https://hdl.handle.net/11000/406 2026-04-03T20:08:58Z https://hdl.handle.net/11000/38449 Título : Microwave Imaging System Based on Signal Analysis in a Planar Environment for Detection of Abdominal Aortic Aneurysms Autor : Martínez-Lozano, Andrea; Guiterrez, Roberto; Juan, Carlos G.; Blanco-Angulo, Carolina; García-Martínez, Héctor; Torregrosa, Germán; Sabater-Navarro, José María; Ávila-Navarro, Ernesto Resumen : A proof-of-concept of a microwave imaging system for the fast detection of abdominal aortic aneurysms is shown. This experimental technology seeks to overcome the factors hampering the fast screening for these aneurysms with the usual equipment, such as high cost, long-time operation or hazardous exposure to chemical substances. The hardware system is composed of 16 twin antennas mastered by a microcontroller through a switching network, which connects the antennas to the measurement instrument for sequential measurement. The software system is run by a computer, mastering the whole system, automatizing the measurement process and running the signal processing and medical image generation algorithms. Two image generation algorithms are tested: Delay-and-Sum (DAS) and Improved Delay-and-Sum (IDAS). Own-modified versions of these algorithms adapted to the requirements of our system are proposed. The system is carefully calibrated and fine-tuned with known objects placed at known distances. An experimental proof-of-concept is shown with a human torso phantom, including an aorta phantom and an aneurysm phantom placed in different positions. The results show good imaging capabilities with the potential for detecting and locating possible abdominal aortic aneurysms and reporting acceptable errors. 2025-11-24T12:52:48Z https://hdl.handle.net/11000/38448 Título : Non-Invasive Microwave-Based Imaging System for Early Detection of Breast Tumours Autor : Blanco-Angulo, Carolina; Martínez-Lozano, Andrea; Gutiérrez-Mazón, Roberto; Juan, Carlos G.; García-Martínez, Héctor; Arias Rodríguez, Julia; Sabater-Navarro, José M.; Ávila-Navarro, Ernesto Resumen : This work introduces a microwave-based system able to detect tumours in breast phantoms in a non-invasive way. The data acquisition system is composed of a hardware system which involves high-frequency components (antennas, switches and cables), a microcontroller, a vector network analyser used as measurement instrument and a computer devoted to the control and automation of the operation of the system. Concerning the software system, the computer runs a Python script which is in charge of mastering and automatising all the required stages for the data acquisition, from initialisation of the hardware system to performing and saving the measurements. We also report on the design of the high-performance broadband antenna used to carry out the measurements, as well as on the algorithm employed to build the final medical images, based on an adapted version of the so-called Improved Delay-and-Sum (IDAS) algorithm improved by a Hamming window filter and averaging preprocessing. The calibration and start-up of the system are also described. The experimental validation includes the use of different tumour models with different dielectric properties inside the breast phantom. The results show promising tumour detection capabilities, even when there is low dielectric contrast between the tumoural and healthy tissues, as is the usual case for dense breasts in young women. 2025-11-24T12:51:56Z https://hdl.handle.net/11000/38447 Título : Low-Cost Direct-Writing of Silver-Based Ink for Planar Microwave Circuits up to 10 GHz Autor : Blanco-Angulo, Carolina; Martínez-Lozano, Andrea; Arias Rodríguez, Julia; Rodríguez-Martínez, Alberto; Vicente-Samper, José María; Sabater-Navarro, José María; Ávila-Navarro, Ernesto Resumen : Direct ink writing (DIW) of conductive ink is a printed electronics technology that allows a variety of electronic circuits to be produced in a simple way and with minimal waste of materials. In recent years it has been used for rapid prototyping of RF circuits typically working at S-band frequencies (2 4 GHz). In an attempt to extend this frequency range while maintaining cost-effective prototyping, this work has focused on proving the feasibility of DIW of silver-conductive (SC) ink for the fabrication of planar microwave circuits beyond 10 GHz, more speci cally, ultra-wideband (UWB) antennas for medical applications. For this purpose, the DC and RF performance of the SC ink, as well as the FR4 substrate used, were rst evaluated. Based on the comparison between experimental and simulated results, we have found that the effective RF conductivity of the SC ink is approximately 27.6% of its DC value and 3.4% of the copper conductivity. A few test microstrip circuits were fabricated by DIW, namely two S-band lters and one UWB antenna. The overall measured performance of all of them agreed well with simulations. In particular, the DIW antenna exhibited a bandwidth of 8.2 GHz (between 2.4 and 10.6 GHz), and was compared with an identical copper antenna showing that both have very similar characteristics. It was also found that the lower conductivity of SC ink as compared to copper led to a gain reduction of only 0.3 dB. 2025-11-24T12:50:54Z https://hdl.handle.net/11000/38135 Título : Electromagnetic Pulses: A Novel Framework for Helicity, Chirality, and Their Flows Autor : Acebal, Pablo; Carretero, Luis; Blaya, Salvador Resumen : This article delves into conserved quantities of electromagnetic pulses, which are crucial for understanding their behavior. We introduce a precise framework for computing scalar properties (energy, helicity, and chirality) and vector properties (Poynting vector, spin, and chirality flux) of electromagnetic pulses with gauge-invariant equations. Based on the far-field behavior of radiated electric field, our methodology offers accurate results akin to traditional volume integrals but at a lower computational cost. In addition, our findings enable a reinterpretation of these properties as statistical average parameters of the pulse. This innovative approach not only simplifies calculations but also enhances their accuracy, making it useful for studying the main conserved quantities for complex electromagnetic field structures, as those formed by multiple interference of pulses. 2025-11-12T09:19:26Z https://hdl.handle.net/11000/38134 Título : Theoretical Analysis of Airy-Gauss Bullets Obtained by Means of High Aperture Binary Micro Zonal Plate Autor : Blaya, Salvador; López-Sola, Edmundo; Acebal, Pablo; Carretero, Luis Resumen : We theoretically analyze the methodology for obtaining vectorial three-dimensional bullets, concretely Airy–Gauss bullets. To do this, binary micro zonal plates (BZP) were designed in order to obtain different Airy–Gauss bullets with sub-diffraction main lobe width. Following the vectorial diffraction theory, among the electrical field, we extend the theory to the magnetic field, and thus we analyze several properties such as the Poynting vector and the energy of Airy–Gauss vectorial bullets generated by illuminating the designed BZP with a temporal Gaussian circular polarized pulses. 2025-11-12T09:17:47Z https://hdl.handle.net/11000/38133 Título : Generation of Huygens' dipoles for any spherical nanoparticle excited by counter-propagating plane waves: study of scattered helicity Autor : Carretero, Luis; Acebal, Pablo; Blaya, Salvador Resumen : Helicity and directionality control of scattered light by nanoparticles is an important task in different photonic fields. In this paper, we theoretically demonstrate that scattered light of lossy spherical nanoparticles excited by using two counter-propagating dephased plane waves with opposite helicity ±1 and the adequate selection of dephase and intensity shows a well defined helicity and a controllable scattering directivity. Numerical examples of Si nanospheres are studied showing their potential application to directional nanoantennas with a well defined helicity. The proposed method is valid for any type of nanoparticle, not only lossy ones. Notas: Contiene un suplemento, con DOI: https://doi.org/10.6084/m9.figshare.17185877 2025-11-12T09:16:40Z https://hdl.handle.net/11000/38127 Título : Few-Cycle Electromagnetic Pulses with Finite Energy and Bounded Angular Momentum: Analysis of the Skyrmionic Texture at Focal Plane Autor : Carretero, Luis; Acebal, Pablo; Blaya, Salvador Resumen : Exact solutions to Maxwell equations with topological charge based on a modi cation to Brittingham's single cycle pulses are analyzed demonstrating that they have nite values of energy, momentum, and angular momentum. Moreover, the ratio of angular momentum to energy is bounded due to the dependence of the mean frequency on topological charge. We have also analyzed the skyrmionic texture of the electric and magnetic elds showing that it is possible to obtain skyrmionic numbers higher than the one for the magnetic eld by means of a superposition of pulses with different topological charges and null skyrmionic number. 2025-11-11T12:48:15Z https://hdl.handle.net/11000/38126 Título : Extraordinary spin to orbital angular momentum conversion on guided zone plates Autor : Acebal, Pablo; Carretero, Luis; Blaya, Salvador Resumen : Focusing systems with high numerical aperture can be used to convert spin angular momentum into orbital angular momentum with efficiencies of 50%, while for low numerical apertures this conversion vanishes. In this paper, based on the properties of binary Fresnel zone plates, we propose a structure that is achieved by making an accurate selection of the width and the depth of the rings. This allows us to obtain a large increase in the spin to orbital angular momentum conversion of the resulting focusing fields, and it also has the special characteristic that the obtained conversion is higher for low numerical aperture structures, where standard focusing systems do not work. The ability of the system to perform this extraordinary conversion is demonstrated by FDTD methods and an analytical model developed using a combination of guided mode theory for the structure and Stratton–Chu diffraction theory. 2025-11-11T12:46:31Z https://hdl.handle.net/11000/38125 Título : Vectorial analysis of Airy-Airy bullets generated by high aperture binary micro zonal plate Autor : Blaya, Salvador; Carretero, Luis; Acebal, Pablo Resumen : Intense research has recently been carried out in the study of three dimensional light bullets. Based on the experi- mental approach for obtaining Airy-Bessel light bullets by Chong et al [1], we propose a theoretical methodology for obtaining and analyzing vectorial three dimensional bullets. First of all, we present the design criteria of binary micro zonal plates (BZP) that make it possible to obtain Airy-Airy bullets with sub-diffraction main lobe width. Following the vectorial diffraction theory, we analyze Airy-Airy vectorial bullets generated by illuminat- ing the designed BZP with temporal Airy circular polarized pulses. The propagation dynamics of the resulting vectorial light bullets have been studied; the width of the resulting FWHM of the spatial main lobe at the focal plane being close to 0.75 𝜆0 . 2025-11-11T12:45:38Z https://hdl.handle.net/11000/38124 Título : Dynamic of Si nanoparticles inside of a quadrupolar trap: Analysis of the angular momentum transfer Autor : Carretero, Luis; Acebal, Pablo; Blaya, Salvador; Pérez-Molina, Manuel Resumen : We investigate the dynamics of Si spherical nanoparticles for different infrared wavelengths in a system based on two circularly polarized counter-propagating Gaussian beams. Through the analysis of the dipolar and quadrupolar forces, we obtain several conditions under which these nanoparticles describe different types of attractive or repulsive spirals at focus plane depending on the efficiency of the quadrupole trap obtained. We demonstrate that these spirals are generated by the angular momentum transfer from the electromagnetic field to the particles, and this is mainly due to the interference forces dipole–dipole and quadrupole–dipole. Through the adequate selection of the wavelength, angular momentum transfer can only take place with quadrupolar– dipolar interference forces. We study particle dynamics by solving the deterministic and non-deterministic over-damped Langevin equation. 2025-11-11T12:44:48Z