Open Access
Study of photonic crystal structures and their applications in the field of antennas
(2000) Gonzalo García, Ramón; Maagt, Peter de; Sorolla Ayza, Mario; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
El propósito principal perseguido en esta tesis ha sido el diseño de estructuras “Photonic Crystal” y sus aplicaciones como substratos para antenas. Estos “Photonic Crystal” se definen como estructuras periódicas en una, dos o tres dimensiones las cuales no permiten la propagación de una onda electromagnética en su interior para cualquier dirección de propagación de la onda incidente en un determinado rango de frecuencias (“bandgap”). Uno de los principales problemas que presentan hoy en día las antenas es la potencia que se transfiere a los modos de substratos. Esta energía no contribuye a la radiación principal de la antena, considerándose un mecanismo de pérdidas. Además, esta energía, dependiendo de la constante dieléctrica del substrato y de su grosor puede suponer más del 70% de la potencia total. Incluso algunas veces esta energía contribuye de forma negativa a la radiación principal, deteriorando en gran medida el diagrama de radiación de la antena. La idea fundamental es utilizar estructuras “Photonic Crystal” como substratos de antenas. Al no permitir la propagación de la onda electromagnética en su interior, no se excitarán modos de substrato y toda la potencia será radiada por la antena. Esto se traducirá en un incremento de la eficiencia y de la directividad de la antena, en la obtención de diagramas de radiación más simétricos y en la reducción de la radiación trasera.
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Near-field electromagnetic trapping through curl-spin forces
(American Physical Society, 2013) Liberal Olleta, Íñigo; Ederra Urzainqui, Íñigo; Gonzalo García, Ramón; Ziolkowski, Richard W.; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
Near-field electromagnetic trapping of particles is generally obtained bymeans of gradient forces. In this paper, we discuss the attractive behavior of curl-spin forces, as well as their potential for near-field electromagnetic trapping and manipulation. It is demonstrated that curl-spin forces enable the trapping of particles operating at their resonant frequency. Such phenomena can be exploited to design more efficient and selective electromagnetic traps, to boost near-field energy exchange systems, and to bring stability to coupled resonant radiators. It also is illustrated how the balance between the gradient, radiation pressure, and curl-spin force components leads to the formation of zero-force rings around their sources, which explicitly demarcate the trapping regions. Analytical and numerical analyses are presented to assess the stability of the trapping mechanism.
Open Access
Upper bounds on scattering processes and metamaterial-inspired structures that reach them
(IEEE, 2014) Ederra Urzainqui, Íñigo; Liberal Olleta, Íñigo; Gonzalo García, Ramón; Ziolkowski, Richard W.; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
The physical limitations on time-harmonic scattering processes are investigated on the basis of the optical theorem. Previously derived least upper bounds on the total scattering and absorption cross-sections are obtained from it in a straightforward manner. In addition, it reveals a practical upper bound for the bistatic cross-section when evaluated in any direction. It is proved further that the maximum upper bound of the bistatic cross-section occurs in the forward scattering direction and that the corresponding upper bound for the backscattering direction is four times smaller than this maximum value. Metamaterialinspired electrically small antennas and scattering particles that approach these upper bounds are demonstrated. These examples numerically validate the derived upper bounds, as well as illustrate the important physical principles underlying them.
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
New approach to the design of corrugated horn antennas
(1997) Gonzalo García, Ramón; Teniente Vallinas, Jorge; Río Bocio, Carlos del; Sorolla Ayza, Mario; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
In this paper, we present two new corrugated horn antenna designs in circular waveguide. The first one is a converter horn antenna from monomode circular waveguide TE11 to corrugated waveguide HE11 mode in a very efficient way. The conversion efficiency varies between 98 % and 99%. The HE11 mode has highly desired radiation pattern characteristics for applications like satellite communications, radar, remote- sensing, etc, nevertheless, when the requirements are more stringent this mode is not good enough and we must look for other solution. This one corresponds to the fundamental gaussian beam, which has outstanding features, such as being a free space mode, having high matching efficiency with a reflector, no sidelobes, perfect symmetry, etc. The second horn antenna presented generates very efficient fundamental gaussian beams at the output (99%-99.9%). It is important to say that the input must look like a gaussian beam, an HE11 for instance, which presents a 98.4% of gaussian beam or similar. We also show a new design in which we are working now, consisting in the junction of the two aforementioned designs. They form an unique horn antenna that results in the TE11 mode, from the fundamental gaussian beam mode. These components have been analysed using the Mode Matching and the Generalised Scattering Matrix techniques and the Moment Method as well as the equations in [1] to get the far field radiation pattern. Our results have been checked against those obtained by other authors.
Open Access
A millimeter-wave 4th-harmonic Schottky diode mixer with integrated local oscillator
(MDPI, 2021) Pérez Escudero, José Manuel; Quemada Mayoral, Carlos; Gonzalo García, Ramón; Ederra Urzainqui, Íñigo; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación
In this paper the design and experimental validation of a fourth-harmonic mixer based on Schottky diodes working around 300 GHz is presented. The main novelty of this work consists in the integration of an MMIC-based local oscillator, working around 75 GHz, and a mixer in the same metallic block housing. A prototype has been characterized using the Y-Factor method and yields a best measured conversion loss and an equivalent noise temperature of 14 dB and 9600 K, respectively. This performance is comparable to the state-of-the-art for this type of mixer.
Open Access
Generation of the HE11 mode from monomode smooth circular waveguide
(1996) Gonzalo García, Ramón; Río Bocio, Carlos del; Sorolla Ayza, Mario; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
In this paper, we present an original taper design to obtain the HE11 corrugated circular waveguide mode exciting with a pure TE11 monomode smooth circular waveguide mode. The proposed corrugated taper has a longitudinal section composed of two hyperbolic profiles in series, one concave and the other convex united at a point, such that the derivative is continuous. Superimposed there is an additional tapering of the corrugation depth that goes from l/2 at taper input to l/4 within the first hyperbola. This original synthesis procedure has been successfully tested by computational simulation. The calculation method has been validated be experimental results of other authors.
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A gap waveguide-based compact rectangular waveguide to a packaged microstrip inline transition
(MDPI, 2020) Pérez Escudero, José Manuel; Torres García, Alicia E.; Gonzalo García, Ramón; Ederra Urzainqui, Íñigo; Institute of Smart Cities - ISC
In this paper two different simple to design and easy to manufacturing transitions from a microstrip to rectangular waveguide based on ridge and groove gap waveguides are studied. The first one is based on a combination of a groove and ridge gap waveguide. In this case, the microstrip substrate occupies the whole bottom metallic housing block, namely, the transition and the gap between the bed of nails and the lid; therefore, it does not require any substrate shaping. Nevertheless, the transition needs to replace groove waveguide by ridge gap waveguide sections to avoid higher-order mode excitation. In the second approach, based on only a groove gap waveguide, the substrate is shaped to be only in the microstrip section, that is, outside the bed of nails area. This leads to a simplification of the design procedure. Prototypes of both transitions have been characterized, showing good agreement with the simulations taking into account the manufacturing tolerances. Performance comparable to the state-of-the-art in this frequency band has been achieved.
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.
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Experimental validation of a Ku-band dual circularly polarized metasurface antenna
(IEEE, 2018) Tellechea Pereda, Amagoia; Caminita, Francesco; Martini, Enrica; Ederra Urzainqui, Íñigo; Teniente Vallinas, Jorge; Iriarte Galarregui, Juan Carlos; Gonzalo García, Ramón; Maci, Stefano; Ingeniaritza Elektrikoa eta Elektronikoa; Institute of Smart Cities - ISC; Ingeniería Eléctrica y Electrónica
The experimental validation of a Ku-band dual circularly polarized (CP) broadside-beam metasurface (MTS) antenna is presented. A radially modulated anisotropic single layer MTS has been synthesised employing sub-wavelength elliptical slotted metallic patches printed on top of a thin Arlon grounded substrate. In the structure, two decoupled phasematched transverse magnetic and transverse electric surface waves (SWs) are excited, which interact with the modulated surface leading to a CP broadside radiation. Two different orthomode transducers have been designed to excite the SWs with orthogonal polarization and equal amplitude. The first feeding system is composed of a metallic stepped septum inside an airfilled square waveguide. A conical section is included to match the output port of the square waveguide with the terminal, dielectric filled circular waveguide. The second feed is much more compact and efficient and it is composed of a circular waveguide completely filled by a dielectric. Depending on the input port excited on the feeds, two TE11 modes are excited with ±90° phase shift, which determine the right-hand or left-hand sense of the broadside beam generated by the MTS. Manufacturing details of the MTS and excitations are given and the measurements are compared with the simulation results. Finally, conclusions are drawn.