Lluis Jofre

Bio: Lluis Jofre is an academic researcher from Polytechnic University of Catalonia. The author has contributed to research in topics: Antenna (radio) & Reconfigurable antenna. The author has an hindex of 28, co-authored 90 publications receiving 2880 citations. Previous affiliations of Lluis Jofre include Center for Turbulence Research & Supélec.

Circular Beam-Steering Reconfigurable Antenna With Liquid Metal Parasitics

Abstract: A novel antenna reconfiguration mechanism based on the displacement of liquid metal sections is presented. The liquid nature of the moving parts of the antenna helps avoid the main disadvantage of mechanically-actuated reconfigurable antennas which is the mechanical failure of their solid parts due to material fatigue, creep or wear. Furthermore, the displacement of liquid elements can be more effectively performed than in the case of solid materials by applying precise microfluidic techniques such as continuous-flow pumping or electrowetting. The reconfiguration mechanism is demonstrated through the design, fabrication and measurement of a radiation pattern reconfigurable antenna. This antenna operates at 1800 MHz with 4.0% bandwidth and is capable of performing beam-steering over a 360° range with fine tuning. The antenna is a novel circular Yagi-Uda array, where the movable parasitic director and reflector elements are implemented by liquid metal mercury (Hg). The parasitics are placed and rotated in a circular microfluidic channel around the driven element by means of a flow generated and controlled by a piezoelectric micropump. The measured results demonstrate good performance and the applicability of the microfluidic system.

Active microwave imaging of inhomogeneous bodies

Abstract: A numerical method and experimental technique for microwave imaging of inhomogenous bodies is presented. This method is based on the interpretation of the diffraction phenomena and leads to tomographic reconstruction of the body under investigation. Various numerical examples are given on spatial impulse response, recognition of dielectric rods, inhomogeneous bodies, and simulated human arm. Different experimental results on dielectric rods and isolated animal organs are also given.

Medical imaging with a microwave tomographic scanner

Abstract: A microwave tomographic scanner for biomedical applications is presented. It consists of a 64-element circular array with a useful diameter of 20 cm. Electronically scanning the transmitting and receiving antennas allows multiview measurements with no mechanical movement. Imaging parameters-a spatial resolution of 7 mm and a contrast resolution of 1% for a measurement time of 3 s-are appropriate for medical use. Measurements on tissue-simulating phantoms and volunteers, together with numerical simulations, are presented to assess the system for absolute imaging of tissue distribution and for differential imaging of physiological, pathological, and induced changes in tissues. >

RF MEMS Integrated Frequency Reconfigurable Annular Slot Antenna

Abstract: A new kind of double- and single-arm cantilever type DC-contact RF MEMS actuators has been monolithically integrated with an antenna architecture to develop a frequency reconfigurable antenna. The design, microfabrication, and characterization of this ?reconfigurable antenna (RA) annular slot? which was built on a microwave laminate TMM10i ( ?r = 9.8, tan ? = 0.002), are presented in this paper. By activating/deactivating the RF MEMS actuators, which are strategically located within the antenna geometry and microstrip feed line, the operating frequency band is changed. The RA annular slot has two reconfigurable frequencies of operation with center frequencies f low = 2.4 GHz and f high = 5.2 GHz, compatible with IEEE 802.11 WLAN standards. The radiation and impedance characteristics of the antenna along with the RF performance of individual actuators are presented and discussed.

Microwave Diffraction Tomography for Biomedical Applications

Abstract: This short paper points out the realizability of a method suitable for quasi real-time coherent microwave tomography for biomedical applications.

Boundary Layer Theory

Abstract: The boundary layer equations for plane, incompressible, and steady flow are $$\matrix{ {u{{\partial u} \over {\partial x}} + v{{\partial u} \over {\partial y}} = - {1 \over \varrho }{{\partial p} \over {\partial x}} + v{{{\partial ^2}u} \over {\partial {y^2}}},} \cr {0 = {{\partial p} \over {\partial y}},} \cr {{{\partial u} \over {\partial x}} + {{\partial v} \over {\partial y}} = 0.} \cr }$$

Properties Of Concrete

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Enhancing breast tumor detection with near-field imaging

Abstract: This article outlines the main features of active, passive, and hybrid systems under investigation for breast cancer detection. Our main focus is on active microwave systems, in particular microwave tomography and confocal microwave imaging.