Oddvar Søråsen

Microscale electrostatic energy harvester using internal impacts

This article presents a new concept for electrostatic energy harvesting devices that increase output power under displacement limited inertial mass motion at sufficiently large acceleration amplitudes. The concept is illustrated by two demonstrated electrostatic energy harvesting prototypes in the same die dimension: a reference device with end-stops and an impact device with movable end-stops functioning as slave transducers. Both devices are analyzed and characterized in small and large excitation regimes. We found that significant additional energy from the internal impact force can be harvested by the slave transducer. The impact device gives much higher, up to a factor of 3.7, total output power than the reference device at the same high-acceleration amplitude. The bandwidth of the response to frequency sweeps is beneficially enlarged by up to a factor of 20 by the nonlinear mechanisms of the impact device.

A variable word-width content addressable memory for fast string matching

This work deals with off-boding some time critical parts in the process of performing intrusion detection from software to reconfigurable hardware (FPGA). Signatures of known attacks must typically be compared to high speed network traffic, and string matching becomes a bottleneck Content Addressable Memories (CAMS) are known to be fast string matchers, but offer little flexibility. For that purpose a Variable Word- Width CAM for fast string matching has been designed and implemented in an FPGA A typical feature for this CAM is that the length of each word is independent from the others, in contrast to common CAMs where all words have the same length. The design has been functionally tested on a development board for a CAM of size 1822 bytes (128 words). This design processes 8 bits per clock cycle and has a reported maximum clock speed of 100 MHL This gives a thoughput of 800 Mbit/s.

Wireless Sensor Networks for Off-shore Oil and Gas Installations

Underwater development and production of oil and gas needs networked sensors and actuators to monitor the production process, to either prevent or detect oil and gas leakage or to enhance the production flow and yield of the wells. Sensors used today are large and expensive, both to manufacture and to deploy sub-sea. We suggest sensor networks created by inexpensive and small wireless sensor nodes in a redundant multi-hop topology. Preliminary designs and results are shown for two such nodes using ultrasound and infrared light as wireless commutation.

Wideband excitation of an electrostatic vibration energy harvester with power-extracting end-stops

An electrostatic energy harvester with two-stage transduction is investigated for enhancement of bandwidth and dynamic range. The harvester includes a primary proof mass with two main transducers and end-stops for the proof mass functioning as secondary transducers. In the small acceleration regime, the power is primarily obtained from the main transducers. In the high acceleration regime, the mass impacts the end-stops and actuates the secondary transducers, generating additional output power. The device is designed and fabricated using the SOIMUMPs process and has a total active area of 4 5 mm 2 . Under wideband acceleration at high levels, the experimental results show that the total output power increases to about twice the output power of the main transducers, while the 3 dB-bandwidth is enlarged by a factor of 6.7 compared to the linear-response bandwidth at low levels. In comparison with a reference device made with the same die dimensions, the two-stage device improves output power instead of saturating when the maximum mass displacements of both devices reach the same limit. Measurement of output power demonstrates that the device with the transducing end-stops give an efficiency of 23.6%, while this value is 14.1% for the reference device with the conventional end-stops, at an acceleration spectral density of SaD 19:2 10 3 g 2 Hz 1 . The efficiency is improved about by 9.5% in the impact regime. (Some figures may appear in colour only in the online journal)

Characterization and Modeling of Nonlinearities in In-Plane Gap Closing Electrostatic Energy Harvester

This paper investigates in detail a micro scale in-plane gap closing electrostatic energy harvester with strong nonlinearities in squeeze-film damping, electromechanical coupling, and impacts on end-stops. The device shows softening response on increasing the bias voltage and saturation behavior on impact with end-stops at high enough acceleration amplitude. We demonstrate that a lumped model can adequately describe the measured nonlinear behavior for a range of operating conditions with nonlinear fluid damping force and impact force included in the model. While modeling capacitances, a finite-element method (FEM) is used to analyze fringing field effects on the capacitance variation for gap closing electrodes. The nominal capacitance is obtained from FEM analysis, for a range of under-cut values in the fabrication process treated as a free parameter in the model. The device modeled for linear and nonlinear squeeze-film damping force highlights the importance of nonlinear damping force to understand the device behavior over the range of operating conditions. With the compliant end-stops treated as spring-dampers and with proper choice of end-stop damping-coefficient, the model successfully captures the end-stop nonlinearities for a particular operating point and reproduces the dynamic pull-in phenomena at 8 V bias, and rms acceleration 0.6 g , as observed in the experiments. Thus, the model described in this paper reproduces the subtle nonlinear effects dominating the dynamics of an in-plane gap closing electrostatic energy harvester.

A high performance data driven packet-switching network for detector data readout and event building in an LHC inner detector experiment

The paper describes a concept for implementing a combined data collecting, control and trigger system for Large Hadron Collider experiments at CERN. The system, called SWIPP, is based on a flexible interconnection of fast crossbar switches, interfaced to various transducer, storage and computer nodes by Protocol Engines. This infrastructure offers a common framework for various kinds of information, being programmable and scalable in an easy way. It endeavours to solve the extremely demanding instrumentation needs of these experiments in particle physics. >

Evaluation of SU8 photo polymer for microwave packaging applications

Epoxy based photo polymer - SU8 is evaluated as microwave packaging material for packaging of Radio Frequency Micro Electro Mechanical Systems (RFMEMS). Standard and Slotted Coplanar Waveguide transmission lines are chosen as test vehicles. Transmission lines of lengths up to 10mm are formed on ST-Cut Quartz substrates. The fabricated transmission lines are subjected to wafer level packaging. The measured S-parameter data shows a significant difference prior to and after packaging. Further, the effects due to the packaging are modeled using lumped components and the measured data are validated with simulations in Advanced Design System. The measured and simulated data agree favorably with each other, for both before and after packaging.

High aspect ratio lateral electrode nano gap rectangular plate micro-resonator novel process

This work describes a simple process method for obtaining sub-micron and high aspect ratio lateral electrode gaps for rectangular plate micro-resonators and the resulting advantages. The structures are built of [110] single crystal silicon substrate by KOH etching, a novel combined two step oxidation processes and post-process electrostatic actuation method is proposed to achieve nearly smooth vertical walls and 100nm electrode resonator gaps. This is below the fabrication limitation given by conventional optical lithography. The process sequence and simulation results for submicron electrostatic gaps are presented.

Low-power Sensor Interfacing and MEMS for Wireless Sensor Networks

The need for low-power and miniaturized electronics is prominent in wireless sensor network (WSN) nodes—small sensor nodes containing sensors, signal processing electronics, and a radio link. The demand for long battery life of such systems, especially if used in biomedical implants or in autonomous installations, forces the development of new circuit topologies optimized for this application area. Through a combination of efficient circuit topologies and intelligent control systems, keeping the radio idle when signal transmission is not needed, the radio link budget may be dramatically reduced. However, due to the demands for continuously monitoring of the sensor in many critical applications, the sensor front-end, analog-to-digital converter (ADC), and the control logic handling the radio up/down-link may not be turned off, and for systems with long intervals between transmissions, the energy consumed by these parts will have a large impact on battery life. In this chapter, we focus on Frequency ∆Σ Modulator (FDSM) based ADCs because of their suitability in WSN applications. Using FDSM based converters, both sensors with analog and frequency modulated outputs may be conveniently interfaced and converted to a digital representation with very modest energy requirements. Microelectromechanical systems (MEMS) integrated on-die with CMOS circuitry enables very compact WSN nodes. MEMS structures are used for realizing a wide range of sensors, and form vital components in radio circuits, such as mixers, filters, mixer-filters, delay lines, varactors, inductors, and oscillators. In this chapter a MEMS oscillator will be used to replace Voltage Controlled Oscillators (VCOs). The MEMS oscillator is made using a post-CMOS process. Before the die is packaged, the CMOS die is etched in order to release the MEMS structures. The top metal layers in the CMOS process acts as a mask to prevent CMOS circuitry from being etched in addition to be used as a mask to define the MEMS structures. The resulting MEMS structure consists of a metal-dielectric stack where its thickness is determined by the number of metal layers available in the CMOS process. In this chapter, we will use a deep sub-micron CMOS process to illustrate the possibility for combining MEMS and CMOS in a small die area. The MEMS oscillator is to be used as a frontend for the FDSM. FDSM andMEMS integrated in CMOS is a versatile platform for miniaturized low-power WSN nodes. In this chapter we illustrate the benefits of this approach using simulation, showing the potential for efficient miniaturized solutions. 1

Improving a network security system by recongurable hardware

Improving network security systems by using recon gurable hardware is an important research eld since the speed of the Internet is increasing. In this work, we have implemented stateful TCP inspection in a Field Programmable Gate Array (EPGA) to help alleviating a bottleneck in network intrusion detection systems (NIDSs). Todays software based NIDSs (eg. Snort) show inef ciency and even fail to perform for the faster Internet. Implementing stateful TCP inspection in EPGA aims at achieving an ef cient, fast NIDS in general, - Snort speci cally. By dividing a TCP connection into two ows, one to the Sewer and another to the Client, monitoring of the TCP ow can be sped up. A TCP ow deals not only with a single packet but also with multiple packets over the network. Reassembly of those packets is one of the main tusks that the TCP ow monitoring should accomplish. By parallelizing the tasks of reassembling TCP packets on the Sewer and the Client on an EPGA, the performance of stateful TCP inspection can be greatly improved. The performance obtained by this work is a throughput of 2.75 Gbps.