Publication: Sistemas RFID en UHF y microondas
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2011-01-10
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2011-01-10
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Abstract
El presente documento hace un breve resumen de la tecnología RFID (identificación por radio-frecuencia) en todos sus ámbitos: desde los aspectos técnicos que la conforman hasta las numerosas aplicaciones que tienen cabida en la actualidad. Dicha tecnología se basa en dos componentes fundamentales: un lector (reader) y una etiqueta (tag o transponder). El reader identificará de forma automática al objeto (tag) dentro de un radio de acción determinado. Desde el punto de vista práctico se propone un sistema activo full-duplex a las frecuencias de 900 MHz y 2.45 GHz. Para el tag se ha diseñado un dipolo impreso antipodal cargado con resonadores LC o con metamateriales, en aras de comparar cuál de ellos posee las mejores características. Con la inserción de resonadores o de metamateriales se consigue la antena de doble banda. La mejor solución resultó ser la del dipolo cargado con resonadores LC, la cual se construyó y se obtuvieron valores de coeficiente de reflexión por debajo de -15 dB para las dos frecuencias de funcionamiento. Además también se llevó a cabo la miniaturización de la antena del tag mediante la utilización de un dipolo doblado. Por otro lado, para la antena del reader se propone una novedosa estructura: un parche cargado con resonadores LC para conseguir la funcionalidad de doble banda. Se estudiaron y construyeron diseños de 1 y 2 puertos, consiguiéndose muy buenos resultados en la práctica y con diagramas de radiación dipolares (broadside y de un lóbulo) para ambas frecuencias. Aparte se estudió la alimentación de acoplo por proximidad en este tipo de estructura para comprobar su correcto funcionamiento y poder utilizarla en el futuro, en una posible solución auto-diplexada. Para la realización de todas las simulaciones se ha utilizado la herramienta software CST®. Además se ha propuesto un modelo de equivalente circuital para las antenas cargadas con resonadores LC mediante la utilización conjunta CST®-AWR®. __________________________________________________________________________________________________________________
This paper presents the RFID technology (Radio Frequency IDentification). It relates all RFID technical aspects and the applications it has nowadays. This technology is based on two main components: a reader and a tag or transponder. The reader will be able to identify an object (tag) in an automatic way, within a certain radio. Besides, this paper proposes a full-duplex active RF identification system working at 900 MHz and 2.45 GHz. The tag antenna consists of an antipodal printed dipole loaded with LC resonators or with metamaterials, in order to compare their characteristics. The dual-band antenna is achieved with these resonators or metamaterials. The best solution was the dipole loaded with LC resonators, and it was built and measured. The reflection coefficient at the two working frequencies was lower than -15 dB. Also, the paper proposes a folded dipole to reduce the antenna dimensions. On the other hand, the reader antenna is based on a novel structure: a patch loaded with LC resonators to achieve, again, the dual-band antenna. Two antennas have been simulated and built: a one port loaded patch and a two port loaded patch. The experimental results agreed with the simulated ones, i.e. two dipolar (broadside and one beam) radiation patterns at both working frequencies. The proximity coupled feed has also been studied for the loaded patch with the aim of using it as a self-diplexed structure in the future. To perform these antennas, the CST® software has been used. In addition, an equivalent circuit has been proposed for antennas loaded with LC resonators using both CST® and AWR® software.
This paper presents the RFID technology (Radio Frequency IDentification). It relates all RFID technical aspects and the applications it has nowadays. This technology is based on two main components: a reader and a tag or transponder. The reader will be able to identify an object (tag) in an automatic way, within a certain radio. Besides, this paper proposes a full-duplex active RF identification system working at 900 MHz and 2.45 GHz. The tag antenna consists of an antipodal printed dipole loaded with LC resonators or with metamaterials, in order to compare their characteristics. The dual-band antenna is achieved with these resonators or metamaterials. The best solution was the dipole loaded with LC resonators, and it was built and measured. The reflection coefficient at the two working frequencies was lower than -15 dB. Also, the paper proposes a folded dipole to reduce the antenna dimensions. On the other hand, the reader antenna is based on a novel structure: a patch loaded with LC resonators to achieve, again, the dual-band antenna. Two antennas have been simulated and built: a one port loaded patch and a two port loaded patch. The experimental results agreed with the simulated ones, i.e. two dipolar (broadside and one beam) radiation patterns at both working frequencies. The proximity coupled feed has also been studied for the loaded patch with the aim of using it as a self-diplexed structure in the future. To perform these antennas, the CST® software has been used. In addition, an equivalent circuit has been proposed for antennas loaded with LC resonators using both CST® and AWR® software.
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Tecnología RFID, Metamateriales