Villa-González, F. (Fátima)
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- A 5.8-GHz-Direction of an arrival localization radio system with a reconfigurable monopole antenna array.(IEEE, 2019-08) Solar-Ruiz, H. (Hector); Villa-González, F. (Fátima); Urain, A. (Alvaro); Cortés-Vidal, I. (Iñigo); Valderas Gazquez, D.(Daniel)This article presents the design of a complete radio system receiver to detect, in real time, the direction of arrival (DOA) of an incoming industrial, scientific, and medical (ISM)-band signal at 5.8 GHz. When a transmitter continuously sends a binary phase-shift keying (BPSK), modulated pseudo-noise (PN) code, the receiver estimates the DOA based on the received signal strength (RSS) and performs the channel sounding. The device that we describe includes a pattern-reconfigurable monopole antenna array, a front end, and a systemon-module (SOM). The SOM controls the antenna's main lobe direction by positive-intrinsic-negative (p-i-n) diode switching, configures the front-end modules, completes the data acquisition, and performs the digital signal processing (DSP) for the DOA estimation. The system has an average DOA resolution of 90° in the horizontal plane, with a success rate higher than 90%. It is presented as an educational platform for electrical engineering undergraduate and M.S. degree students.
- Time–temperature excursion monitoring using chipless RFID tags and organic oils.(2023-09) Villa-González, F. (Fátima); Bhattcharyya, R. (Rahul); Sarma, S. (Sanjay); Valderas Gazquez, D.(Daniel)A food-safe cost-effective time-temperature indicator (TTI) sensor for cold chain disruption detection at the item level is proposed. The sensor is based on the radar cross section (RCS) readout from a chipless square split ring resonator (SSRR) exposed to organic oils with customizable melting temperatures and defined flow paths. The inclusion of several oil mixtures into the same sensor allows for the determination of a range of configurable temperatures/times. The same sensor has two modes of operation: one for threshold detection and another for gradual change detection. These modes depend on the orientation of the sensor on the packaging and the influence of gravity. The provided design, along with a convenient signal conditioning strategy, accurately detects four time exposure thresholds in the 7-30 min range when placed in upright position at ambient temperature, while it exhibits linear response between 10 and 30 min just by turning it by 90 degrees. Prospective future directions are also discussed.
- SDR-based monostatic Chipless RFID Reader with Vector Background Subtraction Capabilities(IEEE, 2023-11) Del-Rio-Orduña, D. (David); Villa-González, F. (Fátima); Bhattcharyya, R. (Rahul); Rezola-Garciandia, A. (Ainhoa); Valderas Gazquez, D.(Daniel)This article presents a high-performance frequency-domain chipless RFID reader with vector background subtraction capabilities, implemented in a software-defined radio (SDR) for the first time. The proposed reader is low-cost, compact size, and versatile. It is implemented in a USRP N210 paired to a modified CBX-40 daughterboard, enabling magnitude and phase data acquisition in a monostatic (one antenna) set up. The reader can perform a vector background subtraction operation between two complex measurements (with and without a chipless tag) to suppress the self-interference (SI) that hinders the response of the tag and provide 40 dB of dynamic range. To demonstrate the performance of the reader, the spectral signatures of three frequency-coded (FC) tags with four resonant frequencies are captured over the 1.5-4-GHz band scanned with 10-MHz resolution in 251 ms, obtaining comparable measurements to those of an expensive laboratory vector network analyzer (VNA) from 20 to 40 cm. The detected resonant frequency offset between both devices is Delta f(r) <= 4.18% . It is also demonstrated that the proposed reader can track a resonant frequency shift and therefore be used in real-time sensing applications.
- Chipless RFID tag implementation and machine-learning workflow for robust identification(IEEE, 2023-12) García-Gardarell, P. (Pablo); Ochoa-Álvarez, I. (Idoia); Villa-González, F. (Fátima); Díaz-Dorronsoro, J. (Javier); Valderas Gazquez, D.(Daniel); Sokoudjou, J.F. (Junior Fodop)In this work, we describe a complete step-by-step workflow to apply machine-learning (ML) classification for chipless radio-frequency identification (RFID) tag identification, covering: 1) the tag implementation criteria for circular ring resonator (CRR) and square ring resonator (SRR) arrays for ML interoperability; 2) the data collection procedure to get a sufficiently representative dataset of real measurements; 3) the ML techniques to visualize the data and reduce its dimensionality; 4) the evaluation of the ML classifier to ensure high-accuracy predictions on new measurements; and 5) a thresholding scheme to increase the certainty of the predictions. The differences in the tags' frequency responses are maximized by optimizing the Hamming distance between the tag identifiers (IDs) and by controlling each resonator array's radar cross section (RCS) level. We show that the proposed workflow achieves perfect accuracy for the identification of four tags at a fixed distance of 160 cm. We also evaluate the performance of the proposed workflow to identify up to 16 tags within a flexible range (up to 140 cm), showcasing the tradeoff between the number of tags that can be correctly classified based on the reading range.
- Reader Arquitecture Characterization for Chipless Wireless Sensors Applications.(2019) Villa-González, F. (Fátima); Valderas Gazquez, D.(Daniel)The main goal of this project is to design, implement and characterize a portable chipless reader for resonator chipless tags by comparing it with a non-portable chipless reader. In laboratory settings, test equipment such as Vector Network Analyzers (VNAs), Signal Analyzers and Digital Storage Oscilloscopes (DSO) are used. However, it is not economical to use these expensive and heavy laboratory pieces of equipment for the real-world applications of chipless RFID systems. Therefore, apart from reducing the cost by using chipless technologies, it is essential to develop a low-cost reader device that makes the system even more inexpensive. This is basically done by replacing the large and bulky equipment with some commercial components that make the device light and portable. Concretely, the design of the reader presented in this document, implements a Wideband Synthesizer with Integrated VCO in order to replace the Signal Generator. The most challenging task is the correct synchronization of the new device with the rest of the elements of the reader. This is achieved by a new computer software specifically programmed to control the whole reader, which is based on a previous version. The system’s performance is tested with several chipless tags; resonators with different resonance frequencies. The obtained results are compared to the measurements taken with a VNA and with a previous version of the reader composed by laboratory instruments. The measurements are made with a gain/phase detector that sends its data to an Arduino. Moreover, the information is processed by a Visual Studio project written in C Language that also contains the software with the user interface to control the synthesizer from the computer and all the data processing and visualization algorithms. The aim of the project is to describe the characterization of a reader based on frequency domain detection techniques and obtain the most accurate and effective performance of it to improve the previous version of the system and approach to an applicable device.
- SDR-Based monostatic chipless RFID reader with vector backgroud substration capabilities(IEEE, 2023) Del-Rio-Orduña, D. (David); Bhattacharyya, R. (RahuL); Villa-González, F. (Fátima); Rezola-Garciandia, A. (Ainhoa); Valderas Gazquez, D.(Daniel)This article presents a high-performance frequency-domain chipless RFID reader with vector background subtraction capabilities, implemented in a software-defined radio (SDR) for the first time. The proposed reader is low-cost, compact size, and versatile. It is implemented in a USRP N210 paired to a modified CBX-40 daughterboard, enabling magnitude and phase data acquisition in a monostatic (one antenna) set up. The reader can perform a vector background subtraction operation between two complex measurements (with and without a chipless tag) to suppress the self-interference (SI) that hinders the response of the tag and provide 40 dB of dynamic range. To demonstrate the performance of the reader, the spectral signatures of three frequency-coded (FC) tags with four resonant frequencies are captured over the 1.5-4-GHz band scanned with 10-MHz resolution in 251 ms, obtaining comparable measurements to those of an expensive laboratory vector network analyzer (VNA) from 20 to 40 cm. The detected resonant frequency offset between both devices is Delta f(r) <= 4.18% . It is also demonstrated that the proposed reader can track a resonant frequency shift and therefore be used in real-time sensing applications.