Simplified approach to low-cost multiparameter monitoring based on low frequency polarization modulation

We experimentally revisit a technique of low-cost multiparameter monitor for optical performance monitoring based on low frequency polarization modulation. A simplified calibration procedure, which significantly reduces the mathematical complexity and processing effort is proposed. Validation is achieved by carrying out relative optical power, wavelength, and differential group delay measurements. (C) 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:18201824, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26956

Experiments on through-wall imaging using ultra wideband radar

Through-wall imaging (TWI) may provide vital information on interior environment in cases when physically entering such environment would pose danger to the person involved. The concept of ultra wideband radar (UWB radar) is an emerging technology, which offers high spatial resolution, as opposed to narrow band radars. Thus, TWI applications using UWB radar have become a growing field of research with several applications in the civil and defense areas such as rescue and surveillance. For this study, a prototype system of UWB radar to TWI has been built. Analyses and result to several kinds of experiments have been presented, that is, detection and visualization of metallic targets behind wooden board wall and concrete blocks wall. The results are encouraging and show the advantages of using UWB radar for TWI. (C) 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 54:339-344, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26543

Desarrollo y aplicaciones de radares de alta resolución en bandas milimétricas

Las bandas de las denominadas ondas milimétricas y submilimétricas están situadas en la región del espectro entre las microondas y el infrarrojo. La banda de milimétricas se sitúa entre 30 y 300 GHz, considerada normalmente como la banda EHF (Extremely High Frequency). El margen de frecuencias entre 300 y 3000 GHz es conocido como la banda de ondas submilimétricas o de terahercios (THz). Sin embargo, no toda la comunidad científica está de acuerdo acerca de las frecuencias que limitan la banda de THz. De hecho, 100 GHz y 10 THz son considerados comúnmente como los límites inferior y superior de dicha banda, respectivamente. Hasta hace relativamente pocos años, la banda de THz sólo había sido explotada para aplicaciones en los campos de la espectroscopía y la radioastronomía. Los avances tecnológicos en la electrónica de microondas y la óptica lastraron el desarrollo de la banda de THz. Sin embargo, investigaciones recientes han demostrado las ventajas asociadas a operar en estas longitudes de onda, lo que ha aumentado el interés y los esfuerzos dedicados a la tecnología de THz. A pesar de que han surgido un gran número de aplicaciones, una de las más prometedoras está en el campo de la vigilancia y la seguridad. Esta tesis está dedicada al desarrollo de radares de onda continua y frecuencia modulada (CW-LFM) de alta resolución en la banda de milimétricas, más concretamente, en las ventanas de atenuación situadas en 100 y 300 GHz. Trabajar en estas bandas de frecuencia presenta beneficios tales como la capacidad de las ondas de atravesar ciertos materiales como la ropa o el papel, opacos en el rango visible, y la posibilidad de usar grandes anchos de banda, obteniéndose así elevadas resoluciones en distancia. Los anchos de banda de 9 y 27 GHz seleccionados para los sistemas de 100 y 300 GHz, respectivamente, proporcionan resoluciones en distancia alrededor y por debajo del cm. Por otro lado, las aplicaciones objetivo se centran en la adquisición de imágenes a corto alcance. En el caso del prototipo a 300 GHz, su diseño se ha orientado a aplicaciones de detección a distancia en escenarios de vigilancia y seguridad. La naturaleza no ionizante de esta radiación supone una ventaja frente a las alternativas tradicionalmente usadas tales como los sistemas de rayos X. La presente tesis se centra en el proceso de diseño, implementación y caracterización de ambos sistemas así como de la validación de su funcionamiento. Se ha elegido una solución basada en componentes electrónicos, y no ópticos, debido a su alta fiabilidad, volumen reducido y amplia disponibilidad de componentes comerciales. Durante el proceso de diseño e implementación, se han tenido en cuenta varias directrices tales como la minimización del coste y la versatilidad de los sistemas desarrollados para hacer posible su aplicación para múltiples propósitos. Ambos sistemas se han utilizado en diferentes pruebas experimentales, obteniendo resultados satisfactorios. Aunque son sólo ejemplos dentro del amplio rango de posibles aplicaciones, la adquisición de imágenes ISAR de modelos de blancos a escala para detección automática así como la obtención de datos micro-Range/micro- Doppler para el análisis de patrones humanos han validado el funcionamiento del sistema a 100 GHz. Por otro lado, varios ejemplos de imágenes 3D obtenidas a 300 GHz han demostrado las capacidades del sistema para su uso en tareas de seguridad y detección a distancia. ABSTRACT The millimeter- and submillimeter-wave bands are the regions of the spectrum between the microwaves and the infrared (IR). The millimeter-wave band covers the range of the spectrum from 30 to 300 GHz, which is usually considered as the extremely high frequency (EHF) band. The range of frequencies between 300 and 3000 GHz is known as the submillimeter-wave or terahertz (THz) band. Nevertheless, the boundaries of the THz band are not accepted by the whole research community. In fact, 100 GHz and 10 THz are often considered by some authors as the lower and upper limit of this band, respectively. Until recently, the THz band had not been exploited for practical applications, with the exception of minor uses in the fields of spectroscopy and radio astronomy. The advancements on microwave electronics and optical technology left the well-known THz gap undeveloped. However, recent research has unveiled the advantages of working at these frequencies, which has motivated the increase in research effort devoted to THz technology. Even though the range of upcoming applications is wide, the most promising ones are in the field of security and surveillance. Particularly, this Ph.D. thesis deals with the development of high resolution continuouswave linear-frequency modulated (CW-LFM) radars in the millimeter-wave band, namely, in the attenuation windows located at 100 and 300 GHz. Working at these wavelengths presents several benefits such as the ability of radiation to penetrate certain materials, visibly opaque, and the great availability of bandwidth at these frequencies, which leads to high range resolution. The selected bandwidths of 9 and 27 GHz for these systems at 100 and 300 GHz, respectively, result in cm and sub-cm range resolution. On the other hand, the intended applications are in the field of short-range imaging. In particular, the design of the 300-GHz prototype is oriented to standoff detection for security and surveillance scenarios. The non-ionizing nature of this radiation allows safety concerns to be alleviated, in clear contrast to other traditional alternatives such as X-rays systems. This thesis is focused on the design, implementation and characterization process of both systems as well as the experimental assessment of their performances. An electronic approach has been selected instead of an optical solution so as to take advantage of its high reliability, reduced volume and the availability of commercial components. Through the whole design and implementation process, several guidelines such as low cost and hardware versatility have been also kept in mind. Taking advantage of that versatility, different applications can be carried out with the same hardware concept. Both radar systems have been used in several experimental trials with satisfactory results. Despite being mere examples within the wide range of fields of application, ISAR imaging of scaled model targets for automatic target recognition and micro-Range/micro-Doppler analysis of human patterns have validated the system performance at 100 GHz. In addition, 3D imaging examples at 300 GHz demonstrate the radar system’s capabilities for standoff detection and security tasks.

Comparison of different MIMO antenna arrays and user's effect on their performances

Multiple-input multiple-output (MIMO) systems have entailed a great enhancement in wireless communications performances. The use of multiple antennas at each side of the radio link has been included in recent drafts and standards such as WLAN, WIMAX, or DVB-T2. The MIMO performances depend on the antenna array characteristics and thus several aspects have to be taken into account to design MIMO antennas. In the literature, many articles can be found in terms of capacity or antenna design, but in this article, different types of antenna arrays for MIMO systems are measured in a reverberation chamber with and without a phantom as a user's head. As a result, the MIMO performances are degraded by the user in terms of efficiency, diversity gain, and capacity. Omnidirectional antennas such as monopoles with high radiation efficiency offer the highest performance for a rich scattering nonline of sight indoor environment.

High isolation series-shunt photoconductive microwave switch

This article presents a wide band compact high isolation photoconductive switch, which is based on the series-shunt switch design with three photoconductive switches made of diced high-resistivity silicon wafer placed over a microstrip gap and activated by 808-nm near-infrared laser diodes. The switch shows an insertion loss of 1.2 dB and an isolation of 44.8 dB at 2 GHz. It is easy to operate and control by light, high-speed, electromagnetically transparent and it does not require any biasing circuits.

Estresse oxidativo em porfiria hepática experimental disparada por succinilacetona - um inibidor da ácido 5-aminolevulínico desidratase

Para otimizar um modelo experimental para o estudo do desbalanço redox em porfirias relacionadas ao acúmulo de ácido 5-aminolevulínico-(ALA), via inibição da ALA desidratase-(ALA-D), ratos foram tratados com o éster metílico de succinilacetona-(SAME), um catabólito da tirosina que inibe fortemente a ALA-O, mimetízando o estado metabólico observado nos portadores de portirias e tirosinemias. Estabeleceram-se modelos de tratamento agudo por 36 e 18 h. No primeiro, os animais receberam 3 injeções de SAME (10, 40 ou 80 mg/kg, grupos Ali-IV). No segundo, os animais receberam 3 injeções de 40 mg/kg de SAME, ALA ou éster metílico de ALA (grupos BII-IV), ALA:SAME (30: 10 mg/kg, grupo BV), ou 10 mg/kg SAME (grupo BVI). Paralelamente, avaliou-se se os sintomas neurológicos característicos das portirias decorriam de danos oxidativos mitocondriais. Para isso, aplicou-se uma tecnologia óptica para medidas da difusão da depressão cortical que determinou a oxigenação e o estado redox do cit c em mitocôndrias do córtex cerebral de ratos submetidos ao tratamento crônico com ALA (40 mg/kg), SAME (10 e 40 mg/kg) e ALA:SAME (30: 1O mg/kg), a cada 48 h, durante 30 dias. Tratamento agudo/36 h: Os níveis de ALA no plasma, fígado, cérebro e urina e o clearance renal do ALA aumentaram nos grupos tratados. A atividade de ALA-D e a coproporfirina urinária reduziram. A marcação para proteínas carboniladas, ferro e ferritina aumentou no fígado e cérebro dos grupos tratados, especialmente no All. Os níveis de malondialdeído hepático aumentaram no grupo AIV. A razão GSH/GSH+GSSG e a atividade de GPx cerebrais aumentaram nos grupos AIV e AIII, respectivamente. Consistentemente com estes dados indicando um desbalanço oxidativo induzido pelo SAME, alterações mitocondriais e citosólicas ultraestruturais foram reveladas, especialmente no fígado. Tratamento agudo/18 h: Os níveis de ALA plasmáticos aumentaram nos grupos tratados, exceto em BIV. O grupo BII mostrou aumento dos níveis hepáticos de ALA. Interessantemente, a inibição da atividade de ALA-D não foi evidenciada. O conteúdo de ferro plasmático aumentou no grupo BII. Para os grupos tratados com 10 e 40 mg SAME/kg, a atividade de SOD hepática reduziu ~50% com a extensão do tratamento de 18 para 36 h, sugerindo que este último é mais efetivo em promover danos oxidativos induzidos pelo ALA. Tratamento crônico/30 dias: Embora nenhuma alteração tenha sido evidenciada no estado redox dos animais tratados, o tratamento com ALA reduziu o fluxo sanguíneo cerebral (CBF) e o consumo de oxigênio-(CMRO2), sugerindo uma vasoconstrição mediada pelo ALA, efeito este confirmado por ensaios de reatividade vascular conduzidos em anéis de aorta de ratos incubados com ALA. O tratamento com ALA:SAME restaurou os níveis de CBF e CMRO2. Interessantemente, a disponibilidade do radical superóxido-(O2•-) estava reduzida nos anéis de aorta incubados com ALA. Juntos, estes dados: a)validam o modelo de tratamento agudo/36 h para o estudo bioquímico e dos possíveis efeitos fisiológicos induzidos pelo ALA, e b)sugerem que as alterações mediadas pelo ALA exógeno levam à vasoconstrição.

Perforated corneal hydrops treated with sulfur hexafluoride (SF6) gas and tissue adhesive

Purpose: To report a case of a perforated acute hydrops in a mentally retarded patient that was successfully managed with intracameral sulfur hexafluoride gas and cyanoacrylate tissue adhesive. Methods: Interventional case report. Results: A 14-year-old mentally retarded male patient with keratoconus presented with a perforated acute hydrops. A bandage contact lens was applied. However, following a large emesis 2 days later, the aqueous leak worsened with shallowing of the anterior chamber. Under general anesthesia, sulfur hexafluoride was injected to reform the anterior chamber and cyanoacrylate tissue adhesive was applied to the perforated site and covered by a bandage contact lens and temporary tarsorrhaphy. A follow-up examination at 1 month showed a formed anterior chamber with tissue adhesive in situ and no aqueous leak. Conclusions: The successful use of intracameral sulfur hexafluoride and tissue adhesive in the management of perforated acute hydrops may avoid emergency tectonic penetrating keratoplasty and reduce potential complications in the poorly cooperative patient.

Dual-band Filtenna Array for WLAN Applications

This paper presents the design and results of a dual-band antenna array integrated with bandpass filters for WLAN applications. The array is fed with a single 50 Ω port and consists of two radiating elements; thereby having a 1x2 array structure. The two bands of the antenna array correspond to the two WLAN bands of 2.4 GHz and 5.8 GHz. A standalone array has first been designed. Other than the two fundamental resonant frequencies, the standalone array exhibits spurious harmonics at various other frequencies. For the suppression of these harmonics, the array has been integrated with two bandpass filters, centered at 2.4 GHz and 5.8 GHz. The resulting filtenna array was simulated, fabricated and measured. Obtained simulation and measurement results agree well with each other and have been presented to validate the accuracy of the proposed structure. Measured return loss of the structure shows dual-bands at 2.4 GHz and 5.8 GHz of more than 30 dB each and also a successful suppression of the spurious harmonics of the antenna array has been achieved. Radiation patterns have also been simulated and measured and both results shown. The gain and efficiency have also been presented; with the values being 6.7 dBi and 70% for the 2.4 GHz band and 7.4 dBi and 81% for the 5.8 GHz band respectively.

Magnetically Biased Graphene Based Switches for Microwave Applications

This paper presents a magnetically biased graphene based switch for CPW resonator applications. Graphene patches are set in the gap between signal and ground lines, thus obtaining the whole structures act as switchable elements. Graphene was modeled as a general material with appropriate surface conductivity. The presented CPW resonator structure acts like a switch in ON state even for magnetic bias field of around 0.5 T. The simulated S parameters of the CPW resonator structure with different magnetic field biasing are presented.

Reconfigurable Matching Networks for RF Amplifiers

This article presents applications of reconfigurable matching networks for RF amplifier design. Two possible solutions are given, one where the switching element is a PIN diode, and the other is based on graphene. Due to the fact that its conductivity depends on applied bias voltage, the graphene-based circuits can be used in microwave circuits as controllable elements. The structure of the proposed switch is very simple and it is particularly convenient for microstrip-based circuits. Because of that, a design of reconfigurable amplifier with the graphene-based switch is presented together with the one which has the PIN diode switch. Both amplifiers have the same specifications, and the one with the PIN diode switch is fabricated. The amplifier utilizing the PIN switch was used as a reference to make a comparison the two types of switches. Results of both amplifiers are very similar which indicates possible future applications of the graphene-based switch.

Highly linear reconfigurable UWB filters with independently controlled dual bandnotch

This letter proposes a high-linearity reconfigurable lower ultra-wideband (3.1–5.25 GHz) filter with independently controlled dual bandnotch at WiMAX 3.5 GHz band and satellite communication systems 4.2 GHz band. Reconfigurability has been achieved by the implementation of Graphene based switches (simulation only) and PIN diodes (measurements). The simulation and measurement results in OFF state show an entire bandpass response from 3.1 GHz to 5.25 GHz and with a very low insertion loss. In ON state, the results show that sharp rejections at 3.5 GHz and 4.2 GHz are achieved, with a low passband insertion loss. The two bandnotch operate independently of each other; thus allowing to control the behaviour of the required bandnotch. The third order intermodulation products were also measured in OFF and ON states and the linearity results have been presented. The filter is able to achieve a high performance with good linearity and no significant loss.

Evaluation and FMEA of Fabrication Techniques for Metallic Grating Couplers on Polymer Substrates with Low Glass Transition Temperatures

The main task is to analyze the state of the art of grating couplers production and low-cost polymer substrates. Then to provide a recommendation of a new or adapted process for the production of metallic gratings on polymer sheets, based on a Failure Mode and Effect Analysis (FMEA). In order to achieve that, this thesis is divided into four chapters. After the first introductory chapter, the second section provides details about the state-of-the-art in optical technology platforms with focus on polymers and their main features for the aimed application, such as flexibility, low cost and roll to roll compatibility. It defines then the diffraction gratings and their specifications and closes with the explanation of adhesion mechanisms of inorganic materials on polymer substrates. The third chapter discusses processing of grating couplers. It introduces the basic fabrication methods and details a selection of current fabrication schemes found in literature with an assessment of their potential use for the desired application. The last chapter is a FMEA analysis of the retained fabrication process, called Flip and Fuse, in order to check its capability to realize the grating structure.

Análise de conversores de frequência óptica baseados em amplificadores ópticos semicondutores

Dissertação de mest. em Engenharia de Sistemas e Computação, Faculdade de Ciências e Tecnologia, Univ. do Algarve, 2002

Add/drop filters based on SiC technology for optical interconnects

In this paper we demonstrate an add/drop filter based on SiC technology. Tailoring of the channel bandwidth and wavelength is experimentally demonstrated. The concept is extended to implement a 1 by 4 wavelength division multiplexer with channel separation in the visible range. The device consists of a p-i'(a-SiC:H)-n/p-i(a-Si: H)-n heterostructure. Several monochromatic pulsed lights, separately or in a polychromatic mixture illuminated the device. Independent tuning of each channel is performed by steady state violet bias superimposed either from the front and back sides. Results show that, front background enhances the light-to-dark sensitivity of the long and medium wavelength channels and quench strongly the others. Back violet background has the opposite behaviour. This nonlinearity provides the possibility for selective removal or addition of wavelengths. An optoelectronic model is presented and explains the light filtering properties of the add/drop filter, under different optical bias conditions.