Polo-Lopez, Lucas, Masa-Campos, Jose L., and Ruiz-Cruz, Jorge A.
International Journal of RF and Microwave Computer-Aided Engineering. Dec 2019, Vol. 29 Issue 12, n/a
Satellite communications, Antennas (Electronics) -- Design and construction, Waveguides -- Design and construction, Sintering, 3D printing, and Computer-aided design
Keywords: additive manufacturing; fused filament fabrication; phase shifter; reconfigurable; selective laser sintering; waveguide Abstract This work presents the design and manufacturing of a K-band reconfigurable phase shifter completely implemented in waveguide technology for reduced insertion loss, good matching, and large phase shifting range. The device is based on the combination of a short slot coupler and two tunable reactive loads implemented as a section of short-circuited waveguide where an adjustable metallic post is inserted. Three prototypes of this design have been manufactured using different techniques (conventional computer numerical control machining, a low-cost fused filament fabrication technique and direct metal laser sintering) in order to assess its performance for different applications. The prototypes have been characterized experimentally and the achieved results are evaluated and compared. The proposed phase shifter, since it is fully developed in waveguide technology, eliminates the need of adding transitions to planar structures in order to integrate lumped components like pin diodes or varactors. Therefore, this device has a great potential in high-power beam steering phased arrays. Biographical information: Lucas Polo-Lopez received the BSc and MSc degrees in Telecommunication Engineering from the Universidad Autonoma de Madrid, Madrid, Spain in 2014 and 2016, respectively. Since 2015 he has been with the Radiofrequency Circuits, Antennas and Systems (RFCAS) group of this same university, where he works toward the PhD degree. His current research interests include the computer-aided design of horn antennas and passive waveguide devices, as well as the application of additive manufacturing techniques to the construction of waveguide devices. Jose L. Masa-Campos received the Master degree in 1999 and the PhD Degree in 2006, from the Universidad Politecnica de Madrid, Spain. From 1999 to 2003 he developed his professional activity in the R&D department of the company RYMSA with the design of base station antennas for mobile communications and satellite antennas. From 2002 to 2003 he directed the R&D department of RYMSA. From 2003 to 2007, he worked as Researcher for Universidad Politecnica de Madrid, and in 2005 he joined to Universidad Autonoma de Madrid as Associate Professor in the Radiofrequency Circuits, Antennas and Systems (RFCAS) group. His main current research interests are in active and passive planar array antennas. Jorge A. Ruiz-Cruz received the Ingeniero de Telecomunicacion degree and the PhD degree from the Universidad Politecnica de Madrid, Madrid, Spain, in 1999 and 2005, respectively. Since 2006, he has been with the Universidad Autonoma de Madrid, Madrid, where he became an Associate Professor in 2009. His current research interests include the computer-aided design of microwave passive devices and circuits (filters, multiplexers, and orthomodes). Byline: Lucas Polo-Lopez,Jose L. Masa-Campos,Jorge A. Ruiz-Cruz
Byline: Mohamed Farid Shehab, Nabila Mohammed Abdel Hamid, Nevien Abdullatif Askar, Ahmed Mokhtar Elmardenly Keywords: CAD-CAM, electron beam melting; immediate mandibular reconstruction; patient-specific titanium mesh; rapid prototyping Abstract Background Immediate mandibular reconstruction was performed using a patient-specific titanium mesh tray fabricated by electron beam melting (EBM) /rapid prototyping techniques. Methods Patient-specific titanium trays were virtually designed and fabricated using EBM technology/rapid prototyping for patients requiring mandibular resection and immediate reconstruction using an iliac crest bone graft. Dental implants were placed in the grafted sites and the patients received prosthetic rehabilitation with a follow-up of one year. Clinical data, postoperative bone formation and complications were evaluated. Results A symmetric appearance of facial contours was achieved. The titanium tray incorporated the particulate iliac crest bone graft that provided significant bone formation (mean 18.97 [+ or -] 1.45 mm) and predictable results. Stability of the dental implants was achieved. Conclusion The patient-specific titanium meshes and immediate particulate autogenous bone graft showed satisfactory clinical and surgical results in improving patients' quality of life and decreasing the overall treatment time with adequate functional rehabilitation.
The Digital Signal Processing (DSP) systems used in mobile wireless communication, such as MIMO detection, beam formation in smart antennas, and compressed sensing, all rely on quickly solving linear systems of equations. These applications of DSP have vastly different throughput, latency and area requirements, necessitating substantially different hardware solutions. The QR decomposition (QRD) method is an efficient way of solving linear equation systems using specialized hardware, and is known to be numerically stable . We present the design and FPGA implementation of smart IP (intellectual property) for QRD based on Givens-Rotation (GR) and Modified-Gram- Schmidt (MGS) algorithms. Our configurable designs are flexible enough to meet a wide variety of application requirements. We demonstrate that our area and timing results are comparable, and in some cases superior, to state-of-art hardware-based QRD implementations. Our QRD design based on a Log-domain GR Systolic array achieved a throughput of 10.1M rows/sec for a complex valued 3x3 matrix on Virtex-6 FPGA, whereas our QRD design based on a Log-domain GR Linear array was found to be an area optimized solution requiring the fewest FPGA slices. Overall the Logdomain GR Systolic array implementation was found to be the most resource efficient design (IP for all of our proposed architectures have been prepared and are available at http://saqib.scripts.mit.edu/qr-code.php). Our set of IP can be configured to satisfy variety of application demands, and can be used to generate hardware designs with nearly zero design and debugging time. Moreover the reported results can be used to pick the optimal design choice based on a given set of design requirements. Since our architectures are completely modular, their sub-units can be independently optimized and tested without the need for re-testing the whole system. by Sunila Saqib. Thesis: S.M. in Engineering, Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2014. Cataloged from PDF version of thesis. Includes bibliographical references (pages 103-105).