Target Distance Estimation Based On Variation In Spectral Propagation

With the development of modern military technology,it is especially important to measure the distance of ground targets and air targets accurately.The high-precision ranging system can improve attacking performance of the missile against invading targets,and greatly enhance national defense strength of China.However,the weapon system is gradually developing in the direction of high speed,intelligence and stealth and makes electronic detection Equipments such as traditional radar unable to fully meet the requirements of modern warfare.With the development of optoelectronic technology,the related research on atmospheric transmission characteristics is becoming more and more in-depth.The passive infrared system based on the difference of spectrum transmission has a very important position in detection and warning for its good concealment performance,anti-counterfeiting ability and strong anti-jamming ability.Starting from measuring the distance of aerial target,this thesis designs a set of medium-wave window dual-band passive ranging system with infrared photoelectric detection as a technical means and designing weak signal detection amplifier circuit as the main purpose.The results of simulation and measurement show that the system can effectively and accurately amplify the weak photoelectric signals and accurately predict the target distance.This thesis focuses on the dual-band passive ranging system with a mid-wave window.The main contents include:1.Study the composition of infrared photoelectric systems,compare the performance of the heat detectors and the photon dector,select the appropriate infrared detector,and obtain the weak current output value of the infrared detector by the response rate of the detector,which provides the reference for the subsequent hardware circuit design.Aiming at the weak current signal to be detected in this thesis and designing a weak signal conditioning circuit based on InAsSb photovoltaic infrared detector,which includes power conversion circuit,photoelectric conversion preamplifier circuit,secondary amplifier circuit,AD conversion circuit,DSP main control circuit and data transmission circuit,etc.The noise sources of infrared detector and preamplifier in the circuit are analyzed.The equivalent noise model of the photodiode and the E_n-I_n model of the preamplifier is built by the standard circuit in combination with the theory,and the overall noise of the photodetection circuit is estimated through the"superposition principle".2.Analyze the target Diatance related spectral characteristics features.By analyzing the correlation between the original spectrum and the differential spectrum of the target in the medium-wave window and the long-wave window under four meteorological conditions,combining the correlation coefficients of the different windows radiation flux and distance with the root mean square error of the iPLS regression of the different windows radiation flux and distance,finding the spectral intervals with higher modeling accuracy.The radiant flux of the black body in different windows from 300 to 900K is calculated,and the Wien's displacement law is combined,and finally the dual-narrowband scheme of medium-wave is determined.In order to overcome the shortcomings of the previous non-linear ranging model in the iteration process,such as the large influence of initial values,multiple solutions and poor generalization ability of the model,an improved Elman neural network passive ranging algorithm is proposed in this thesis.Compared with the traditional Elman neural network algorithm,OIF-Elman neural network algorithm,OHF-Elman neural network algorithm and the nonlinear ranging model,the results show that the proposed ranging algorithm is effective.The convergence speed is faster and the ranging accuracy is higher.3.The hardware circuit test is described,and the circuit simulation is completed on the Multisim14.0 platform.The result shows that the 50Hz power frequency trap circuit can effectively filter out the 50Hz interference signal,and the photoelectric conversion circuit and the secondary amplifier circuit can achieve the purpose of weak signal amplification;Calibrating the black body for the infrared detector,recording temperature-voltage values and making the least-square fitting ensure the accuracy of the experiment;In the CCS8.0 development environment,the AD sampling,median Value average filtering,data transmission and improved Elman neural network ranging algorithm programs based on the TMS320F28335 chip are written,the compiled project file is transmitted to the DSP to predict distance value,and the distance prediction value is sent to the PC through the serial port RS232.The result shows that the algorithm predicts the distance of 1~8km target more accurately and the ranging error is controlled within 15%.