RF non-ideality characterisation and compensation by Saeed Farsi
RF circuits have always some amount of non-ideality. The most important types of non-idealities in nonlinear circuits are nonlinearity and memory. If these two phenomena are not properly dealt with, they will have considerable degrading effects on the quality of RF systems. In this seminar we are going to address some important classes of memory and nonlinearity in common RF circuits. Some approaches to tackle these degrading effects will be discussed. Then, some successful memory compensation and linearisation techniques that have been investigated in our group will be demonstrated.
Broadband power line communications for reliable smart grids by Linyu Wang
Many challenges are encountered with the evolution from the traditional electrical
grid to the new smart grid. One of these main challenges is the need for a
reliable communication network to exchange information and control the loads
of each important end user in real time. The most attractive access solution is
the use of Power Line Communication (PLC) technology that uses the grid as the
transmission medium. The access PLC systems represent the area between the
transformer to the end users in the same network, where the power line channel
is made of the interconnection of various multi-conductor cables. A well designed
PLC system in the access network can smoothly bridge the transmission grid and
the customers together, and play a key role in the realization of smart grid.
Study of automatic configuring RF Sensor Networks by Anneleen Van Nieuwenhuyse
In this seminar, indoor localization of objects based on Angle of Arrival measurements is presented. Using beam steering, of an antenna array, makes it possible to find the direction of an object. The development of a linear antenna array with 4 antenna elements operating at 2.4 GHz is discussed.
Beam scanning is presented as the easiest algorithm to find the direction of an object. Despite its simplicity this algorithm is unable to cope with multipath reflections. Therefore other Direction of Arrival estimation algorithms, such as ESPRIT and MuSiC are introduced. The improvement of the measurement results using these techniques is clarified
Solar Power Satellite: Antenna Aspects by Zhongkun Ma
Recently, upper bounds have been derived for the efficiency of nantenna (= nano antenna) systems for solar energy harvesting. The maximum upper bounds were found to be in the order of 60 % - 70 % for dipoles made of silver. These upper bounds are determined solely by the losses in the nantenna. In this paper, the second crucial factor in the efficiency product for a real nano-rectenna topology is studied: the matching efficiency due to the unavoidable mismatch between nantenna and rectifier impedance. Since suitable rectifiers do not exist yet, and since it would be totally unfeasible to optimize the nantenna – rectifier system based on experiments, for obvious reasons of cost per fabricated sample, an optimization technique is used based on full-wave simulations to assess the efficiency that can be reached when the two impedances are optimally compatible. To this goal, first a comprehensive numerical study is made of the impedance of nano dipoles made from three different metals and deposited on a glass substrate. Then the rectifier impedance is determined for which the matching efficiency is maximum. Two different rectifier impedance models are involved. They are 1) the polynomial (0th, 1st, and 2nd order) model and 2) the equivalent circuit (EC) model for the non-packaged case. The result is that a maximum matching efficiency of about 97 % can be reached for Al dipoles, while a maximum efficiency product of upper bound and matching efficiency of about 54 % can be reached, in this case for Ag dipoles. These values are reached for a 2nd order polynomial model. Important is also that the results for the EC model are almost identical to the results of the 0th order polynomial model. Finally, the maximum power delivered by a single linearly polarized dipole is shown to be in the order of 5-10 pW.
Free Space and On-Body Efficiency Evaluations using a Reverberation Chamber by Ping Jack Soh
This seminar presents the efficiency validation of textile/flexible planar inverted-F antennas (PIFAs) in free space and on-body. Free space measurements are carried out using two methods, the first using conventional reverberation chamber (RC), and another using a new source-stirred cap (SSC) method. The former technique is then used to evaluate efficiencies on a real human subject. Two types of flexible antenna builds are evaluated; one fabricated using flexible copper foil and the other using ShieldIt conductive textile. The results from both methods showed that the PIFAs are highly efficient, and provided a good agreement against a simulated model. Less than 7 % of total efficiency difference is observed in free space, which shows that the theoretical properties used are accurate and comparable to the real life model. When placed on-body, measured efficiencies are indicating between 15 % and 25 % of degradation compared to free-space, depending on the antenna materials and distance from the body.
Optimization of RFID systems in unfriendly operating environments by Kevin D'hoe
It is very challenging to create reliable RFID systems within the vicinity of metallic environments.
Most solutions for this kind of applications are given by a multi antenna setup with circular loop antennas.
In this seminar, an optimized shape of a loop antenna is presented, this loop antenna is placed in a metallic tunnel.
The setup with a single loop antenna has the same reliability compared to a multi antenna setup.
This new type of loop antenna is the result of an automated antenna design tool which combines MATLAB and CST EM Studio.
A genetic algorithm with smart defined RFID goal functions is implemented and forms the core of the automated antenna design tool.
The current status and evolution of the KU Leuven NET by Herman Moons
This lecture by Herman Moons, responsible of the development of the University network, will discuss actual and future evolutions. This is intended for students in the framework of the course: H05J6A Modelling and Performance Analysis of Telecom Networks, but is open to everybody. The lecture will be given in English.
High-SNR Asymptotics of Mutual Information for Discrete Constellations with Applications to BICM by dr. Alex Alvarado, U. of Cambridge
In this talk, we discuss the high-signal-to-noise ratio (SNR) asymptotic behavior of the mutual information (MI) for discrete constellations over the scalar additive white Gaussian noise channel. Exact asymptotic expressions for the MI for arbitrary one-dimensional constellations and input distributions are presented. Using the relationship between the MI and the minimum mean-square error (MMSE), asymptotics of the MMSE are also developed. We show that for any input distribution, the MI, MMSE and symbol-error probability have an asymptotic behavior proportional to the Gaussian Q-function, whose argument depends only on the minimum Euclidean distance of the constellation and the SNR, and where the proportionality constants are functions of the number of pairs of constellation points at minimum Euclidean distance and their corresponding probabilities. The developed expressions are then used to prove the long-standing conjecture that Gray codes are the binary labelings that maximize the generalized mutual information for bit-interleaved coded modulation at high SNR.
A novel RSS-based indoor localization system for use in healthcare environments by Jeroen Wyffels
In past research, a broad range of indoor localization algorithms based on Received Signal Strength (RSS) have been developed. However, these algorithms either require a lot of processing power, or are not able to locate a mobile device with a reasonable accuracy, especially when there are a lot of different small rooms, long corridors etc…
In this seminar, an overview of a new indoor localization algorithm is presented for use in healthcare facilities, which has this mentioned specific building topology . As an application of this algorithm, Location Based Services for patients as well as nurses become feasible, such as automated access control, automated alarm generation (i.e. when patients fall out of bed,…). The aims of the PhD research in which this algorithm is developed, are as follows: 1) A lot of mobile devices need to be located (>1000), 2) A lot of RF beacons are available (max 4 in each room), 3) alarms must be delivered with a 100% certainty (no packet loss) and 4) This all needs to be done in a time-,resource- and power efficient way.
Extension of the MAGMAS software for a gyrotropic medium by Zhanna Khaymedinova
Nuclear fusion antennas are used for delivering huge amounts of energy to the plasma. Plasma is a particular case of a gyrotropic medium. This term implies that the permittivity is a tensor, not a scalar as in the case of more regular dielectrics. When it comes to the calculation of the antenna for irradiation of a gyrotropic medium the workflow can be subdivided in two equally important parts. The first part is strongly theoretical and implies a calculation of the Green’s Function for the gyrotropic medium. In this first part approximating models and initial conditions are established for the particular case of ICRH antennas. The second part is dedicated to the modification of the existing software tool MAGMAS in such a way that it will allow a calculation of the new type of Green’s functions. The key feature of such extension is that the modification of already existing, tested and working lines of code is minimized. Within the framework of this seminar both crucial steps will be elaborated.