Notes on the Extraction of Aspect-Independent Parameters of Chipless RFID Tags

Abstract

This paper presents the extraction of aspectindependent parameters for dual-L dipoles based chipless radio frequency (RF) identification (RFID) tags using spectrogram method using single measurement. The implemented spectrogram method is based on a single short-time Fourier transform (STFT) averaging window. The performance of the spectrogram method is compared to the matrix pencil method (MPM). A computational time comparison between the spectrogram method and MPM is presented.Index Terms-Chipless radio frequency (RF) identification (RFID), matrix pencil method (MPM), quality factor, short time Fourier transform (STFT).

A Review of Chipless RFID Measurement Methods, Response Detection Approaches, and Decoding Techniques

“…Another approach is to extract the complex natural resonances (CNRs) of tags, which are considered to be aspect independent (i.e., they do not change location due to angle of arrival of the interrogating wave or the observation point) [118,134,[329][330][331]. It should be noted that CNRs are sensitive to changes in tag's substrate permittivity and structure effective permittivity, which makes the following discussed CNR extraction methods suitable for sensing, as well as identification, applications [332,333].…”

“…It should be noted that CNRs are sensitive to changes in tag's substrate permittivity and structure effective permittivity, which makes the following discussed CNR extraction methods suitable for sensing, as well as identification, applications [332,333]. CNRs can be extracted by using methods like the singularity expansion method (SEM), matrix pencil method (MPM), short time matrix pencil method (STMPM), and spectrogram method [19,245,304,329,333]. The latter three can be considered as more optimized methods to estimate and extract the poles described by SEM theory, of which there is a detailed explanation provided in [299] and [334].…”

“…Although, there are still limitations with the STFT method, including fixed resolution in time and frequency, sensitivity to the window length, and limited performance in terms of distinguishing resonant frequencies when they are densely packed in the operational frequency band of the tag [334]. Overall, the STFT method has been shown to be more accurate, require fewer measurements, and require less computation time than the STMPM and MPM methods while still being able to extract the resonant frequency information in an aspect independent fashion [19,193,245,329].…”

“…'21 [19] MPM and Spectrogram Variation in RCS, resonance frequency, and Q-factor, and computation time as a function of window length '21 [329] Temporal Separation [245] and Differential Dual-Polarization [75] Reliability when tag is attached to different objects, memory storage, and design complexity '21 [77] compared). Another thing to note from Table V, is that some works refer to methods like background response subtraction and time gating as decoding methods, while other works may refer to these as calibration or pre-processing methods.…”