Research On 3-D Cylindrical Imaging Algorithm Of Terahertz Radar

Terahertz wave has obvious advantages in target detection and radar imaging because of its short wavelength and high frequency comparing to the millimeter wave and the microwave. That makes the research of the terahertz become a hot issue in academic circles. Terahertz radar can be used for the security check in the airport or train station because of the strong penetrability to dielectric materials of the Terahertz wave. The accuracy of the detecting to the concealed object can be improved to ensure the safety of passengers.This dissertation focuses on the research of cylindrical imaging of terahertz radar,analysing from the basic theory. And the imaging algorithm is also simulated. The main work is as follows:(1)The special properties of terahertz radar are introduced, including the near-field theory of imaging and the dechirping method. And the echo model of terahertz radar cylindrical imaging system is established. Then the three-dimensional imaging principle of the system is analysed. The resolution formula of cylindrical imaging system is deduced. These establish the foundation for the terahertz radar cylindrical imaging.(2)A cylindrical imaging algorithm of terahertz radar based on the range migration algorithm(RMA) is researched and achieved. The algorithm targets on the specific problems in terahertz radar cylindrical imaging system. First the traditional principle of range migration algorithm is analysed. Then the application of the RMA on the cylindrical geometry is researched :In the algorithm, the second order terms of taylor expansion is adopted to approximate the range expression and the cylindrical imaging is achieved finally.(3)Targeting on the low efficiency of the interpolation in the traditional range migration algorithm which will effect the speed and precision, A cylindrical imaging algorithm based on NUFFT transform is researched and achieved. The computer simulation is used to verify the validity of the method. And the performance of the RMA imaging algorithm and the NUFFT algorithm is also compared.(4)Because of the range formula can’t be approximated in the wide angle range,the value of the stationary phase is obtained successfully by numerical method. Then thecompesating phase is obtained, the imaging problem of the range formula with the cosine term is solved. The computer simulation is used to validate the effectiveness of algorithm in the theoretical case.