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You searched for subject:(Micro wave imaging). Showing records 1 – 3 of 3 total matches.

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University of Waterloo

1. Khaira, Navjot Kaur. SOI RF-MEMS Based Variable Attenuator for Millimeter-Wave Applications.

Degree: 2019, University of Waterloo

The most-attractive feature of microelectromechanical systems (MEMS) technology is that it enables the integration of a whole system on a single chip, leading to positive effects on the performance, reliability and cost. MEMS has made it possible to design IC-compatible radio frequency (RF) devices for wireless and satellite communication systems. Recently, with the advent of 5G, there is a huge market pull towards millimeter-wave devices. Variable attenuators are widely employed for adjusting signal levels in high frequency equipment. RF circuits such as automatic gain control amplifiers, broadband vector modulators, full duplex wireless systems, and radar systems are some of the primary applications of variable attenuators. This thesis describes the development of a millimeter-wave RF MEMS-based variable attenuator implemented by monolithically integrating Coplanar Waveguide (CPW) based hybrid couplers with lateral MEMS varactors on a Silicon–on–Insulator (SOI) substrate. The MEMS varactor features a Chevron type electrothermal actuator that controls the lateral movement of a thick plate, allowing precise change in the capacitive loading on a CPW line leading to a change in isolation between input and output. Electrothermal actuators have been employed in the design instead of electrostatic ones because they can generate relatively larger in-line deflection and force within a small footprint. They also provide the advantage of easy integration with other electrical micro-systems on the same chip, since their fabrication process is compatible with general IC fabrication processes. The development of an efficient and reliable actuator has played an important role in the performance of the proposed design of MEMS variable attenuator. A Thermoreflectance (TR) imaging system is used to acquire the surface temperature profiles of the electrothermal actuator employed in the design, so as to study the temperature distribution, displacement and failure analysis of the Chevron actuator. The 60 GHz variable attenuator was developed using a custom fabrication process on an SOI substrate with a device footprint of 3.8 mm x 3.1 mm. The fabrication process has a high yield due to the high-aspect-ratio single-crystal-silicon structures, which are free from warping, pre-deformation and sticking during the wet etching process. The SOI wafer used has a high resistivity (HR) silicon (Si) handle layer that provides an excellent substrate material for RF communication devices at microwave and millimeter wave frequencies. This low-cost fabrication process provides the flexibility to extend this module and implement more complex RF signal conditioning functions. It is thus an appealing candidate for realizing a wide range of reconfigurable RF devices. The measured RF performance of the 60 GHz variable attenuator shows that the device exhibits attenuation levels (|S21|) ranging from 10 dB to 25 dB over a bandwidth of 4 GHz and a return loss of better than 20 dB. The thesis also presents the design and implementation of a…

Subjects/Keywords: millimeter-wave applications; RF-MEMS; variable attenuator; thermal imaging; impedance tuner; chevron actuator; micro-fabrication; SOI MEMS; silicon-on-insulator; microelectromechanical systems

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Khaira, N. K. (2019). SOI RF-MEMS Based Variable Attenuator for Millimeter-Wave Applications. (Thesis). University of Waterloo. Retrieved from http://hdl.handle.net/10012/14672

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Khaira, Navjot Kaur. “SOI RF-MEMS Based Variable Attenuator for Millimeter-Wave Applications.” 2019. Thesis, University of Waterloo. Accessed November 22, 2019. http://hdl.handle.net/10012/14672.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Khaira, Navjot Kaur. “SOI RF-MEMS Based Variable Attenuator for Millimeter-Wave Applications.” 2019. Web. 22 Nov 2019.

Vancouver:

Khaira NK. SOI RF-MEMS Based Variable Attenuator for Millimeter-Wave Applications. [Internet] [Thesis]. University of Waterloo; 2019. [cited 2019 Nov 22]. Available from: http://hdl.handle.net/10012/14672.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Khaira NK. SOI RF-MEMS Based Variable Attenuator for Millimeter-Wave Applications. [Thesis]. University of Waterloo; 2019. Available from: http://hdl.handle.net/10012/14672

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

2. Kpre, Ettien lazare. Contribution à l’étude de techniques de codage analogique pour l’imagerie microonde active et passive : Contribution to the study of analog encoding for active and passive microwave imaging.

Degree: Docteur es, Electronique des hautes fréquences, photonique et systèmes, 2017, Limoges

Les systèmes d’imagerie microonde suscitent un grand intérêt actuellement dans le domaine de la recherche, notamment pour des applications de sécurité (scanners corporels, vision à travers les murs, etc). Plusieurs techniques d’acquisition déjà existantes permettent d’optimiser l’ouverture rayonnante afin de garantir une bonne résolution sur l’image finale. Cependant, le verrou actuel des systèmes d’imagerie est de pouvoir atteindre un temps de rafraîchissement temps réel et d’adresser un grand nombre d’antennes. La majorité des systèmes actuels peinent à concilier la rapidité et la résolution, tout en garantissant une bonne sensibilité. Les travaux réalisés dans ce manuscrit visent à proposer une alternative aux systèmes existants en se basant sur des techniques de codage analogique des signaux d’antennes. Globalement, l’objectif est de minimiser le nombre de récepteurs sans affecter les performances. Les architectures proposées sont essentiellement basées sur le concept du Radar MIMO (pour les systèmes actifs) et du radiomètre à synthèse d’ouverture interférométrique ou SAIR (pour les systèmes passifs). Ces deux systèmes permettent de réduire considérablement le nombre d’antennes sans affecter la résolution de l’image, ce qui permet une première levée de contraintes. En sus, des composants compressifs entièrement passifs sont utilisés pour réduire le nombre de récepteurs des systèmes Radar MIMO et SAIR. Ces composants à diversité spatiale et fréquentielle présentent des fonctions de transfert orthogonales. Utilisés en émission, ils permettent un adressage simultané et indépendant des antennes du réseau. En réception, ils permettent de coder les signaux reçus par les antennes vers un nombre de voies RF considérablement réduit. En appliquant des techniques de décodage appropriées, les signaux reçus par chacune des antennes peuvent être estimées afin d’appliquer les algorithmes dédiés à la reconstruction de l’image. Ces composants offrent l’avantage de réduire fortement le nombre de voies RF tout en conservant la même ouverture rayonnante et en autorisant une acquisition simultanée des signaux. Des démonstrateurs laboratoires ont été réalisés en bande S afin de montrer une preuve de faisabilité des alternatives proposées. Enfin, les résultats obtenus ont fait l'objet d'une demande de brevet et un prototype d'imageur radiométrique à ondes millimétriques est en cours de prototypage dans le cadre du projet ANR-PIXEL.

Microwave imaging systems are currently attracting great attention in the field of research, especially for security applications (body scanners, vision through walls, etc.). Several acquisition techniques already exist to optimize the antenna aperture in order to guarantee a good resolution on the final image. However, the current lock of imaging systems is to be able to achieve a real-time acquisition and address numerous antennas. Most of the current systems struggle to reconcile fast imaging and resolution while ensuring good sensitivity. The work carried out in this manuscript aims at proposing an…

Advisors/Committee Members: Decroze, Cyril Nicolas (thesis director).

Subjects/Keywords: Radar MIMO; Radiomètre à synthèse d’ouverture interférométrique (SAIR); Imagerie microonde; Cavité microonde; Codage passif; Signaux orthogonaux; Problème inverse; MIMO Radar; Synthetic aperture interferometric radiometer (SAIR); Micro-wave imaging; Microwave cavity; Passive coding; Orthogonal signals; Inverse problem; 621.382 4

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Kpre, E. l. (2017). Contribution à l’étude de techniques de codage analogique pour l’imagerie microonde active et passive : Contribution to the study of analog encoding for active and passive microwave imaging. (Doctoral Dissertation). Limoges. Retrieved from http://www.theses.fr/2017LIMO0060

Chicago Manual of Style (16th Edition):

Kpre, Ettien lazare. “Contribution à l’étude de techniques de codage analogique pour l’imagerie microonde active et passive : Contribution to the study of analog encoding for active and passive microwave imaging.” 2017. Doctoral Dissertation, Limoges. Accessed November 22, 2019. http://www.theses.fr/2017LIMO0060.

MLA Handbook (7th Edition):

Kpre, Ettien lazare. “Contribution à l’étude de techniques de codage analogique pour l’imagerie microonde active et passive : Contribution to the study of analog encoding for active and passive microwave imaging.” 2017. Web. 22 Nov 2019.

Vancouver:

Kpre El. Contribution à l’étude de techniques de codage analogique pour l’imagerie microonde active et passive : Contribution to the study of analog encoding for active and passive microwave imaging. [Internet] [Doctoral dissertation]. Limoges; 2017. [cited 2019 Nov 22]. Available from: http://www.theses.fr/2017LIMO0060.

Council of Science Editors:

Kpre El. Contribution à l’étude de techniques de codage analogique pour l’imagerie microonde active et passive : Contribution to the study of analog encoding for active and passive microwave imaging. [Doctoral Dissertation]. Limoges; 2017. Available from: http://www.theses.fr/2017LIMO0060


University of Central Florida

3. Chaoulov, Vesselin. Design And Assessment Of Compact Optical Systems Towards Special Effects Imaging.

Degree: 2005, University of Central Florida

A main challenge in the field of special effects is to create special effects in real time in a way that the user can preview the effect before taking the actual picture or movie sequence. There are many techniques currently used to create computer-simulated special effects, however current techniques in computer graphics do not provide the option for the creation of real-time texture synthesis. Thus, while computer graphics is a powerful tool in the field of special effects, it is neither portable nor does it provide work in real-time capabilities. Real-time special effects may, however, be created optically. Such approach will provide not only real-time image processing at the speed of light but also a preview option allowing the user or the artist to preview the effect on various parts of the object in order to optimize the outcome. The work presented in this dissertation was inspired by the idea of optically created special effects, such as painterly effects, encoded in images captured by photographic or motion picture cameras. As part of the presented work, compact relay optics was assessed, developed, and a working prototype was built. It was concluded that even though compact relay optics can be achieved, further push for compactness and cost-effectiveness was impossible in the paradigm of bulk macro-optics systems. Thus, a paradigm for imaging with multi-aperture micro-optics was proposed and demonstrated for the first time, which constitutes one of the key contributions of this work. This new paradigm was further extended to the most general case of magnifying multi-aperture micro-optical systems. Such paradigm allows an extreme reduction in size of the imaging optics by a factor of about 10 and a reduction in weight by a factor of about 500. Furthermore, an experimental quantification of the feasibility of optically created special effects was completed, and consequently raytracing software was developed, which was later commercialized by SmARTLens(TM). While the art forms created via raytracing were powerful, they did not predict all effects acquired experimentally. Thus, finally, as key contribution of this work, the principles of scalar diffraction theory were applied to optical imaging of extended objects under quasi-monochromatic incoherent illumination in order to provide a path to more accurately model the proposed optical imaging process for special effects obtained in the hardware. The existing theoretical framework was generalized to non-paraxial in- and out-of-focus imaging and results were obtained to verify the generalized framework. In the generalized non-paraxial framework, even the most complex linear systems, without any assumptions for shift invariance, can be modeled and analyzed. Advisors/Committee Members: Rolland, Jannick.

Subjects/Keywords: optical systems design; image formation; micro-optics; photonics; image analysis; noise in imaging systems; image quality; resolution; physical optics; scalar diffraction theory; wave propagation; Electromagnetics and Photonics; Optics

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Chaoulov, V. (2005). Design And Assessment Of Compact Optical Systems Towards Special Effects Imaging. (Doctoral Dissertation). University of Central Florida. Retrieved from https://stars.library.ucf.edu/etd/295

Chicago Manual of Style (16th Edition):

Chaoulov, Vesselin. “Design And Assessment Of Compact Optical Systems Towards Special Effects Imaging.” 2005. Doctoral Dissertation, University of Central Florida. Accessed November 22, 2019. https://stars.library.ucf.edu/etd/295.

MLA Handbook (7th Edition):

Chaoulov, Vesselin. “Design And Assessment Of Compact Optical Systems Towards Special Effects Imaging.” 2005. Web. 22 Nov 2019.

Vancouver:

Chaoulov V. Design And Assessment Of Compact Optical Systems Towards Special Effects Imaging. [Internet] [Doctoral dissertation]. University of Central Florida; 2005. [cited 2019 Nov 22]. Available from: https://stars.library.ucf.edu/etd/295.

Council of Science Editors:

Chaoulov V. Design And Assessment Of Compact Optical Systems Towards Special Effects Imaging. [Doctoral Dissertation]. University of Central Florida; 2005. Available from: https://stars.library.ucf.edu/etd/295

.