Local Sensitivity Analysis and Monte Carlo Simulation to Examine the Effects of Chipless RFID Measurement Uncertainties—Part I: Misalignment-Based Uncertainty

Abstract

Measurement and response decoding is an ongoing challenge in the chipless radio frequency identification (RFID) field. Measurement uncertainties, including tag/reader misalignment, RCS or S-parameter error, and clutter, can cause response distortions, such as magnitude changes and resonant frequency shifts. These response distortions can lead to the improper assignment of a binary code or sensing parameter (i.e., improper decoding). This work aims to use local sensitivity analysis and Monte Carlo simulation to fully characterize the effects of misalignment, response parameter measurement error (e.g., VNA S-parameter error), and clutter on chipless RFID tag responses. From this type of comprehensive characterization, conclusions are drawn about the identification (ID) and sensing capabilities of the tags. In this work the simulations are performed for two specific tags and the results are then corroborated with measurements of one of the tags. While the work is done for a near-field monostatic measurement setup, it is presented such that the same procedures can be applied to other tags and measurement setups, including far-field scenarios. Thus, a novel comprehensive tag performance assessment framework is provided. This work is divided into two parts. In this part, Part I, the effects of tag/reader misalignment uncertainty are examined in depth through both simulations and measurements. In Part II, the effects of S-parameter error, clutter-based uncertainty, and the combination of these uncertainties with misalignment uncertainty are investigated. An example demonstrating the application of this tag performance assessment framework is also provided in Part II.

Local Sensitivity Analysis and Monte Carlo Simulation to Examine the Effects of Chipless RFID Measurement Uncertainties—Part II: Consideration of Multiple Measurement Uncertainties

“…In order to corroborate the simulation results in the previous section, a set of measurements was completed with the 4C tag. The fabricated tag and loaded waveguide measurements at Xband (8.2-12.4 GHz) have been previously reported in [1,16]. For the measurements used to corroborate the Monte Carlo analysis, an X-band (8.2-12.4 GHz) waveguide with an engineered flange was attached to a set of rotational stages on an XY scanner and the tag was placed below the waveguide aperture at a standoff distance of 10 mm.…”

“…This analysis was done for two different tags and two different coding methods, which are also used here for continuity. It was seen that while local sensitivity analysis can provide insight into the types of misalignment that most important to control for during measurement, Monte Carlo analysis is necessary to fully characterize the effects of misalignment on tag performance [1].…”