| Passive receivers are used to deal with the threat of modern electronic warfare. It can reliably intercept radar emissions and extract the signal characters which provide an effective means to verify the performance of the aircraft RF stealth. With the increasing complexity of signal environment, traditional analog receivers have been unable to process complex mixture of different signals with different power levels and distributed over a wide frequency range. In this thesis, the functions of interception, measurement, sorting and location for airborne digital passive receivers are studied. And, the airborne passive receiver simulat ion software is designed and implement ed. The main research contents and results are as follows:(1) The design scheme of passive receiver system is described. The composition and function of each subsystem of the aircraft RF stealth simulat ion system are introduced in detail. The software interfaces of passive receiver subsystem and the other subsystems are given. Interception range and probability of intercept(POI), as the technical indexs of interception performance, are studied and their influence factors are analyzed. The passive receiver software is divided into five functional modules: reception, detection, measurement, analysis and display and the design ideas of each function module are given respectively.(2) The modeling and Simulat ion of airborne passive receivers are studied. Mathematical models of the cavity-back spiral antenna and the passive phased array antenna are established. Gaussian function and Sinc function are used to simulate the pattern of omnidirectional and directional antennas. The measurement methods of single pulse parameters are studied. The error sources of RF, DOA and TOA are analyzed to derive the theoretical lower bound of measurement precision. To avoid the deficiency of the "Pigeon-hole" signal sorting algorithm, an algorithm based on support vector clustering(SVC) is studied and the critical steps of SVC algor ithm are derived. By applying SVC algor ithm to four simulated interleaved radar pulses stream, it is proved that the SVC algor ithm can correctly deinterleave single-frequency signals and frequency agile signals. Angle joint phase difference rate location and TDOA locat ion technologies are studied. The CRB of positioning accuracy is analyzed and the GDOP is given. The numerical analys is shows that the precision of mult i-station location based on TDOA is better. When the observation platforms are employed in the form of triangle, the positioning performance is optimal and a uniform observation area coverage is obtained.(3) The lower bound of the parameter estimation error in the condit ion of low SNR is studied. A simple derivation of BB is introduced and the relationship between BB and CRB is revealed. It is proved that BB is tighter than CRB. The probability dens ity function of the observed data in the stochastic signal model and deterministic signal model is studied. Since BB is a solution of a set of integral equat ions which is usually incomputable, then two simplif ied approxim ations of BB are introduced as well as the parameter test point selection method. At last, BB is applied to passive DOA estimation of uniform linear array. Simulat ion results show that BB can predict the SNR threshold and provide accurate estimation variance of DOA under low SNR condition.(4) The airborne passive receiver simulat ion software is designed and implemented. The software is divided into five function modules which are interception, detection, measurement, analysis and display. The definition of software simulat ion types, interface, data exchange method and major tools for display are introduced. The interception range and the software function modules were tested. Test results are in line with the expected outputs. It is shown that this simulat ion software realizes the interception of radar signals and becomes an important means to verify the RF stealth performance of aircrafts. |
PDF Full Text Request