56 research outputs found

    CHARACTERIZATION AND HANDLING OF UNCERTAINTIES IN EMC/EMI MEASUREMENTS

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    Ph.DDOCTOR OF PHILOSOPH

    Wireless Low-Power Transfer for Galvanically Isolated High-Voltage Applications

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    For various applications, such as gate drivers for transistors, wireless chargers for mobile devices and cars, and isolated measurement equipment, an isolated DC power supply for electronic components is required. In this work, a new concept for an isolated power supply with insulation strength of 50 kV and power transmission of up to 60 W to supply measurement equipment with 12 or 24 V is presented. Furthermore, high overall efficiency of 82.5% at 55 W is achieved. Feasibility is demonstrated in a real application powering data acquisition electronics at high reference potential. Our new concept uses a coreless printed circuit board (PCB) transformer (15 cm × 10 cm × 4 cm and a weight of 480 g) designed for maximum efficiency via a coil layout and close proximity of adjacent coils on one PCB while reaching high isolation strength via the PCB material and potted coils. To increase efficiency, we investigated different coil geometries at different frequencies. A low-cost design consisting of two Qi charging coils mounted on one PCB is compared with our integrated PCB transformers manufactured from a four-layer PCB with ferrites applied on the outside. With this new design, high isolation voltages are possible while reaching high transformer efficiency of up to 90%. © 2022 by the authors. Licensee MDPI, Basel, Switzerland

    Increased bandwidth microstrip antennas for road tolling applications

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    This thesis provides the results of research that has been carried out in order to develop the microstrip patch antennas required by a high speed digital communication link for road traffic applications. The operating frequency is 5.8GHz. Although a single compact broad band radiating element is developed for use within the vehicle, the main focus of the research is increasing the frequency bandwidth of the antenna arrays used within the road side unit of such a system. This is achieved by investigation into radiating element design, the orientation of the radiating elements within the array and the arrays feed networks geometry. A single layer circularly polarised dual feed microstrip patch antenna is optimised for use within the array. Using a genetic algorithm to aid design of the dual feed network, the input impedance at the dual feed point is increased beyond what can normally be achieved when a tradition design process is adopted. This results in a more compact structure that allows thinner tracks to be used in the arrays feed network. These radiating elements are sequentially rotated to form the array. The traditional corporate feed network is replaced by a series feed network and the effect this has upon the performance of a two, three and four element array is investigated. The four element array is suited to a vehicle access control application; due to the complexity of the feed network an adaptation of simulated annealing is required to both generate and optimise the series feed line sections of this array. Not only does the new series feeding method result in doubling the VSWR 2:1 bandwidth of the four element array to over 10%, it also produces a more compact structure. Both mathematical modelling and experimental measurement are used to confirm the performance of these new arrays. The four element array is then sequentially rotated to form a larger sixteen element array, that adopts the same series feeding method, suitable for motorway tolling applications. This new array demonstrates a VSWR 2:1 bandwidth of 14.7% and a 3dB axial ratio bandwidth of 12.4%, an improvement factor of two over the same array using a traditional corporate feed. The side lobes of this larger array are reduced by modifying the power distribution within the series feed network. A single compact circularly polarised wide band microstrip patch antenna for use within the in-vehicle equipment is developed using an adaptation of the cavity model. The radiating patch is excited by a single feed line via a cross slot aperture. Air is used for the antenna substrate, increasing frequency bandwidth while simplifying the fabrication process hence reducing the manufacturing costs of the in-vehicle equipment. The inclusion of the wide band radiating element within the series fed four element array is also investigated. This new structure results in a VSWR 2:1 bandwidth of at least 22.8% and 3 dB axial ratio bandwidth of 17.5%, a significant improvement over traditional designs. As a result of this research papers have been published in the lEE Electronic Letters (2000), the lEE Electronic Letters (2003) and Microwave and Optical Technology Letters (2003). Papers have been accepted and presentations have been made at the Ansoft microwave workshop in London (2001) and Los Angeles (2001). This work has also contributed towards publications in the lEE Electronic Letters (2000) and in the lEE Transactions on Antenna and Propagation (2001). The antenna arrays developed during the course of this research have been used within a commercially viable traffic management system and installed at a large shopping centre. It is pleasing to note that the fruits of this research have been used in a 'real life' situation

    Electromagnetic Scattering from a Cavity in a Ground Plane: Theory and Experiment

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    The electromagnetic scattering from an arbitrarily shaped open cavity embedded in a perfectly conducting, infinite ground plane is examined. The cavity is filled with a linear, isotropic, homogeneous material. The fields in the cavity interior and above the ground plane are expressed in terms of the tangential fields on the cavity surface and aperture. A coupled set of three integral equations is developed governing the tangential fields on the aperture and cavity surface. The support of the unknown tangential fields is finite. A moment-method based algorithm to approximate the solution to the integral equations for axisymmetric geometries is developed. The unknown tangential fields are expanded using piecewise-linear functions in the elevation plane and complex exponentials in the azimuth plane. Orthogonality is exploited to reduce the size of the matrix. The algorithm yields a well-conditioned numerical solution. The solution obeys the edge condition at the aperture rim. The integral equations are uniquely solvable at frequencies where other integral equation-based techniques admit spurious solutions. Radar cross section calculations are compared to experimental measurements of full-scale physical models. Results show that an open cavity can serve as an effective radar cross section enhancement device

    The use of a Digital Image Correlation method with a low-speed camera to obtain characteristics of surface velocity and sound radiation for automotive-type panels

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    The perceived quality of a vehicle is highly influenced by the driver s experience of the vehicle interior noise. Significant research has been carried out all over the world in order to characterize structural and acoustic characteristics, to control and minimize the vibration and noise from entering or emitted to vehicles. Designers require tools to inform them whether the design changes are positive or negative in terms of the noise and vibration, and to help validate numerical finite element models of complicated structures. This research explores the use of Digital Image Correlation (DIC) equipment and methods by using a relatively inexpensive low speed camera to investigate the structural-acoustics characteristics applied to automotive-type panels, where otherwise a highly expensive and sensitive scanning laser Doppler vibrometer would be required. Experimental measurements based on Noise Path Analysis (NPA) have been carried out and theoretical and numerical predictions on sound radiation behaviour have been developed. The prediction values have been evaluated and validated with experimental measurements. Using a DIC measurement method to obtain spatially averaged surface velocities, averaged over several cycles through phase locking, the results for the sound power predictions for the selected mode shape and the resonance frequencies provided a good estimation when comparing with the experiment. For mode (1, 1), the sound power prediction was 80.9 dB while the measured one was 77.2 dB with a difference of 3.7.while the other selected modes showed a difference not more than 3.7 dB. It was within the range suggested by considering the mathematical simplification approach during the prediction development stage. To conclude, it was found that the prediction of sound power throughout the vibrating structure can provide a good accuracy by using the DIC method Therefore, it can be an alternative technique to evaluate the sound radiation for characterizing one of the structural propertie

    Physical approaches for the performance optimization and investigation of organic batteries

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    The increasing awareness of the negative impacts humanity has on the global ecosystem resulted in an ever growing demand for a more sustainable energy and material consumption over the past decades. Environmentally benign electricity generation and energy storage represent two of the key technological approaches to address this issue. In this context, organic radical batteries (ORB) and redox flow batteries (RFB) possess significant advantages as energy storage technologies due to the sustainable material basis they rely on and the performance characteristics they offer. However, while material development is continuously advancing in this research field, methods for the proper characterization and performance optimization of ORBs and RFBs still need to keep pace with this development to exploit the full potential of these technologies. This thesis, therefore, aims to contribute with a physical perspective to the investigation and optimization of these novel energy storage systems. In particular, porous electrode morphologies in ORBs and special methods to produce them are investigated. Furthermore, non-conventional cell designs for the electrochemical reactors of RFBs are investigated and their impact on the performance parameters of the RFB are explored. Finally, two methods for the reliable and accurate measurement of the electrolytes' state-of-charge as one of the most important key parameters were developed and characterized

    Satellite communication antenna technology : summer school, 1982, Technische Hogeschool Eindhoven: lectures

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    Satellite communication antenna technology : summer school, 1982, Technische Hogeschool Eindhoven: lectures

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    Indirect methods of obtaining activity and mobility of structure-borne sound sources

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    The work reported in this thesis focuses on the development of indirect methods for the experimental determination of important source parameters for structure-borne sound source characterization. In the first part of the thesis, matrix inversion methods for the determination of blocked forces are investigated. A simplified measurement procedure is proposed which offers a solution to the two major challenges to these methods, namely the acquisition of the FRF matrix and the problems associated with matrix inversion. The proposed procedure involves a free, low-mobility receiver plate which is modelled numerically. Calculated FRFs are used together with measured velocity responses to inversely determine the blocked forces. It is found that while the method has great potential in principle, in practice the accurate modelling of the receiver plate is of critical importance. In the second part of the thesis, three formulations are considered for the indirect determination of source mobility. Instead of performing measurements on the source in the free state, the source mobility is obtained from measurements made in-situ. This approach is beneficial if the source is difficult to suspend, or if it contains non-linear structural elements. The three formulations are validated numerically and experimentally. It is found that the methods can quantify source mobilities of single-contact and multi-contact sources from in-situ measurements. However, typical measurement errors, such as background noise or inaccuracies in sensor positioning, can significantly reduce the accuracy and reliability of the methods. In the final part of the thesis, the reception plate method for the determination of the power injected by a high-mobility source into a low-mobility receiver is reviewed, and a source substitution method proposed as a development. The substitution method circumvents problems that may arise when the reception plate method is applied to coupled walls and floors. A special focus of investigation is on the calibration of the receiver structure. It is found that the calibration can be performed with shaker or hammer, and that an average calibration factor may be used. The source substitution method thus offers a potential alternative to the reception plate method, for application with coupled plates
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