Research On Short Range Millimeter Wave Imaging System Signal Processing And Algorithm

In recent years,with terrorist attacks becoming more and more frequent,there is growing emphasis on security checks in public places.However,faced with weapons of new types keeping coming into being,such as ceramic knives and liquid bombs,we find traditional security-checking methods not sufficient for modern applications.As a result,millimeter wave imaging technology,which is much safer and more effective,emerges as the times require.The millimeter wave,located between the microwave and the far infrared wave in the electromagnetic wave,has characteristics of them both.The millimeter wave with certain penetrability can penetrate the clothing to detect hidden objects on the human body,and generate images of high resolution on millimeter scale.In addition,the millimeter wave is non-ionized.Compared with X ray backscatter imaging,millimeter wave imaging is more secure for human health.Based on the above characteristics of millimeter waves,it can be assumed that millimeter wave imaging technology has a wide range of applications in security check.The development of millimeter wave security imaging technology is of great significance to deal with today's terrorist crisis.This thesis,derived from the research of millimeter wave imaging system which I am engaged in,mainly focuses on the engineering realization of its imaging algorithm.The main research contents are as follows:(1)Introduction of the principles and model of active millimeter wave imaging system,and discussion in detail on its send and receive front end and the way its antenna scans.(2)Correction of the phase position errors of antenna arrays.Aiming at the defocusing and blurring of the imaging image caused by the phase error of the array antenna,this thesis uses an external reference calibration method to improve the quality of the image.(3)Improvement and application of millimeter wave imaging algorithm.According to the characteristics of near field and close range of millimeter wave imaging system,two kinds of imaging algorithms suitable for the scene are presented:range migration algorithm(RMA)based on frequency domain and back projection algorithm(BPA)based on time domain.In order to meet the needs of rapid imaging of human security,firstly,on the basis of the range migration algorithm,an imaging method combining multi-distance compensation with maximum projection is introduced,which improves the imaging speed under the premise of ensuring the image quality.Secondly,the GPU is used to accelerate the improved range migration algorithm in MATLAB,which can further improve the image processing speed and make the image processing time less than 1s.In this thesis,the improved range migration imaging algorithm is applied to the security imaging system.In the premise of ensuring the quality of the image,it has the ability to quasi-real-time imaging.