Design And Implementation Of Signal Processing Circuit For Handheld Millimeter Wave Passive Radiation Security Instrument

In recent years,the threat of terrorism at home and abroad has become increasingly serious,and its damage has been dominated by cold weapons and bomb attacks.It poses a major challenge to the security inspection equipment at each security checkpoint,requiring it to detect dangerous metals and non-metals quickly and efficiently,and to ensure that citizens' safety is not compromised while protecting citizens' privacy.Metal detectors can only detect metal dangerous goods,and it is difficult to detect dangerous substances such as liquids,plastic explosives,and non-metal tools hidden in personnel;when X-ray equipment is used for security inspection,due to its ionization,it has Potential radiation risks;infrared technology relies on the surface temperature imaging of objects,which is difficult to use for human security screening.Due to its penetrability,millimeter wave technology can not only detect metal objects hidden under textiles,but also detect other non-metallic dangerous materials such as explosives,ceramic knives and dangerous liquids.Early single-channel mechanical scanning millimeter-wave passive radiometers have been gradually eliminated due to slow scanning speed and poor detection performance of moving objects.The current development trend is multi-channel parallel scanning structure,which is arranged according to a certain array of rules.Multiple radiometer channels are simultaneously collected and processed to obtain radiation in the measured area to achieve better imaging or detection functions.In this paper,the actual test of the millimeter wave passive radiometer confirms that the main circuit problems faced by the multichannel radiometer are poor channel consistency and low brightness sensitivity.The difference in channel consistency of the radiometer is reflected in the inconsistent DC component of each channel and the inconsistent brightness temperature sensitivity;the low temperature sensitivity of the radiometer is low except for the limitation of the radiometer itself,and because the radiometer works under a strong background,the strong background DC signal will Limit the brightness sensitivity of the channel.In view of the above problems,the solution of this thesis is:(1)Eliminating the DC signal in the strong background;(2)Improving the gain and consistency of the signal of each channel in the analog domain;(3)Adjusting the gain in the digital domain.According to the actual security instrument system index requirements,combined with the above solutions,this paper studies and implements the handheld millimeter wave passive radiation security instrument signal processing circuit.The determination of the overall scheme,the design of the hardware circuit and software program,the verification of the system function and the system joint test of the handheld millimeter wave passive radiation security detector were carried out.Finally,the problem of poor consistency and low brightness temperature of the multi-channel millimeter-wave passive radiometer is solved,and the function of detecting the hidden object by the handheld millimeter wave passive radiation security detector is realized.