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University of Twente Publications (47,767 recursos)
University of Twente Repository provides publications of UT scientific staff, in many cases full text and publicly available.

Group = KEUR

Mostrando recursos 1 - 20 de 6,726

1. A 500 MHz – 2.7 GHz 8-Path weaver downconverter with harmonic rejection and embedded filtering - Struiksma, Remko E.; Klumperink, Eric A.M.; Nauta, Bram; Vliet, Frank E. van
This paper describes a combination of a Weaver mixer and an N-path filter for a superheterodyne receiver with a reconfigurable frequency plan. It uses an N-path topology driven with two different frequencies, effectively realizing a frequency shift together with band-pass filtering. To reduce transfers via harmonics other than the fundamental, a harmonic rejection scheme is used. A 28nm FDSOI CMOS implementation with 30 dB harmonic rejection and an out-of-band IIP3 of >20dBm is demonstrated.

2. Analysis of the signal transfer and folding in N-Path filters with a series inductance - Duipmans, Lammert; Struiksma, Remko; Klumperink, Eric A.M.; Nauta, Bram; Vliet, Frank E. van
N-path filters exploiting switched-series-R-C networks can realize high-Q blocking-tolerant band-pass filters. Moreover, their center frequency is flexibly programmable by a digital clock. Unfortunately, the time variant nature of these circuits also results in unwanted signal folding. This paper proves analytically that folding can be reduced and band pass filtering can be improved by adding an inductance in series with the switched-R-C network. In contrast, a shunt capacitor degrades band-pass filter performance. The interaction between the reactive series impedance and the switched capacitors of an N-path filter complicates analysis due to memory effects associated with reactive components. Assuming $N$ identical signal...

3. Analog/rf solutions enabling compact full-duplex radios - Debaillie, B.; Broek, D.J. van den; Lavín, C.; Liempd, B. van; Klumperink, E.A.M.; Palacios, C.; Craninckx, J.; Nauta, B.; Pärssinen, A.
In-band full-duplex sets challenging requirements for wireless communication radios, in particular their capability to prevent receiver sensitivity degradation due to self-interference (transmit signals leaking into its own receiver). Previously published self-interference rejection designs require bulky components and/or antenna structures. This paper addresses this form-factor issue. First, compact radio transceiver feasibility bottlenecks are identified analytically, and tradeoff equations in function of link budget parameters are presented. These derivations indicate that the main bottlenecks can be resolved by increasing the isolation in analog/RF. Therefore, two design ideas are proposed, which provide attractive analog/RF-isolation and allow integration in compact radios. The first design...

4. Constructive Technology Assessment and the Methodology of Insertion - Rip, Arie; Robinson, Douglas K.R.
Constructive Technology Assessment (CTA) started out (in the Netherlands in the late 1980s) as an attempt to broaden technology developments by including more aspects and more actors, and has been further positioned as a way to overcome the institutionalised division of labour between promotion and control of technology. For newly emerging technologies like nanotechnology, which live on promises, CTA has to address uncertain futures. It does so by analysing dynamics and emerging irreversibilities in a technology domain, identifying “endogenous futures” and creating socio-technical scenarios exploring what could happen. Such scenarios are a platform for interaction between stakeholders in strategy-articulation workshops....

5. Nano-images as hybrid monsters - Ruivenkamp, Martin; Rip, Arie
This chapter discusses the role of images in nanotechnology. Nanotechnology includes an array of scientific and engineering fields in which researchers observe and manipulate materials at or near the nanometer scale (one billionth of a meter). The very idea of visualizing nanoscale phenomena is controversial, as such phenomena are far smaller than a wavelength of light; nevertheless, nanoimages are ubiquitous in research articles, press releases, and other displays of nanoscale phenomena. This chapter shows how such images often take a hybrid form, freely combining elements of traditional scientific representation with speculative portrayals that showcase promised and imagined possibilities. Three emerging...

6. Multiplexed microfluidic device for parallel electrophysiological measurements on independent planar lipid bilayers - Prokofyev, Alexander; Stimberg, Verena; Bomer, Johan; Boer, Hans de; Berg, Albert van den; Le Gac, Séverine
Bilayer lipid membranes (BLMs) are excellent platforms to study ion channels in a functional environment, and for drug screening assays. However, conventional electrophysiological BLM approaches do not meet the requirements for high throughput experiments due to the large volumes utilized, and the extensive manual procedures involved. In that context, microfluidics is a promising format to develop new platforms for high throughput electrophysiological measurements on ion channels incorporated in BLMs.

7. Probing simultaneously membrane dynamics and protein activity in suspended bilayers in a microfluidic format - Stimberg, Verena; Bomer, Johan G.; Boer, Hans de; Berg, Albert van den; Le Gac, Séverine
Membrane dynamics affect the structure and function of ion channels, a point that deserves more attention while studying membrane proteins. One important factor in the local lipidic environment of the ion channels, is the membrane fluidity which is directly connected to the free diffusion and packing of the phospholipids. Typically, FRAP is utilized to investigate this parameter in simplified cell membrane models, and preferably supported bilayer lipid membranes (BLMs), which are more stable than their free-standing counterparts. However, supported membranes are less suitable for the incorporation of ion channels and electrophysiological monitoring of their activity than suspended ones.

8. A multivariate analysis of water quality in lake Naivasha, Kenya - Ndungu, J.N.; Augustijn, D.C.M.; Hulscher, S.J.M.H.; Fulanda, B.; Kitaka, N.; Mathooko, J.M.
Water quality information in aquatic ecosystems is crucial in setting up guidelines for resource management. This study explores the water quality status and pollution sources in Lake Naivasha, Kenya. Analysis of water quality parameters at seven sampling sites was carried out from water samples collected weekly from January to June and biweekly from July to November in 2011. Principal component analysis (PCA) and cluster analysis (CA) were used to analyse the dataset. Principal component analysis showed that four principal components (PCA-1 to PCA-4) explained 94.2% of the water quality variability. PCA-1 and PCA-2 bi-plot suggested that turbidity in the lake...

9. Design of wave breaking experiments and A-Posteriori Simulations - Kurnia, R.; Groesen, E. van
This report presents results of 30 wave breaking experiments conducted in the long wave tank of TU Delft, Department of Maritime and Transport Technology (6,7 and 10-12 March 2014), together with simulations performed before the experiment to determine the required wave maker motion and a-posteriori simulations that use a measured time trace as inux for calculation further downstream.

10. High order Hamiltonian water wave models with wave-breaking mechanism - Kurnia, R.; Groesen, E. van
Based on the Hamiltonian formulation of water waves, using Hamiltonian consistent modelling methods, we derive higher order Hamiltonian equations by Taylor expansions of the potential and the vertical velocity around the still water level. The polynomial expansion in wave height is mixed with pseudo-differential operators that preserve the exact dispersion relation. The consistent approximate equations have inherited the Hamiltonian structure and give exact conservation of the approximate energy. In order to deal with breaking waves, we extend the eddy-viscosity model of Kennedy et al. (2000) to be applicable for fully dispersive equations. As breaking trigger mechanism we use a kinematic...

11. Microfluidics for electronic paper-like displays - Shui, Lingling; Hayes, Robert A.; Jin, Mingliang; Zhang, Xiao; Bai, Pengfei; Berg, Albert van den; Zhou, Guofu
Displays are ubiquitous in modern life, and there is a growing need to develop active, full color, video-rate reflective displays that perform well in high-light conditions. The core of display technology is to generate or manipulate light in the visible wavelength. Colored fluids or fluids with particles can be used to tune the light intensity (greyscale) or wavelength (colors) of reflective displays by different actuation methods. Microfluidic technology plays an increasing role in fluidic manipulation in microscale devices used in display areas. In this article, we will review microfluidic technologies based on different actuation methods used for display applications: pressure-driven...

12. Phaseguides as tunable passive microvalves for liquid routing in complex microfluidic networks - Yildirim, Ender; Trietsch, Sebastiaan J.; Joore, Jos; Berg, Albert van den; Hankemeier, Thomas; Vulto, Paul
A microfluidic passive valving platform is introduced that has full control over the stability of each valve. The concept is based on phaseguides, which are small ridges at the bottom of a channel acting as pinning barriers. It is shown that the angle between the phaseguide and the channel sidewall is a measure of the stability of the phaseguide. The relationship between the phaseguide-wall angle and the stability is characterized numerically, analytically and experimentally. Liquid routing is enabled by using multiple phaseguide with different stability values. This is demonstrated by filling complex chamber matrices. As an ultimate demonstration of control,...

13. Make it spin: individual trapping of sperm for analysis and recovery using micro-contact printing - Frimat, J.-P.; Bronkhorst, M.; Wagenaar, B. de; Bomer, J.G.; Heijden, F. van der; Berg, A. van den; Segerink, L.I.
In this article, we describe the development of a high throughput platform to spatially manipulate viable sperm for motility measurements and recovery of the best single sperm for fertilization purposes. Micro-contact printing was used to pattern islands of adhesive proteins (fibronectin) separated by sperm repellent species (Pluronic acid F-127) on commercially available polystyrene substrates. Following washing, arrays of viable single sperm were captured onto the islands demonstrating for the first time that sperm can be trapped by micro-contact printing with patterning efficiency of 90% while retaining 100% viability. These were then subjected to motility analysis whilst remaining spatially confined to...

14. Modeling and simulations of the amplitude-frequency response of transmission line type resonators filled with lossy dielectric fluids - Hoog, N.A.; Mayer, M.J.J.; Miedema, H.; Olthuis, W.; Leferink, F.B.J.; Berg, A. van den
Stub resonators can be used to assess the dielectric properties of fluids. The resonance frequencies, determined from the amplitude versus frequency (AF) response of such resonators, are mainly determined by the permittivity of the fluid while damping arises from dielectric losses. Even though this methodology has been extensively reported in the literature, without almost any exception these studies refer to (near) ideal behavior regarding for example, geometry and negligibly low conductivity of the fluid studied. Online stub resonator-based sensors (i.e., flow-through) in use for industrial applications, however, quite often suffer from high dielectric losses, non-ideal material choice of the conductors...

15. Effect of pH waves on capacitive charging in microfluidic flow channels - Roelofs, Susan H.; Soestbergen, Michiel van; Odijk, Mathieu; Eijkel, Jan C.T.; Berg, Albert van den
Novel energy-efficient desalination techniques, such as capacitive deionization (CDI), are a key element for the future of the fresh water supply, which is increasingly under stress due to the ever-growing world population and ongoing climate changes. CDI is a desalination technique where salt ions are removed from a flow channel by the application of an electrical potential difference across this channel and are stored in electrical double layers. The aim of this work is to visualize and explain the charging process of CDI using a new microfluidic approach. Namely, we implement the geometry of CDI on a chip and visualize...

16. Pressure-driven ballistic Kelvin's water dropper for energy harvesting - Xie, Yanbo; Boer, Hans L. de; Sprenkels, Ad J.; Berg, Albert van den; Eijkel, Jan C.T.
In this paper, we introduce a microfluidic-based self-excited energy conversion system inspired by Kelvin's water dropper but driven by inertia instead of gravity. Two micro water jets are produced by forcing water through two micropores by overpressure. The jets break up into microdroplets which are inductively charged by electrostatic gates. The droplets land on metal targets which are gradually charged up to high voltages. Targets and electrostatic gates are cross-connected in a way similar to Kelvin's water dropper. Application of pressure as driving force instead of gravity as in Kelvin's dropper allows for much higher energy densities. To prevent overcharging...

17. Software defined radio receivers exploiting noise cancelling: a tutorial review - Klumperink, Eric; Nauta, Bram
Traditional radio receivers were narrowband and dedicated to a single frequency band exploiting LC tanks, whereas software defined radios target a flexibly programmable frequency. The broadband noise cancelling circuit technique has proven useful to achieve this target, as it breaks the traditional trade-off between low noise and broadband impedance matching. Different variants exist, with noise cancellation in the voltage or current domain, either at RF or after frequency translation to baseband. This article reviews the development of the noise cancelling technique and its role in inductorless interference robust software defined radio receivers.

18. A 110mW, 0.04mm2, 11GS/s 9-bit interleaved DAC in 28nm FDSOI with >50dB SFDR across Nyquist - Olieman, Erik; Annema, Anne-Johan; Nauta, Bram
A 9-bit 11GS/s current-steering (CS) digital-to-analog converter (DAC) is designed in 28nm FDSOI. The DAC uses two-times interleaving to suppress the effects of the main error mechanisms of CS DACs while its clock timing can be tuned by the back gates bias voltage of the multiplexer transistors. The DAC achieves higher than 50dB SFDR and less than -50dBc IM3 over Nyquist at a sampling rate of 11GS/s, occupying only 0.04mm2 and consuming 110mW from a single 1V supply.

19. An ultra low energy FSK receiver with in-band interference robustness exploiting a 3-Phase chirped LO - Dutta, Ramen; Zee, Ronan van der; Kokkeler, André B.J.; Bentum, Mark J.; Klumperink, Eric; Nauta, Bram
An ultra-low-energy Binary Frequency Shift Keying (BFSK) receiver is proposed. It features improved in-band interference tolerance by chirping the transmission frequency. To reduce the receiver power consumption, a novel three-phase passive mixer along with a three stage digitally controlled ring oscillator is proposed, while still allowing quadrature detection. A mixer-first direct conversion receiver architecture moves the required gain to lowest frequency and lowest bandwidth to reduce power consumption. A low power flip-flop based BFSK demodulator is proposed that reduces the baseband power further. The receiver is designed and fabricated in a 65 nm complementary metal-oxide-semiconductor process. It consumes 219 μW...

20. Effective coastal boundary conditions for tsunami wave run-up over sloping bathymetry - Kristina, W.; Bokhove, O.; Groesen, E.W.C. van
An effective boundary condition (EBC) is introduced as a novel technique for predicting tsunami wave run-up along the coast, and offshore wave reflections. Numerical modeling of tsunami propagation in the coastal zone has been a daunting task, since high accuracy is needed to capture aspects of wave propagation in the shallower areas. For example, there are complicated interactions between incoming and reflected waves due to the bathymetry and intrinsically nonlinear phenomena of wave propagation. If a fixed wall boundary condition is used at a certain shallow depth contour, the reflection properties can be unrealistic. To alleviate this, we explore a...

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