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Leicht J.,Albert Ludwigs University of Freiburg | Maurath D.,Albert Ludwigs University of Freiburg | Manoli Y.,Albert Ludwigs University of Freiburg | Manoli Y.,HSG IMIT Institute of Micromachining and Information Technology
European Solid-State Circuits Conference | Year: 2012

This paper presents an efficient autonomous micro energy harvesting interface optimized for high-resistive vibration-driven electromagnetic energy transducers. A novel active voltage doubler and an energy processing scheme with adaptive maximum power point tracking (MPPT) is implemented. The interface enables wide voltage range harvesting for amplitudes between 0.44 V and 4.15V. Harvesting with tracking efficiencies of up to 93% and total efficiencies of up to 72% is enabled. In order to supply energy harvesting applications such as low power wireless sensor nodes a programmable voltage stabilization is implemented. The prototype chip is fabricated in a 0.35 μm CMOS process and is self-supplied needing no start-up help. © 2012 IEEE. Source


Mohamed S.A.S.,Albert Ludwigs University of Freiburg | Manoli Y.,Albert Ludwigs University of Freiburg | Manoli Y.,HSG IMIT Institute of Micromachining and Information Technology
IEEE Transactions on Circuits and Systems I: Regular Papers | Year: 2013

A 402-MHz fully differential RF front-end was designed and implemented using 0.13 μ m CMOS process. This design was targeted for low-power and low-cost direct conversion applications such as short-range radio in biomedical devices. This RF front-end consists of a differential CG-CS LNA with a positive-or negative-feedback technique and a frequency doubler subharmonic quadrature passive mixer. The subharmonic conversion passive mixer driven by current input signals (from a transconductor) and loaded with low impedance is implemented to minimize the LO self-mixing dc-offset and introduces a high linearity. The front-end was implemented on a 0.13 μ m CMOS process and occupies 380 μ m × \330 μ m active chip area, which is approximately 50% of that of the conventional front-end. The RF front-end achieves 31 dB conversion gain, 13.6 dB noise figure (NF) and an in-band IIP3 of 3 dBm. The design consumes 2.25 mA from a 1.2 V power supply. © 2004-2012 IEEE. Source


Hoffmann D.,HSG IMIT Institute of Micromachining and Information Technology | Folkmer B.,HSG IMIT Institute of Micromachining and Information Technology | Manoli Y.,HSG IMIT Institute of Micromachining and Information Technology | Manoli Y.,Albert Ludwigs University of Freiburg
Journal of Micromechanics and Microengineering | Year: 2011

This paper investigates triangular electrode structures for electrostatic energy-harvesting devices. By analysis of the electrode geometry, we identified the angle α, which is half the angle defined by the two equal sides of the isosceles triangle, to be an important design parameter. Moreover, triangular electrodes provide a larger capacitance change per unit displacement and also a larger total capacitance change than area-overlap and gap-closing designs. Fabricated devices were characterized using two different circuit configurations. Our results show a nonlinear frequency response (softening behaviour) due to the nonlinear capacitance characteristic of the triangular electrodes. However, the nonlinear capacitance characteristic allows tuning the resonance frequency of the device. We also observed that a bias voltage as low as 8 V allows effective operation of the energy-harvesting device. Finally, we demonstrate successful charging of a 20 νF energy storage capacitor to a practical voltage level of 3.5 V. The harvested energy was applied to a low power transmission module which successfully transmitted a data communication protocol. © 2011 IOP Publishing Ltd. Source


Becker P.,HSG IMIT Institute of Micromachining and Information Technology | Hymon E.,HSG IMIT Institute of Micromachining and Information Technology | Folkmer B.,HSG IMIT Institute of Micromachining and Information Technology | Manoli Y.,HSG IMIT Institute of Micromachining and Information Technology | Manoli Y.,Albert Ludwigs University of Freiburg
Sensors and Actuators, A: Physical | Year: 2013

A new vibration driven energy harvesting device with an additional synchronized switching interface for optimizing the power transfer from the energy harvester to a storage element is presented. The new type of piezoelectric energy transducer consists of 2 piezoelectric coupled generator structures. One of these structures acts as main generator. The other structure acts as injection generator, which provides the energy for an energy injection process. Both structures are realized on the same substrate and are therefore exposed to the same mechanical excitation. The transducer uses a four-point-bending principle. Both ends of the piezoelectric beam are pivot-mounted on the housing. Thus a uniform stress distribution over the whole generator structure is achieved. A novel interface circuitry, based on the initial energy injection described by Lallart et al. [1], is added to the system. It enables a harvesting process that is almost independent of the load and allows an almost ideal energy storage process. The results of parameter studies for an optimal generator design as well as measurement results obtained with the direct initial energy injection circuitry are presented and discussed in the presentation. The results show that an efficiency benefit by a factor of 3, compared to standard devices can be achieved by the presented device. © 2013 Elsevier B.V. All rights reserved. Source


Northemann T.,Albert Ludwigs University of Freiburg | Maurer M.,Albert Ludwigs University of Freiburg | Rombach S.,Albert Ludwigs University of Freiburg | Buhmann A.,Albert Ludwigs University of Freiburg | And 2 more authors.
Sensors and Actuators, A: Physical | Year: 2010

This paper demonstrates a micro-electro-mechanical gyroscope system with extensive use of sigma-delta (ΣΔ) modulation in both, primary and secondary modes. Both control schemes are implemented digitally on a field programmable gate array (FPGA). The primary loop has a bandpass ΣΔ digital-to-analog converter (DAC) driving the primary mass into resonance using a two-level driver. With this strategy of replacing the discrete DAC of the primary oscillation control with a bandpass ΣΔ-DAC, the analog circuit complexity is enormously reduced. The Coriolis rate signal is converted into a bit stream with a new excess loop delay (ELD) compensated micro-electro-mechanical ΣΔ modulator (ΣΔM) incorporating the gyroscope in the loop with a second-order electrical bandpass filter (BPF). To investigate the ELD effect, this electro-mechanical ΣΔM is implemented on the FPGA emulating continuous-time (CT) behavior. Measurements show stable modulators, with an ELD of nearly one clock period of the sampled system, achieving in-band noise (IBN) below -60 dBFS. The full-scale (FS) is measured to 1019°/s. This paper demonstrates that the stability of ΣΔ modulators with large ELD can be ensured with the new ELD compensation technique. © 2010 Elsevier B.V. All rights reserved. Source

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