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- Bekers, D.J. (author) article 2022
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Bekers, D.J. (author)In this paper we revisit and generalize the Multi-Tone Sinusoidal Frequency Modulation (MTSFM), which has been used in the past decade for various Radar and Sonar applications including optimal transmit waveform design, modelling non-linear frequency modulation, high-duty cycle sensors . In its original form, the MTSFM describes a phase...conference paper 2022
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Marinovic, T. (author), de Villiers, D.I.L. (author), Bekers, D.J. (author), Johansson, M.N. (author), Stjernman, A. (author), Maaskant, R. (author), Vandenbosch, G.A.E. (author)A new method is proposed to analyze antenna arrays including mutual coupling (MC), which is based on the concept of multiple scattering, and relates to the iterative Jacobi and Gauss–Seidel methods. The method employs sampled far-field data of an isolated element, which can be obtained by any full-wave simulator and consists of far fields for...conference paper 2021
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van Heijningen, M. (author), Bekers, D.J. (author), Gandini, E. (author), Grooters, R. (author), Jacobs, S. (author), Bolt, R.J. (author), Monni, S. (author)TNO has a long heritage in the research and development of radio frequency (RF) and microwave technology for phased array systems, ranging from high-level system design to hardware design, including integrated circuits and antennas. Customers include the Dutch ministries, the European Union (EU) and the European Space Agency (ESA). Innovative RF...article 2019
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Bekers, D.J. (author), Jacobs, S. (author), Monni, S. (author), Bolt, R.J. (author), Fortini, D. (author), Capece, P. (author), Toso, G. (author)The article presents the design of a Ka-band synthetic aperture radar (SAR) instrument based on innovative phased-array antennas, with steering capability in azimuth and elevation. To limit the complexity and costs associated with conventional large active arrays with regular layouts, a sparse array concept is presented. The proposed approach...article 2019
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Capece, P. (author), Fortini, D. (author), Bekers, D.J. (author), Jacobs, S. (author), Monni, S. (author), Toso, G. (author)A novel sparse layout for the receiving aperture of a Ka-band spaceborne SAR has been designed. The devised array antenna layout allows reducing the number of active controls of 40%, from 10000 to 6000. The antenna is designed to steer the beam ±10° in elevation and ±2° in azimuth, and satisfies the prescribed pattern mask. In this paper, after...conference paper 2018
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Bekers, D.J. (author), Jacobs, S. (author), Bolt, R.J. (author), Monni, S. (author), Fortini, D. (author), Germani, C. (author), Capece, P. (author), Toso, G. (author)In this paper a novel sparse layout for the radiating aperture of a Ka-band spaceborne SAR is outlined. Starting from a set of typical requirements and the definition of a benchmark antenna, an approach to achieve sparsity (in terms of the number of active modules) is proposed, which reduces significantly the fill factor as compared to the...conference paper 2017
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Woelders, H. (author), de Wit, A. (author), Lourens, A. (author), Stockhofe, N. (author), Engel, B. (author), Hulsegge, I. (author), Schokker, D. (author), van Heijningen, P. (author), Vossen, S. (author), Bekers, D.J. (author), Zwamborn, A.P.M. (author)The objective of this study is to investigate possible biological effects of radiofrequency electromagnetic fields (RF-EMF) as used in modern wireless telecommunication in a wellcontrolled experimental environment using chicken embryo development as animal model. Chicken eggs were incubated under continuous experimental exposure to GSM (1.8 GHz)...article 2017
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Giodini, S. (author), Hunter, A.J. (author), Naus, H.W.L. (author), Bakker, B. (author), Bekers, D.J. (author), Ditzel, M. (author), van Vossen, R. (author), Dugelay, S. (author), Baralli, F. (author), Beckers, A.L.D. (author)Minehunting operations can benefit from the use of Autonomous Underwater Vehicles (AUVs) because these vehicles are able to acquire high-resolution images of the seabed leaving the man out of the minefield. However, because there are severe communication constraints between the AUV and the control platform, the AUV needs to be capable of...conference paper 2014
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Schiavon, G. (author), Ruggiero, A. (author), Bekers, D.J. (author), Barry, P.A. (author), Sleijfer, S. (author), Kloth, J. (author), Krestin, G.P. (author), Schöffski, P. (author), Verweij, J. (author), Mathijssen, R.H.J. (author)Purpose: Tumour response assessment to therapy is crucial in oncology. We analysed the morphology of liver metastases (LM) in gastrointestinal stromal tumour (GIST) patients to determine whether uni-dimensional measurement of lesions by Response Evaluation Criteria in Solid Tumours (RECIST), accurately reflects lesion volume. Materials and...article 2014
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Bekers, D.J. (author), van Dijk, R. (author), van Vliet, F.E. (author)The transmit and receive modules of a large phased array are often calibrated for amplitude and phase variations by an internal calibration network and an offline characterization of the complete array in an anechoic chamber. Such a solution is less obvious in view of current trends towards integration and modularity. An alternative to surpass...conference paper 2013
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Bekers, D.J. (author), Lepelaars, E.S.A.M. (author)Steel ships with a magnetic signature requirement are equipped with a degaussing system to reduce their perceptibility for magnetic influence mines. To be able to reduce the magnetic signature accurately, a proper distribution of coils over the ship is essential. Finding the best distribution of coils is a complex optimisation problem, involving...conference paper 2013
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Schiavon, G. (author), Ruggiero, A. (author), Sleijfer, S. (author), Bekers, D.J. (author), van der Holt, B. (author), Kloth, J.S.L. (author), Krestin, G.P. (author), Schoffski, P. (author), Verweij, J. (author), Mathijssen, R.H.J. (author)Background: Tumor response assessment to therapy is crucial in oncology, both in daily practice and research.We analyzed the morphology of liver metastases (LM) in gastrointestinal stromal tumors (GIST). Aims were to 1) determine whether uni-dimensional measurements of tumor lesions (according to RECIST 1.1) are accurate reflections of their...article 2012
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Bekers, D.J. (author), van Eijndhoven, S.J.L. (author)The current on a linear strip or wire solves an equation governed by a linear integro-differential operator that is the composition of the Helmholtz operator and an integral operator with a logarithmically singular displacement kernel. Investigating the spectral behaviour of this classical operator, we first consider the composition of the...article 2012
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- Bekers, D.J. (author), van Eijndhoven, S.J.L. (author) article 2012
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Schiavon, G. (author), Ruggiero, A. (author), Schoffski P., (author), van der Holt, B. (author), Bekers, D.J. (author)Background:Assessment of tumor size changes is crucial in clinical trials and patient care. We compared imatinib-induced volume changes of liver metastases (LM) from gastro-intestinal stromal tumors (GIST) to RECIST and Choi criteria and their association with overall survival (OS).Methods:LM from 84 GIST patients (training and validation set)...article 2012
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Coenen, T.J. (author), Bekers, D.J. (author), Tauritz, J.L. (author), van Vliet, F.E. (author)Waveguide structure integration in planar substrates for use in microwave components has received considerable attention in recent years. Waveguides with side walls consisting of cylindrical posts (postwall waveguides or PWWGs) are of interest, since they are compatible with standard PCB fabrication technology and exhibit low loss. In this paper...article 2011
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Coenen, T.J. (author), Bekers, D.J. (author), Tauritz, J.L. (author), van Vliet, F.E. (author), TNO Defensie en Veiligheid (author)During the past five years, dielectric and metallic post-wall waveguides (PWWGs) have been analyzed at TNO Defence, Security and Safety, using both an integral equation approach and a modal approach. The model developed focuses on TE<sub>n0</sub> modes facilitating the analysis of infinitelylong, straight PWWGs as well as finite PWWGs with...conference paper 2010
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Iacono, A. (author), Coenen, T.J. (author), Bekers, D.J. (author), Neto, A. (author), Gerini, G. (author), TNO Defensie en Veiligheid (author)Kinetic Inductance Detectors are widely accepted as receivers for Terahertz imaging. They are realized on superconductors and, exploiting the Cooper-pairs breaking by photons, they are able to sense incoming Terahertz radiation. In this paper we investigate the impact that the related absorption mechanism has on the angular dependence of the...conference paper 2010
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Bekers, D.J. (author), van Eijndhoven, S.J.L. (author), Tijhuis, A.G. (author), TNO Defensie en Veiligheid (author)To describe the behavior of a finite array, the current distribution on each of its elements is represented by a finite number of eigencurrents or modes. Subsequently, the eigencurrents of the array are expanded in terms of these element eigencurrents. For uniform linear arrays of loops and dipoles, the array-eigencurrent expansions and their...article 2009