Nuestros investigadores

Daniel Valderas Gázquez

Líneas de investigación
Wireless sensors, Electromagnetic Simulation, Antennas and Wireless links

Publicaciones científicas más recientes (desde 2010)

Autores: Villa, F., (Autor de correspondencia); Cortes, I.; Urain, A.; et al.
ISSN 1045-9243  Vol. 61  Nº 4  2019  págs. 90 - 96
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.
Autores: Benli, K.P.; Casado, F.; et al.
ISSN 0278-0046  Vol. 64  Nº 10  2017  págs. 7749 - 7757
The potential of inkjet printing technology (IjP) for the fabrication of coils for biomedical applications in inductively coupled power transfer systems is studied in terms of needed compensations, bifurcation phenomena, and power transfer efficiency. The effect of using coils manufactured with IjP in the secondary side has been analyzed by studying the effect of the increase in internal resistance. The present study makes it possible to select the best topology depending on the load impedance, the coupling coefficient, and coil design. In terms of the compensations needed at the primary side, IjP does not significantly affect the behavior of the system; however, the series¿series topology is preferable since the compensating capacitance is independent from the internal resistance. In terms of bifurcation, a more restricted condition is obtained for parallel compensated secondary circuits. There is a decrease on the power transfer efficiency due to the increase of the internal resistance introduced by IjP. However, it is important to select the best topology according to the application since the decrease could be from 63% to only 6%. It is concluded that IjP is a promising fabrication technique for coils for biomedical applications.
Autores: Alonso, D.; Zhang, Q. Y.; Gao, Y.; et al.
ISSN 0895-2477  Vol. 59  Nº 7  2017  págs. 1709 - 1715
This article aims to propose a RFID system to detect the humidity of the soil in flowerpots and help farmers to judge whether the plants should be watered or not. By tuning the tag to dry soil state, it achieves higher dynamic range and sensitivity (20 dB) compared to a commercial RFID tag performance. This approach saves the addition of a sensor element to the RFID tag to operate as a wireless sensor.
Autores: Daniel Valderas; Mesa, I.; Adin, Íñigo; et al.
ISSN 0018-9545  Vol. 66  Nº 11  2017  págs. 9743 - 9752
This paper presents a model that anticipates the emissions from eddy current brakes (ECBs) installed in high-speed trains. The emissions are computed in the 10 KHz-1.3 MHz range, where trackside signaling devices operate and issues related to electromagnetic compatibility have arisen, hindering ECB's promise of full deployment. The electromagnetic model provides a transfer function in the frequency domain between the nondesired harmonic currents produced by the train power supply and the subsequent radiated emissions by the ECBs at the trackside. The model includes the influence of the on-board ECB system's electric circuitry on the three-dimensional field computation of the electromagnets by a cosimulation approach (circuit and electromagnetic cross talk). After the data are post-processed, the simulated results are compared with the results of an extensive measurement campaign on board a high-speed ICE 3 train equipped with ECBs. The high correlation makes it possible to anticipate ECB emissions in order to save costly on-track test runs, to suggest ECB design strategies and to provide safe limits when the worst cases occur.
Autores: Ge, H.; Yao, Y.; Yu, J.; et al.
ISSN 0013-5194  Vol. 52  Nº 3  2016  págs. 181 - 182
A method using 180 degrees hybrid coupler and vector network analyser to measure the radio frequency identification tag antenna impedance is presented. The impedance of a prototype antenna is measured by different experimental methods and compared with simulation results. The comparison results show that the proposed method has a good accuracy and it is more convenient.
Autores: Schmidt, C.; Casado, F.; Arriola, A.; et al.
ISSN 0018-926X  Vol. 62  Nº 3  2014  págs. 1433-1444
A broadband UHF antenna for implanted central venous catheters (CVC) is designed, implemented, and properly characterized. According to the requirements, the CVC antenna (CVCA) is low profile, surface integrated, and 3-D conformal to a 16 mm base radius, 10 mm upper radius, and 16 mm high truncated cone. It operates at the MedRadio band (401-406 MHz) for implant communication and at the ISM 2.45 GHz band for electronics wake up. A prototype implementation including a test-bed within a phantom that is representative of a body is introduced. The antenna exhibits S-11 < -10 dB at the bands of interest with broadband behavior. The measured gain is -28.95 dBi in vertical and -36.9 dBi in horizontal polarization in the MedRadio band and -25.5 dBi and -19.9 dBi at 2.45 GHz. The gain is corroborated by the link characterization between an implanted node with electronics and an external base station. Base station antenna, electronics sensitivity, transmitted power, and path loss are independently measured and introduced in a broken down link budget for read range estimate. This is 18.95 m for the MedRadio band in free space conditions. By using the power saving mode at 2.45 GHz, it is reduced to an estimate of 1.88 m.
Autores: Paredes, J; Alonso-Arce, Maykel; Schmidt, C.; et al.
ISSN 1387-2176  Vol. 16  Nº 3  2014  págs. 365 - 374
Central venous catheters (CVC) are commonly used in clinical practice to improve a patient's quality of life. Unfortunately, there is an intrinsic risk of acquiring an infection related to microbial biofilm formation inside the catheter lumen. It has been estimated that 80 % of all human bacterial infections are biofilm-associated. Additionally, 50 % of all nosocomial infections are associated with indwelling devices. Bloodstream infections account for 30-40 % of all cases of severe sepsis and septic shock, and are major causes of morbidity and mortality. Diagnosis of bloodstream infections must be performed promptly so that adequate antimicrobial therapy can be started and patient outcome improved. An ideal diagnostic technology would identify the infecting organism(s) in a timely manner, so that appropriate pathogen-driven therapy could begin promptly. Unfortunately, despite the essential information it provides, blood culture, the gold standard, largely fails in this purpose because time is lost waiting for bacterial or fungal growth. This work presents a new design of a venous access port that allows the monitoring of the inner reservoir surface by means of an impedimetric biosensor. An ad-hoc electronic system was designed to manage the sensor and to allow communication with the external receiver. Historic data recorded and stored in the device was used as the reference value for the detection of bacterial biofilm. The RF communication system sends an alarm signal to the external receiver when a microbial colonization of the port occurs. The successful in vitro analysis of the biosensor, the electronics and the antenna of the new indwelling device prototype are shown. The experimental conditions were selected in each case as the closest to the clinical working conditions for the smart central venous catheter (SCVC) testing. The results of this work allow a new generation of this kind of device that could potentially provide more efficient treatments for catheter-related infections.
Autores: Garcia, J.; Arriola, A.; Casado, F.; et al.
ISSN 1751-8725  Vol. 6  Nº 9  2012  págs. 1070 - 1078
This study presents a comparison between two dipoles acting as representatives of ultra-high frequency radio frequency identification (RFID) circularly polarised (CP) and linearly polarised (LP) tag antennas, respectively. As the CP dipole is derived from the LP dipole, they have equivalent reflection coefficient and radiation efficiency values, allowing the comparison to be focused on polarisation and radiation pattern. Then, a comparison of RFID angular and read range is investigated. This is conducted by combining the interrogation of CP and LP tags emulators by CP and LP readers with regulated power. The emulators are made up of the CP and LP dipoles embedded onto RFID tags with analog front-ends. A methodology is described for measuring the maximum angular and read ranges, involving maximum power allowed by European regulation. A 17.9% extra range is achieved by the CP tag and the CP reader compared to the LP tag with any kind of reader. Furthermore, null cancellation is observed in the former case in the region of interest.
Autores: Sanchez, N.; Garcia, J.; et al.
ISSN 1687-5869  2012 
The aim of this paper is to examine the potential of inkjet printing technology for the fabrication of Near Field Communication (NFC) coil antennas. As inkjet printing technology enables deposition of a different number of layers, an accurate adjustment of the printed conductive tracks thickness is possible. As a consequence, input resistance and Q factor can be finely tuned as long as skin depth is not surpassed while keeping the same inductance levels. This allows the removal of the typical damping resistance present in current NFC inductors. A general methodology including design, simulation, fabrication, and measurement is presented for rectangular, planar-spiral inductors working at 13.56 MHz. Analytical formulas, computed numerical models, and measured results for antenna input impedance are compared. Reflection coefficient is designated as a figure of merit to analyze the correlation among them, which is found to be below -10 dB. The obtained results demonstrate the suitability of this technology in the fabrication of low cost, environmentally friendly NFC coils on flexible substrates.
Autores: Daniel Valderas; Crespo, Pedro M.; Ling, C.;
ISSN 0895-2477  Vol. 52  Nº 4  2010  págs. 889-895
Antenna arrays that incorporate MIMO technology for indoor-outdoor network interconnection on the same terminal, i.e., for DCS 1800. PCS 1900, WCDMA, 3G. 802.11a/b/g. Bluetooth (R). ZigBee (R), WiMAX (TM), and UWB standards, are proposed. Staircase profile printed circuit antenaas, monopoles (PCM). and slots (PCS) with VSWR < 2 bandwidth mainly from 1.12 to 10.1 GHz are previously designed, simulated. constructed, and measured as antenna elements for those arrays. For comparison. prototypes for two-element PCM and PCS MIMO arrays have been constructed and measured, The choice should be made according to the directivity required by the final application and portable device size. For the worst signal interference case, the operational bandwidth ranges from 1.5 to 9.9 GHz and from 1.7 to 11.4 GHz for the PCM and the PCS MIMO arrays, respectively. VSWR is basically below two, average capacity loss 0.32 bps/Hz with respect to the ideal uncorrelated (2,2) case and envelope correlation lower than 20 dB. (C) 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 889-895, 2010: Published online in Wiley InterScience ( DOI:10.1002/mop.25047
Autores: Daniel Valderas; Sancho, Juan Ignacio; Puente, D.; et al.
Ultrawideband (UWB) technology, positioned as the cutting edge of research and development, paves the way to meet the emerging demands set by broadband wireless applications, such as high-speed data transmission, medical imaging, short-range radars, electromagnetic testing, etc. This breathtaking resource builds upon the basics of UWB technology to provide a complete compilation of figures of merit along with a vital state-of-the-art of the different antenna alternatives that are to be employed according to the specific application. Without excessive recourse to mathematics, this volume emphasizes on the UWB antenna design and equips readers with practical prediction techniques based on simple formulas and models. The big picture of UWB antenna technology would not be complete without addressing its applications, and this will serve to provide consultants with key clues for market gap analysis. Containing over 150 supporting illustrations and figures, this comprehensive overview of UWB technology, antenna design and applications is a vital source of information and reference for R&D organizations, researchers, practitioners, consultants, RF professionals and communication engineers.


Dr. Daniel Valderas received the MSc. degree and the PhD. from Tecnun, University of Navarra, in 1998 and 2006 respectively. He was Academic Visitor at Florida Atlantic University in 2003. He joined Ceit-IK4 as Research Scientist and Tecnun as Assistant Lecturer in 2006. He was visiting researcher at Imperial College in 2007 and at Queen Mary, University of London, in 2008. He has participated in many different research projects on the Antenna and Electromagnetics with practical background in Electromagnetic Simulation. He has published 8 book chapters and a number of journal papers and conference contributions. His research interests focus on UWB and broadband antennas, RFID and implanted antennas, wireless chipless sensors and radar. Starting in 2018, he is currently Lecturer and Research Scientist with Tecnun, University of Navarra.