Objectives In recent years, the demand of indoor and outdoor emergency location service is growing rapidly. Affected by indoor space environment, signal types, sensor performance and other factors, the existing positioning methods of single signal source, single sensor source, integrated navigation, fusion positioning are not perfect in accuracy, stability, reliability, rapidity and other aspects. The main objective of this study is to propose a high precision wireless location method for single base station in emergency positioning environment.
Methods A method of angle measurement with high precision was proposed to eliminate redundant phase caused by modulated signal and sequential sampling. Firstly, a circular antenna array was constructed which sampling received signal on one channel by switching the dual polarized antenna array element in turn, and on the second channel by comparison antenna. Then, the echo signal mathematical model of dual channel antenna was established. Finally, the super-resolution angle estimation algorithm of Capon spectral and polarization decoupling was given for multipath indoor environment. In order to reduce the computational complexity of four-dimensional search, the steering vector was rewritten by hardard product, and target angle estimation was obtained by solving the minimum eigenvalue to minimize the cost function.
Results From the comparison results of array phases between single channel and dual channel, it can be seen that the proposed two channel antenna has better phase stability. Experimental results on several fixed location points demonstrate that the root mean square(RMS) positioning error in X direction and Z direction is better than 0.5 m. Both static and dynamic tests show that the influence of source signal phase and frequency synchronization error to switch-antenna array can be effectively eliminated.
Conclusions The proposed method can achieve two-dimensional accurate localization with a single base station, which has wider application than the single channel switch-antenna array and is easy to rapid deployment in emergency positioning environment.