| Recent years,with the rapid development of the small size and low cost devices,such as the wireless sensor networks(WSN),the internet of things(IoT),and unmanned aerial vehicles(UAV),the technology of the wireless emitter passive localization becomes the focus of the scientific research for the scholars,which has gotten widespread application in the fields of civil and military.The emitter passive localization technology of the time different of arrival(TDOA)has been taken as the most popular method for the advantages of high precision,fast reaction speed and good concealment.While there are many technical problems unresolved for some special localization application scenarios and requirements.In this paper,we focus on the key technologies to resolve the TDOA passive localization in the fields of civil and military application,and propose the corresponding solutions.The achievements of the paper mainly summarized as follows:(1)For co-frequency interference environment,we address the problem of passive and blind estimation of time delay parameter for uncorrelated interference signals based on wireless sensor networks.The received mixture signals at the sensors are taken as linear combinations of the differently delayed versions of the communication signal and the inter-ference signal.Blind source separation(BSS)and secondary interference signal extracting are both introduced in the proposed method.The interference signals in the mixed receiving signals of all the sensors are extracted effectively and the effect of the mixed communication signals can be significantly reduced.Simulations show that the proposed method has a more accurate performance compared to other TDOA estimation methods,and is therefore valid and practical in the TDOA localization systems.(2)To accurately locate the signal source passively in downtown area,sensors are carried on the UAVs flying in the air,where the wireless sensor network can be established with an optimal geometry configuration conveniently.In this case,the multipath fading effect can be avoided and the TDOA measurement is estimated precisely in Rician channel.By employing the operating center as a calibration source to refine the positions of the UAVs,we present a simplified formulation of the TDOA localization method according to the min-max criterion.To accurately estimate the position of the source,the nonlinear equations are relaxed by using a semidefinite programming(SDP)to obtain an initial solution,which is utilized as the starting point of the iterative algorithm to refine the solution.In the simulation section,the validity and the robustness of the proposed methods are verified through the performance comparison with the Cramer-Rao lower bound(CRLB).(3)In the military field,single UAV is employed to passive localize the enemy’ s re-connaissance radar source according to the synthetic aperture technical.Taking the charac-teristics of the radar pulse signal,in the localization parameter estimation stage,the norm approximation algorithm is introduced to approximate fitting the main beam pattern(MBP)of the radar antenna,and taking the time different of the amplitude peak as the localization parameter estimation.At the same time,due to the antenna scan cycle of the radar is an important parameter in the localization process,the UAV is operated hovering in the sky to receive the radar pulse signal then the scan cycle of the radar antenna is estimated.Based on reasonable simplification of nonlinear equation the closed solution of radar source passive localization is deduced.In the computer simulation section,the VTDOA estimation per-formance of the optimal norm approximation method and the corresponding base function are given according to the performance comparison.At the same time,the factors such as the radar pulse repetition frequency and pulse width are considered in the scan cycle esti-mation.Finally,the virtual aperture and the PRF are considered to verify the localization performance. |
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