DSpace Repository :: Browsing by Author "Maagt, Peter de"

Browsing by Author "Maagt, Peter de"

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Open Access
Análisis de efecto de un superestrato left-handed en la apertura de una guía rectangular
(2005) Sáenz Sáinz, Elena; Gonzalo García, Ramón; Ederra Urzainqui, Íñigo; Maagt, Peter de; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
In this paper, results showing the experimental verification of the gain improvement of a rectangular waveguide antenna when a left-handed material (LHM) is used as superstrate are presented. The improvement has been characterized by means of measuring the increase of transmission (S21 parameter) obtained when this LHM is placed between two open-ended rectangular waveguide antennas. An average increase of transmission of about 6.5 d.B has been obtained. Besides, improvements in the radiation patterns of a rectangular waveguide with a LH superstrate are analyzed. An enhancement of 3.5 dB in the directivity and a reduction of 15 dB in the back radiation have been obtained.
Open Access
Boresight radiation of a dipole antenna with a uniform or non-uniform left handed superstrate
(2006) Sáenz Sáinz, Elena; Gonzalo García, Ramón; Ederra Urzainqui, Íñigo; Maagt, Peter de; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
In this paper measurements of the radiation performances of a dipole fed by a coaxial balun and a dipole with a left handed superstrate based on a finite periodic repetition of a unit cell are compared. Two types of superstrates, uniform and non-uniform, have been characterised in terms of impedance matching, resonant frequency and gain. First of all the dependence of the impedance matching and resonant frequency with the size of the superstrate has been analysed, having a good impedance matching and a decrease in the resonant frequency as the number of cells increase. By using an anechoic chamber and a receiver horn antenna, the power transmitted at boresight has been measured for different frequencies, observing a filtering behaviour due to the resonant characteristic of the superstrate and an improvement of the power transmitted at the resonant frequency of approximately 3 dB. Comparing the H and E plane radiation patterns of a dipole and the dipole with superstrate, more symmetrical and directive radiation patterns can be observed. Finally, a comparison between the simulated and measured aperture efficiency is presented with a good agreement.
Open Access
Broadband radar cross-section reduction using AMC technology
(IEEE, 2013) Iriarte Galarregui, Juan Carlos; Tellechea Pereda, Amagoia; Martínez de Falcón, José Luis; Ederra Urzainqui, Íñigo; Gonzalo García, Ramón; Maagt, Peter de; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
This paper presents the design, fabrication and characterization of a planar broadband chessboard structure to reduce the radar cross-section (RCS) of an object. The chessboard like configuration is formed by combining two artificial magnetic conductor (AMC) cells. The bandwidth limitations intrinsic to AMC structures are overcome in this work by properly selecting the phase slope versus frequency of both AMC structures. 180 degrees phase difference has been obtained over more than 40% frequency bandwidth with a RCS reduction larger than 10dB. The influence of the incidence angle in the working bandwidth has been performed. A good agreement between simulations and measurements is achieved.
Open Access
A dedicated numerical technique for field simulations of antennas on electromagnetic band-gap substrates
(2004) Hon, B.P. de; Beurden, M.C. van; Gonzalo García, Ramón; Martínez Pascual, Beatriz; Ederra Urzainqui, Íñigo; Río Bocio, Carlos del; Azcona, L.; Alderman, B.; Huggard, P.G.; Marchand, L.; Maagt, Peter de; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
Open Access
Design of a multifrequency antenna array with the use of left-handed superstrates
(2005) Sáenz Sáinz, Elena; Gonzalo García, Ramón; Ederra Urzainqui, Íñigo; Maagt, Peter de; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
In this paper, the radiation performances of different antenna configuration based on Left-Handed superstrates are presented. First of all, the behaviour of a Left- Handed (LH) unit cell is analysed, showing a resonant response with pass band and stop band frequencies. In order to improve the radiation performances of a single dipole, ie., to increase the directivity and efficiency and to reduce the back radiation, diverse LH superstrates working at the resonant frequency of the dipole are analysed. With these configurations, improvements in terms of directivity higher than 6 dB with efficiency closer to 100 % have been obtained.
Open Access
Design of a planar meta-surface based on dipoles and wires for antenna applications
(2006) Sáenz Sáinz, Elena; Gonzalo García, Ramón; Ederra Urzainqui, Íñigo; Maagt, Peter de; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
In this paper, the design of a planar meta-surface based on dipoles and wires is presented. The unit cell is formed by three independent layers, which contain two parallel dipoles and one wire. The behaviour of these elements have been analysed separately as an independent unit cell, i.e., the one dipole unit cell, the two dipoles unit cell and the two dipoles and wire unit cell, by means of the transmission response and the dispersion diagrams. For a normal incident plane wave with the E field parallel to the wires and the H field axial to the dipoles, the electric and magnetic responses are excited producing a pass band behaviour which exhibit negative refractive index. This cell has been used to create meta-surfaces for antenna applications. Two configurations have been analysed; the first one is a superstrate of a dipole antenna with the pass band tuned to the resonant frequency of the dipole. It has been observed that the power goes through the meta-surface and is radiated mainly in boresight direction, which increases the directivity up to 8 dBi and the aperture efficiency of the whole configuration. In the second case, a substrate with the stop band tuned to the pass band of the superstrate and the resonant frequency of the dipole has been added. A directivity higher than 9 dBi with a back radiation of -20 dBi have been obtained.
Open Access
Dipolos y metamateriales: mejora de las características de radiación
(2004) Sáenz Sáinz, Elena; Gonzalo García, Ramón; Ederra Urzainqui, Íñigo; Maagt, Peter de; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
In this work, pass band properties of Left Handed Media (LHM) are demonstrated. These properties have been used in order to make a LHM super-substrate that is put over a dipole antenna. This super-substrate is going to determine the characteristics of radiation patterns. Simulation with different types of configurations are presented in order to enhance the features of radiation patterns at bore-sight direction.
Open Access
Domain integral equations for electromagnetic band-gap slab simulations
(2004) Hon, B.P. de; Beurden, M.C. van; Gonzalo García, Ramón; Martínez Pascual, Beatriz; Ederra Urzainqui, Íñigo; Río Bocio, Carlos del; Azcona, L.; Alderman, B.; Huggard, P.G.; Maagt, Peter de; Marchand, L.; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
Electromagnetic band-gap substrates o er advantages regarding cross-coupling in sub-mm range imaging array applications. Electromagnetic scattering by such substrates may e ectively be formulated in terms of integro- di erential equations. The scattered elds are evaluated via the spectral domain in which the 3-D problem reduces to an in nite system of coupled 1-D integro-di erential equations. The associated matrix-vector products are dominated by FFTs. For moderate frequencies an elementary preconditioner in combination with a prudent initial estimate usually su ces to reach rapid convergence using the transpose-free quasi-minimal residual method.
Open Access
Electromagnetic band gap technology for millimetre wave applications
(2004) Ederra Urzainqui, Íñigo; Gonzalo García, Ramón; Maagt, Peter de; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
En esta tesis se ha estudiado el uso de estructuras Electromagnetic Bandgap (EBG) para frecuencias en la banda de las millimétricas. Estas frecuencias son muy apropiadas para aplicaciones de generación de imágenes (“imaging”) debido a las diferentes propiedades de los materiales con respecto a las que presentan a frecuencias ópticas. El uso de antenas planas para estas aplicaciones, el cual sería la opción preferida en cuanto a coste y complejidad de fabricación puede verse limitado debido a las pérdidas causadas por la excitación de ondas de sustrato. Estos problemas se pueden superar mediante el uso de la tecnología EBG, dado que dichos modos son inhibidos en estas estructuras periódicas. A pesar de que algunas demostraciones preliminares del uso de la tecnología EBG para aplicaciones de antenas ya han tenido lugar, ´estas pueden considerarse como meras pruebas de concepto. El propósito de esta tesis ha sido tratar de superar este estado inicial y utilizar configuraciones basadas en esta tecnología para el diseño de receptores. En particular, se han estudiado varios aspectos relacionados con el diseño de receptores a frecuencias de milimétricas implementando tecnología EBG. Primeramente se han estudiado las características principales de los sustratos basados en tecnología EBG. Para ello, se han considerado dos estructuras EBG, el “woodpile” y la estructura de Fan. Con respecto a los materiales dieléctricos utilizados para su construcción, se han utilizado silicio y Titanato de Zr/Sn, ZTT. El uso de un material de elevada constante dieléctrica es de gran interés, ya que permite la reducción del tamaño del EBG y el aumento de su ancho de banda. Se han estudiado tanto la impedancia de entrada como el diagrama de radiación de las configuraciones para las diferentes posiciones de un dipolo sobre el substrato EBG. Se ha encontrado que ambas características dependen fuertemente de la posición y de la orientación del dipolo con respecto de las zonas dieléctricas y de aire en la superficie de la estructura EBG. Así mismo, nuestros estudios han mostrado que el uso de materiales de alta constante dieléctrica no conlleva una disminución del tamaño de los elementos radiantes. Basándonos en estos resultados, varias configuraciones han sido estudiadas con más detalle, siendo alimentadas por una línea Coplanar Stripline (CPS). Solamente aquellas configuraciones que presentan alta impedancia de entrada pueden ser adaptadas apropiadamente, dado que la línea CPS presenta alta impedancia característica. Así mismo, el efecto de la las pérdidas de los materiales ha sido estudiado para estas configuraciones, resultando ser despreciables. Los resultados anteriores mostraron que es difícil encontrar una configuración de dipolo sobre “woodpile” que presente simultáneamente buenas características de radiación y adaptación. Por tanto, se ha propuesto una modificación de esta estructura EBG que mejora notablemente tanto el diagrama de radiación como la adaptación de la configuración inicial. Esta modificación es fácil de implementar, dado que se basa en el desplazamiento de las barras de la capa superior del woodpile. Finalmente se han diseñado dos configuraciones de receptor implementando tecnología EBG: un detector directo y un mezclador subharmónico. En ambos casos el elemento radiante consiste en un dipolo colocado sobre un “woodpile” de silicio. En el caso del detector directo, el diseño trató de conseguir la máxima sensibilidad, manteniendo al mismo tiempo un diagrama de radiación no distorsionado. Se han fabricado diversos prototipos de estas configuraciones cuyas medidas están de acuerdo con las predicciones. Con respecto al mezclador subharmónico, se diseñó para minimizar su temperatura de ruido. En este caso la mínima temperatura de ruido medida fueron 950K, a pesar de que se detectaron ciertos problemas debido a la presencia de mezclado harm´onico.
Open Access
Enhanced radiation properties of a rectangular waveguide by means of a left handed media
(2005) Sáenz Sáinz, Elena; Ederra Urzainqui, Íñigo; Gonzalo García, Ramón; Maagt, Peter de; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
In this paper, the results of experimental investigations to improve the gain between two antennas by means of a Left Handed Material (LHM) are presented. The basic idea is the use of a LHM media acting as a resonator to concentrate the power radiated by a rectangular waveguide achieving larger directivities and consequently larger gains. The transmission and radiation properties of this metamaterial (MTM) have been measured using a network analyser and two rectangular waveguides in the X band. Comparing the transmission parameter S21 with and without the LHM media between the waveguides, an appreciable improvement in the power received can be observed.
Open Access
Enhancement of the power radiated by a dipole antenna at boresight by means of a left handed superstrate
(IEEE, 2006) Sáenz Sáinz, Elena; Ederra Urzainqui, Íñigo; Gonzalo García, Ramón; Maagt, Peter de; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
In this paper a comparison between the measured radiation performances of a single dipole and a dipole with a left handed superstrate based on a finite periodic repetition of a unit cell is presented. First of all the return losses and resonant frequency of the dipole has been measured for different sizes of the superstrate, having a good impedance matching and a decrease in the resonant frequency as the number of cells increase. By using an anechoic chamber and a receiver horn antenna, the power transmitted at boresight has been measured for different frequencies, observing a filtering behaviour due to the resonant characteristic of the superstrate and an improvement of the power transmitted at the resonant frequency of around 3 dB. Comparing the H and E plane radiation patterns of a dipole and the dipole with superstrate, more symmetrical and directive radiation patterns can be observed. Finally, a comparison between the simulated and measured aperture efficiency is presented with a good agreement.
Open Access
High efficient dipole antennas by using left-handed superstrates
(2004) Sáenz Sáinz, Elena; Gonzalo García, Ramón; Ederra Urzainqui, Íñigo; Maagt, Peter de; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
This paper deals with pass band properties of Left Handed Media (LHM) to enhance dipole antenna performances. The LHM properties have been used in order to make high directivity antennas with good return loss features. The LHM structure is used as superstrate and placed over a dipole antenna. This superstrate is determining the characteristics of radiation patterns. Simulations of different types of LHM configurations are presented. The improvements of the radiation and matching parameters for each configuration are presented. High efficient antennas are obtained with this technique.
Open Access
Low profile multi-frequency dipole antenna array based on planar meta-surfaces
(IEEE, 2007) Sáenz Sáinz, Elena; Ikonen, Pekka; Gonzalo García, Ramón; Ederra Urzainqui, Íñigo; Tretyakov, Sergei A.; Maagt, Peter de; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
In this paper, the radiation performance of a low profile multi-frequency dipole antenna array with a planar meta-surface is presented. The meta-surface consists of two closely located parallel grids of short dipoles and one grid of continuous wires in between. By tuning a dipole to the pass band of the superstrate and due to the magnetic dipole moments induced in the unit cells, a uniform illumination is achieved and therefore an enhancement of the directivity. Placing a second meta-surface under the dipole with the stop-band tuned to the working frequency, the back radiation is reduced. By combining low and high resonant-frequency unit cells and tuning dipoles to these frequencies, a double-frequency array is formed.
Open Access
Manufacture and characteristics of wide bandwith, 3-D, EBG crystals for sub-millimetre antenna substrates
(2004) Azcona, L.; Alderman, B.; Huggard, P.G.; Gonzalo García, Ramón; Martínez Pascual, Beatriz; Ederra Urzainqui, Íñigo; Río Bocio, Carlos del; Hon, B.P. de; Beurden, M.C. van; Marchand, L.; Maagt, Peter de; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
Open Access
A metamaterial T-junction power divider
(IEEE, 2007) Sáenz Sáinz, Elena; Cantora Álvarez, Alejandro; Ederra Urzainqui, Íñigo; Gonzalo García, Ramón; Maagt, Peter de; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
A metamaterial based compact microstrip T-junction power divider working at 10 GHz is proposed. The metamaterial unit cell consists of microstrip gaps and via holes whose behavior is equivalent to the combination of series capacitors and shunt inductors respectively, that is, a dual TL (high-pass) configuration. By adjusting the parameters of these structures, the characteristics of the Metamaterial-medium can be set to achieve a desired phase shift. To validate the design, a T-junction power divider is fabricated and measured. A 70% reduction of the length of the impedance transformer, without significant performance degradation, has been achieved.
Open Access
Metamaterials as super-substrate to enhance dipole antenna performances
(2004) Sáenz Sáinz, Elena; Gonzalo García, Ramón; Ederra Urzainqui, Íñigo; Maagt, Peter de; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
In this work, pass band properties of Left Handed Media (LHM) are demonstrated. These properties have been used in order to make a LHM super-substrate that is put over a dipole antenna. This super-substrate is going to determine the characteristics of radiation patterns. Simulation with different types of configurations are presented in order to enhance the features of radiation patterns at bore-sight direction.
Open Access
Planar DNG superstrate for dipole antenna gain enhancement
(2007) Sáenz Sáinz, Elena; Gonzalo García, Ramón; Ederra Urzainqui, Íñigo; Ikonen, Pekka; Tretyakov, Sergei A.; Maagt, Peter de; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
In this paper, a volumetric double-negative (DNG) superstrate based on grids of dipoles and wires for dipole antenna applications is proposed.
Open Access
Radiation performances of a dipole array configuration inserted in a left-handed media
(IEEE, 2005) Sáenz Sáinz, Elena; Gonzalo García, Ramón; Ederra Urzainqui, Íñigo; Maagt, Peter de; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
In this work, the radiation improvements achieved when Left Handed Media (LHM) are combined with dipole antennas has been analysed. The behavior of two dipole antennas in array configuration when a Left Handed superstrate and substrate are placed over and under them has been analysed. Different positions of the dipoles have been studied. Besides, dielectric losses and copper SRRs and CLSs have been taken into account for different distance between dipoles in order to analysed their influence in the radiation properties. Simulation results are presented showing high efficiency antennas with enhanced gain patterns.
Open Access
Radiation performances of a multifrequency dipole antenna array with a left handed superstrate
(2005) Sáenz Sáinz, Elena; Gonzalo García, Ramón; Ederra Urzainqui, Íñigo; Maagt, Peter de; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
In this paper, the radiation performances of a multifrequency antenna array (MFAA) which consists of two dipoles (1 and 3) that are radiating at 9.57 GHz and other one (dipole 2) radiating at 11.98 GHz are presented. In order to improve the directivity and to reduce the coupling between the dipoles, a non-uniform Left Handed (LH) superstrate formed by cells of different resonant frequencies has been placed over them. Each dipole is tuned to the resonant frequency of the cells that are on top of it allowing the power transmission and producing a very uniform illumination that enhance the radiation performances of the whole structure. With this configuration, directivity values of 10.1 dB when dipoles 1 and 3 are radiating and 8.1 dB when dipole 2 is radiating have been obtained, with a gap between dipoles of 0.23 0 at resonant frequency of the first dipole and a coupling smaller than - 17 dB.
Open Access
Research on metamaterials for antenna applications
(2005) Gonzalo García, Ramón; Ederra Urzainqui, Íñigo; Iriarte Galarregui, Juan Carlos; Martínez Pascual, Beatriz; Sáenz Sáinz, Elena; Cantora Álvarez, Pablo; Maagt, Peter de; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
During the last 20 years a lot of attention has been paid to apply Electromagnetic Band Gap (EBG) technology in different frequency ranges, from microwaves to optics. EBG technology is based on the use of periodic structures to prevent the electromagnetic propagation in certain frequency ranges, known as the bandgap [1]. In the last years the new and revolutionary field of Metamaterials is trying to be applied to similar applications. Although different, both technologies have some similitudes as it has been proven for different authors. For instance when working with EBG structures Left-Handed properties can be obtained in some frequency ranges. In this paper, research efforts focussed on applying EBG technology and the more recent Metamaterials, in particular, left-handed materials, to antenna subsystems at microwave and (sub)millimetre wave frequencies are introduced.