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
On the determination of the phase center of gaussian horn antennas
(1998) Río Bocio, Carlos del; Teniente Vallinas, Jorge; Gonzalo García, Ramón; Sorolla Ayza, Mario; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
Gaussian horn antenna designs have experimentally demonstrated excellent performance to produce a very pure Gaussian beam mode with extremely low sidelobes and crosspolarization levels. These results make very attractive these antennas for high performance applications as satellite communications, radar and remote sensing. The particular position of the phase center inside the horn antenna is crucial in the subsequent process to design the mirror system to be illuminated by the antenna. The Gaussian horn antennas, because the feature to excite a Gaussian beam modes, have the phase center close to the horn throat instead of the output horn aperture as usual. This feature is particular of Gaussian horn antennas, and it supposes a change in the design process using these antennas. The mathematical determination, by correlation of the output fields with Gaussian structures, and the numerical demonstration, will be showed in this paper. Also, some considerations of the advantages or disadvantages of this property will be commented.
Open Access
Línea de transmisión cuasi-óptica con modos gaussianos de orden superior para sistemas basados en gyrotrones tecnológicos para aplicaciones cerámicas
(1997) Río Bocio, Carlos del; Gonzalo García, Ramón; Möbius, Arnold; Sorolla Ayza, Mario; Thumm, Manfred; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
In this paper, a description of a new compact microwave oven system based on a tecnological gyrotron for material processing applications is presented. The whole system has been designed by the Institute of Applied Physics in Nizhny Novgorod (Russia) and nowadays is installed in the Forschungszentrum (Karlsruhe, Germany). It consists ot a technological gyrotron working at 30 GHz giving 10 Kw CW in the TE02 circular waveguide mode, a quasi-optical transmission line (optimized in this work) and the final very oversized cavity or applicator. The original transmission line had a transmission efficiency of about 70%, by using a Vlasov launcher to generate a fundamental gaussian beam from the TE02 mode. The power was driven through a total of three mirrors. The improved design presented here increases the transmission efficiency up to 91%, by using a higher order gaussian beam mode, azimuthaly polarized and conical profile, by using only two ellipsoidal mirrors.
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.
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
Diseño óptimo de antenas de bocina multimodo para excitar un haz gaussiano fundamental de alta pureza
(1996) Gonzalo García, Ramón; Río Bocio, Carlos del; Teniente Vallinas, Jorge; Sorolla Ayza, Mario; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
In this paper, we present an original and optimal multimode horn antenna design to excite the fundamental Gaussian beam from an overmoded waveguide. In particular, we focus the study in overmoded circular corrugated waveguide. The main idea to design this multimode horn antenna, is to increase the waveguide radius as the desired gaussian mode expands. This principle has also been applied to smooth circular waveguides to excite higher order Gaussian beams from TE0n modes. The horn antenna design considered here, improves the gaussian conversion efficiency, the crosspolarisation and the sidelobes level of some good mixture ( aprox. 85% of TE11 and 15% of TM11 ).
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.
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.
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.