Open Access Open Access  Restricted Access Subscription or Fee Access

A Method of Displacement Measurement for Structural Constructions Based on the Microwave Radar and Active Transponder



In order to solve problems of the GPS and total station to achieve the needs of all-weather, high-precision and low-cost displacement measuring for long-distance target, a new method of displacement measuring and its system for structural constructions are proposed in the article based on the microwave radar and active transponder. In the system, the microwave signal is used as measurement signal for all-weather work of the system, and the high- frequency microwave and high-precision phase measuring with the method of Discrete Fourier Transforms are employed to achieve high-precision displacement measuring. Moreover, the active transponder is adopted to boost reflected signal and meet the need of displacement measuring for long-distance target, and the mature and standardized components is used to reduce the measurement costs. The microwave radar fixed at the reference point transmits a single-tone 2.4 GHz signal and receives a returning signal at 2.4001GHz from the active transponder fixed at the target, then, 0.1MHz signal is obtained as a reference signal for phase measuring by frequency mixing and low pass filtering. Similarly, the active transponder receives a 2.4GHz signal and mixes it with the internal 2.4001GHz signal from the transponder to get 0.1MHz signal, then the 0.1MHz signal is sent to the microwave radar via a frequency modulation transmitter at 5.8GHz. The phase difference between the two 0.1MHz signals is measured to further get the displacement of target if the target moves. Finally, the experiment results show that the system has a resolution of 0.0425mm and a measuring speed of 30~40 ms for a target of 100m away and costs only $300~400, which verifies the proposed method.

doi: 10.12783/SHM2015/117

Full Text: