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http://hdl.handle.net/2117/657
20150125T14:37:00Z

Regularization of the 2D TEEFIE for homogeneous objects discretized by the Method of Moments with discontinuous basis functions
http://hdl.handle.net/2117/25527
Title: Regularization of the 2D TEEFIE for homogeneous objects discretized by the Method of Moments with discontinuous basis functions
Authors: Sekulic, Ivan; Úbeda Farré, Eduard; Rius Casals, Juan Manuel; Heldring, Alexander
Abstract: The discretization of the ElectricField Integral Equation (EFIE) by the Method of Moments (MoM) for a transversal electric (TE) illuminating wave impinging on an infinitely long cylinder (2Dobject) is traditionally carried out with continuous piecewise linear basis functions. In this paper, we present a novel discretization of the TEEFIE formulation for the scattering analysis of homogeneous, perfectly conducting 2Dobjects based on the expansion of the currents around the lineboundary through discontinuous piecewise linear or piecewise constant basis functions. We show for several infinitely long cylinders, with smooth or sharpedged sections, the good accuracy of the proposed approach in the computation of farfield and nearfield quantities, such as RCS and currents, with respect to the observed accuracy in conventional continuous piecewise linear discretizations.
20150114T17:52:55Z

Threedimensional microfabricated broadband patch antenna for wiGig applications
http://hdl.handle.net/2117/25126
Title: Threedimensional microfabricated broadband patch antenna for wiGig applications
Authors: Mopidevi, Hema Swaroop; Hurneli, H. V.; Cagatay, E.; Biyikli, N.; Imbert Villà, Marc; Romeu Robert, Jordi; Jofre Roca, Lluís; Cetiner, Bedri Artug
Abstract: The design, microfabrication, and characterization of a broadband patch antenna capable of covering the entire IEEE 802.11ad (WiGig) frequency band (5766 GHz) are presented in this letter. A conductorbacked (CB) coplanar waveguide (CPW)fed loop slot couples the energy to the patch antenna, resulting in a broad bandwidth. The feed circuitry along with the loop is formed on a quartz substrate (epsilon(r) = 3.9, tan delta = 0.0002 at 60 GHz), on top of which an SU8based threedimensional (3D) structure with air cavities is microfabricated. The patch metallization is deposited on top of this 3D structure. While the main role of the structure made out of SU8 material is to provide a mechanical support for the patch metallization, the antenna takes advantage of the air cavities underneath, thus resulting in an antenna substrate with a very low loss. This, in turn, improves the overall antenna performances. The simulated and measured impedance characteristics agree well, showing similar to 15% bandwidth. Also, the radiation pattern results demonstrate the integrity of radiation pattern with reasonably constant gain values (average similar to 6.4 dB) in the broadside direction over the entire WiGig band.
20141222T15:49:02Z

Increased dynamic range for RFID EMfield measurements
http://hdl.handle.net/2117/25070
Title: Increased dynamic range for RFID EMfield measurements
Authors: Capdevila Cascante, Santiago; Romeu Robert, Jordi; Jofre Roca, Lluís; Bolomey, Jean Charles
Abstract: This paper presents a new methodology to measure the electromagnetic (EM) field using RFID tags, overcoming the limitations in dynamic range arisen by the conventional excitation of RFID tags. The methodology consists in the use of two different signals when interrogating the RFID tag. The first signal is in charge of powering up and triggering the response of the RFID tag, while the second one, with lower power, performs the EMfield measurement. With this approach the dynamic range of the EMfield measurement is increased up to the sensitivity of the receiver, and additionally the nonlinearities in the measured field distribution are completely removed.
20141217T16:17:28Z

Design and performance evaluation of a dielectric flat lens for millimeterwave applications
http://hdl.handle.net/2117/25067
Title: Design and performance evaluation of a dielectric flat lens for millimeterwave applications
Authors: Imbert Villà, Marc; Papió, Anna; de Flaviis, Franco; Jofre Roca, Lluís; Romeu Robert, Jordi
Abstract: In this paper, a practical fabrication of a dielectric flat lens for millimeterwave applications is presented. A previous theoretical dielectric flat lens antenna design, consisting of a set of concentric rings with different permittivity values for each, is now modeled and analyzed for a practical prototype fabrication and preliminary performance evaluation at 75 GHz. Preliminary measurements show that with the dielectric flat lens antenna prototype we can achieve beamsteering capabilities from 30 to +30 with around 17 dB of gain, and up to ±45 beamsteering capabilities with around 15 dB of gain, with low sidelobe levels. This design also leads to a lowprofile antenna configuration, easy to manufacture and lowcost, in order to integrate the whole structure in a compact millimeterwave commercial wireless system.
20141217T15:53:36Z

Passive acoustic method for aircraft states estimation based on the Doppler effect
http://hdl.handle.net/2117/24983
Title: Passive acoustic method for aircraft states estimation based on the Doppler effect
Authors: Martín Román, SaraRegina; Genesca, Meritxell; Romeu Robert, Jordi; Arcos Villamarín, Robert
Abstract: A passive acoustic method to locate moving sound sources is applied to maneuvering aircraft. The advantages of the method are that it is suitable for all kinds of aircraft, not only propellerdriven, and is not restricted to low height above the ground. Its applicability could be, for instance, to supplement aircraft noise monitoring systems or to supervise small airports' activities. The method is based on the relation between the relative Doppler effect observed from a set of at least seven microphone receivers, distributed in the airport surroundings, and the aircraft position and speed. The method requires knowledge of the position of the aircraft at the start of takeoff. The ambiguity function is used to calculate the relative Doppler stretch of the spectrum of the sound between pairs of microphones. The results of applying the ambiguity function are the inputs to a system of equations that relates the aircraft position and speed to the relative Doppler frequency stretches. This system of equations is solved using a genetic algorithm. The performance of the method was tested by computer simulation. The results showed that the location errors are of the same order of magnitude as the size of an average aircraft, even if the takeoff position is not accurately known.
20141210T13:39:40Z

Kuband flat lens design for satellite TV applications
http://hdl.handle.net/2117/24724
Title: Kuband flat lens design for satellite TV applications
Authors: Imbert Villà, Marc; Romeu Robert, Jordi; Jofre Roca, Lluís; Papió, Anna; de Flaviis, Franco
Abstract: In this paper, the design of a dielectric flat lens to operate in the Kuband for satellite communications is presented. Modern dishes intended for home television are generally bulky and heavy. Moreover, the costs of installation and alignment with the desired satellite are high. Satellite television providers are therefore looking for alternatives to the traditional dishes that could provide narrow beamwidths (5° max.), high gains, low sidelobe levels and beam steering capabilities. To satisfy the aforementioned requirements, we propose a dielectric flat lens to steer and enhance the radiation of the feed in a particular direction. Our simulation results indicate that we can achieve up to 31 dB of gain with 2.3° beamwidth, and beamsteering capabilities from +15° to 15° in both azimuth and elevation with more than 28 dB of gain with around 4° beamwidth, with low sidelobe levels, in the entire frequency band of interest (from 11.7 to 12.2 GHz). Moreover, the proposed design leads to a lowprofile antenna configuration, easy to manufacture and lowcost.
20141113T17:15:25Z

Switchedbeam antenna array for 60 GHz WPAN applications
http://hdl.handle.net/2117/24723
Title: Switchedbeam antenna array for 60 GHz WPAN applications
Authors: Imbert Villà, Marc; Romeu Robert, Jordi; Jofre Roca, Lluís; Papió, Anna; de Flaviis, Franco
Abstract: In this paper, the design of a switchedbeam antenna array to operate in the 60 GHz band for shortrange WPAN applications is presented. In order to overcome the high pathloss attenuation at millimeterwave frequencies and, moreover, to achieve high data rate wireless communications, highly directive antennas are required. In addition, beamsteering antennas are also needed to deal with the high user random mobility and humanbody shadowing characteristic of indoor environments. For these reasons, we propose a design based on a five by five slot antenna array, in which each single element can be selected individually, and a dielectric flat lens to steer and enhance the radiation in a particular direction. A total of 25 fixed highgain beams can be selected individually to scan in both theta and phi directions. Our simulation results indicate that we can achieve up to 18.4 dB of gain, and beamsteering capabilities from +30° to 30° with more than 15 dB of gain, and up to ±45° with around 14 dB, with lowside lobe levels, in the entire frequency band of interest (from 57 to 64 GHz).
20141113T15:44:11Z

Nonconforming discretization of the MagneticField Integral Equation with volumetric testing
http://hdl.handle.net/2117/24721
Title: Nonconforming discretization of the MagneticField Integral Equation with volumetric testing
Authors: Úbeda Farré, Eduard; Rius Casals, Juan Manuel; Heldring, Alexander
Abstract: The RWGdiscretization in Method of Moments (MoM) of the MagneticField and ElectricField Integral Equations (MFIE, EFIE) show evident discrepancy in the computed RCS, especially for small objects with edges and corners. The nonconforming monopolarRWG discretization of the MFIE exhibits a smaller a deviation with respect to the EFIE. The CombinedField Integral Equation (CFIE), which arises from the combination of the EFIE and the MFIE, is very often implemented with the RWG basis functions, whereby some accuracy with respect to EFIE is lost too. In this paper, we present a new nonconforming monopolarRWG discretization of the MFIE, based on testing the magnetic field over small tetrahedral elements attached to the surface, inside the body under analysis. This formulation is compatible with a successful nonconforming discretization of the EFIE with the monopolarRWG expansion of the current and volumetric testing. This allows the development of a nonconforming discretization of the CFIE.
20141113T15:34:59Z

Volumetric testing with wedges for a nonconforming discretization of the ElectricField Integral Equation
http://hdl.handle.net/2117/24720
Title: Volumetric testing with wedges for a nonconforming discretization of the ElectricField Integral Equation
Authors: Úbeda Farré, Eduard; Rius Casals, Juan Manuel; Heldring, Alexander
Abstract: The discretization in Method of Moments (MoM) of the ElectricField Integral Equation (EFIE) is traditionally carried out with divergenceconforming sets of basis functions, like the RWG set. This enforces the normal continuity of the current across the edges arising from the discretization and makes the quasisingular Kernel contributions numerically manageable. However, these MoMimplementations of the EFIE show little flexibility when handling nonconformal meshes, normally arising from from the juxtaposition or interconnection of independent meshes in the modular design of composite objects. A nonconforming discretization of the EFIE is possible if the testing procedure is carried out over volumetric elements attached to the surface triangulation, inside the body. In this paper, we present a new nonconforming discretization of the EFIE, where wedges attached to the source triangles are used as testing volumetric elements.
20141113T15:30:46Z

RF monitoring of commercial vascular stents with dipole scattering resonances
http://hdl.handle.net/2117/24702
Title: RF monitoring of commercial vascular stents with dipole scattering resonances
Authors: Arauz Garofalo, Gianluca; López Domínguez, Víctor; Hernández Ferras, Joan Manel; Rodríguez Leor, Oriol; Bayés Genis, Antoni; Rius Casals, Juan Manuel; O'Callaghan Castellà, Juan Manuel; García Santiago, Antoni; Tejada Palacios, Javier
Abstract: We have compared measurements and simulations of the microwave forward scattering of several commercial coronary stents. We immerse the stents in water to replicate the permittivity of biological tissues and find that their dipole scattering resonances can be detected at frequencies close to 300 MHz even though the stents are not purposely designed to facilitate such detection. We discuss how stent resonances can be used to monitor restenosis with noninvasive and nonionizing techniques.
20141112T14:35:01Z

On the convergence of the ACA algorithm for radiation and scattering problems
http://hdl.handle.net/2117/24654
Title: On the convergence of the ACA algorithm for radiation and scattering problems
Authors: Heldring, Alexander; Úbeda Farré, Eduard; Rius Casals, Juan Manuel
Abstract: The adaptive cross approximation (ACA) algorithm, when used to accelerate the numerical solution of integral equations for radiation and scattering problems, sometimes suffers from inaccuracies. These inaccuracies occur when the ACA convergence criterion, which is based on an approximation of the residual relative error, is prematurely satisfied. This paper identifies the two sources of this problem and proposes adaptations of the algorithm that remedy them.
20141110T17:44:02Z

A quadband antenna for public safety applications
http://hdl.handle.net/2117/24294
Title: A quadband antenna for public safety applications
Authors: Mopidevi, Hema Swaroop; Damgaci, T; Rodrigo López, Daniel; Jofre Roca, Lluís; Cetiner, Bedri Artug
Abstract: The design, fabrication, and characterization of a frequencyreconfigurable antenna for the United States Public Safety (PS) wireless communication applications are presented. This antenna is quadband operating in the PS bands220, 470, 800, and 4960 MHz. It is an electrically small antenna with calculated ka similar to 0.55 at 220 MHz. The antenna has two reconfigurable modes of operations. In mode 1, 220, 470, and 4960MHz bands are excited. Mode 2 provides operation over 800 and 4960MHz bands. This dynamic frequency reconfiguration is accomplished by two radio frequency microelectromechanical systems switches strategically located within the antenna architecture. The measured and simulated results for impedance and radiation characteristics agree well, where similar to 3%, 4%, 21%, and 17% fractional bandwidths have been measured in the four bands, respectively, while maintaining integrity of radiation pattern.
20141007T13:24:32Z

Nonconforming discretization of the electricfield integral equation for closed perfectly conducting objects
http://hdl.handle.net/2117/24163
Title: Nonconforming discretization of the electricfield integral equation for closed perfectly conducting objects
Authors: Úbeda Farré, Eduard; Rius Casals, Juan Manuel; Heldring, Alexander
Abstract: Galerkin implementations of the method of moments (MoM) of the electricfield integral equation (EFIE) have been traditionally carried out with divergenceconforming sets. The normalcontinuity constraint across edges gives rise to cumbersome implementations around junctions for composite objects and to less accurate implementations of the combined field integral equation (CFIE) for closed sharpedged conductors. We present a new MoMdiscretization of the EFIE for closed conductors based on the nonconforming monopolarRWG set, with no continuity across edges. This new approach, which we call
20140925T14:15:46Z

New graphical processing technique for fast shadowing computation in PO surface integral
http://hdl.handle.net/2117/23208
Title: New graphical processing technique for fast shadowing computation in PO surface integral
Authors: Rius Casals, Juan Manuel; Carbó Meseguer, Alexis; Bjerkemo, Jakob; Úbeda Farré, Eduard; Heldring, Alexander; Mallorquí Franquet, Jordi Joan; Broquetas Ibars, Antoni
Abstract: This paper presents a new graphical processing technique for fast computation of PO surface integral. In contrast with the original graphical processing approach introduced by the authors in 1993, the new one combines a novel shadowing computation algorithm together with the conventional facetbased Gordon's formula, instead of the pixelbased Asvestas' approximation. The resulting hybrid approach needs more CPU power for very complex radar targets, but is free from the pixel discretization noise inherent to graphical processing. It has the same accuracy as conventional Physical Optics computation, but shadowed facets detection is more than 10 times faster than with the most efficient alternative algorithms of O(N log N) computational cost. © 2014 IEEE.
20140612T13:33:08Z

Unit cell for frequencytunable beamscanning reflectarrays
http://hdl.handle.net/2117/23126
Title: Unit cell for frequencytunable beamscanning reflectarrays
Authors: Rodrigo López, Daniel; Jofre Roca, Lluís; Perruisseau Carrier, Julien
Abstract: A reflectarray cell able to dynamically control the reflection phase at a variable frequency is presented. This capability enables beamscanning reflectarrays with frequency reconfigurability, which is a novel capability with applications in frequencyhopping systems, cognitive radio and satellite communications. The proposed cell combines switching and variable impedance loading techniques to maximize the frequency range over which a large dynamic phase range can be obtained. Analytical and numerical approaches are used to design and optimize the reflecting cell, which uses two semiconductor RFswitches and one varactor. An analog phase range above 270 degrees is achieved over a 50% frequency range, from 1.88 GHz to 3.07 GHz, with flat losses of 0.8 dB. For an analog phase range of 180 degrees the cell achieves a 1: 2 frequency reconfiguration range. It is also verified that the cell preserves good performance, and in particular low crosspolarization, under oblique incidence as well. A fully operational cell was fabricated and measured, demonstrating good agreement with simulation results.
20140602T15:12:00Z