Research On Active Millimeter-wave Imaging Algorithms And System For Security Inspection

In resent years, the increasing threat of terrorism has made personnel surveillanceincreasingly important. Millimeter-wave imaging is well suited for the detection ofconcealed weapons or other contraband carried on personnel at airports and other securelocations, since millimeter-wave can penetrate common clothing material and isnonionizing. In this thesis, the wavenumber domain algorithms based on the nonuniformfast Fourier transform (NUFFT) and the frequency-modulated continuous-wave (FMCW)radar system, and the imaging algorithms based on compressed sensing (CS) are researched.And a W-band prototype of imaging system for security applications is developed.Firstly, the two dimensional (2-D) wavenumber domain algorithms based on NUFFTfor the linear and arcuate arrays are studied, respectively. The Stolt interpolation and FFTare substituted by NUFFT which overcomes the limitation of equally spaced samplingneeded by FFT and reduces the errors of interpolations.Secondly, the three dimensional (3-D) wavenumber domain algorithms based on theplane aperture and cylindrical aperture are developed for the FMCW systems. The effectsof the platform motion within the signal duration time are compensated. The focusingperformance of the image is improved. To reduce the computational time of the imagereconstruction process, the Stolt interpolation and FFT are substituted again with a3-DNUFFT.Thirdly, the2-D and3-D imaging algorithms based on CS are deeply researched forsecurity inspection. The implicit measurement matrix is used to avoid the computation oflarge-scale explicit measurement matrix. The imaging method based on CS overcomes thelimitation of the traditional Nyquist sampling theorem in the precondition of ensuring theimage quality. Thus, the number of antenna elements and frequencies can be reducedresulting in the reduction of hardware cost and of the signal transmitting and receiving time,which is meaningful for optimizing the imaging systems. In addition, exploratory researchon the system design based on CS is performed.Finally, according to the existing conditions of our laboratory, we develop a W-bandprinciple prototype of the imaging system. And the phase errors caused by the system andthe movement of the antenna are studied and compensated. The suitability and effectiveness of the wavenumber domain algorithms and the imaging algorithms based on CS are verifiedby using the measurement data obtained by the imaging system.