Doa And Polarization Parameters Estimation For Unequal Power Signals

The increasingly fierce electronic countermeasure creates complicated electromagnetic environment for passive radar. Generally, the electromagnetic wave power radiated from the interference and the real target, the distance between the passive radar and the radiation source, the antenna scanning mode of the interference and the real target are all different, which leads to that the signals received by the passive radar are unequal-powered. Our research focuses on the DOA and polarization estimation of the unequal power signals and the main contents are summarized as follows:The estimation performances degradation of the MUSIC algorithm caused by the unequal power signals is analyzed. The resolution criterion of the expected spectrum for unequal power signals is proposed. The conclusion that the unequal power signals will decrease the resolution of the MUSIC algorithm is obtained based on the proposed resolution criterion and the expected spatial spectrum of the MUSIC algorithm. The influence of the CRBs for the DOA estimation caused by unequal power signals is studied. It is found that the CRBs of the weak signal’s DOA estimation increase slightly. With the CRBs and the estimation error’s probability distribution, the resolution probability based on the CRB is defined, which provides a reference for different DOA estimation methods.The target radiation polarization information improves passive radar for target detection, recognition and tracking. To deal with non-equal power signal, dual-polarized array-based noise space eigenvalues reconstruction was proposed. It can be used to conduct DOA and polarization joint estimation and study the influence of inconsistent incident signal on DOA and CRB. A dual-polarized microstrip antenna was specially designed to meet engineering requirements, this antenna was novel at extending the bandwidth of the antenna to improve the polarized port isolation by its asymmetric feeding structure, breaking the symmetry limitations of the past dual polarization feed network and improving the freedom in antenna designing. In the applications, the asymmetry of feed structure will leads to the non-fully symmetry of antenna in polarized radiation pattern. The performance of MUSIC algorithm is decling in parameter estimation when using those radiation patterns. However, the proposed algorithm can supply an effective parameter estimation. It is proved that proposed algorithm are not limited by the symmetry of antenna pattern. Moreover, the proposed algorithm supplies a reference for engineering applications of non-equal power signal parameter estimation.The polarization information of the incident signals can be used for classification and recognition of different radiation sources. The influence of the CRBs for the joint DOA and polarization estimation caused by unequal power signals is studied. Then, the ERNS algorithm based on dual polarized array is proposed and its performance is simulated. The simulation results indicate that the resolution capability of the ERNS algorithm better than that of the IPNSDL and IPNS algorithms as well as the MUSIC algorithm. The performance analysis is conducted based on the ideal symmetrical two polarization radiation patterns, which can hardly be realized for real antenna. Hence, an aperture-coupled dual-polarized microstrip antenna using asymmetric feeding is designed, which expands the bandwidth and increase the isolation and designing flexibility, the asymmetrical radiation patterns are obtained. The performances of the ERNS algorithm using the asymmetrical radiation patterns are analyzed, which certificat e the ERNS algorithm is more adaptable to asymmetrical radiation patterns than the polarimetric MUSIC algorithm.The joint DOA and polarization estimation for incident signals can be realized using conformal antenna array. The influence of the CRBs for the joint DOA and polarization estimation caused by unequal power signals in conformal antenna array is studied. Then, the ERNS algorithm based on conformal antenna array is proposed, and its performances using different conformal array are simulated. The sim ulation results show the resolution capability of the ERNS algorithm is better than that of the IPNS algorithms and the polarimetric MUSIC algorithm. The theoretical radiation patterns of planar antenna are used to replace the real radiation patterns of conformal antenna when the performances of the ERNS algorithm are studied. However, these two types of radiation patterns have some differences. Thus, the conformal microstrip and bowtie antenna arrays are designed. The performances of the ERNS algorithm using theoretical and real radiation patterns are compared, which exhibits that the ERNS algorithm when using the theoretical radiation patterns has better performances.