Nobby Stevens

Analysis of the Realistic Resolution with Angle of Arrival for Indoor Positioning

Increasing importance of localizing objects in indoor environments is the motivation for many research on localization algorithms. This paper focuses on the maximum achievable resolution for Angle of Arrival as a means to position objects inside rooms using equipment within the field of wireless sensor networks, thus dealing with restricted resources. A clear view on beam forming using antenna arrays is represented and is proven to be useful in Angle of Arrival measurements. The choice of the linear antenna array as most appropriate solution is motivated. A detailed overview of the algorithm, used to calculate the maximum realistic resolution, leads us to draw conclusions concerning the resolution. Depending on the number of anchor nodes and the composition of the antenna arrays, a reference value can be defined to calculate the realistic resolution for all room dimensions.

Design and reliability evaluation of passive HF RFID systems in metal environments

In spite of the popularity of passive Radio Frequency Identification (RFID) systems, reliability is an important topic to achieve the adoption of this technology in certain areas of applications. Maintaining this reliability is especially challenging in applications where metals are ubiquitous. This article describes how a passive HF RFID system is optimized for implementation within a closed metal case. The ideal orientation of a transponder within a metal environment is determined. Various simulations were executed in order to predict the areas where the magnetic field exceeded the activation field of the tags. The findings, resulting from these simulations, are verified by hardware measurements which show high prediction accuracy for the practical test setup. In this paper we optimized the reliability of RFID systems by adjusting the radius of a circular loop antenna to the metal construction. In future work, the simulation and measurement tools presented here will be used to evaluate and, eventually automatically generate, optimal antennas with other (non-circular) shapes for different environments.

Optimization of an RFID loop antenna with smart goal functions

It is very challenging to create reliable RFID systems within the vicinity of metallic environments. Most solutions for this kind of applications are accommodated with a multi antenna setup of circular loop antennas. Within this paper we will present an optimized loop antenna which is placed in a metallic tunnel. The setup with a single loop antenna has a comparable reliability with a multi antenna setup. The presented 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 paper shows some promising results for the optimized loop antenna within this typical application.

Zigbee as a means to reduce the number of blind spot incidents of a truck

Every year in Europe, about 1500 people die in traffic because they are not noticed by the truck driver. This problem could be solved by developing a wireless communication system where the truck driver and the cyclist are informed about each others presence. In this paper a test setup is presented in which the position of the cyclist is determined and displayed on a screen when being in the neighborhood of a truck. The cyclist gets an indication about notification by the truck. Because of the fast changing network, the cyclist must be added quickly to the network and the position must be updated very fast. For this reason a Zigbee communication system is used. The position of the cyclist is displayed in zones around the truck. The setup is experimentally tested and it is demonstrated that the proposed setup leads to a reliable and fast method to reduce the number of blind spot incidents.

Linear equalization filter for PMMA fiber channels

The use of PolyMethylMethAcrylate, Step Index Plastic Optical Fiber (PMMA-SI-POF) channels for high speed data communications is impeded by its intrinsic large intermodal dispersion. The resulting Inter-Symbol-Interference (ISI) makes the successful data recovery at the optical receiver a daunting task. One possible approach to mitigate the ISI problem is the use of an electrical equalization filter to be placed after the Optical-Electrical Conversion block (OEC). To serve this purpose, a 2 biquad, CMOS gm-C filter with individually tunable low and high frequency gain is presented. As the equalization should be independent of fiber length and variation prone OEC characteristics, the filters tuning range needs to be sufficiently large to accommodate for fiber lengths up to 150 m and OEC bandwidths down to 100 MHz. The presented filter consists of 2 stages; the first has a fixed bandwidth of 150 MHz and a DC gain range of 26 dB. The second stage implements 0 to 24 dB additional signal boosting in a frequency band centered at 110 MHz, which enables the overall system bandwidth to be placed at approximately 100 MHz. The filter was used in a fully integrated, adaptive linear feedforward equalizer implemented in a 3.3 V supply, 0.35 μm CMOS process, targetting a 150 Mbps link.

Electronic dispersion correction circuit for Plastic Optical Fiber channels

Large core, Step-Index Plastic Optical Fiber (SIPOF) is a cheap alternative to existing copper network interconnects. The low material, production and installation costs come at the price of large values of attenuation and intermodal dispersion for fibers reaching beyond 50 m. For a 150 m, 150 Mb/s link, the dispersion induced optical power penalty can be as large as 13 dB. Combined with a nominal attenuation of up to 0.22 dB/m, the signal drops under the sensitivity levels of current POF receivers. A non-intrusive solution to this problem could be receiver side electronic equalization. To ease integration with existing receivers and keep power consumption low, an analog implementation is proposed. As the optical channel does not behave like any low order electrical system, the design of an electrical filter with a fully matched response could result in a very complex system. Therefore, the performance of a general, low order, electrical filter was evaluated and compared with the theoretical case of full equalization in high level simulations. Based on these results, a 2 biquad adaptive gm-C filter was designed and implemented in a blind adaptive equalizer. The filter allows for individually tunable low and high frequency gain, enabling equalization of a 150 Mb/s link for fiber lengths ranging from 1 to 150 m.