Emmanuel Van Lil

A Robust Semantic Overlay Network for Microgrid Control Applications

In an electric power converting apparatus comprising a plurality of branches each including a plurality of serially connected semiconductor switching elements, a non-linear resistor is connected in parallel with each semiconductor switching element, and a voltage division element including serially connected capacitor and a resistor is connected in parallel with each semiconductor switching element. A reactor is connected in series with each one of the branches and an arrestor is connected in parallel with a serially connected reactor and an associated branch.

Implementation of a Project-Based Telecommunications Engineering Design Course

This paper describes and discusses the implementation of a project-based graduate design course in telecommunications engineering. This course, which requires a combination of technical and soft skills for its completion, enables guided independent learning (GIL) and application of technical knowledge acquired from classroom learning. Its main implementation challenge is the need for instructors to define graduate-level GIL activities that are unique for the project objectives and scope. This process is required at both the system and subsystem levels. These activities must also satisfy the program learning outcomes and course outcomes (PLOs and COs). The course initiation, implementation, and management are first described from the instructors perspective. Technical specifications and outcomes from a recently implemented project titled “A Human-Inspired Telecommunication System” is taken as a case study. Besides explaining the methodology used to evaluate both the course and the students, an empirical assessment of PLOs and COs against the associated educational activities is also presented. Results of a student exit survey, in which each instrument was mapped to specific COs, indicated that the intended course objectives had been accomplished and that there was a good level of student satisfaction.

Direction of a arrival (DOA) parameter estimation with the SAGE algorithm

In this study, we investigate the estimation of the relative delay, the azimuth and elevation angle and the complex amplitude of a known received signal with the space alternating generalised expectation (SAGE) maximisation algorithm. This optimisation algorithm is used to replace the high-dimensional optimisation procedure, necessary to compute the joint maximum likelihood estimate of the parameters using several separate maximisation processes, which can be performed sequentially. Spherical arrays provide wide scan coverage with low grating lobe levels. Because a uniform antenna element distribution on this spherical surface gives rise to the smallest variations in received signal levels over the whole angular space, a uniform distribution of antennas on a sphere is used. For this completely general three-dimensional array, we have for the fitst time investigated the resolution of the SAGE algorithm, the convergence and the bit error rate as a function of the signal to noise ratio. We will show that this algorithm is a powerful tool that can be applied successfully for high-resolution parameter extraction.

Split Formulation of the Charge and Current Integral Equations for Arbitrarily Shaped Dielectrics

The low-frequency instability in the method of moments can be resolved by reformulating the underlying integral equations to explicitly include charge as an unknown. A new technique based on this charge and current formulation that reduces the computational complexity, both in time and memory, will be introduced. Considerations when using a charge and current technique include the practical problems of basis functions and the evaluation of the singular surface integrals, well as more theoretical problems such as whether the continuity equation still holds. The technique is implemented using a simple set of basis and testing functions and has been verified quantitatively, checking the charge and current distributions against analytic solutions where existing, as well as qualitatively against the boundary conditions for the scattered field. These results show the method to be both stable and accurate.

Improving Slow-start based probing mechanisms for flow adaptation after handovers

In a heterogeneous mobile networking environment, when a mobile user needs to perform a handover and switch to a new network, besides all the mobility management procedures to keep its connections alive and divert its on-going flows to the new location, the transmission rate of these flows should also be correctly adapted to match the conditions of the new network. One of the common practices is to let the flows to go through a fresh new Slow-start (or its variants) phase to probe along the path between the new location of the mobile user and its correspondent for the appropriate rate. Unfortunately, in many situations packets from these flows will be leaked into the new path at the old rate already before the Slow-start probing is performed, which not only interferes with the probing process but also disturbs the new network and affects the cross traffic along the new path. In this paper we propose to introduce some intelligence into the network, more specifically onto the mobility agent, so that this packet leaking issue is well taken care of before and during the Slow-start probing. On the other hand, with the introduced intelligence the probing process can also be improved in the sense of promptness, speed and data throughput, and these improvements are clearly demonstrated by simulation results.

A comparison of implementations of a combined charge and current formulation of the method of moments

The Method of Moments (MoM, also referred to as the Boundary Element Method outside of electromagnetics [1]) is a well-known and oft-used technique for complex electromagnetics simulations based on a numerical approach to Maxwells equations. Results can be very accurate, but as it requires solving a dense matrix equation it is very computationally intensive. MoM has traditionally been used for narrow-band antenna simulations, but thanks to advances in processing power and in the technique itself, it is slowly becoming feasible to perform simulations of electrically large objects and of diverse scenarios over a broad frequency band.

On the accuracy of MoM solutions for RCS and propagation computations

By investigating propagation problems for wind turbines, and more in particular near-field RCS computations, we have noticed that sometimes, even stabilized MoM solutions do not behave as expected. In this paper, we will give examples of some RCS computations in different scenarios. We found out that discrepancies in some RCS values are due to the choice of the meshing. Usually, standard meshers like gmsh only take into account one object. Unfortunately, to be accurate, all the positions of all objects have to be taken into account, to allow an accurate interaction between the objects. We will go deeper into the fundamentals of the relation between the accuracy and the mesh size and shape for some canonic problems of which the solution is exactly known.

Computing the influence of wind turbines on RF systems taking into account terrain

The main effects of wind turbines on radars have been described in previous papers [1–3]. They include shadowing by the larger parts and generation of false echoes. Previous studies have been focusing on the influence of moving objects, such as wind turbines, on aeronautical and maritime radars, usually working in the L/S band and in the X-band respectively. Here, we will not only take into account terrain properties, but also compute systems very close to each other and at lower frequencies, where UTD is not valid any more. Also, particular attention will be paid to the computations of systems that are in the near-field of the antenna.

Non-separable solutions of Helmholtz' equation revisited

Even if the idea is already very old (proposed first by Moseley in 1965), it offers analytical solutions of Helmholtz equations for curved waveguides. One of the key elements in their successful use is the computation of recursion formulas to find a numerical solution to the problem of analysis of generally shaped waveguides. They will be derived in this paper. Even if the original theory includes a generalisation to 3 dimensional cavities we will limit ourselves to 2 dimensional waveguide cases.

SAR for wearable antennas with AMC made using PDMS and textiles

Besides the radiation and reflection performance of wearable antennas, arguably one of the most important parameters is their Specific Absorption Rate (SAR). This work aims to evaluate SAR for wearable antennas integrated with Artificial Magnetic Conductor (AMC) plane made using different material categories — textiles and a flexible polymer,. Two types of textiles, felt and ShieldIt Super are used to build the first, textile-based antenna, while polydimethylsiloxane (PDMS) and the fluidic metal eutectic gallium indium alloy (EGaIn) are used to build the second, polymer-based antenna. Both materials are chosen due to their flexibility conformity to the human body, thus providing comfort to users. Despite the SAR for both antenna types did not exceed the European regulatory limits of 2 W/kg averaged over 10g of tissues; there are considerable differences between them.