Active reflectors: possible solutions based on reflectarrays and Fresnel reflectors

An overview about some of the recent Spanish developments on active reflectors is presented. In the first part, a novel beamsteering active reflectarray is deeply studied. It is based on implementing in each elementary radiator an IQ modulator structure, in which amplitude and phase control of the scattered field is achieved. Finally, a special effort is made in offering solutions to overcome the active antenna integration problems. In the second part, the active concept is firstly extended to Fresnel reflectors. Thanks to the development of a proper simulator, this special structure can be easily analysed. This simulator allows the study of performance of this kind of reflectors and, applying evolutionary algorithms, to find optimal configurations of reflector in accordance with the given specifications for the conformal radiation pattern

Estructura transductora de modos de guía de onda basada en secciones octogonales

Estructura transductora de modos para la conversión de señales electromagnéticas entre una guía de onda de entrada y una guía de onda de salida, teniendo dichas guías de onda de entrada y salida igual o distinta geometría. La estructura transductora de modos comprende una pluralidad de secciones de guía octogonales concatenadas donde dichas secciones de guía octogonales comparten los mismos ejes de simetría entre sí y con dicha guía de onda de entrada y con dicha guía de onda de salida, y donde los parámetros geométricos de dichas secciones de guía octogonales están diseñados y ajustados para acondicionar progresivamente los modos de propagación electromagnéticos entre dicha guía de onda de entrada y dicha guía de onda de salida. Proporciona un ancho de banda superior al de otras técnicas anteriores. Además, la simetría eléctrica y magnética que proporciona la estructura octogonal elimina de forma efectiva la excitación de los modos superiores. Es aplicable en sistemas de transmisión y recepción de señales electromagnéticas a las frecuencias de microondas, milimétricas y sub-milimétricas.Solicitud: 201100440 (15.04.2011)Nº Pub. de Solicitud: ES2394819A1 (05.02.2013)Nº de Patente: ES2394819B2 (14.06.2013

Contribution to the development of flat Fresnel reflectors in W band for new imaging applications

This work presents an experimental study in W band about the behavior of a plane Fresnel reflector when the feeder changes its position on the surface of a sphere whose centre is the same of the Fresnel plate zones. For this purpose, an experimental system based on seven Fresnel plate zones and two different levels has been developed. The center frequency of the reflector is 96 GHz, the focal length is 100 mm and height between levels is 0.78 mm. Based on this Fresnel reflector, an experimental set up has been developed. The horn antenna feeder is fixed and situated in far field and the receiver is also a horn antenna located at the Fresnel focal distance. Both the reflector and the receiving antenna have some rotation capability to enable measurements from different angles. The experimental results show a good, stable behavior in gain versus the angular position of the feeder. This special property of Fresnel reflectors is impossible in parabolic reflectors and consequently, Fresnel reflectors could be used in new applications as radar imaging, increasing the radar field of view or improving the resolution by means of several squint feeders working simultaneously on the same lens or reflector. Therefore, the main objective of this paper is to analyze the behavior of this experimental set up for developing new Fresnel reflector-based applications.The authors would like to thank the Spanish Ministry of Economy and Competitiveness for the financial support provided through the projects CSD2008-00068 TERASENSE, CSD2008-00066 EMET and the co-finance from FEDER funds TEC2011-29126-C03-01

Antena margarita

A new antenna concept, which is named by us as “DAISY ANTENNA”, is presented in this communication. The antenna concept is based on a circular array of wire radiating elements, and its radiating field behaviour is determined by the current distribution in wire elements. This configuration provides a linear polarised field with a maximum of radiation pattern in the perpendicular direction to the daisy surface. This special array concept can be also applied to other kind of linear polarisation radiating elements, as for example to microstrip patches or waveguide horns, and consequently, the antenna directivity can be improved

Antena margarita para emisión y recepción de ondas electromagnéticas polarizadas lineal y circularmente

La presente invención es una antena constituida por el agrupamiento coplanar de un número par de hilos radiantes cuyo conjunto adopta una forma parecida a la distribución de pétalos en una flor margarita. Los hilos radiantes o pétalos de la antena margarita trabajan en resonancia, tienen geometría plana, todos tienen la misma estructura y están contenidos en un mismo plano, llamado plano de la antena. La única diferencia entre los pétalos está en la distribución relativa de los sentidos de circulación de la corriente, que determina la forma del diagrama de radiación y caracteriza el comportamiento de la antena con el objetivo de permitir al usuario un amplio rango de aplicaciones.Solicitud: 201130473 (29.03.2011)Nº Pub. de Solicitud: ES2395429A1 (12.02.2013)Nº de Patente: ES2395429B1 (07.01.2014

Antena de seguimiento en acimut para comunicaciones vía satélite

We present in this paper a first step of a feasibility study about a geo-satellite link from aeronautical, maritime and land mobiles, where the antenna provides a mechanical scanning in azimuth, based on a new beam tracking system. The novelty of this system is on the radiating element, which provides simultaneously at the input of the control card, the signals of both beams. This system avoids the waiting time due to the state change of the beam switch in a classical process. A laboratory prototype of the antenna has been designed, manufactured and measured, to demonstrate the possibilities of the developed technology

Antena activa de alta linealidad

In this paper, a novel highly linear amplifier active antenna is presented. The printed radiator serves as an in-phase spatial power combiner of two HEMTbased amplifier branches. The auxiliary branch is added for cancelling the third order intermodulation distortion (IMD3) current of the main branch, without diminishing its gain

Generación de campo polarizado circularmente en geometría plana con alimentación asimétrica

This paper presents a novel feeding system for obtaining circular polarized microstrip antennas, which is based on electromagnetic coupling in a single layer. The proposed circularly-polarized (CP) operation can be achieved simply by lengthening a microstrip line in the feeding system, without modifying the microstrip radiator. From the experimental results, the 3-dB axial-ratio bandwidth can reach as large as 98 MHz (3.9% relative to the center frequency of 2.44MHz) for the application as a 2.45-GHz RFID reader, or communication in ISM band

Antena polarizada circularmente con control de ganancia y alta linealidad

In this paper, a novel highly linear circularly polarized active antenna with gain control is presented. In this approach, the antenna serves as a 90º hybrid and the active part has been implemented using a branch line coupler as the 90º input hybrid circuit, and two PHEMT based amplifiers. The amplifiers are based on a new strategy for gain control with low distortion

ARCO: resumen de un proyecto en colaboración sobre tecnología de antenas

This paper presents a summary of the work realised in collaboration by six research groups of Spanish Companies and Publish Research Organisms (OPIs), to find the development of new and innovative technologies about arrays and reflectarrays having the common characteristic of a beam control. The idea of this paper is to inform to the Spanish scientific community the development of this Project that has been sponsored by the Ministry of Education and Science, under P4 modality. Due to the magnitude of the of the Project, just finished, its results have been published in different congress proceedings and journals, and by this reason the objective of this paper is to present a summary of the story and management evolution of the project, besides of its more relevant results