Carbon Nanotube Composites for Wideband Millimeter-Wave Antenna Applications

In this paper, we explore using carbon nanotube (CNT) composite material for wideband millimeter-wave antenna applications. An accurate electromagnetic model of the composite antenna is developed using Microwave Studio for numerical analysis. Good agreement between computed and measured results is shown for both copper and CNT antennas, and their performance is compared. The CNT antenna shows stable gain and radiation patterns over the 24 to 34 GHz frequency range. The dispersion characteristics of the CNT antenna show its suitability for wideband communication systems. Using a quarter-wave matched T-junction as feed network, a two-element CNT antenna array is realized and the performance is compared with a copper antenna. The housing effect on the performance of the CNT antenna is shown to be much lower than for the copper antenna

Meta-scheduling Issues in Interoperable HPCs, Grids and Clouds

Over the last years, interoperability among resources has been emerged as one of the most challenging research topics. However, the commonality of the complexity of the architectures (e.g., heterogeneity) and the targets that each computational paradigm including HPC, grids and clouds aims to achieve (e.g., flexibility) remain the same. This is to efficiently orchestrate resources in a distributed computing fashion by bridging the gap among local and remote participants. Initially, this is closely related with the scheduling concept which is one of the most important issues for designing a cooperative resource management system, especially in large scale settings such as in grids and clouds. Within this context, meta-scheduling offers additional functionalities in the area of interoperable resource management, this is because of its great agility to handle sudden variations and dynamic situations in user demands. Accordingly, the case of inter-infrastructures, including InterCloud, entitle that the decentralised meta-scheduling scheme overcome issues like consolidated administration management, bottleneck and local information exposition. In this work, we detail the fundamental issues for developing an effective interoperable meta-scheduler for e-infrastructures in general and InterCloud in particular. Finally, we describe a simulation and experimental configuration based on real grid workload traces to demonstrate the interoperable setting as well as provide experimental results as part of a strategic plan for integrating future meta-schedulers

Interconnect-aware scheduling and resource allocation for high-level synthesis

A high-level architectural synthesis can be described as the process of transforming a behavioral description into a structural description. The scheduling, processor allocation, and register binding are the most important tasks in the high-level synthesis. In the past, it has been possible to focus simply on the delays of the processing units in a high-level synthesis and neglect the wire delays, since the overall delay of a digital system was dominated by the delay of the logic gates. However, with the process technology being scaled down to deep-submicron region, the global interconnect delays can no longer be neglected in VLSI designs. It is, therefore, imperative to include in high-level synthesis the delays on wires and buses used to communicate data between the processing units i.e., inter-processor communication delays. Furthermore, the way the process of register binding is performed also has an impact on the complexity of the interconnect paths required to transfer data between the processing units. Hence, the register binding can no longer ignore its effect on the wiring complexity of resulting designs. The objective of this thesis is to develop techniques for an interconnect-aware high-level synthesis. Under this common theme, this thesis has two distinct focuses. The first focus of this thesis is on developing a new high-level synthesis framework while taking the inter-processor communication delay into consideration. The second focus of this thesis is on the developing of a technique to carry out the register binding and a scheme to reduce the number of registers while taking the complexity of the interconnects into consideration. A novel scheduling and processor allocation technique taking into consideration the inter-processor communication delay is presented. In the proposed technique, the communication delay between a pair of nodes of different types is treated as a non-computing node, whereas that between a pair of nodes of the same type is taken into account by re-adjusting the firing times of the appropriate nodes of the data flow graph (DFG). Another technique for the integration of the placement process into the scheduling and processor allocation in order to determine the actual positions of the processing units in the placement space is developed. The proposed technique makes use of a hybrid library of functional units, which includes both operation-specific and reconfigurable multiple-operation functional units, to maximize the local data transfer. A technique for register binding that results in a reduced number of registers and interconnects is developed by appropriately dividing the lifetime of a token into multiple segments and then binding those having the same source and/or destination into a single register. A node regeneration scheme, in which the idle processing units are utilized to generate multiple copies of the nodes in a given DFG, is devised to reduce the number of registers and interconnects even further. The techniques and schemes developed in this thesis are applied to the synthesis of architectures for a number of benchmark DSP problems and compared with various other commonly used synthesis methods in order to assess their effectiveness. It is shown that the proposed techniques provide superior performance in terms of the iteration period, placement area, and the numbers of the processing units, registers and interconnects in the synthesized architectur

Advanced Carbon Fiber Composite Materials for Shielding and Antenna Applications

Due to the low weight, ease of fabrication, low cost, high stiffness, high thermal and electrical conductivity, advanced carbon fiber composite (CFC) material is one of the most desirable materials which have been considered recently in the aerospace, electronic, and infrastructure industry. This thesis examines the use of CFC materials for electromagnetic field shielding and antenna applications. Using a suitable electromagnetic model of composite materials, we evaluate the shielding effectiveness (SE) and other EM properties of composites paying attention to antenna design. Analytical and simulation results are compared with experimental data. Two kinds of composite materials are investigated, namely reinforced continuous carbon-fiber (RCCF) composites and carbon nanotube (CNT) composites. For analytical SE analysis of multilayer RCCF composites, the material shows anisotropic behavior along the direction of the fibers, and we employ the transmission matrix method in conjunction with the anisotropic properties of each layer. The shielding performance of composites is also experimentally investigated. In order to enhance the conductivity of an RCCF composite, a small volume fraction of multi-walled carbon nanotubes (MWCNTs) is added to the RCCF material. We investigate the SE of the proposed MWCNT “nanocomposite” over a wide frequency band up to 26.5 GHz. The effect of aspect ratio on shielding performance is addressed as well. The effective conductivity of the nanocomposites was determined over the frequency range of interest. The use of RCCF and single-walled carbon nanotube (SWCNT) composite is investigated for building antennas, by replacing the metal with CFC. We use an RCCF composite to build resonant and wideband antennas. The effect of the conductivity tensor of RCCF composite on the antenna performance is addressed. We also study the performance of a microstrip patch antenna with the ground plane made of RCCF composite. As one of the most highly-conductive composite materials, single wall carbon nanotube (SWCNT) buckypapers are used to build composite antennas. A new fabrication method is proposed to print arbitrarily-shaped full-composite SWCNT antenna on any type of substrate. Various types of SWCNT antennas are fabricated for different antenna applications, namely UHF-RFID, WLAN, UWB, and mm-wave applications. Good agreement is observed between simulation and experimental results for all the aforementioned composite antennas. Using the spectral domain method, the Green’s function is obtained for an infinitesimal HED on a dielectric slab over a CFC ground plane. Due to the high conductivity, CFCs are modeled using a surface impedance. The expressions for the electric field components are derived. The numerical integration details particularly dealing with low-converged tail of the integrand for fields at the air-dielectric interface are addressed. Numerical results based on this method compare well with results based on a time-domain finite integration technique. The effect of conductivity and anisotropy of the composite ground plane on electric field is investigated

Multi-rate real-time simulation of modular multilevel converter using CPU and FPGA

This thesis presents the real-time simulation of a modular multilevel converter (MMC) using Field Programmable Gates Array (FPGA). Undertaking such a project raises challenges due to the very high number of components in MMC. The choice of the hardware used is justified by this particular problematic. Using FPGA, a very large number of inputs and outputs can be easily managed. By simulating the converter on FPGA reduces latency and the delays between the IOs and the MMC. It also allows using very small time-step ensuring accuracy for pulses detection. Only the converter is simulated on FPGA and the remaining component of the simulation, such as the AC system and its distribution network are simulated on CPU. Doing so gives the user access to large library of component from commercial software. Using two distinct platforms, CPU and FPGA, then requires the model not only to be decoupled, but also to use different sampling time. This thesis debuts by a presentation of the problematic. Then, the required sampling time for accurate simulation of MMC is demonstrated. In order to achieve such a small time-step, a decoupling method and its validation is proposed. The method is then generalized and applied to multi-rate simulation. Using those methods, a details implementation of the converter, using OPAL-RT technologies real-time simulator, is given. Finally, numerical and experimental validation of this model are presented

Electromagnetic Waves

This volume is based on the contributions of several authors in electromagnetic waves propagations. Several issues are considered. The contents of most of the chapters are highlighting non classic presentation of wave propagation and interaction with matters. This volume bridges the gap between physics and engineering in these issues. Each chapter keeps the author notation that the reader should be aware of as he reads from chapter to the other