Research of Compressive Sensing Imaging Technology Based on Metamaterial

Author:Bai Jia Jun

Supervisor:fu yun qi


Degree Year:2018





Millimeter wave has an important role in medical and security field because of its abundant frequency band resources and good penetrating performance.Common scanning imaging,staring imaging and SAR imaging system,aperture size and working bandwidth determine the spatial resolution,the theory of compression perception breaks the traditional Naquist sampling theorem.And by solving the optimization problem,the original signal can be reconstructed from the high probability of a small number of measured values.In the millimeter wave band,there are many problems to be solved in the compression perception imaging from theory to practice.Taking this as the starting point,combined with the unique radiation characteristics of the super materials and using the powerful spatial regulation ability of millimeter wave,this paper focuses on the key measurement matrices in the compression sensing imaging,and puts forward several structural millimeter wave "mask plates".And the simulation and experimental verification of the imaging system are carried out.In this paper,a millimeter wave sensing imaging model based on sparse array distribution is proposed,which is equivalent to the row and column superposition random feed in the array complexity,but the imaging capability is comparable to all the independent random feed of all the elements,and the performance of the measured matrix is approximated by the Gaussian random matrix.In the case of reducing the complexity of the system,the imaging effect is not affected,and the model is extensible,which can be used to design the aperture in the way of sparse distribution,feed-phase and so on.Based on the frequency selective surface(FSS),a millimeter-wave sensing imaging system is designed,which can change the diode breaking state by switching pin diode bias loaded at both ends of the ring slot structure,thus controlling the breaking of the FSS unit.When the pin diode in the FSS is randomly switched to the working state,when the annular gap in different positions is involved in radiation,a sparse array with different feed distributions can be obtained,and after 800 random combinations of full wave simulation,the Near Field distribution is deduced,and the 800*1024 pixel measurement matrix is constructed,and the matrix is used to realize the 32*32 pixel millimeter wave pistol pattern reconstructed,and the signal to noise ratio can reach 30 dB when the sampling rate is only 25%,which satisfies the practical demand.Based on the difference of the radiation characteristics between different frequencies of the materials,one-dimensional frequency-sweep compression sensing imaging system is designed,which realizes the variation of the array sparse distribution by frequency switching,and uses the frequency to index the measuring mode.In this paper,onedimensional super material imaging aperture based on cELC is simulated and the aperture is worked at Ka-Band,and 121 resonant units are loaded on 32 cm transmission line,including 50 kinds of different parameters and 50 resonant frequency points respectively.The spatial field distribution of the different frequencies of the super material aperture is strong,the structure of the measurement matrix has a better ability to reconstruct,in the imaging process,the standard horn antenna to do the launch,the super material caliber to do the reception,through a few times measured values can achieve 5cm square metal plate positioning in the distance of 50 cm.Finally,based on the research of two-dimensional string-fed sparse distribution array,two-dimensional imaging aperture of the two-dimensional super material is designed.By randomly distributing different sizes of the super material units on the back of the substrate integrated waveguide(SIW),the aperture can have different radiation characteristics at different frequencies,and then the 16 different distributions of one dimensional aperture are placed paralleled,each row of independent random feed phase.With the change of the phase distribution of the line,the radiation characteristics of the aperture also change,the system introduces frequency and phase two variables,which greatly improves the number of measurement modes.The corresponding measurement matrix can be constructed after the near-field distribution of different frequencies under different phase distributions of the full wave simulation array,and the target image is sampled and reconstructed by using the matrix,which has better reconstruction effect after the sampling rate is greater than 30%.