Vicente Gonzalez Posadas - Academia.edu (original) (raw)
Papers by Vicente Gonzalez Posadas
Sensors (Basel, Switzerland), 2020
Development of contaminant detection systems in various natural and industrial environments has b... more Development of contaminant detection systems in various natural and industrial environments has been favored in recent years thanks to the evolution of processors and sensors. Our group works specifically on contaminant detection systems in inland waters: immediate and continuous detection is a fundamental requirement in this type of sensing. Regarding the sensors, the proposed system is based on fluorescence, since it offers a method in which there is no contact with water, which means less wear on the components and a great saving in cleaning and maintenance. On the other hand, the spectrum processing is of great importance, since it is used both in the generation of a library of fluorescence spectra taken in the laboratory and in the continuous analysis of the samples and in the comparison algorithm for identification. The validity of the system is based on the last process that is carried out in a very short time. This article describes a system to process spectra in a more acce...
European Respiratory Journal, Sep 1, 2014
Background: NEHI, initially known as "persistent tachypnea of infancy", is a rare early... more Background: NEHI, initially known as "persistent tachypnea of infancy", is a rare early debut disorder (tachypnea, hypoxemia, crackles and failure to thrive), with a characteristic high resolution computerized tomography (HRCT), and usually favorable evolution without specific treatment, which make doubts about the need for routine biopsy. Objectives: To compare clinical and radiological course of 5 children, 2 with diagnosis of NEHI by lung biopsy and 3, classified as NEHI syndrome (diagnosis by clinical and radiological data without biopsy). Patients: All cases debuted before one year of age (mean 5 months). All had tachypnea (>60 breaths/minute), failure to thrive, oxygen saturation between 85-94% and crackles. HRCT shows a characteristic pattern of ground-glass opacity in the central regions of lungs (more in middle lobe and lingula). No specific changes in bronchoalveolar lavage. Surfactant protein deficiency and mutations were excluded (only one patient with low Pro-SC but normal surfactant protein C). In 2 cases with poor outcome, lung biopsy, which confirmed the diagnosis, was performed (European reference center/Dr. Griese). The outcome was favorable in all cases, without receiving any specific treatment. Conclusion: The clinic and radiological evolution is very similar in our patients. Basing on this, in infants who meet clinical and radiological criteria of NEHI and have favourable evolution, it could be avoid biopsy, as long as they behave as we expect in a NEHI.
Microwave and Optical Technology Letters, 2001
We show, in this paper, the results obtained in the sterilization process by using different irra... more We show, in this paper, the results obtained in the sterilization process by using different irradiating structures. Starting from our earlier findings of the existence of an important synergy on the killing effect caused by the simultaneous application of oxidant agents such as hydrogen peroxide and microwa¨e irradiation, we ha¨e now extended the work to identify the power threshold and the optimum frequency range for the effect.
…, 2008
In this paper a self-diplexed antenna is proposed for a RFID transponder application. The develop... more In this paper a self-diplexed antenna is proposed for a RFID transponder application. The development cycle is divided into two stages: antenna design and filters design. The antenna is based on a square microstrip patch filled with metamaterial structures. The inclusion of these structures allows simultaneous operation over several frequencies, which can be arbitrarily chosen. The antenna working frequencies are chosen to be 2.45 GHz (receiver) and 1.45 GHz (transmitter). In addition, the antenna is fed through two orthogonal coupled microstrip lines, what provides higher isolation between both ports. Some filters based on metamaterial particles are coupled or connected to the antenna feeding microstrip lines to avoid undesired interferences. This approach avoids using of an external filter or diplexer, providing larger size reduction and a compact self-diplexed antenna.
2020 IEEE International Symposium on Antennas and Propagation and North American Radio Science Meeting
This paper presents the study of different reflector shapes for obtaining stable radiation patter... more This paper presents the study of different reflector shapes for obtaining stable radiation pattern in the frequency of 1.4-2.7 GHz while maintaining good return losses values. Single and dual polarization dipole-like element have been used as feeders. Flat, parabolic, elliptical and ellipsoid based reflectors are presented in this paper with some measurements, to conclude with the significance of selecting the appropiate reflector shape.
2021 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting (APS/URSI)
A compact wideband implantable antenna working at industrial, scientific, and medical (ISM) 2.45 ... more A compact wideband implantable antenna working at industrial, scientific, and medical (ISM) 2.45 GHz band is presented. The fractal geometry strategy based on the Peano curve is used to miniaturize the size of the antenna. An impedance bandwidth (BW) of 85.7 % is achieved from 1.2 to 3 GHz with overall dimensions of boldsymbol7times8.2textmm2\boldsymbol{7\times 8.2\text{mm}^{2}}boldsymbol7times8.2textmm2. A gain value of -19.8 dBi is obtained and good omnidirectionality performance at 2.45 G Hz. These features make the antenna a good candidate for invasive biomedical applications.
In this paper, a dual-circular-polarized antenna is presented. The compactness of the design is t... more In this paper, a dual-circular-polarized antenna is presented. The compactness of the design is the greatest contributionof this work, achieving dual circular polarizationwith a single antenna. The design is based on a four-armspiral with differential feeding to achieve the desired polarization. The antenna achieves a bandwidth of 60% (from 4 to 7.5 GHz) for an axial ratio below 3 dB, return losses below-8 dB and isolation below -30 dB. Symmetric radiationpattern with gain higher than 7 dB is obtained
IEEE Transactions on Instrumentation and Measurement, 2022
In this article, the design of a photometer circuit based on a current-to-frequency converter is ... more In this article, the design of a photometer circuit based on a current-to-frequency converter is presented. This circuit is a piecewise linear circuit that makes the most of feedback to ensure a linear relationship between the input photocurrent and the output frequency. Here, Proteus simulations were used to verify the performance of the proposed circuit, and the electronic simulations and the experimental results were shown to be in total agreement. The experimental results showed that the proposed circuit rejected better additive white Gaussian noise signals than the classic photometer circuit based on the transimpedance amplifier. In addition, despite that the proposed circuit is more complex than the classic one, its high linearity, noise rejection, and easy implementation make it suitable for applications where measurement precision and noise rejection are of paramount importance. Index Terms-Current-to-frequency converter (CFC), currentto-voltage converter (CVC), photometer circuit, relative proximity coefficient, transimpedance amplifier. I. INTRODUCTION O PTOELECTRONIC devices transform light energy into electrical energy or vice versa, connecting optical systems with electronic systems. In this way, researchers and engineers design instruments to generate, detect, and/or control light in many applications of science and engineering put at the service of society. Some optoelectronic devices of great importance today are the following: solar cells, photodiodes, phototransistors, photoresistors, photomultiplier tubes, chargecoupled imaging devices, laser diodes, and light-emitting diodes, among others. In addition, these devices can be found as part of medical and military equipment, and telecommunication and automatic control systems, among others [1]-[7].
2016 European Radar Conference (EuRAD), 2016
A low-cost, direct FI conversion and high-precision timing test setup for measurements of Mode S ... more A low-cost, direct FI conversion and high-precision timing test setup for measurements of Mode S Monopulse Secondary Surveillance Radar (MSSR) transmission signal is proposed. The objective of this proposed setup is to guarantee fully the compliance of the transmitter under testing with the International Civil Aircraft Organization (ICAO) requirements by using traditional measurement equipment. The low-cost structure proposed in this paper allows the user to perform measurements independently of the measurements performed by the test equipments shelled by the manufacturer of radar, which is a very important aspect since the independence of the verifications is a mandatory requirement established by the safety standards of Civil Aviation. The proposed setup has been validated with some Mode S transmitters and it has also been used for testing other radio navigation aids.
Radioengineering, 2016
Negative impedance converters (NICs) have been proposed as structures to improve the performance ... more Negative impedance converters (NICs) have been proposed as structures to improve the performance of RF circuits and electrically small antennas. However, NICs suffer from stability problems. This paper presents a compact procedure to analyze the stability of NICs. Then, the required and sufficient conditions to predict the stability of a negative impedance converter are given. These conditions can be evaluated using standard computer-aideddesign software. Finally, a NIC prototype is given to validate and illustrate the presented design procedure, it is also integrated with a printed, blade-type, electrically small monopole in the VHF band.
Journal of Electromagnetic Waves and Applications, 2016
ABSTRACT This paper shows the design of an active patch antenna. First, an analysis of the electr... more ABSTRACT This paper shows the design of an active patch antenna. First, an analysis of the electric field inside the patch is performed to determine the compatibility of the modes of the patch with the desired feeding. The desired feeding is as a serial two-port resonator, so the suitable mode is the “Mode 1”. Then a linear analysis of the active antenna is performed. In this particular example, it is possible to use the classic Loop Gain Method, but its use is not guaranteed. So, the proposed NDF Method is used because it is independent of the oscillator topology and it is valid without any restriction or proviso. Then a Harmonic Balance analysis is performed and the results are compared with the measurements of a prototype.
This paper provides a review of printed antennas loaded with metamaterial particles. This novel t... more This paper provides a review of printed antennas loaded with metamaterial particles. This novel technique allows developing printed antennas with interesting features such as multifrequency (simultaneous operation over two or more frequency bands) and multifunctionality (e. g. radiation pattern diversity). Moreover, compactness is also achieved and the main advantages of conventional printed antennas (light weight, low profile, low cost ...) are maintained. Different types of metamaterial-loaded printed antennas are reviewed: printed dipoles and patch antennas. Several prototypes are designed, manufactured and measured showing good results. Furthermore, simple but accurate equivalent models are proposed. These models allow an easy and quick design of metamaterial-loaded printed antennas. Finally, two interesting applications based on the proposed antennas are reviewed: the patch antennas are used as radiating elements of emerging active RFID systems in the microwave band and the met...
IET Seminar Digests, 2007
ABSTRACT Microstrip patches filled with left-handed structures are proposed to obtain dual band c... more ABSTRACT Microstrip patches filled with left-handed structures are proposed to obtain dual band circularly polarized antennas. The proposed antennas have two modes at different frequencies with similar characteristics to the fundamental mode of a conventional patch. These modes are excited in two orthogonal directions with a 90deg phase shift to obtain dual band circularly polarized antennas. The most important feature of the proposed antennas is that the frequency ratio between the working frequencies can be set within a large range: from values smaller than 1.2 to values larger than 2.2. Finally, a dual band circularly polarized antenna for GSM 1800 and WCDMA is designed, manufactured and measured. The working ratio is only 1.17, which cannot be obtained with other approaches.
2010 IEEE Antennas and Propagation Society International Symposium, 2010
2007 19th International Conference on Applied Electromagnetics and Communications, 2007
Leganés (Madrid). E-mail: oscaralberto.garcia@alumnos.uc3m.es, dani@tsc.uc3m.es (2) Dpto. de Inge... more Leganés (Madrid). E-mail: oscaralberto.garcia@alumnos.uc3m.es, dani@tsc.uc3m.es (2) Dpto. de Ingeniería Audiovisual y Comunicaciones. Universidad Politécnica de Madrid . Carretera de Valencia Km. 7, ... 28031, Madrid. E-mail: vgonzalz@diac.upm.es
IET Seminar Digests, 2007
ABSTRACT A hexagonal metallo-dielectric periodic structure is studied to see the propagation mode... more ABSTRACT A hexagonal metallo-dielectric periodic structure is studied to see the propagation modes in the pass bandwidth. The pass bandwidth is constituted by several resonances that are not associated to the same propagation mode. Two kinds of field distributions have been achieved: radial and azimuthal modes. The former are present due to the radial distribution of the metallic or dielectric rods and there are as many modes as the number of layers. The latter are azimuthal modes that come from the azimuth variation.
2007 19th International Conference on Applied Electromagnetics and Communications, 2007
Titanium dioxide nanoparticle was synthesized by the reduction of titanium tetrachloride using bo... more Titanium dioxide nanoparticle was synthesized by the reduction of titanium tetrachloride using borohydride, water as solvent, and polyvinyl-pyrrolidone as stabilizer. The average size of nano-TiO 2 is estimated to be 5-10 nm using a transmission electron microscope (TEM); this was confirmed by X-ray diffraction and UV-Vis spectroscopy. Nano-TiO 2 was impregnated into cotton fabric to impart multifunctional properties and this was confirmed by scanning electron microscope and scanning electron microscope coupled with high energy distribution X-Ray (SEM-EDX). The TiO 2 nanoparticles loaded cotton fabrics showed excellent antibacterial activity against two representative bacteria, Staphylococcus aureus (Gram positive) 96.6% and Klebsiella pneumonia (Gram negative) 95.2%. Also, TiO 2 nanoparticles enhanced the self-cleaning and the protection of cotton fabrics against UV radiation in comparison with the untreated cotton fabrics. The TiO 2 nanoparticles were durable in-situ cotton fabrics even after 20 laundering wash cycles.
Microwave and Optical Technology Letters, 2002
This Letter presents a new radiation model for stackedpatch antennas. The model is based on the t... more This Letter presents a new radiation model for stackedpatch antennas. The model is based on the two-slot model and consists of a four-or six-element array, depending on the supposition of infinite ground plane. The parameters that can be extracted from this model, such as coupling coefficient, surface-wave coefficients, and phases are very useful in stacked-patch design.
IEEE Transactions on Antennas and Propagation, 2006
This paper presents a study of the short circuited ring patch antenna based on the cavity model. ... more This paper presents a study of the short circuited ring patch antenna based on the cavity model. Special attention has been paid to the fundamental mode in this geometry: the TM mode. Analytical expressions for resonant frequency, fields, radiation pattern and input impedance based on this model have been developed. Simulations based on this theoretical model and experimental results show good agreement. The interesting radiation characteristics and resonant frequency of this mode are presented.
Differential amplifiers have been proposed as an efficient solution for the planar aperture array... more Differential amplifiers have been proposed as an efficient solution for the planar aperture arrays in the low frequency band of the SKA project. The characterization of this type of devices is not the typical one, and they need of some specific techniques. On the other hand, the use of antennas matched to a non-50 Omega impedance requires of source-pull techniques
Sensors (Basel, Switzerland), 2020
Development of contaminant detection systems in various natural and industrial environments has b... more Development of contaminant detection systems in various natural and industrial environments has been favored in recent years thanks to the evolution of processors and sensors. Our group works specifically on contaminant detection systems in inland waters: immediate and continuous detection is a fundamental requirement in this type of sensing. Regarding the sensors, the proposed system is based on fluorescence, since it offers a method in which there is no contact with water, which means less wear on the components and a great saving in cleaning and maintenance. On the other hand, the spectrum processing is of great importance, since it is used both in the generation of a library of fluorescence spectra taken in the laboratory and in the continuous analysis of the samples and in the comparison algorithm for identification. The validity of the system is based on the last process that is carried out in a very short time. This article describes a system to process spectra in a more acce...
European Respiratory Journal, Sep 1, 2014
Background: NEHI, initially known as "persistent tachypnea of infancy", is a rare early... more Background: NEHI, initially known as "persistent tachypnea of infancy", is a rare early debut disorder (tachypnea, hypoxemia, crackles and failure to thrive), with a characteristic high resolution computerized tomography (HRCT), and usually favorable evolution without specific treatment, which make doubts about the need for routine biopsy. Objectives: To compare clinical and radiological course of 5 children, 2 with diagnosis of NEHI by lung biopsy and 3, classified as NEHI syndrome (diagnosis by clinical and radiological data without biopsy). Patients: All cases debuted before one year of age (mean 5 months). All had tachypnea (>60 breaths/minute), failure to thrive, oxygen saturation between 85-94% and crackles. HRCT shows a characteristic pattern of ground-glass opacity in the central regions of lungs (more in middle lobe and lingula). No specific changes in bronchoalveolar lavage. Surfactant protein deficiency and mutations were excluded (only one patient with low Pro-SC but normal surfactant protein C). In 2 cases with poor outcome, lung biopsy, which confirmed the diagnosis, was performed (European reference center/Dr. Griese). The outcome was favorable in all cases, without receiving any specific treatment. Conclusion: The clinic and radiological evolution is very similar in our patients. Basing on this, in infants who meet clinical and radiological criteria of NEHI and have favourable evolution, it could be avoid biopsy, as long as they behave as we expect in a NEHI.
Microwave and Optical Technology Letters, 2001
We show, in this paper, the results obtained in the sterilization process by using different irra... more We show, in this paper, the results obtained in the sterilization process by using different irradiating structures. Starting from our earlier findings of the existence of an important synergy on the killing effect caused by the simultaneous application of oxidant agents such as hydrogen peroxide and microwa¨e irradiation, we ha¨e now extended the work to identify the power threshold and the optimum frequency range for the effect.
…, 2008
In this paper a self-diplexed antenna is proposed for a RFID transponder application. The develop... more In this paper a self-diplexed antenna is proposed for a RFID transponder application. The development cycle is divided into two stages: antenna design and filters design. The antenna is based on a square microstrip patch filled with metamaterial structures. The inclusion of these structures allows simultaneous operation over several frequencies, which can be arbitrarily chosen. The antenna working frequencies are chosen to be 2.45 GHz (receiver) and 1.45 GHz (transmitter). In addition, the antenna is fed through two orthogonal coupled microstrip lines, what provides higher isolation between both ports. Some filters based on metamaterial particles are coupled or connected to the antenna feeding microstrip lines to avoid undesired interferences. This approach avoids using of an external filter or diplexer, providing larger size reduction and a compact self-diplexed antenna.
2020 IEEE International Symposium on Antennas and Propagation and North American Radio Science Meeting
This paper presents the study of different reflector shapes for obtaining stable radiation patter... more This paper presents the study of different reflector shapes for obtaining stable radiation pattern in the frequency of 1.4-2.7 GHz while maintaining good return losses values. Single and dual polarization dipole-like element have been used as feeders. Flat, parabolic, elliptical and ellipsoid based reflectors are presented in this paper with some measurements, to conclude with the significance of selecting the appropiate reflector shape.
2021 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting (APS/URSI)
A compact wideband implantable antenna working at industrial, scientific, and medical (ISM) 2.45 ... more A compact wideband implantable antenna working at industrial, scientific, and medical (ISM) 2.45 GHz band is presented. The fractal geometry strategy based on the Peano curve is used to miniaturize the size of the antenna. An impedance bandwidth (BW) of 85.7 % is achieved from 1.2 to 3 GHz with overall dimensions of boldsymbol7times8.2textmm2\boldsymbol{7\times 8.2\text{mm}^{2}}boldsymbol7times8.2textmm2. A gain value of -19.8 dBi is obtained and good omnidirectionality performance at 2.45 G Hz. These features make the antenna a good candidate for invasive biomedical applications.
In this paper, a dual-circular-polarized antenna is presented. The compactness of the design is t... more In this paper, a dual-circular-polarized antenna is presented. The compactness of the design is the greatest contributionof this work, achieving dual circular polarizationwith a single antenna. The design is based on a four-armspiral with differential feeding to achieve the desired polarization. The antenna achieves a bandwidth of 60% (from 4 to 7.5 GHz) for an axial ratio below 3 dB, return losses below-8 dB and isolation below -30 dB. Symmetric radiationpattern with gain higher than 7 dB is obtained
IEEE Transactions on Instrumentation and Measurement, 2022
In this article, the design of a photometer circuit based on a current-to-frequency converter is ... more In this article, the design of a photometer circuit based on a current-to-frequency converter is presented. This circuit is a piecewise linear circuit that makes the most of feedback to ensure a linear relationship between the input photocurrent and the output frequency. Here, Proteus simulations were used to verify the performance of the proposed circuit, and the electronic simulations and the experimental results were shown to be in total agreement. The experimental results showed that the proposed circuit rejected better additive white Gaussian noise signals than the classic photometer circuit based on the transimpedance amplifier. In addition, despite that the proposed circuit is more complex than the classic one, its high linearity, noise rejection, and easy implementation make it suitable for applications where measurement precision and noise rejection are of paramount importance. Index Terms-Current-to-frequency converter (CFC), currentto-voltage converter (CVC), photometer circuit, relative proximity coefficient, transimpedance amplifier. I. INTRODUCTION O PTOELECTRONIC devices transform light energy into electrical energy or vice versa, connecting optical systems with electronic systems. In this way, researchers and engineers design instruments to generate, detect, and/or control light in many applications of science and engineering put at the service of society. Some optoelectronic devices of great importance today are the following: solar cells, photodiodes, phototransistors, photoresistors, photomultiplier tubes, chargecoupled imaging devices, laser diodes, and light-emitting diodes, among others. In addition, these devices can be found as part of medical and military equipment, and telecommunication and automatic control systems, among others [1]-[7].
2016 European Radar Conference (EuRAD), 2016
A low-cost, direct FI conversion and high-precision timing test setup for measurements of Mode S ... more A low-cost, direct FI conversion and high-precision timing test setup for measurements of Mode S Monopulse Secondary Surveillance Radar (MSSR) transmission signal is proposed. The objective of this proposed setup is to guarantee fully the compliance of the transmitter under testing with the International Civil Aircraft Organization (ICAO) requirements by using traditional measurement equipment. The low-cost structure proposed in this paper allows the user to perform measurements independently of the measurements performed by the test equipments shelled by the manufacturer of radar, which is a very important aspect since the independence of the verifications is a mandatory requirement established by the safety standards of Civil Aviation. The proposed setup has been validated with some Mode S transmitters and it has also been used for testing other radio navigation aids.
Radioengineering, 2016
Negative impedance converters (NICs) have been proposed as structures to improve the performance ... more Negative impedance converters (NICs) have been proposed as structures to improve the performance of RF circuits and electrically small antennas. However, NICs suffer from stability problems. This paper presents a compact procedure to analyze the stability of NICs. Then, the required and sufficient conditions to predict the stability of a negative impedance converter are given. These conditions can be evaluated using standard computer-aideddesign software. Finally, a NIC prototype is given to validate and illustrate the presented design procedure, it is also integrated with a printed, blade-type, electrically small monopole in the VHF band.
Journal of Electromagnetic Waves and Applications, 2016
ABSTRACT This paper shows the design of an active patch antenna. First, an analysis of the electr... more ABSTRACT This paper shows the design of an active patch antenna. First, an analysis of the electric field inside the patch is performed to determine the compatibility of the modes of the patch with the desired feeding. The desired feeding is as a serial two-port resonator, so the suitable mode is the “Mode 1”. Then a linear analysis of the active antenna is performed. In this particular example, it is possible to use the classic Loop Gain Method, but its use is not guaranteed. So, the proposed NDF Method is used because it is independent of the oscillator topology and it is valid without any restriction or proviso. Then a Harmonic Balance analysis is performed and the results are compared with the measurements of a prototype.
This paper provides a review of printed antennas loaded with metamaterial particles. This novel t... more This paper provides a review of printed antennas loaded with metamaterial particles. This novel technique allows developing printed antennas with interesting features such as multifrequency (simultaneous operation over two or more frequency bands) and multifunctionality (e. g. radiation pattern diversity). Moreover, compactness is also achieved and the main advantages of conventional printed antennas (light weight, low profile, low cost ...) are maintained. Different types of metamaterial-loaded printed antennas are reviewed: printed dipoles and patch antennas. Several prototypes are designed, manufactured and measured showing good results. Furthermore, simple but accurate equivalent models are proposed. These models allow an easy and quick design of metamaterial-loaded printed antennas. Finally, two interesting applications based on the proposed antennas are reviewed: the patch antennas are used as radiating elements of emerging active RFID systems in the microwave band and the met...
IET Seminar Digests, 2007
ABSTRACT Microstrip patches filled with left-handed structures are proposed to obtain dual band c... more ABSTRACT Microstrip patches filled with left-handed structures are proposed to obtain dual band circularly polarized antennas. The proposed antennas have two modes at different frequencies with similar characteristics to the fundamental mode of a conventional patch. These modes are excited in two orthogonal directions with a 90deg phase shift to obtain dual band circularly polarized antennas. The most important feature of the proposed antennas is that the frequency ratio between the working frequencies can be set within a large range: from values smaller than 1.2 to values larger than 2.2. Finally, a dual band circularly polarized antenna for GSM 1800 and WCDMA is designed, manufactured and measured. The working ratio is only 1.17, which cannot be obtained with other approaches.
2010 IEEE Antennas and Propagation Society International Symposium, 2010
2007 19th International Conference on Applied Electromagnetics and Communications, 2007
Leganés (Madrid). E-mail: oscaralberto.garcia@alumnos.uc3m.es, dani@tsc.uc3m.es (2) Dpto. de Inge... more Leganés (Madrid). E-mail: oscaralberto.garcia@alumnos.uc3m.es, dani@tsc.uc3m.es (2) Dpto. de Ingeniería Audiovisual y Comunicaciones. Universidad Politécnica de Madrid . Carretera de Valencia Km. 7, ... 28031, Madrid. E-mail: vgonzalz@diac.upm.es
IET Seminar Digests, 2007
ABSTRACT A hexagonal metallo-dielectric periodic structure is studied to see the propagation mode... more ABSTRACT A hexagonal metallo-dielectric periodic structure is studied to see the propagation modes in the pass bandwidth. The pass bandwidth is constituted by several resonances that are not associated to the same propagation mode. Two kinds of field distributions have been achieved: radial and azimuthal modes. The former are present due to the radial distribution of the metallic or dielectric rods and there are as many modes as the number of layers. The latter are azimuthal modes that come from the azimuth variation.
2007 19th International Conference on Applied Electromagnetics and Communications, 2007
Titanium dioxide nanoparticle was synthesized by the reduction of titanium tetrachloride using bo... more Titanium dioxide nanoparticle was synthesized by the reduction of titanium tetrachloride using borohydride, water as solvent, and polyvinyl-pyrrolidone as stabilizer. The average size of nano-TiO 2 is estimated to be 5-10 nm using a transmission electron microscope (TEM); this was confirmed by X-ray diffraction and UV-Vis spectroscopy. Nano-TiO 2 was impregnated into cotton fabric to impart multifunctional properties and this was confirmed by scanning electron microscope and scanning electron microscope coupled with high energy distribution X-Ray (SEM-EDX). The TiO 2 nanoparticles loaded cotton fabrics showed excellent antibacterial activity against two representative bacteria, Staphylococcus aureus (Gram positive) 96.6% and Klebsiella pneumonia (Gram negative) 95.2%. Also, TiO 2 nanoparticles enhanced the self-cleaning and the protection of cotton fabrics against UV radiation in comparison with the untreated cotton fabrics. The TiO 2 nanoparticles were durable in-situ cotton fabrics even after 20 laundering wash cycles.
Microwave and Optical Technology Letters, 2002
This Letter presents a new radiation model for stackedpatch antennas. The model is based on the t... more This Letter presents a new radiation model for stackedpatch antennas. The model is based on the two-slot model and consists of a four-or six-element array, depending on the supposition of infinite ground plane. The parameters that can be extracted from this model, such as coupling coefficient, surface-wave coefficients, and phases are very useful in stacked-patch design.
IEEE Transactions on Antennas and Propagation, 2006
This paper presents a study of the short circuited ring patch antenna based on the cavity model. ... more This paper presents a study of the short circuited ring patch antenna based on the cavity model. Special attention has been paid to the fundamental mode in this geometry: the TM mode. Analytical expressions for resonant frequency, fields, radiation pattern and input impedance based on this model have been developed. Simulations based on this theoretical model and experimental results show good agreement. The interesting radiation characteristics and resonant frequency of this mode are presented.
Differential amplifiers have been proposed as an efficient solution for the planar aperture array... more Differential amplifiers have been proposed as an efficient solution for the planar aperture arrays in the low frequency band of the SKA project. The characterization of this type of devices is not the typical one, and they need of some specific techniques. On the other hand, the use of antennas matched to a non-50 Omega impedance requires of source-pull techniques