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http://hdl.handle.net/2117/657
Mon, 22 Dec 2014 02:21:54 GMT
20141222T02:21:54Z
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Universitat Politècnica de Catalunya. Servei de Biblioteques i Documentació
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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.
Wed, 17 Dec 2014 16:17:28 GMT
http://hdl.handle.net/2117/25070
20141217T16:17:28Z
Capdevila Cascante, Santiago; Romeu Robert, Jordi; Jofre Roca, Lluís; Bolomey, Jean Charles
no
Dynamic range, Field measurement
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.

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.
Wed, 17 Dec 2014 15:53:36 GMT
http://hdl.handle.net/2117/25067
20141217T15:53:36Z
Imbert Villà, Marc; Papió, Anna; de Flaviis, Franco; Jofre Roca, Lluís; Romeu Robert, Jordi
no
Dielectric flat lens antenna, Millimeterwave applications, Nearfield to farfield measurements
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.

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.
Wed, 10 Dec 2014 13:39:40 GMT
http://hdl.handle.net/2117/24983
20141210T13:39:40Z
Martín Román, SaraRegina; Genesca, Meritxell; Romeu Robert, Jordi; Arcos Villamarín, Robert
no
Parameterestimation, Timedelay, Localization, Array, Stretch, Sensor
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.

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.
Thu, 13 Nov 2014 17:15:25 GMT
http://hdl.handle.net/2117/24724
20141113T17:15:25Z
Imbert Villà, Marc; Romeu Robert, Jordi; Jofre Roca, Lluís; Papió, Anna; de Flaviis, Franco
no
Beam steering, Dielectric materials, Direct broadcasting by satellite, Lens antennas, Satellite antennas, Television broadcasting, Kuband flat lens, Antenna configuration, Beam steering capabilities, Dielectric flat lens, Frequency 11.7 GHz to 12.2 GHz, Home television, Satellite TV applications, Satellite communications
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.

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).
Thu, 13 Nov 2014 15:44:11 GMT
http://hdl.handle.net/2117/24723
20141113T15:44:11Z
Imbert Villà, Marc; Romeu Robert, Jordi; Jofre Roca, Lluís; Papió, Anna; de Flaviis, Franco
no
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).

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.
Thu, 13 Nov 2014 15:34:59 GMT
http://hdl.handle.net/2117/24721
20141113T15:34:59Z
Úbeda Farré, Eduard; Rius Casals, Juan Manuel; Heldring, Alexander
no
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.

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.
Thu, 13 Nov 2014 15:30:46 GMT
http://hdl.handle.net/2117/24720
20141113T15:30:46Z
Úbeda Farré, Eduard; Rius Casals, Juan Manuel; Heldring, Alexander
no
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.

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.
Wed, 12 Nov 2014 14:35:01 GMT
http://hdl.handle.net/2117/24702
20141112T14:35:01Z
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
no
Monitoring, Restenosis, Stent
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.

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.
Mon, 10 Nov 2014 17:44:02 GMT
http://hdl.handle.net/2117/24654
20141110T17:44:02Z
Heldring, Alexander; Úbeda Farré, Eduard; Rius Casals, Juan Manuel
no
Adaptive cross approximation (ACA), Computational electromagnetics, Method of moments, Adaptive cross approximation, Matrices
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.

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.
Tue, 07 Oct 2014 13:24:32 GMT
http://hdl.handle.net/2117/24294
20141007T13:24:32Z
Mopidevi, Hema Swaroop; Damgaci, T; Rodrigo López, Daniel; Jofre Roca, Lluís; Cetiner, Bedri Artug
no
Antenna measurements, Antenna radiation patterns, Broadband antennas, Electrically small antennas, Frequencyreconfigurable antennas (FRAs), Multiband antennas, Multilayered antennas, UHF antennas
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.

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
Thu, 25 Sep 2014 14:15:46 GMT
http://hdl.handle.net/2117/24163
20140925T14:15:46Z
Úbeda Farré, Eduard; Rius Casals, Juan Manuel; Heldring, Alexander
no
Basis functions, electric field integral equation (EFIE), integral equations, moment method, Electromagnetic scattering, Dielectric objects, Bodies, Frequencies, Junctions, Moments, MFIE
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

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.
Thu, 12 Jun 2014 13:33:08 GMT
http://hdl.handle.net/2117/23208
20140612T13:33:08Z
Rius Casals, Juan Manuel; Carbó Meseguer, Alexis; Bjerkemo, Jakob; Úbeda Farré, Eduard; Heldring, Alexander; Mallorquí Franquet, Jordi Joan; Broquetas Ibars, Antoni
no
Graphical processing, high frequency asymptotic techniques, physical optics, radar cross section (RCS)
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.

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.
Mon, 02 Jun 2014 15:12:00 GMT
http://hdl.handle.net/2117/23126
20140602T15:12:00Z
Rodrigo López, Daniel; Jofre Roca, Lluís; Perruisseau Carrier, Julien
no
Beamscanning, Beam steering, Cognitive radio, Microstrip arrays, Reconfigurable antennas, Reflectarrays
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.

Reconfigurable pixellayer isolator for frequencytunable onfrequency repeaters
http://hdl.handle.net/2117/22788
Title: Reconfigurable pixellayer isolator for frequencytunable onfrequency repeaters
Authors: Rodrigo López, Daniel; Díaz Tapia, Edgar; Jofre Roca, Lluís
Abstract: The maximum gain in onfrequency repeaters is limited by the isolation level between their two antennas due to closeloop stability conditions. In this letter, a novel pixellayer isolator for tunable onfrequency repeaters is presented. The scattered field of the reconfigurable pixel layer is used to dynamically minimize the mutual coupling between the antennas. Insight is given on the linkage between coupling and reflection coefficients, and a useful design procedure is proposed. The optimized pixel repeater can tune the operating frequency over a 40% range, with tunable instantaneous bandwidth (1%3%) and achieving a reliable isolation of 50 dB. The repeater has a radiation efficiency of 93% and a constant radiation pattern for the different configurations. Good agreement is obtained between simulations and measurements.
Wed, 30 Apr 2014 12:30:33 GMT
http://hdl.handle.net/2117/22788
20140430T12:30:33Z
Rodrigo López, Daniel; Díaz Tapia, Edgar; Jofre Roca, Lluís
no
Mutual coupling, Radio repeaters, Reconfigurable antennas
The maximum gain in onfrequency repeaters is limited by the isolation level between their two antennas due to closeloop stability conditions. In this letter, a novel pixellayer isolator for tunable onfrequency repeaters is presented. The scattered field of the reconfigurable pixel layer is used to dynamically minimize the mutual coupling between the antennas. Insight is given on the linkage between coupling and reflection coefficients, and a useful design procedure is proposed. The optimized pixel repeater can tune the operating frequency over a 40% range, with tunable instantaneous bandwidth (1%3%) and achieving a reliable isolation of 50 dB. The repeater has a radiation efficiency of 93% and a constant radiation pattern for the different configurations. Good agreement is obtained between simulations and measurements.

Optical signal processor for millimeterwave interferometric radiometry
http://hdl.handle.net/2117/22617
Title: Optical signal processor for millimeterwave interferometric radiometry
Authors: Nova Lavado, Enrique; Romeu Robert, Jordi; Capdevila Cascante, Santiago; Torres Torres, Francisco; Jofre Roca, Lluís
Abstract: In interferometric radiometry, the correlations between all pairs of radiofrequency (RF) receivers must be performed in order to obtain the scene visibilities. This represents a cumbersome problem in passive imaging where large signal bandwidths are typically required to achieve fastacquisition times and improve the radiometric resolution of the image. In this case, the signal distribution and the correlation at intermediate frequencies require very fast signal acquisition and processing subsystems. This paper presents a technique to perform correlations of millimeterwave signals produced by thermal emission in the optical domain as a solution to the aforementioned problem. The proposed method is based on converting the RF signal to the optical domain by modulating a laser beam with the RF signal using a {\rm LiNbO}3 phase modulator. This conversion allows to perform the signal distribution in the optical domain to obtain the combination of the receiver pairs. The correlation is obtained by measuring the power of the photocurrent produced by photodetecting the combined signal. The results of an experimental validation consisting on the acquisition of passive images using a linear interferometric array are presented to support the feasibility of the method. In addition, performance considerations of the system have been developed and validated by calculating the standard deviation of a visibility measurement.
Fri, 11 Apr 2014 12:01:45 GMT
http://hdl.handle.net/2117/22617
20140411T12:01:45Z
Nova Lavado, Enrique; Romeu Robert, Jordi; Capdevila Cascante, Santiago; Torres Torres, Francisco; Jofre Roca, Lluís
no
Aperture synthesis, optical modulation, passive interferometry, Wband radiometry
In interferometric radiometry, the correlations between all pairs of radiofrequency (RF) receivers must be performed in order to obtain the scene visibilities. This represents a cumbersome problem in passive imaging where large signal bandwidths are typically required to achieve fastacquisition times and improve the radiometric resolution of the image. In this case, the signal distribution and the correlation at intermediate frequencies require very fast signal acquisition and processing subsystems. This paper presents a technique to perform correlations of millimeterwave signals produced by thermal emission in the optical domain as a solution to the aforementioned problem. The proposed method is based on converting the RF signal to the optical domain by modulating a laser beam with the RF signal using a {\rm LiNbO}3 phase modulator. This conversion allows to perform the signal distribution in the optical domain to obtain the combination of the receiver pairs. The correlation is obtained by measuring the power of the photocurrent produced by photodetecting the combined signal. The results of an experimental validation consisting on the acquisition of passive images using a linear interferometric array are presented to support the feasibility of the method. In addition, performance considerations of the system have been developed and validated by calculating the standard deviation of a visibility measurement.