Artículos de revista DIEE - IEES Aldizkari artikuluak

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Open Access
Arrangements of via-holes in microstrip lines as metallodielectric periodic structures
(Wiley, 2000) Gómez Laso, Miguel Ángel; Lopetegui Beregaña, José María; Bacaicoa, Miguel; Hernández, Jorge; Gonzalo García, Ramón; Sorolla Ayza, Mario; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa; Gobierno de Navarra / Nafarroako Gobernua
In this paper, the use of via holes in microstrip lines to design periodic structures that can be regarded as metallodielectric electromagnetic crystals is analyzed. The proposed novel periodic structures achieve a notably increased reflectivity compared to that obtained with a single via hole. Theoretical analysis and experimental results are provided showing a satisfactory performance for these devices as broadband reflectors or short circuits with enhanced behavior at high frequencies.
Open Access
Design of MOS-translinear multiplier/dividers in analog VLSI
(Hindawi Publishing Corporation, 2000) López Martín, Antonio; Carlosena García, Alfonso; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
A general framework for designing current-mode CMOS analog multiplier/divider circuits based on the cascade connection of a geometric-mean circuit and a squarer/ divider is presented. It is shown how both building blocks can be readily obtained from a generic second-order MOS translinear loop. Various implementations are proposed, featuring simplicity, favorable precision and wide dynamic range. They can be successfully employed in a wide range of analog VLSI processing tasks. Experimental results of two versions, based on stacked and folded MOS-translinear loops and fabricated in a 2.4-1am CMOS process, are provided in order to verify the correctness of the proposed approach.
Open Access
Ultra-wide band corrugated profiled horn antenna design
(IEEE, 2002) Teniente Vallinas, Jorge; Gonzalo García, Ramón; Río Bocio, Carlos del; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
Nowadays, an increasing number of applications need stable radiation patterns with low sidelobes and low crosspolar levels in a very wide bandwidth. Gaussian Profiled Horn Antennas (GPHA’s) have demonstrated its feasibility as one of the best solutions. A corrugated gaussian horn antenna design with more than 40% bandwidth is proposed in this letter. The measured radiated far field patterns have a good agreement with the simulated ones. The measured results show a gaussian antenna with extremely wide bandwidth low sidelobes and low crosspolar levels.
Open Access
Analysis of one-dimensional photonic band gap structures with a liquid crystal defect towards development of fiber-optic tunable wavelength filters
(Optical Society of America, 2003) Del Villar, Ignacio; Matías Maestro, Ignacio; Arregui San Martín, Francisco Javier; Claus, Richard O.; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa; Gobierno de Navarra / Nafarroako Gobernua
A theoretical analysis of a fiber optical photonic band gap based tunable wavelength filter is presented. The design presented here is based on the quarter wave reflector with a liquid crystal defect layer in the middle of the structure. The filter generated by the structure is shifted in wavelength as the voltage applied to the structure is modified. Some critical parameters are analyzed: the effect of the consideration of fiber as the first layer and not the input medium in the shape of the filter, the number of layers of the structure, and the thickness of the defect layer. This last parameter determines the width of the wavelength sweep of the filter, but is limited by the creation of more defects. Some rules of practical implementation of this device are also given.
Open Access
A stopband filter design using a 1-D non-periodic defected ground structure
(Wiley, 2003) Garde Irigoyen, Ieltxu Aitor; Río Bocio, Carlos del; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
The one-dimensional (1-D) defected ground structure is used to control the cutoff frequency characteristic. In this paper three non-periodic filters are built, in order to show the versatility of the DGS. Five unit cells different in shape with the same attenuation pole frequency were combined in each filter. The frequency response is essentially the same as for the case of periodic filters with equal square unit cells.
Open Access
Simple modelling of DGS to design 1D-PBG low-pass filters
(Wiley, 2003) Garde Irigoyen, Ieltxu Aitor; Yábar, Miguel Javier; Río Bocio, Carlos del; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
The use of defected ground structures (DGS) is being intensively explored by the microwave filter designer community. The DGSs are one possible implementation of a 1D Photonic Band Gap (1D-PBG) where some defect structures are patterned on the ground plane of a microstrip circuit. In this paper, the relation between the behaviour of the DGS structures and the classical microwave filter design theory is established. In particular, a simple model procedure based on the classical microwave filter design theory by using DGS structures is presented. In order to illustrate the method, two low-pass filters are designed, fabricated and measured.
Open Access
Independent component analysis as a tool to eliminate artifacts in EEG. A quantitative study
(Lippincott, Williams & Wilkins, 2003) Iriarte, Jorge; Urrestarazu, Elena; Valencia Ustárroz, Miguel; Alegre, Manuel; Malanda Trigueros, Armando; Viteri, César; Artieda, Julio; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
Independent component analysis (ICA) is a novel technique that calculates independent components from mixed signals. A hypothetical clinical application is to remove artifacts in EEG. The goal of this study was to apply ICA to standard EEG recordings to eliminate well-known artifacts, thus quantifying its efficacy in an objective way. Eighty samples of recordings with spikes and evident artifacts of electrocardiogram (EKG), eye movements, 50-Hz interference, muscle, or electrode artifact were studied. ICA components were calculated using the Joint Approximate Diagonalization of Eigen-matrices (JADE) algorithm. The signal was reconstructed excluding those components related to the artifacts. A normalized correlation coefficient was used as a measure of the changes caused by the suppression of these components. ICA produced an evident clearing-up of signals in all the samples. The morphology and the topography of the spike were very similar before and after the removal of the artifacts. The correlation coefficient showed that the rest of the signal did not change significantly. Two examiners independently looked at the samples to identify the changes in the morphology and location of the discharge and the artifacts. In conclusion, ICA proved to be a useful tool to clean artifacts in short EEG samples, without having the disadvantages associated with the digital filters. The distortion of the interictal activity measured by correlation analysis was minimal.
Open Access
Split ring resonator-based left-handed coplanar waveguide
(AIP Publishing, 2003) Martín, F.; Bonache, J.; Falcone Lanas, Francisco; Sorolla Ayza, Mario; Marqués, R.; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
In this letter, a planar left-handed propagating medium consisting of a coplanar waveguide (CPW) inductively coupled to split ring resonators (SRR) and periodically loaded with narrow metallic wires is proposed. The wires make the structure behave as a microwave plasma with a negative effective permittivity which covers a broad frequency range. The negative permeability required to achieve left-handed wave propagation is provided by the rings in the vicinity of their resonant frequency. The result is a structure which allows negative wave propagation in a narrow frequency band. The transmission coefficient measured in a fabricated prototype device exhibits very low insertion losses in the pass band and high-frequency selectivity. Since rings are much smaller than signal wavelength at resonance and can be easily tuned, SRR-CPW-based structures are of interest for the design of very compact microwave circuits based on left handedness.
Open Access
Development of an optical refractometer by analysis of one-dimensional photonic bandgap structures with defects
(Optical Society of America, 2003) Matías Maestro, Ignacio; Del Villar, Ignacio; Arregui San Martín, Francisco Javier; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa; Gobierno de Navarra / Nafarroako Gobernua
A theoretical analysis of an optical fiber photonic-bandgap-based refractometer is presented. The design is based on a quarter-wave ref lector with one defect. By modifying both the real and the imaginary parts of the index of refraction of the defects we begin to change either the frequency or the amplitude of the localized optical mode. So we could fabricate a specific optical fiber refractometer by combining all the variables: index of refractive index of the defects and the rest of layers, thickness of the defect, number of layers, etc. to yield a large set of design possibilities, for example, detecting wider or thinner ranges of refractive indices, or controlling the detection accuracy. Some rules for the practical implementation of the refractometer are given.
Open Access
Vibrato in singing voice: the link between source-filter and sinusoidal models
(Springer Open, 2004) Carlosena García, Alfonso; Arroabarren Alemán, Ixone; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
The application of inverse filtering techniques for high-quality singing voice analysis/synthesis is discussed. In the context of source-filter models, inverse filtering provides a noninvasive method to extract the voice source, and thus to study voice quality. Although this approach is widely used in speech synthesis, this is not the case in singing voice. Several studies have proved that inverse filtering techniques fail in the case of singing voice, the reasons being unclear. In order to shed light on this problem, we will consider here an additional feature of singing voice, not present in speech: the vibrato. Vibrato has been traditionally studied by sinusoidal modeling. As an alternative, we will introduce here a novel noninteractive source filter model that incorporates the mechanisms of vibrato generation. This model will also allow the comparison of the results produced by inverse filtering techniques and by sinusoidal modeling, as they apply to singing voice and not to speech. In this way, the limitations of these conventional techniques, described in previous literature, will be explained. Both synthetic signals and singer recordings are used to validate and compare the techniques presented in the paper.
Open Access
Review on electromagnetic band gap technology and applications
(URSI, 2004) Maagt, Peter de; Gonzalo García, Ramón; Vardaxoglou, J.; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
This paper reviews the primary application areas of Electromagnetic BandGap (EBG) technology at microwave and (sub)millimetre wave frequencies. Examples of EBG configurations in the microwave region are shown and include array antennas, high precision GPS, mobile telephony, wearable antennas and diplexing antennas. In the submillimetre wave region a 500 GHz dipole configuration and a novel heterodyne mixer is shown. Some emphasis is also placed on EBG waveguides, high impedance planes (AMC s), resonators and filters. As most fundamental components would be available in EBG technology, a fully integrated receiver could be developed in order to take full advantage of this technology. True integration of passive and active components can now begin to materialise using EBG technology.
Open Access
Fiber optic multiple-wavelength filter based on one dimensional photonic bandgap structures with defects
(IEEE, 2004) Del Villar, Ignacio; Matías Maestro, Ignacio; Arregui San Martín, Francisco Javier; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa; Gobierno de Navarra / Nafarroako Gobernua
In this paper, a theoretical analysis is given of an optical fiber multiple-wavelength tunable filter based on a onedimensional (1-D) photonic bandgap (PBG) structure with four defects. To understand the positioning of the modes in the bandgap, a previous analysis of structures with one and two defects is performed. By adequate parameterization, it will be possible to control the central wavelengths of the various filters of the device. Parameters responsible for this effect are the contrast of refractive indexes of high- and low-index layers, the optical thickness of the defects, and the number of layers stacked among the defects related to those stacked at the extremes. In addition to this, the finesse of the filters can be controlled by the adequate addition of layers among defects. As a result, a simple 1-D PBG structure with defects will permit designing almost any multiple-wavelength filter, with immediate application in the treatment of wavelength-division- multiplexed (WDM) signals. The possibility of the tunability of this device can be introduced if materials are included whose refractive index changes with some parameter, such as temperature, voltage, or strain. As an example, liquid crystals change their refractive index with an applied voltage, leading to a shift of the central wavelengths of the filters.
Open Access
Planar magnetoinductive wave transducers: theory and applications
(AIP Publishing, 2004) Freire, M. J.; Marqués, R.; Medina, Francisco; Gómez Laso, Miguel Ángel; Martín, F.; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
Transduction of magnetoinductive waves (MIWs) in planar technology is demonstrated. A transducer consisting of a one-dimensional periodic array of metallic split squared ring resonators (SSRR), placed between a pair of microstrip lines on a planar substrate has been fabricated and measured. The microstrip lines are inductively coupled to the SSRRs located at the ends of the periodic array and excite MIWs that propagate along the array. The theoretical model for the dispersion of MIWs is used to predict the dispersion relation and the delay time in the device. The delay time was measured and a good agreement was found with the theoretical predictions. The transmission coefficient of the device was also measured. The theoretical and experimental results suggest that the proposed configuration can find application in the design of delay lines and other microwave devices. In fact, the behavior of the proposed transducer is similar to that of the conventional ferrite magnetostatic-wave transducer. However, ferrite devices are fragile, difficult to integrate, and require a heavy external magnet or electromagnet to magnetize the ferrite to saturation. Since all these drawbacks are not present in the proposed configuration, it may be a useful alternative to those devices for many practical applications.
Open Access
Strategies for fabrication of hydrogen peroxide sensors based on electrostatic self-assembly (ESA) method
(Elsevier, 2004) Del Villar, Ignacio; Matías Maestro, Ignacio; Arregui San Martín, Francisco Javier; Echeverría Morrás, Jesús; Claus, Richard O.; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa; Gobierno de Navarra / Nafarroako Gobernua
An optical fiber sensor has been fabricated for detection of 5 M–0.1mM concentrations of hydrogen peroxide with a linear response. The deposition method used is electrostatic self-assembly (ESA) of polymer cationic and anionic layers. Prussian Blue (PB) has been included in the polycation layers. The optical fiber sensor is included in a reflection setup, where the measuring technique is based on the slope of the optical reflected power change caused by oxidation of Prussian White (PW) to Prussian Blue. The sensor recovers after immersion in a reductive agent and is immune against a variety of components. Measurement of hydrogen peroxide has been proved successfully in a wide range pHs between 3 and 9. Some techniques have been applied in order to avoid the lost of indicator.
Open Access
Fiber-optic nanorefractometer based on one-dimensional photonic-bandgap structures with two defects
(IEEE, 2004) Del Villar, Ignacio; Matías Maestro, Ignacio; Arregui San Martín, Francisco Javier; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa; Gobierno de Navarra / Nafarroako Gobernua
A theoretical analysis of a fiber-optic photonic- bandgap (PBG)-based nanorefractometer is presented. Changes up to 11.2 dB in the optical output power in an index of refraction range of 1.7 with a sensitivity of 1.5 10 4 have been demonstrated. The design is based on a one-dimensional PBG structure with two defects, which originates two defect states inside the bandgap. These states correspond to two localized modes in the defects. By selecting adequate parameters, the frequency of one of the localized modes can be fixed at the same time that its peak amplitude varies with the refractive index of the defect associated to the other localized mode. The refractive index of the defect associated to the localized mode that has been fixed in frequency remains constant. This enables a detection scheme based on a simple photodetector instead of an optical spectrum analyzer, as usual. The thickness of the defect whose refractive index varies determines the variation range of the transmitted power amplitude peak of the localized mode fixed at a concrete frequency. In addition, an analysis of the nonlinear dependence on the refractive index of the peak-transmitted power of the localized mode fixed at a concrete frequency is presented.
Open Access
Design methodology for the frequency shift method of islanding prevention and analysis of its detection capability
(Wiley, 2005) Sanchis Gúrpide, Pablo; Marroyo Palomo, Luis; Coloma, Javier; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
Islanding protection is one of the most important sources of discrepancy in gridconnected photovoltaic systems. Even when islanding is not very likely to happen, regulations demand the photovoltaic inverters to implement effective protection methods. Due to its several advantages, the frequency shift method of islanding prevention, commonly known as Sandia Frequency Shift, is one of the most important active methods. This method implements a positive feedback of the frequency that tends to move it outside the trip limits in case of islanding. The method shows a very high detection capability, which depends on both the values of the method parameters and the characteristics of the load that remains in the same power section after islanding. This paper develops a mathematical analysis of the Sandia Frequency Shift method and proposes a new methodology to design its parameters as a trade-off between the detection capability, which is evaluated as a function of the load characteristics, and the distortion that the method could introduce in the grid as a consequence of transitory frequency disturbances. The ability of this methodology to design the method parameters and achieve the highest detection capability is satisfactorily proved by means of both simulation and experimental results on a commercial photovoltaic inverter that implements the method once its parameters have been designed with the proposed methodology.
Open Access
Boost DC-AC inverter: a new control strategy
(IEEE, 2005) Sanchis Gúrpide, Pablo; Ursúa Rubio, Alfredo; Gubía Villabona, Eugenio; Marroyo Palomo, Luis; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
Boost dc–ac inverter naturally generates in a single stage an ac voltage whose peak value can be lower or greater than the dc input voltage. The main drawback of this structure deals with its control. Boost inverter consists of Boost dc–dc converters that have to be controlled in a variable-operation point condition. The sliding mode control has been proposed as an option. However, it does not directly control the inductance averaged-current. This paper proposes a control strategy for the Boost inverter in which each Boost is controlled by means of a double-loop regulation scheme that consists of a new inductor current control inner loop and an also new output voltage control outer loop. These loops include compensations in order to cope with the Boost variable operation point condition and to achieve a high robustness to both input voltage and output current disturbances. As shown by simulation and prototype experimental results, the proposed control strategy achieves a very high reliable performance, even in difficult transient situations such as nonlinear loads, abrupt load changes, short circuits, etc., which sliding mode control cannot cope with.
Open Access
ESA-based in-fiber nanocavity for hydrogen–peroxide detection
(IEEE, 2005) Del Villar, Ignacio; Matías Maestro, Ignacio; Arregui San Martín, Francisco Javier; Claus, Richard O.; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa; Gobierno de Navarra / Nafarroako Gobernua
A fiber-optic sensor sensitive to hydrogen peroxide has been designed based on the electrostatic layer-by-layer selfassembly method. Prussian blue has been deposited in a polymeric structure formed by Poly(allylamine hydrochloride) and poly(acrylic acid). The concentration that can be detected range between 10 6–10 3 M, and recovery of the sensor after immersion into a reductive agent was demonstrated. The response of the sensor is independent of thepHfor values that range between 4–7.4. Some rules for estimation of the refractive index of the material deposited and the thickness of the bilayers are also presented
Open Access
Deposition of an overlay with electrostactic self-assembly method in long period fiber gratings
(Optical Society of America, 2005) Del Villar, Ignacio; Achaerandio Alvira, Miguel; Matías Maestro, Ignacio; Arregui San Martín, Francisco Javier; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa; Gobierno de Navarra / Nafarroako Gobernua
It was proved that the deposition of an overlay material onto a long-period fiber grating causes important shifts in the wavelengths of the typical attenuation bands that are caused by coupling between cladding and core modes [Opt. Lett. 27, 682 (2002)]. A theoretical model for analyzing a multilayer cylindrical waveguide is presented that permits the phenomenon to be understood and predicted. An overlay of higher refractive index than the cladding starts to guide a mode if a certain thickness value is exceeded. This causes large shifts in the resonance wavelength induced by the grating. One important application of this phenomenon to sensors is enhancement of the sensitivity of a long-period fiber grating to ambient conditions. Theoretical results are corroborated with experimental ones obtained by electrostatic self-assembly.
Open Access
Enhancement of sensitivity in long period fiber gratings with deposition of low refractive index materials
(Optical Society of America, 2005) Del Villar, Ignacio; Matías Maestro, Ignacio; Arregui San Martín, Francisco Javier; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
It was proved [Opt. Lett. 30, 720 (2005)] that the deposition of an overlay of higher refractive index than that of the cladding on a long-period fiber grating (LPFG) causes large shifts in the attenuation bands induced by the grating. The result is an enhancement of the sensitivity of the LPFG to variations in the ambient and overlay refractive indices or the overlay thickness. The limitation of the previous design to materials with higher refractive indices than that of the cladding of the LPFG is overcome with a five-layer model. To this purpose, a first overlay of higher refractive index than that of the cladding of the LPFG will enhance the sensitivity of the device to variations in the refractive index of a second overlay of lower refractive index than that of the cladding of the LPFG. Moreover, it is proved that, if the second overlay is thick enough, its behavior resembles that of an infinite layer