Non-atmospheric Window Millimeter Wave Propagation Characteristics And Short-range Detection Technology Research

Under the environment of complex battlefield,the existing millimeter-wave fuze system has the problem of insufficient anti-interference ability.Detectors in a single mode and conventional frequency range cannot meet the military combat missions any more.In order to improve the detection performance,much attention should be paid to new frequency ranges as well as multi-mode compound millimeter-wave systems.Due to the severe atmospheric attenuation of millimeter wave in non-atmospheric window,it is difficult to adapt to long-distance communication and long-range radar detection.The operating distance of millimeter-wave fuze is just between meters and hundreds of meters,so that atmospheric attenuation has minor effects on the performance of detection system.Furthermore,system working with non-atmospheric window millimeter-wave has a very superior ability to resist the detection and interference of the enemy.In conclusion,non-atmospheric window band has a very broad application prospect in millimeter-wave fuze operating.This paper focuses on the propagation characteristics of the non-atmospheric window millimeter-wave band.According to the propagation attenuation model given by ITU-R,the atmospheric absorption,scattering and refraction of millimeter wave are calculated.The result shows that atmospheric absorption plays a major role in the propagation attenuation of millimeter-wave.Three absorption peaks appear at 60GHz,118.8GHz and 183GHz.At the same time,the effect of rainfall and fog and haze on the millimeter wave propagation is analyzed in this paper.The attenuation models are established and the simulation results are given under two weather conditions.The result shows that the attenuation of millimeter wave is severe under rainfall condition,but the attenuation through fog and haze is very small.That is,millimeter wave has strong ability to penetrate fog and haze and poor ability to penetrate rain.Based on the analysis of propagation characteristics,the influence of propagation attenuation on the working distance of non-atmospheric window detection system is calculated.Further exploration on the anti-reconnaissance and anti-jamming characteristics of millimeter-wave systems operating at 60GHz and 118.8GHz non-atmospheric window frequency bands are conducted in this paper.It uses 3 5 GHz atmospheric window band millimeter-wave systems for comparative analysis by simulating.The results of the analysis verify the feasibility of applying the non-atmospheric window bands to the near range millimeter-wave fuze in theory.Based on the feasibility verification,this paper presents the scheme demonstration and designs of signal processing part of the FMCW active detection system working in 60GHz non-atmospheric window frequency band.Firstly,the principle of FMCW active range measuring is described.Then the beat signal is analyzed in time domain and frequency domain,and principles of selecting system parameters are discussed.Thirdly,this paper designs the signal processing part of the 60GHz active detection system both in software and hardware based on FPGA.At last,we conduct experiments to verify the above design and implementation of the system.The experiment results show that the detecting range of the 60GHz system is more than 120m with an error less than 5%,meeting the requirement of the system.Theoretical analysis,modeling and simulation of the transmission characteristics of the non-atmospheric window frequency bands,as well as design of active detection system and experimental verification have provided theoretical and data support for the application of this frequency band in the short-range detection and millimeter-wave fuze.