In wireless sensor networks (WSN), location information acquisition is critical to guarantee their performance. This paper presents a new positioning method in WSN with high precision at reasonable implementation cost for 3D case. Reference nodes with known locations transmit linear frequency modulation continuous wave (FMCW), while other sensor nodes estimate the range difference to them based on the received signals' frequency difference, called time frequency difference arrival (TFDA). The location information can be obtained by solving a set of hyperbolic equations. Two different positioning methods: Taylor iterative method and Chan's method are inspected and compared in terms of accuracy, constraints and computational complexity. This proposed technique is cost-effective, scalable and easy to implement. The simulation results show that the new method enjoys high precision.