TCAI),PL-TCAI uses the metamaterial coded aperture antenna to randomly modulate terahertz waves,which makes the imaging area generate randomly distributed radiation field.The main characteristic of PL-TCAI is that it uses incoherent detector to detect the intensity of the echo signal.PL-TCAI associates the intensity of the echo signal with the inferred reference signal to establish the imaging equation,and obtains the scattering coefficient distribution of the imaging area by the computational imaging method,so as to realize the accurate reconstruction of the target.Different from terahertz imaging technologies such as terahertz array real aperture radar imaging and terahertz synthetic aperture radar imaging,PL-TCAI does not rely on the relative motion between radar and target,or on phased array beam scanning,or on the precise lens system of terahertz camera,so it can achieve high-resolution imaging of forward-looking and staring,which is an important supplement to terahertz radar imaging.Based on the principle of TCAI imaging,this paper introduces the system configuration and imaging principle of PL-TCAI,establishes the corresponding quadratic imaging equation,analyzes the target reconstruction criteria and imaging algorithm,and proposes a fast algorithm for PL-TCAI system considering and combining the practical application requirements,which provides the theoretical basis and technical support for the practical application of PL-TCAI.In Chapter 1,the background and significance of the project are introduced and analyzed in detail,in which the necessity of studying PL-TCAI technology is pointed out,and the important value and wide application prospect of PL-TCAI in terahertz radar imaging are emphasized.Then,the research status of PL-TCAI at home and abroad is introduced,and the main research content and structure of this paper are given finally.In Chapter 2,the basic principle and imaging model of TCAI are introduced firstly,and the principle of realizing intra beam resolution of TCAI is pointed out.Then the influence of the random distribution of radiation field in the imaging area on the imaging performance of TCAI is analyzed,and the simulation results show that the higher the randomness of radiation field,the better the imaging performance.Finally,the influence of range error on the performance of terahertz aperture coded imaging is studied.In Chapter 3,the method of PL-TCAI is proposed.Firstly,the basic system configuration and imaging principle are introduced,and the corresponding quadratic imaging equation is established.Then,the target reconstruction criterion and imaging algorithm of PL-TCAI are given by analyzing the solution method of quadratic equation.Finally,the PL-TCAI method based on array multiple-output technology is proposed,the imaging equation of array reception is established,the influence of array element spacing on imaging performance is analyzed,and the simulation experiment shows that it can accelerate the receiving speed of imaging system,reduce the coding and sampling times in imaging system,shorten the imaging time,and provide reference for fast imaging or even real-time imaging.In Chapter 4,two phase retrieval algorithms are introduced in detail,and the basic theory and characteristics of initialization of truncated spectral method and stepsize optimization of iteration are analyzed.Then based on the sparse prior of the target,combined with the truncated spectral method and stepsize optimization,a fast algorithm for PL-TCAI is proposed.Finally,the simulation results show that the fast algorithm proposed in this paper has good performance in PL-TCAI,which can effectively reduce the amount of measurement data needed in the imaging process,further reduce the number of coding and sampling of the imaging system,and has obvious advantages in accelerating the imaging speed.Finally,the main innovations and research contents of this paper are summarized,and more problems and research directions of PL-TCAI technology are put forward.