Improving the capabilities from the antenna point of view at THZ and SUB-THZ frequencies

Mención Internacional en el título de doctorThe main objective of this Ph.D. dissertation is to improve the capabilities of devices (emitters and detectors) and wireless systems (focusing system) at terahertz and sub-terahertz frequencies from the antenna point of view. It has been proved that only acting over the antenna side, devices with better capabilities can be obtained (increased emitted power in emitters and improved responsivity in detectors). This thesis is focused on the analysis and design of planar antennas, so their behaviour at terahertz and sub-terahertz frequencies has been studied. While obtaining the radiation pattern of planar antennas lying on semi-infinite substrate, an anomaly which appears in the radiation pattern is observed. This anomaly does not have a physical meaning but appears in all the published papers. The origin of such anomaly is explained in this thesis. In addition a program capable to obtain in an accurate way the radiation pattern of planar antennas lying on dielectric hyperhemispherical lenses has been designed. Regarding terahertz and sub-terahertz sub-systems a continuous-wave photomixer based power emitter working at 1.05 terahertz has been designed in such a way that maximum power is transferred from the active device to the antenna. The main contribution is that the design has been simplified in such a way that no external elements (filters, etc.) are needed. This emitter is intended to be the local oscillator of a heterodyne detector for radioastronomy applications. In addition, an equivalent circuit based on Hertzian dipoles to obtain the radiation pattern of the so-called “Large Are Emitters" has been derived. Such devices are photomixer based emitters with the main characteristic of not needing an antenna to emit terahertz power. Other important contributions to this Ph.D. dissertation are the complete design of Quasi-Optical Schottky based receiver working within the E-Band (60 - 90 gigahertz) where the power transferred from the antenna to the diode is maximized. This receiver will be part of a complete very high speed wireless communications system. Also in the detectors section, a CMOS FET based receiver working at 300 gigahertz has been designed. Finally, work over a focusing system for a 300 gigahertz radar for security purposes has been done. The main contribution regarding this aspect is that the focusing system, based on two elliptical mirror and a plane one, has been designed in such a way that the beam is capable to scan over a very large area without distortion. To do so it has been imposed that the target distance is always places at the focus of the output mirror.El objetivo de la presente tesis es mejorar las prestaciones de subsistemas (emisores y detectores) y sistemas (sistema de enfoque) en el rango de terahercios y sub-terahercios desde el punto de vista de antena. Se ha demostrado que actuando únicamente sobre la antena se pueden obtener dispositivos con un mejor rendimiento (potencia emitida incrementada en emisores y responsividad mejorada en detectores). La presente tesis se ha centrado en el análisis y diseño de antenas planas y para ello se ha estudiado su comportamiento a frecuencias de terahercios y sub-terahercios. Obteniendo los diagramas de radiación de antenas planas sobre sustrato semi-infinito se ha observado una anomalía en el diagrama de radiación que no tiene significado físico, pero que aparece en todas las publicaciones. El origen de esta anomalía se explica en el presente trabajo. Asimismo se ha diseñado un programa capaz de obtener de una manera rápida y precisa el diagrama de radiación de antenas planas que tienen como substrato una lente dieléctrica hiperhemiesférica. Con respecto a sub-sistemas de terahercios y sub-terahercios se ha diseñado un emisor para generar señales de onda continua basado en “photomixers" a 1.05 terahercios de tal manera que la potencia transferida de éste a la antena sea maximizada. La mayor aportación es que se ha simplificado el diseño del mismo de tal manera que no hacen falta elementos externos (filtros, etc.). Este emisor está previsto que sirva como oscilador local para un receptor heterodino en aplicaciones de radioastronomía. Con respecto a emisores de terahercios también se ha obtenido un circuito equivalente para obtener el diagrama de radiación basado en dipolos Hertzianos de los conocidos como “Large Area Emitters", que son dispositivos basados también en “photomixers" pero que no necesitan ningún tipo de antena para radiar potencia de terahercios. Otras contribuciones importantes en esta tesis han sido el diseño de un receptor completo Quasi-Óptico basado en diodo Schottky trabajando en la banda E (60 - 90 gigahercios) donde se ha maximizado la potencia entregada al diodo desde la antena. Este receptor está pensado para formar parte de un sistema de comunicaciones inalámbrico de muy alta velocidad. Dentro del apartado de receptores se ha diseñado también un receptor basado en tecnologíaa CMOS y FET trabajando a 300 gigahercios. Finalmente se ha actuado sobre un sistema completo de enfoque para un radar a 300 gigahercios para aplicaciones de seguridad. La mayor contribución en este aspecto es que el sistema de enfoque, basado en dos espejos elípticos y uno plano, se ha diseñado de tal manera que el haz es capaz de escanear en un amplio rango sin apenas distorsión. Para ello se ha forzado que la distancia de escaneo se encuentre siempre en el foco del espejo de salida.Programa Oficial de Doctorado en Multimedia y ComunicacionesPresidente: Jordi Romeu Robert.- Secretario: Luis Emilio García Castillo.- Vocal: Yi Huan

Pomace Olive Oil Concentrated in Triterpenic Acids Restores Vascular Function, Glucose Tolerance and Obesity Progression in Mice

Pomace olive oil, an olive oil sub-product, is a promising source of bioactive triterpenoids such as oleanolic acid and maslinic acid. Considering the vascular actions of pomace olive oil and the potential effects of the isolated oleanolic acid on metabolic complications of obesity, this study investigates for the first time the dietary intervention with a pomace olive oil with high concentrations of the triterpenic acids (POCTA), oleanolic and maslinic acid, during diet-induced obesity in mice. The results demonstrate that obese mice, when switched to a POCTA-diet for 10 weeks, show a substantial reduction of body weight, insulin resistance, adipose tissue inflammation, and particularly, improvement of vascular function despite high caloric intake. This study reveals the potential of a functional food based on pomace olive oil and its triterpenic fraction against obesity progression. Our data also contribute to understanding the health-promoting effects attributable to the Mediterranean dietSpanish Ministerio de Economía, Industria y Competitividad (MINECO), Agencia Estatal de Investigación (AEI), and Fondo Europeo de Desarrollo Regional (FEDER) (Grants SAF2017-82813-C3-3-R and PCI2018-092997/AEI to R.R.-R.

Meander dipole antenna to increase CW THz photomixing emitted power

The success in conquering the terahertz (THz) gap is subject to some facts such as maximizing the emitted power. Traditionally resonant antenna designs for continuous-wave (CW) THz photomixing include a RF choke to compensate the capacitive part of the photomixer and an antenna with a very high input impedance at its resonance to match the low value of the photomixer conductance. This communication considers that the antenna itself can provide this large impedance margin needed to directly match the photomixer, so that the RF choke can be avoided. The meander antenna constitutes an excellent candidate to achieve that goal based on the Active Integrated Antenna concept to improve both matching and radiation efficiencies. The main objective is to maximize the total efficiency and, as a consequence, the THz emitted power. A prototype working at 1.05 THz is designed and manufactured and results show a 6 dB output power improvement when compared with a conventional log-periodic antenna.This work was supported by Consolider CSD 2008–00068. The work of J. Montero-de-Paz was supported by the Spanish Education Minister under the program FPU (AP2009–4679) . The work of E. Ugarte-Muñoz was supported by the Spanish Economy Minister under the program FPI (BES2010–037676).Publicad

Photonic heterodyne pixel for imaging arrays at microwave and MM-Wave frequencies

The use of photonic heterodyne receivers based on semiconductor optical amplifiers to be used in imaging arrays at several GHz frequencies is evaluated. With this objective, a 3×3 imaging array based on such photonic pixels has been fabricated and characterized. Each of the receiving optoelectronic pixels is composed of an antipodal linear tapered slot antenna (LTSA) that sends the received RF signal directly to the electrical port of a semiconductor opticalamplifier (SOA) acting as the optoelectronic mixer. Both the local oscillator (LO) and the intermediate frequency (IF) signals are directly distributed to/from the array pixels using fiber optics, that allows for remote LO generation and IF processing to recover the image. The results shown in this work demonstrate that the performances of the optoelectronic imaging array are similar to a reference all-electronic array, revealing the possibility of using this photonic architecture in future high-density, scalable, compact imaging arrays in microwave and millimeter wave ranges.Publicad

300 GHz CMOS video detection using broadband and active planar antennas

Using CMOS transistors for terahertz detection is currently a disruptive technology that offers the direct integration of a terahertz detector with video preamplifiers. The detectors are based on the resistive mixer concept and performance mainly depends on the following parameters: type of antenna, electrical parameters (gate to drain capacitor and channel length of the CMOS device) and foundry. Two different 300 GHz detectors are discussed: a single transistor detector with a broadband antenna and a differential pair driven by a resonant patch antenna

Receptores homodinos a 300 GHz basados en tecnología CMOS

Using CMOS transistors for terahertz detection is currently a disruptive technology that offers the direct integration of a terahertz detector with video preamplifiers. The detectors are based on the resistive mixer concept and its performance mainly depends on the following parameters: type of antenna, electrical parameters (gate to drain capacitor and channel length of the CMOS device) and foundry. Two different 300 GHz detectors are discussed: a single transistor detector with a broadband antenna and a differential pair driven by a resonant patch antenna

New device for continuous-wave THz emission: large area emitter

We discuss two different approaches to overcome the power limitations of CW THz generation imposed to conventional photomixers. The increase in power achievable by using arrays of AEs is studied. Then ?large area emitters? are proposed as an alternate approach to overcome the power limitations. In this antenna-free new scheme of photomixing, the THz radiation originates directly from the acceleration of photo-induced charge carriers generated within a large semiconductor area. The quasi-continuous distribution of emitting elements corresponds to a high-density array and results in particularly favorable radiation profiles

From arrays of THz antennas to large-area emitters

Arrays of coherently driven photomixers with antenna (antenna emitter arrays, AEAs) have been evaluated as a possibility to overcome the power limitations of individual conventional photomixers with antenna (?antenna emitters?, AEs) for the generation of continuous-wave (CW) THz radiation. In this paper, ?large area emitters? (LAEs) are proposed as an alternative approach, and compared with AEAs. In this antenna-free new scheme of photomixing, the THz radiation originates directly from the acceleration of photo-induced charge carriers generated within a large semiconductor area. The quasi-continuous distribution of emitting elements corresponds to a high-density array and results in favorable radiation profiles without side lobes. Moreover, the achievable THz power is expected to outnumber even large AEAs. Last not least, the technological challenge of fabricating LAEs appears to be significantly less demanding

TERASENSE: THz device technology laboratory

The use of THz frequencies, particularly W and G band allows reaching higher resolution and deeper penetration in emerging applications like imaging, sensing, etc. The development of those new applications lays on reliable technologies, background of expertise and know-how. The CDS2008-00068 TERASENSE CONSOLIDER project has given the opportunity to extent upwards in frequency the previous background of the microwaves research group partners. This article summarizes the developments of the TERASENSE work package “THz Device Technology Laboratory”

TERASENSE: THz device technology laboratory: final summary

The use of THz frequencies, particularly W and G band allows reaching higher resolution and deeper penetration in emerging applications like imaging, sensing, etc. The development of those new applications lays on reliable technologies, background of expertise and know-how. The CDS2008-00068 TERASENSE CONSOLIDER project has given the opportunity to extent upwards in frequency the previous background of the microwaves research group partners. This article summarizes the developments of the TERASENSE work package “THz Device Technology Laboratory”.This work was supported by the Spanish Ministerio de Ciencia e Innovación through the CONSOLIDER-INGENIO 2010 program reference CSD2008-00068 TERASENSE