Near-field Passive Location Technology Based On Phase Measurements Among Distributed Fiber Sensor Nodes

In modern warfare, passive location has been considered to be a key technology for electronic surveillance system due to its advantages of good concealment, long effective distance and strong concealment. It is of great interest but presents a major challenge to improve the location accuracy, which could provide more accurate location information of radiation source in the electronic warfare. However, the influences of atmosphere and transmission medium on the radiation source signal are two main factors to limit the location accuracy. Therefore, it’s very essential to propose more effective methods to reduce their effects.In order to improve the accuracy of passive location, a novel near-field passive location technology based on phase measurements in distributed fiber sensor network is proposed. Firstly, several related techniques about the passive location are introduced. Based on the principle of time-difference location, a novel passive location method is proposed in the paper. In the method, measured phase difference information could be transformed into the time difference information to realize passive location following the ambiguity cancellation algorithm. It consists of nearby sensor array and remote sensor array connected with the central processing unit over fiber. Thus, the whole configuration works as a distributed measurement system, which can overcome the loss and fuzzy phase problem. Then time difference can be indirectly obtained through phase difference and the location of the radiation source can be quickly and accurately achieved finally. Secondly, a troposphere error correction scheme is also proposed to reduce the effect of atmosphere on the passive location. By utilizing the Hopfield profile model to correct the refractive index, the location result can be corrected after the iterative algorithm. Our simulation results indicate that the proposed approach can effectively reduce the location error with a rapid convergence. The precision of location can achieve the order of10-6under the iteration of-4times at the elevation angle of more than3。. On the other hand, phase fluctuation of transmitted microwave signal would decrease the accuracy of the location owing to the fiber in our system being sensitive to temperature and vibration. Therefore, a phase fluctuation cancellation approach for microwave signal transmission over fiber link is proposed to further improve the accuracy of location. It achieves2.45GHz microwave signal transmission over fiber link with only5.48ps root-mean-value phase jitter in5hours, which demonstrates the effectiveness and availability of our proposed system.