The dropout rate of engineering students is a concerning problem at the present time in many coun... more The dropout rate of engineering students is a concerning problem at the present time in many countries, resulting in difficulties to follow the demand of professionals in certain technological sectors as well as an associated negative economic impact. This study identifies a number of factors affecting the motivation degree of current electrical and computer engineering students, as well as the main reasons behind the dropout. A survey was completed by 624 students belonging to 8 different Spanish universities, rating the factors that could influence them to abandon their studies and those affecting their motivation to continue studying. Non-parametric analyses were performed in order to test the association of motivation as well as self-reported likelihood of dropping out with several variables. According to the research results, 23 of the 40 analyzed factors are correlated with the degree of motivation and 14 factors are correlated with the self-reported probability of dropping out. About 46% of the students declared to have thought about dropping out at some point in the past. Difficulty, followed by bad academic performance and negative relationships with professors are the main reasons for dropping out given by the students. Lack of vocation and distance to their home address were less frequent reasons.
Water has always been a very precious resource. However, many of us do not fully understand or ap... more Water has always been a very precious resource. However, many of us do not fully understand or appreciate water-s value until there will be a shortage. We intended to analyze the water consumption into the Spanish households to understand their behavior according to the habitants of the house. In this research was carried out a survey of users, asking for water consumption of their households. The aim of this paper is get a reference value of consumers in Spanish households to help to check their bill and realize if their consumption is excessive, including some tips to decrease it.
The implementation of a web-based application to estimate the path loss in outdoor environments i... more The implementation of a web-based application to estimate the path loss in outdoor environments is presented in this article. The tool provides the results of an empirical formulation in a user-friendly interface. The benefit of the proposed system is that the required information of the environment is obtained from OpenStreetMap, which allows the calculation of the propagation everywhere easily. In addition, the formulation is applicable to both rural and urban environments. The web application has been implemented using HTML5 and Cascading Style Sheets (CSS)3. The open source JavaScript library Leaflet has been used to include interactive maps. The simulation tool has been validated with measurements in a real environment. A good agreement between simulated and measured results has been found.
This work presents a new indoor localization method based on the fingerprinting technique. A Ray-... more This work presents a new indoor localization method based on the fingerprinting technique. A Ray-Tracing model is used to provide information about the multipath effects. The fingerprinting technique uses the direction of arrival (DOA) and the received signal strength (RSS) of the received rays. The location estimation is calculated while taking into account the Euclidian distance between the DOA and
Antenna Technology (iWAT), 2010 International Workshop on, 2010
A numerical technique for the analysis of the radiation pattern of antennas which interact with c... more A numerical technique for the analysis of the radiation pattern of antennas which interact with complex structures is presented in this work. Different parts of the geometry are isolated and the primary currents are obtained. In the next steps, we compute the interactions between different parts of the geometry and update the total currents. This method is especially well suited
Progress In Electromagnetics Research Letters, 2010
This work presents an accurate and realistic positioning approach for indoor environments based o... more This work presents an accurate and realistic positioning approach for indoor environments based on fingerprinting and raytracing techniques. Fading caused by multipath seriously degrades the performance of communication systems operating inside buildings. For this reason, the proposed localization method considers multipath effects due to reflections and diffraction from walls, roof and floor. However, fading in indoor environments can also be caused by the movement of people or the presence of furniture. Because people are the primary absorption agents in indoor channels, their influence on the radio propagation channel must be considered. The proposed localization method takes into account the effects of human body shadowing to provide a realistic estimation of the mobile station position. Numerical calculations in real indoor scenarios show reasonable results.
A novel optimization method to design the layout of printed reflectarrays for multibeam operation... more A novel optimization method to design the layout of printed reflectarrays for multibeam operation is presented in this paper. The proposed approach allows using different classes of cell elements to design the layout of reflectarrays. Therefore, phase curves do not have to fulfill the requirement of having a phase range wider than 360°. The dimensions of each cell element are adjusted to achieve the required phase distribution to radiate symmetric or asymmetric multiple beams. Five different reflectarrays have been designed by using this technique. Numerical simulations demonstrate high gain performance and low side lobe levels.
2012 15 International Symposium on Antenna Technology and Applied Electromagnetics, 2012
Full Paper -A new computer tool for designing reflectarray antennas is presented. The implemented... more Full Paper -A new computer tool for designing reflectarray antennas is presented. The implemented method generates the geometrical model of the reflectarray antenna by defining the properties of each unit cell. The number of layers, the cells dimensions, the dielectric materials, the cells orientation, periodicity, etc., are some cell parameters that can be studied. The reflection coefficient introduced by each cell is previously computed by applying a Moment Method code considering a periodic structure of identical cells. Once the focus and direction of the radiating main beam have been set, the required phases at each point are obtained. Finally, the geometry of the reflectarray antenna is generated considering the spatial phase delay at each unit cell depending on its position and its reflection coefficient.
An accurate realistic localization approach for indoor environments based on fingerprinting and r... more An accurate realistic localization approach for indoor environments based on fingerprinting and ray-tracing techniques is presented in this paper. The method considers fading in indoor environments due to multipath effects such as reflections and diffractions on walls, roof and floor. However, fading can also be caused by the movement of people or the presence of furniture. The influence of moving
This work presents a new indoor localization method based on the fingerprinting technique. The pr... more This work presents a new indoor localization method based on the fingerprinting technique. The proposed method uses a ray-tracing model that provides information about multipath effects. This information is stored in a dataset during the first stage of the fingerprinting method. The direction of arrival (DOA) and received signal strength (RSS) are used in the fingerprinting technique as a hybrid system. The localization estimation is calculated while taking into account the Euclidian distance between the DOA and the RSS from each unknown position and the information of the fingerprints. Numerical calculations were performed to show the mean and the standard deviation of the estimated error.
International Journal of Antennas and Propagation, 2012
A novel electromagnetic bandgap (EBG) antenna has been designed, optimized, and analyzed using an... more A novel electromagnetic bandgap (EBG) antenna has been designed, optimized, and analyzed using an efficient electromagnetic solver based on the moment method. Very good agreement between simulations and measurements in anechoic chamber has been obtained. Comparisons of the antenna with and without the EBG structure have been conducted to study its influence in terms of gain. This new EBG antenna is an excellent candidate for several applications due to its high gain and good polarization purity.
International Journal of Antennas and Propagation, 2012
A novel computed aided technique for designing reflectarray antennas is presented. The developed ... more A novel computed aided technique for designing reflectarray antennas is presented. The developed approach automatically generates the geometrical model of reflectarray antennas taking into account some input parameters, such as, the unit cell type and dimensions, frequency, focal length, periodicity, dielectric materials, and desired main beam radiating direction. The characteristics of the reflecting elements are selected considering the spatial phase delay at each unit cell to achieve a progressive phase shift. The implemented procedure also provides the phase characteristic of the unit element, which is rapidly computed by using a parallelized Moment Method (MoM) approach. The MoM is also used to obtain the radiation pattern of the full reflectarray antenna. In order to evaluate the new technique, a dual-interface prototype has been designed and simulated showing high-performance capability.
International Journal of Antennas and Propagation, 2012
We present an efficient method for the analysis of different objects that may contain a complex f... more We present an efficient method for the analysis of different objects that may contain a complex feeding system and a reflector structure. The approach is based on a domain decomposition technique that divides the geometry into several parts to minimize the vast computational resources required when applying a full wave method. This technique is also parallelized by using the Message Passing Interface to minimize the memory and time requirements of the simulation. A reflectarray analysis serves as an example of the proposed approach.
A metal-only Fresnel zone plate antenna (FZPA) to operate at millimetre wave frequency bands is p... more A metal-only Fresnel zone plate antenna (FZPA) to operate at millimetre wave frequency bands is presented in this work. The proposed antenna is a very attractive alternative to parabolic reflectors and reflectarrays because of its several advantages such as low profile, low cost, easy to manufacture and lossless. A centre-fed Fresnel zone plate whose diameter is 300 mm has been designed and analysed at 75 GHz providing a gain of 44.29 dBi, an aperture efficiency of 48.42% and a cross-polarised level lower than −40 dB for the diagonal plane (φ = 45°). A second prototype has been designed and analysed from 54 to 68 GHz to evaluate the performance of the proposed antenna compared with an already published FZPA.
IEEE Antennas and Wireless Propagation Letters, 2013
This letter investigates the effect of varying the feed position along the focal axis on the perf... more This letter investigates the effect of varying the feed position along the focal axis on the performance of a conformed Fresnel zone reflector. Bandwidth and aperture efficiency are analyzed by illuminating the proposed reflector antenna with a pyramidal horn at Ku band. The antenna under study is a new type of Fresnel zone plate antenna that, compared to the conventional parabolic reflectors, has the benefits of flat profile and small weight. In comparison to reflectarrays, conformed Fresnel zone reflectors present lower losses and are easier to fabricate. An offset-fed square reflector of 40 × 40 cm2 was designed and analyzed, providing 26% of 1.5-dB gain-bandwidth and 55% of aperture efficiency. Numerical results show that modifying the feed position leads to a remarkable shift in operating frequency band. Therefore, the proposed design offers the possibility of changing the operating band by moving the feed without redesigning the entire antenna. Also, a notable increase in gain is observed when the feed is moved away from the center of the antenna.
The dropout rate of engineering students is a concerning problem at the present time in many coun... more The dropout rate of engineering students is a concerning problem at the present time in many countries, resulting in difficulties to follow the demand of professionals in certain technological sectors as well as an associated negative economic impact. This study identifies a number of factors affecting the motivation degree of current electrical and computer engineering students, as well as the main reasons behind the dropout. A survey was completed by 624 students belonging to 8 different Spanish universities, rating the factors that could influence them to abandon their studies and those affecting their motivation to continue studying. Non-parametric analyses were performed in order to test the association of motivation as well as self-reported likelihood of dropping out with several variables. According to the research results, 23 of the 40 analyzed factors are correlated with the degree of motivation and 14 factors are correlated with the self-reported probability of dropping out. About 46% of the students declared to have thought about dropping out at some point in the past. Difficulty, followed by bad academic performance and negative relationships with professors are the main reasons for dropping out given by the students. Lack of vocation and distance to their home address were less frequent reasons.
Water has always been a very precious resource. However, many of us do not fully understand or ap... more Water has always been a very precious resource. However, many of us do not fully understand or appreciate water-s value until there will be a shortage. We intended to analyze the water consumption into the Spanish households to understand their behavior according to the habitants of the house. In this research was carried out a survey of users, asking for water consumption of their households. The aim of this paper is get a reference value of consumers in Spanish households to help to check their bill and realize if their consumption is excessive, including some tips to decrease it.
The implementation of a web-based application to estimate the path loss in outdoor environments i... more The implementation of a web-based application to estimate the path loss in outdoor environments is presented in this article. The tool provides the results of an empirical formulation in a user-friendly interface. The benefit of the proposed system is that the required information of the environment is obtained from OpenStreetMap, which allows the calculation of the propagation everywhere easily. In addition, the formulation is applicable to both rural and urban environments. The web application has been implemented using HTML5 and Cascading Style Sheets (CSS)3. The open source JavaScript library Leaflet has been used to include interactive maps. The simulation tool has been validated with measurements in a real environment. A good agreement between simulated and measured results has been found.
This work presents a new indoor localization method based on the fingerprinting technique. A Ray-... more This work presents a new indoor localization method based on the fingerprinting technique. A Ray-Tracing model is used to provide information about the multipath effects. The fingerprinting technique uses the direction of arrival (DOA) and the received signal strength (RSS) of the received rays. The location estimation is calculated while taking into account the Euclidian distance between the DOA and
Antenna Technology (iWAT), 2010 International Workshop on, 2010
A numerical technique for the analysis of the radiation pattern of antennas which interact with c... more A numerical technique for the analysis of the radiation pattern of antennas which interact with complex structures is presented in this work. Different parts of the geometry are isolated and the primary currents are obtained. In the next steps, we compute the interactions between different parts of the geometry and update the total currents. This method is especially well suited
Progress In Electromagnetics Research Letters, 2010
This work presents an accurate and realistic positioning approach for indoor environments based o... more This work presents an accurate and realistic positioning approach for indoor environments based on fingerprinting and raytracing techniques. Fading caused by multipath seriously degrades the performance of communication systems operating inside buildings. For this reason, the proposed localization method considers multipath effects due to reflections and diffraction from walls, roof and floor. However, fading in indoor environments can also be caused by the movement of people or the presence of furniture. Because people are the primary absorption agents in indoor channels, their influence on the radio propagation channel must be considered. The proposed localization method takes into account the effects of human body shadowing to provide a realistic estimation of the mobile station position. Numerical calculations in real indoor scenarios show reasonable results.
A novel optimization method to design the layout of printed reflectarrays for multibeam operation... more A novel optimization method to design the layout of printed reflectarrays for multibeam operation is presented in this paper. The proposed approach allows using different classes of cell elements to design the layout of reflectarrays. Therefore, phase curves do not have to fulfill the requirement of having a phase range wider than 360°. The dimensions of each cell element are adjusted to achieve the required phase distribution to radiate symmetric or asymmetric multiple beams. Five different reflectarrays have been designed by using this technique. Numerical simulations demonstrate high gain performance and low side lobe levels.
2012 15 International Symposium on Antenna Technology and Applied Electromagnetics, 2012
Full Paper -A new computer tool for designing reflectarray antennas is presented. The implemented... more Full Paper -A new computer tool for designing reflectarray antennas is presented. The implemented method generates the geometrical model of the reflectarray antenna by defining the properties of each unit cell. The number of layers, the cells dimensions, the dielectric materials, the cells orientation, periodicity, etc., are some cell parameters that can be studied. The reflection coefficient introduced by each cell is previously computed by applying a Moment Method code considering a periodic structure of identical cells. Once the focus and direction of the radiating main beam have been set, the required phases at each point are obtained. Finally, the geometry of the reflectarray antenna is generated considering the spatial phase delay at each unit cell depending on its position and its reflection coefficient.
An accurate realistic localization approach for indoor environments based on fingerprinting and r... more An accurate realistic localization approach for indoor environments based on fingerprinting and ray-tracing techniques is presented in this paper. The method considers fading in indoor environments due to multipath effects such as reflections and diffractions on walls, roof and floor. However, fading can also be caused by the movement of people or the presence of furniture. The influence of moving
This work presents a new indoor localization method based on the fingerprinting technique. The pr... more This work presents a new indoor localization method based on the fingerprinting technique. The proposed method uses a ray-tracing model that provides information about multipath effects. This information is stored in a dataset during the first stage of the fingerprinting method. The direction of arrival (DOA) and received signal strength (RSS) are used in the fingerprinting technique as a hybrid system. The localization estimation is calculated while taking into account the Euclidian distance between the DOA and the RSS from each unknown position and the information of the fingerprints. Numerical calculations were performed to show the mean and the standard deviation of the estimated error.
International Journal of Antennas and Propagation, 2012
A novel electromagnetic bandgap (EBG) antenna has been designed, optimized, and analyzed using an... more A novel electromagnetic bandgap (EBG) antenna has been designed, optimized, and analyzed using an efficient electromagnetic solver based on the moment method. Very good agreement between simulations and measurements in anechoic chamber has been obtained. Comparisons of the antenna with and without the EBG structure have been conducted to study its influence in terms of gain. This new EBG antenna is an excellent candidate for several applications due to its high gain and good polarization purity.
International Journal of Antennas and Propagation, 2012
A novel computed aided technique for designing reflectarray antennas is presented. The developed ... more A novel computed aided technique for designing reflectarray antennas is presented. The developed approach automatically generates the geometrical model of reflectarray antennas taking into account some input parameters, such as, the unit cell type and dimensions, frequency, focal length, periodicity, dielectric materials, and desired main beam radiating direction. The characteristics of the reflecting elements are selected considering the spatial phase delay at each unit cell to achieve a progressive phase shift. The implemented procedure also provides the phase characteristic of the unit element, which is rapidly computed by using a parallelized Moment Method (MoM) approach. The MoM is also used to obtain the radiation pattern of the full reflectarray antenna. In order to evaluate the new technique, a dual-interface prototype has been designed and simulated showing high-performance capability.
International Journal of Antennas and Propagation, 2012
We present an efficient method for the analysis of different objects that may contain a complex f... more We present an efficient method for the analysis of different objects that may contain a complex feeding system and a reflector structure. The approach is based on a domain decomposition technique that divides the geometry into several parts to minimize the vast computational resources required when applying a full wave method. This technique is also parallelized by using the Message Passing Interface to minimize the memory and time requirements of the simulation. A reflectarray analysis serves as an example of the proposed approach.
A metal-only Fresnel zone plate antenna (FZPA) to operate at millimetre wave frequency bands is p... more A metal-only Fresnel zone plate antenna (FZPA) to operate at millimetre wave frequency bands is presented in this work. The proposed antenna is a very attractive alternative to parabolic reflectors and reflectarrays because of its several advantages such as low profile, low cost, easy to manufacture and lossless. A centre-fed Fresnel zone plate whose diameter is 300 mm has been designed and analysed at 75 GHz providing a gain of 44.29 dBi, an aperture efficiency of 48.42% and a cross-polarised level lower than −40 dB for the diagonal plane (φ = 45°). A second prototype has been designed and analysed from 54 to 68 GHz to evaluate the performance of the proposed antenna compared with an already published FZPA.
IEEE Antennas and Wireless Propagation Letters, 2013
This letter investigates the effect of varying the feed position along the focal axis on the perf... more This letter investigates the effect of varying the feed position along the focal axis on the performance of a conformed Fresnel zone reflector. Bandwidth and aperture efficiency are analyzed by illuminating the proposed reflector antenna with a pyramidal horn at Ku band. The antenna under study is a new type of Fresnel zone plate antenna that, compared to the conventional parabolic reflectors, has the benefits of flat profile and small weight. In comparison to reflectarrays, conformed Fresnel zone reflectors present lower losses and are easier to fabricate. An offset-fed square reflector of 40 × 40 cm2 was designed and analyzed, providing 26% of 1.5-dB gain-bandwidth and 55% of aperture efficiency. Numerical results show that modifying the feed position leads to a remarkable shift in operating frequency band. Therefore, the proposed design offers the possibility of changing the operating band by moving the feed without redesigning the entire antenna. Also, a notable increase in gain is observed when the feed is moved away from the center of the antenna.
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