Displacement Sensor Based on Radar Cross-Polarization Measurements

Abstract

This article presents the feasibility of measuring submillimeter displacements of objects in real environments using simple resonant radar targets. These scatterers, also known as chipless tags, have their own radar signature that can be used not only for identification but also for sensing. The chipless RFID is a highly promising technology since it paves the way for the development of easily implementable communication systems where tags have costs similar to barcodes. Object displacements are extracted by just evaluating at different times the variation of the signals backscattered in cross polarization from the tags. Based on this analog RFID sensing principle, an analytical model is developed to perform the direct derivation of the displacements. Therefore, the approach does not require complex and specific calibration procedures based on lookup table for compensating variations due to the presence of surrounding unknown objects. It is possible to add this functionality to already designed chipless RFID tag operating in cross-polarization without decreasing their coding capacity. Experimentations inside and outside anechoic chamber have been done, and very good agreement was obtained with simulations. It has been proved that sub-millimeter displacements can be monitored with this approach. Chipless tag displacement of 0.5 mm with less than ±45 µm error can be detected in real environment for a read range of up to 40 cm.

A Chipless RFID Method of 2D Localization Based on Phase Acquisition

“…The following result can be obtained: Note that (3) holds in cross-polarization and only at the neighbourhood of the resonant frequency since at other frequencies, power reflected by other objects surrounding the reader can be higher than the power backscattered by the tag [6]. Moreover if one distance is known (e.g., d 0 ), absolute distance d 1 can thus be determined.…”

“…Since the tag can be located at a given distance from the antenna, block T C represents the phase offset due to propagation [6]:…”

“…These approaches use at least 3 different antennas and have been focused on the structural mode of the tag (i.e., the early part response of the backscattered wave) to determine the distance information. In [6], the author has used the phase of the reflected signal to measure distance variation with submillimeter accuracy along a single direction. Moreover, in [7], the authors have determined the localization of a chipless tag using the change of the magnitude of the backscattered signal using the information of each of the tag's scatterer.…”

A Novel Metamaterial Inspired High-Temperature Microwave Sensor in Harsh Environments

“…It is widely used in environment parameter sensing, as it can simultaneously identify targets and detect information about the target object. The tags do not need to be powered by a battery [ 8 ], can be fabricated at a low cost, and have a long lifetime [ 9 ]. For example, Herrojo et al [ 10 ] proposed a novel near-field chipless RFID system used for angular velocity measurements by operating in time domain and based on sequential bit reading.…”

A Novel Displacement and Tilt Detection Method Using Passive UHF RFID Technology

“…Based on power measurements [ 24 , 25 , 26 ], phase detection [ 27 , 28 , 29 , 30 ], antenna polarization [ 31 ], system analysis [ 32 , 33 ], or multiple tag cooperation [ 34 , 35 , 36 ], RFID tags can work as sensors for an optional low-cost WSN solution. Different displacement detection approaches can be found in previous works [ 37 , 38 , 39 , 40 , 41 ]. In these papers, tag antennas are physically deformed or damaged by displacement.…”