Interferometric Approaches for Accurate Location and Displacement Measurement Using Passive Frequency-Doubling Reflectennas

This paper presents a novel localization and displacement sensing approach that uses a pair of passive sensors and a mobile interrogator. One of the potential applications of this approach is structural health monitoring, where the sensors are embedded in environments such as concrete or soil. The interferometric technique provides location and displacement information via the destructive and constructive interference pattern of the signals returned from the two sensors as the interrogator moves. The measurement results with two sensors reveal that the location information can be obtained with approximately 5 times greater accuracy compared to using a single sensor. The experimental results are in good agreement with analytical calculations.