This paper presents a novel frequency coded chipless RFID tag, which exploits the backscattered co-polarized and cross-polarized responses from a tag illuminated with a linear polarized wave. Consequently, the tag-ID is configured in two orthogonal planes. The frequency notches are encoded in the co-polarization plane and the re-radiation peaks are encoded in the cross-polarization plane. Therefore, the co/cross-polarizing Notch/Peak modulation scheme presents a novel criterion for maximizing the coding capacity of the chipless RFID systems. Moreover, the cross-polarized response enhances the tag detection in a real environment. The proposed tag and the associated physical modulation scheme are validated using EM simulations and measurements.

This paper focuses on the frequency coded chipless Radio Frequency Identification (RFID) wherein the tag’s information bits are physically encoded by the resonators’ notch position which has an effect on the frequency spectrum of the backscattered or retransmitted signal of the tag. In this regard, the notch analytical model is developed to consider the notch position and quality factor. Besides, the radar cross section (RCS) mathematical representation of the tag is introduced to consider the incident wave’s polarization and orientation angles. Hence, the influences of the incident wave’s orientation and polarization mismatches on the detection performance are quantified. After that, the tag measurement errors and limitations are comprehensively explained. Therefore, approaches to measureing RCS- and retransmission-based tags are introduced. Furthermore, the maximum reading range is theoretically calculated and practically verified considering the Federal Communications Commission (FCC) Ultra Wideband (UWB) regulations. In all simulations and experiments conducted, a mono-static configuration is considered, in which one antenna is utilized for transmission and reception.

The aim of this work is to introduce a novel tag design enhancing the coding efficiency for the Frequency Coded (FC) chipless RFID system. The proposed approach relies on exploiting the backscattered co/cross-polarized signals from a tag excited with a linear-polarized wave. Consequently, the tag signature is encoded into Notch/Peak (N/P) format in two orthogonal planes. Furthermore, the introduced tag design exhibits narrow resonance bandwidth ensuring best utilization of the operating frequency range and sufficient coding capacity with compact tag size. Hence, 80-bit coding capacity is reached employing physical amplitude On Off-N/P (OO-N/P) modulation and N/P-Position (N/P-P) modulation principles. The presence or absence of a resonator resembles the OO-N/P modulation while the shift in the frequency position imitates the (N/P-P) modulation. In addition, the depolarization property increases the probability of tag detection in a real-world heavily dense multi-path environment. An asymmetry crossed dipole structure is employed to facilitate coding in both divergent polarities separately. The manufactured tags are verified in indoor real-world environment to proof the robustness of the introduced tag design and encoding algorithm. In the full paper, various parameters such as reading range, tag miniaturization and angular stability will be investigated.

This paper details the design and implementation of a harmonic frequency-modulated continuous-wave (FMCW) radar system, specialized in detecting harmonic tags and achieving precise range estimation. Operating within the 2.4–2.5 GHz frequency range for the forward channel and 4.8–5.0 GHz for the backward channel, this study delves into the various challenges faced during the system’s realization. These challenges include selecting appropriate components, calibrating the system, processing signals, and integrating the system components. In addition, we introduce a single-layer passive harmonic tag, developed specifically for assessing the system, and provide an in-depth theoretical analysis and simulation results. Notably, the system is characterized by its low power consumption, making it particularly suitable for short-range applications. The system’s efficacy is further validated through experimental evaluations in a real-world indoor environment across multiple tag positions. Our measurements underscore the system’s robust ranging accuracy and its ability to mitigate self-interference, showcasing its significant potential for applications in harmonic tag detection and ranging.

This paper investigates the impact of phase noise on range estimation accuracy in harmonic Frequency-Modulated Continuous-Wave (FMCW) radar systems. Harmonic FMCW radars offer advantages in many applications due to their ability to suppress clutter. However, phase noise, particularly in harmonic systems, presents a significant challenge by degrading range accuracy and increasing frequency measurement errors. In this study, a comprehensive theoretical model is developed to quantify the effects of phase noise on range estimation errors, providing a foundation for understanding its implications on system performance. This model is rigorously validated through both extensive simulations and real-world measurements, offering a holistic assessment of phase noise behavior under practical operating conditions. The results demonstrate that phase noise severely impacts range estimation accuracy, with its effects becoming more pronounced at greater target distances. These findings are further substantiated by experimental evaluations using a practical harmonic radar system, where the system’s range accuracy is analyzed under realistic conditions. This study provides valuable insights and design guidelines for mitigating its impact in harmonic FMCWradar architectures. The results highlight the necessity of advanced phase noise suppression techniques, including optimized hardware configurations and adaptive signal processing methods, to enhance performance in high-precision applications such as industrial positioning and biomedical sensing.

The main focus of this research paper is to develop a realistic mathematical framework to accurately characterize the performance of the harmonic identification system. This mathematical framework incorporates the essential factors that affect the harmonic identification system such as, the radiation pattern and polarization of the reader and transponder antennas, the angle of incidence and reflection, conversion efficiency of the non-linear element, besides the environmental effects which are multipath and clutter reflections. To validate the proposed analytical model, simulations and measurements are conducted using a state-of-the-art transponder equipped with a Schottky diode that exhibits non-linear characteristics in output power. The performance of the transponder is evaluated in both scenarios, with and without environmental reflections, where a significant drop in the backscattered signal is observed due to the multipath reflections. Accordingly, a Ray-tracing model is utilized to investigate the environmental reflections, and thus the system performance could be evaluated analytically. The close agreement between the results obtained from developed analytical framework and Ray-tracing simulations together with the corresponding measurements demonstrate the effectiveness of the proposed analytical framework in accurately predicting the performance of the harmonic identification systems.