Optimal deployment of multiple passive sensors in the sense of minimum concentration ellipse

In the sense of minimum concentration ellipse, the optimal deployment of multiple passive sensors in bearing-only location system is studied in terms of cut angle. It is found that the optimum cut angle depends only on l, the ratio of the distance between target and the baseline of the two sensors to the baseline length. When l is greater than 0.5, the optimum cut angle can be obtained if the deployment of the target and the two passive sensors is an isosceles triangle with the baseline length as its base side. When l is less than 0.5, the optimum cut angle can be obtained if the target and the two passive sensors are located on the circle with the baseline length as its diameter, that is, the deployment of the target and the two passive sensors being a right triangle. When l equals 0.5, the optimum cut angle can be obtained if the target and the two passive sensors are deployed on an isosceles right triangle. The global minimum value of concentration ellipse can be asymptotically reached by decreasing the ratio l to zero based on these properties of the optimum cut angle.