| The terahertz wave is located between infrared and microwave which has unique characteristics in the detection,imaging,and interaction mechanisms.Its broad application prospects in the fields of biomedical engineering and anti-terrorism security inspection make it a hot topic at home and abroad.Target scattering characteristic is an important foundation for the development of terahertz radar technology.Due to the limitations of terahertz source low transmit power and poor signal stability,terahertz RCS measurement experiments are mainly performed indoors,resulting in the measurement accuracy is relatively low,and the far-field measurement conditions are difficult to meet.For the above reasons,the measurement data cannot be directly used in the calculation of RCS.To solve the above problems,this subject has carried out research and analysis on the terahertz RCS preprocessing technology and the terahertz RCS near and far field transformation.In terms of terahertz RCS measurement preprocessing technology,the existing methods are optimized combining the characteristics of terahertz RCS.Through the analysis of background cancellation technology,software distance gate technology and calibration technology,this paper focuses on the calibration technology.The main purposes of background cancellation technology and software range gate technology are to suppress clutter signals,while the main purpose of terahertz RCS calibration technology is to calibrate the measurement system.Aiming at the singularity and one-sidedness of metal ball calibration in classical calibration technology,the multi-theoretical calibration technology is proposed.This technology uses four typical values of the cylindrical RCS as calibration parameters,taking into account multiple factors such as unstable terahertz frequency source power,incomplete target placement,and sudden changes in background noise during RCS measurement.In terms of terahertz far field RCS extrapolation technology based on ISAR images,the image RCS far field extrapolation technology based on NUFFT acceleration algorithm is proposed to solve the problem of the huge amount of data calculation caused by the large bandwidth of terahertz.This technology establishes the terahertz high-resolution image,and obtains the relationship between the target image and the far-field RCS,effectively determining the far field RCS.A 0.33 THz measurement system is used to measure the cylindrical target to verify the effectiveness of the proposed algorithm.In terms of terahertz far-field RCS acquisition technology based on convolution method,the effect of angular sampling interval on the algorithm is analyzed,and a convolution algorithm based on double-valued weighting is proposed to optimize the algorithm.In terms of terahertz far field RCS acquisition technology based on spherical toroidal scattering,according to the 0.44 THz experimental measurement results of the algorithm,the influence of the range gate filtering algorithm on the accuracy of the technology is studied,reducing the effect of truncation error on the accuracy of RCS extrapolation.This subject has effectively improved the measurement accuracy of terahertz RCS through the research of terahertz RCS preprocessing technology and near-far field conversion technology.These methods have guiding significance for the research of complex target RCS measurement and scaling law. |
