Showing papers by "Bart Nauwelaers published in 2014"

Optical CDMA codes for an indoor localization system using VLC

Abstract: This paper describes the use of optical Code Division Multiple Access (CDMA) codes for an indoor localization system using Visible Light Communication. VLC uses Intensity Modulation and Direct Detection (IM/DD) so the CDMA codes can be used as baseband signals which makes the driving electronics less complex. In order to keep the installation cost low, a backbone network between the LEDs is not present. This makes it an asynchronous CDMA system where the cross- correlation is random and can in some cases introduces large distance errors. There are two groups of Optical CDMA codes namely uni- and bi- polar. When bipolar codes are used, the receiver should be equipped with an appropriated High Pass Filter (HPF). The results show that there is no large difference in cross- correlation between the codes but bipolar codes can reduce the distance error and so the position error even when there is static surrounding light like e.g. sunlight.

Distributed, signal strength-based indoor localization algorithm for use in healthcare environments.

Abstract: In current healthcare environments, a trend toward mobile and personalized interactions between people and nurse call systems is strongly noticeable. Therefore, it should be possible to locate patients at all times and in all places throughout the care facility. This paper aims at describing a method by which a mobile node can locate itself indoors, based on signal strength measurements and a minimal amount of yes/no decisions. The algorithm has been developed specifically for use in a healthcare environment. With extensive testing and statistical support, we prove that our algorithm can be used in a healthcare setting with an envisioned level of localization accuracy up to room revel (or region level in a corridor), while avoiding heavy investments since the hardware of an existing nurse call network can be reused. The approach opted for leads to very high scalability, since thousands of mobile nodes can locate themselves. Network timing issues and localization update delays are avoided, which ensures that a patient can receive the needed care in a time and resources efficient way.

Implementation of a Project-Based Telecommunications Engineering Design Course

Abstract: 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 instructor's 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.

Characterization of Intermodulation and Memory Effects Using Offset Multisine Excitation

Abstract: This paper proposes a new class of multisine excitations that allows efficient characterization of nonlinear circuits. By offsetting the frequency of tones, one can distinguish between different intermodulation products in a multisine response. This property leads to many applications for nonlinear circuit characterization, such as in-band distortion measurements, memory effects characterization, and model performance assessment. Some applications are highlighted in this paper, focusing especially on the characterization of memory effects. The effectiveness of the approach is demonstrated with a series of measurement results.

Simple and Scalable Methodology for Equivalent Circuit Modeling of IC Packages

Abstract: This paper presents a methodology for scalable modeling of IC packages by lumped element equivalent circuits. The response surface methodology is used for modeling of the IC package pins, lead frame, and bond wires, whereas the paddle is modeled as a pair of planes. The design of experiment (DOE) approach is used to systematically vary geometrical parameters of the simplified package structures, which are then simulated in a 3-D electromagnetic (EM) simulator. These simplified structures are used as building blocks of the IC packages and EM simulations of the simplified structures are used to build their parameterized equivalent circuit models. The extracted parameters of the equivalent circuit model form the response surface. Simple regression models are used for the response surface modeling. The model of the whole IC package is generated by cascading the models of the simplified structures. The range of the geometrical parameters used in the DOE is selected to cover a wide range of IC package geometries. The response surface models are verified against measurements performed on several IC package types and the accuracy is very good. The scalability and accuracy of the response surface models make this methodology suitable for modeling of a wide range of IC packages. The efficiency and accuracy of the presented models enable the statistical analysis of package performance with respect to package manufacturing parameters.

Broadband dielectric spectroscopy calibration using calibration liquids with unknown permittivity

Abstract: This paper presents a calibration method for broadband dielectric spectroscopy of micro-liter samples of biological liquids with transmission line sensors up to 110 GHz. The method uses water and methanol as calibration liquids to perform a probe-tip-to-liquid calibration without prior knowledge of their complex permittivity. Extracted complex permittivities of the calibration liquids show good agreement with literature values. Furthermore, sensors with different first-tier calibrations and geometries show consistent results.

An FPGA-based digital predistorter for RF power amplifier linearization using cross-memory polynomial model

Abstract: A cost-effective and flexible FPGA-based system architecture for digital predistortion (DPD) based linearization of power amplifiers (PAs) is proposed. The system is used to show the effectiveness of the cross-memory polynomial model (CMPM) for DPD. Two commercial amplifiers are linearized using single and two-carrier Wideband Code Division Multiple Access (WCDMA) signals as excitation and the performance of CMPM for DPD is compared to those of the memory polynomial (MPM) and memoryless models (MLM).

Evaluation of angle of arrival estimation for localization in multiple indoor environments

Abstract: The performance of indoor localization systems based on angle of arrival strongly depends on the environment Consequently, a characterization of localization errors in different environments is necessary to correctly assess the accuracy of these systems This paper focuses on the localization errors in multiple environments using basic 24 GHz linear antenna arrays First, a theoretical algorithm is elaborated to predict the expected localization error in various environments Subsequently, this algorithm is tested in practical tests performed in an anechoic room, an empty room and a room with obstacles In these tests, various techniques for error minimization are evaluated, as well as the Beamscan, ESPRIT and MUSIC angle of arrival algorithms It is shown that the accuracy in an anechoic room can also be obtained in an empty room for certain configurations This is not the case for a room with obstacles preventing line-of-sight connections For this case, a new type of localization system is proposed

Matlab based platform for the evaluation of modulation techniques used in VLC

Abstract: In this paper, we describe an experimental evaluation platform, which enables us to obtain the performance of baseband modulation techniques for usage in Visible Light Communication (VLC) applications. For the demonstration of the evaluation platform, we have chosen for Manchester encoding. This choice is exemplary, the described system is able to deal with a large set of analog and digital modulation techniques like Non-Return to Zero (NRZ), Return to Zero (RZ), Pulse Position Modulation (PPM), Binary Frequency Shift Keying, Dual Tone Multi-Frequency (DTMF), Phase Shift Keying (PSK), ... For the Manchester encoding, it is experimentally demonstrated that the statistical distribution of the received signal after matched filter operation, is Gaussian in nature. This allows us to make an estimation of the Bit Error Rate (BER) using Q-functions for Gaussian distributions. Our results demonstrate that the estimated BER strongly depends on the sampling rate at the receiver end. The sampling rate will therefor determine whether or not the receiver can receive NonLine Of Side (NLOS) signals at normal light intensities.

Straightforward modeling of dynamic I–V characteristics for microwave FETs

Abstract: This work presents a straightforward approach aimed at modeling the dynamic I–V characteristics of microwave active solid-state devices The drain-source current generator represents the most significant source of nonlinearity in a transistor and, therefore, its correct modeling is fundamental to predict accurately the current and voltage waveforms under large-signal operation The proposed approach relies on using a small set of low-frequency time-domain waveform measurements combined with numerical optimization-based estimation of the nonlinear model parameters The procedure is applied to a gallium nitride HEMT and silicon FinFET The effectiveness of the modeling procedure in terms of prediction accuracy and generalization capability is demonstrated by validation of the extracted models under operating conditions different than the ones used for the parameters estimation Good agreement between measurements and model simulations is achieved for both technologies and in both low- and high-frequency range © 2013 Wiley Periodicals, Inc Int J RF and Microwave CAE 24:109–116, 2014

A 90 GHz liquid sensing substrate integrated cavity resonator in LTCC for microfluidic sensing applications

Abstract: This paper presents a reflection-type 90 GHz substrate integrated cavity resonator sensor realized in LTCC technology for lab-on-chip microfluidic applications. A linear relationship between the resonance frequency of the sensor and the permittivity of the material under test was observed from measurements on low-loss materials. Calibration curves are also obtained for water-isopropanol mixtures which show monotonic behaviours with respect to the isopropanol concentrations. Measurements of the sensor thus demonstrate that it is promising for lab-on-chip microfluidic sensing applications.

Influence of Bluetooth Low Energy on WIFI Communications and Vice Versa

Abstract: In modern mobile devices such as smartphones and tablets, multiple wireless communication standards are supported. Since many of those standards operate at the licence free 2.4GHz ISM band, these standards use different modulation schemes and error correcting techniques in order to avoid interference when communicating over a wireless link (WIFI, Bluetooth, Bluetooth Low Energy...). For commercial use, these techniques are sufficient, but for industrial or medical use, in perhaps life threatening circumstances, all communications should perform at peak efficiency whilst not influencing each other. In this paper, a case study is presented where a healthcare setting is envisioned in which a WIFI network is deployed and used formedical purposes.We investigate the influence of a lot of transceiving Bluetooth Low Energy devices on theWIFI throughput, and vice versa. Conclusions and suggestions about the coexistance of both standards are also given.

Broadband dielectric spectroscopy calibration for microliter samples of biogenic liquid

Abstract: This paper reports on dielectric spectroscopy for microliter liquid samples using reference materials. In order to fully determine the calibration coefficients, air and water are used as known reference materials, while methanol is used as an unknown material, which is also used to validate the approach up to 5 GHz for which reference data is available. The method is then used up to 110 GHz for yeast cell suspensions and beef protein solutions.

Automated design of an HF RFID loop antenna based on parametric geometry modification

Abstract: In this paper, we take an innovative approach to the design of RFID loop antennas. As we want to increase the reliability of HF RFID systems, we need to step away from the traditional circular antenna shape. Adapting the shape of the antenna to its environment will improve the reliability of the HF RFID systems with a single loop antenna. We compare various shapes to serve as a reader antenna in a metallic tunnel. The optimized loop antennas are created by an antenna design tool which combines MATLAB® and CST EM Studio®. One of the optimized loop antennas is selected to serve in a practical case. Measurements were performed on this practical case with some promising results.

Error Profiling for Indoor Localization with Angle of Arrival

Abstract: Exploring the world of indoor localization leaves us with many technologies to achieve the desired accuracy. This paper focuses on Angle of Arrival, and the effect that the inaccuracies of the angle measurement have on the localization error. A theoretical method is developed to calculate an error profile for the entire considered rectangular space. A trade-off is made between the different number of intelligent nodes which could be used and the accuracy which can be achieved. As an outcome, four intelligent nodes will be placed in the corners of the room. Theoretical calculations are compared to practical results for the test set-up of four intelligent nodes trying to determine the position of one mobile node. Each intelligent node consist of a linear antenna array with four antenna elements operating on 2.4 GHz. The direction of the transmitting mobile node, to each intelligent node, is determined through three different Direction of Arrival algorithms: simple beamscan, ESPRIT and MUSIC.

FEM simulation and measurement validation of a cMUT cell

Abstract: This paper presents Finite Element Modeling (FEM) simulation and experimental results of the acoustic and mechanical behavior of an isolated cMUT cell. cMUT cells fabricated in the SiGeMEMS technology of imec are used as test vehicles. Dynamic characteristics of a cMUT cell actuated by a pulse superimposed on a DC bias, such as resonance frequency, Q-factor and transient displacement, are studied using ANSYS FEM and Polytec vibrometer measurements. A good agreement is achieved between the FEM simulation results and optical measurements. The Rayleigh integral method is used to construct the spatial pressure field based on the transducer surface information obtained both from ANSYS and the optical measurements. The results are compared with hydrophone measurements, and good agreements are achieved. Acoustic measurements on a typical cMUT cell (measuring ∼60µm on the side) in a fluorinert medium (FC-84) show a 7MHz center frequency, ∼100% −6dB fractional bandwidth (FBW) and several kilo Pascal peak-to-peak pressure at millimeters scale. Our method provides a clear methodology to accurately predict the transient spatial pressure field of a cMUT cell, especially in the far field region, with little time cost.

Temperature controlled measurement setup for permittivity extraction of water up to 40 GHz from 10 to 40 °C

Abstract: The proposed system in this paper enables the temperature controlled permittivity extraction of liquids up to 40 GHz from 10 to 40 °C. The temperature controlled environment consists of a temperature controlled chuck, probe station and a CPW microwave sensor that is coupled to a miniature T-type thermocouple. A large thermal mass and a platinum wire resistor ensure a precise reference temperature. Challenges in the sensor fabrication and measurements are discussed and further improvements are proposed for higher accuracy measurements. Extracted permittivity of water agrees well with the empirical models available in the literature.

Using a decision tree for real-time distributed indoor localization in healthcare environments

Abstract: Decision trees can be of great importance when trying to perform indoor localization on room level basis. These decision trees enable mobile nodes with limited computational resources to locate themselves inside a building without the need of heavy computations. This paper elaborates on the use of a decision tree for tracking moving mobile nodes inside healthcare facilities with possibly thousands of mobile nodes which need to be tracked at the same time. By avoiding a centralized localization attempt for all of the mobile nodes, we prove a distributed localization algorithm based on a decision tree can enable the tracking and tracing of this amount of mobile nodes. The same decision tree is used for determining if indoor localization without Line-Of-Sight between beacons and mobile nodes is feasible, for instance when people are standing between a mobile unit and a fixed beacon.

A 2.4 GHz phase locked loop for a linear phased antenna array

Abstract: One way of performing indoor localization of objects is by means of Angle of Arrival (AoA). This technology is based on a phased antenna array which estimates the angle of arrival of an incident wave transmitted by a mobile node. This is achieved by measuring the relative phase shifts between the received signals. This paper presents the construction of a Phase Locked Loop (PLL) which synchronizes on the carrier transmitted by the mobile node in order to provide a carrier at exactly the same frequency and a reference phase to the receiving antenna elements. The PLL is designed to operate at 2.4 GHz which holds additional challenges. Since, at this frequency, the most commonly available phase detectors are of the frequency insensitive EXOR type, the PLL will, besides the standard PLL building blocks, such as phase detector, a loop filter and a voltage controlled oscillator, need a sweep circuit. On top of that, sufficient amplification and filtering of the received signal will be mandatory.

Transmit and receive of a cMUT cell: Modeling and experiments

Abstract: This paper presents the equivalent circuit modeling and experimental verification of the transmit and receive properties of a single cell capacitive micromachined ultrasonic transducer (cMUT). A key achievement of this paper is a confirmation that the equivalent circuit model, presented in one of our previous publications, provides a sound model. The results predicted by the model are in rather good agreement with experimental results, and this for a single cMUT cell operated in both transmit and receive mode. The equivalent circuit model thus provides an easy way to rapidly predict the behavior of cMUT cells of arbitrary shape. The model can further be adapted and used to study a family of cells as in elements or arrays.

Circuit modelling of printed circuit boards for a DC-DC converter design

Abstract: In this paper a SPICE-compatible distributed circuit modelling method is applied to the modelling of printed circuit boards (PCBs) typically found in a DC-DC converter design. The method consists of identifying each pair of parallel plates present in a PCB and modelling it by a two-dimensional array of lossy transmission line elements. The impedance profile of the PCB is simulated in SPICE. The simulation results of the distributed circuit model are validated by comparing them to the simulation results obtained from a commercial electromagnetic (EM) solver. The presented method enables a fast and numerically efficient design, analysis and optimization of PCBs for DC-DC converters.

Electromagnetic-Analysis-Based Transistor De-embedding and Related Radio-Frequency Amplifier Design

Abstract: This chapter aims to describe methodologies and techniques for de-embedding device measurements from extrinsic measurements by characterizing the parasitic network surrounding the intrinsic device, through the use of a three-dimensional (3D) physical model of the network and its electromagnetic (EM) analysis. The electromagnetic behavior is obtained employing 3D EM solvers and internal ports. In the first part, the de-embedding processes for field-effect transistor (FET) devices to be used for monolithic microwave integrated circuit designs are studied by four different approaches; in the second part of this chapter, the de-embedding of FET devices for hybrid circuit design purposes is described.

Resolving positions of coherent sources using linear antenna arrays at 2.4 GHz

Abstract: In this paper we intend to find out what resolution can be achieved with two-dimensional Angle of Arrival localization when using linear antenna arrays at 2.4 GHz. A theoretical resolution calculation method is presented. Room dimensions, number of cooperating anchor nodes (provided with a linear antenna array) which track the position of a mobile node and number of antenna elements can be chosen. These theoretical calculations lead to the definition of a reference value which can be used to calculate the expected resolution for all rectangular shaped rooms with the desired variable settings. It is also shown that square rooms result in the best resolution and adding extra antenna elements improves the resolution. The design and calibration of a practical linear antenna array, with four linearly positioned 2.4 GHz antenna elements and inter distance of λ/2, is presented. Measurements of practical beam patterns, and the corresponding −3dB beam widths, for different incident angles show that influences such as mutual coupling and reflections can not be neglected. The practical resolutions are compared with expected theoretical values and it is shown that besides I/Q and phase offset calibration, manifold calibration is necessary.

Generic high-frequency small-signal look-up table model extraction for Si-Ge heterojunction bipolar transistors

Abstract: The objective of this paper is to provide a generic and versatile small-signal look-up table model extraction approach for Si-Ge heterojunction bipolar transistors. In this paper, parameter extraction at high frequencies, especially in the millimeter-wave region, is described. The approach is experimentally demonstrated on a Si-Ge heterojunction bipolar transistor with eight fingers and the emitter size of 0.18×0.84µm2. Copyright © 2014 John Wiley & Sons, Ltd.

Study and Simulations of an Angle of Arrival Localization System for Indoor Multipath Environments

Abstract: Present-day RF indoor localization systems generally underperform due to multipath propagation. This paper presents a new localization method based on Angle of Arrival estimation and ray tracing. This system exploits the reflections that are generally considered as a burden in conventional systems. In order to design the proposed system, a virtual test bench is created that enables adjusting all parameters. This test bench is then used to evaluate various antenna array elements. Also the Beamscan, MVDR, MUSIC and ESPRIT angle of arrival estimation algorithms are being tested and the effect of spatial smoothing is studied for each of these algorithms. The tests demonstrate that directional microstrip patch antennas result in the best array response for the proposed system and that spatial smoothing is indispensable in multipath environments.

A bottom-up cell modeling strategy using broadband microwave and millimeter wave dielectric spectroscopy

Abstract: In this paper we introduce a bottom-up microwave and millimeter wave modeling strategy for membrane bound biological systems. The approach is based on the stepwise integration of bulk liquid and membrane dielectric spectroscopy data into 3D biophysical models that are amenable to efficient electromagnetic computation. The purpose of this modeling effort is to develop more understanding of microwave electric field interactions with biological systems from a molecular biology point of view. The proposed strategy allows the systematic study of dielectric interactions within increasingly more complex membrane bound biological systems.

An inexpensive backside-sensing coplanar waveguide sensor for characterization of liquids and solids up to 40 GHz

Abstract: We present in this paper an inexpensive sensor realized on printed circuit board for broadband dielectric characterization of both liquids and solids. It is based on a CPW-CPW transition and statistical calibration. The specific property of the approach is that no assumption regarding cascading transmission lines with different properties has to be made as permittivity is obtained by a single-tier calibration. The sensor is validated by measurements of methanol and PDMS.