9,827 research outputs found
Radio Frequency (RF) Time-of-Flight Ranging for Wireless Sensor Networks
No full textPosition information of nodes within Wireless Sensor Networks (WSNs) is often a requirement in order to make use of the data recorded by the sensors themselves. On deployment the nodes normally have no prior knowledge of their position and thus a locationing mechanism is required to determine their positions. In this paper, we describe a method to determine the point-to-point range between sensor nodes as part of the locationing process. A two-way Time-of-Flight (TOF) ranging scheme is presented using narrow-band RF. The frequency difference between the transceivers involved with the point-to-point measurement is used to obtain a sub-clock TOF phase offset measurement in order to achieve high resolution TOF measurements. The ranging algorithm has been developed and prototyped on a TI CC2430 development kit with no additional hardware being required. Performance results have been obtained for the line-of-sight (LOS), non-line-of-sight (NLOS) and indoor condition. Accuracy is typically better than 7.0m RMS for the LOS condition over 250.0m and 15.8m RMS for the NLOS condition over 120.0m using a one-hundred sample average. Indoor accuracy is measured to 1.7m RMS using a 1000 sample average over 8.0m. Ranging error is linear and does not increase with increased transmitter-receiver distance. Our TOA ranging scheme demonstrates a novel system where resolution and accuracy are time dependent in comparison to alternative frequency dependent methods using narrowband RF
Time-of-Flight Ranging for WSN Locationing (Project Information Sheet)
No full textTo develop a narrow-band RF-based Time-of-Flight (ToF) ranging method with sub-meter ranging resolution which can be adopted in wireless sensor networks (WSNs) for the purpose of localising sensor nodes. The use of RF will enable point-to-point ranging over larger distance (>50m) than current Ultra-wideband (UWB) based TOF systems with significantly less use of channel bandwidth
RF-MEMS switches for reconfigurable antennas
No full textThis thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Reconfigurable antennas are attractive for many military and commercial applications where it is required to have a single antenna that can be dynamically reconfigured to transmit or receive on multiple frequency bands and patterns. RF-MEMS is a promising technology that has the potential to revolutionize RF and microwave system implementation for next generation telecommunication applications. Despite the efforts of top industrial and academic labs, commercialization of RFMEMS switches has lagged expectations. These problems are connected with switch design (high actuation voltage, low restoring force, low power handling), packaging (contamination layers) and actuation control (high impact force, wear, fatique). This Thesis focuses on the design and control of a novel ohmic RF-MEMS switch specified for reconfigurable antennas applications. This new switch design focuses on the failure mechanisms restriction, the simplicity in fabrication, the power handling and consumption, as well as controllability. Finally, significant attention has been paid in the switch’s electromagnetic characteristics. Efficient switch control implies increased reliability. Towards this target three novel
control modes are presented. 1) Optimization of a tailored pulse under Taguchi’s
statistical method, which produces promising results but is also sensitive to fabrication tolerances. 2) Quantification of resistive damping control mode, which produces better results only during the pull-down phase of the switch while it is possible to be implemented successfully in very stiff devices. 3) The “Hybrid” control mode, which includes both aforementioned techniques, offering outstanding switching control, as well as immunity to fabrication tolerances, allowing an ensemble of switches rendering an antenna reconfigurable, to be used.
Another issue that has been addressed throughout this work is the design and
optimization of a reconfigurable, in pattern and frequency, three element Yagi-Uda
antenna. The optimization of the antenna’s dimensions has been accomplished through the implementation of a novel technique based on Taguchi’s method, capable of systematically searching wider areas, named as “Grid-Taguchi” method
Compact modelling in RF CMOS technology
No full textWith the continuous downscaling of complementary metal-oxide-semiconductor (CMOS) technology, the RF performance of metal-oxide-semiconductor field transistors (MOSFETs) has considerably improved over the past years. Today, the standard CMOS technology has become a popular choice for realizing radio frequency (RF) applications. The focus of the thesis is on device compact modelling methodologies in RF CMOS. Compact models oriented to integrated circuit (ICs) computer automatic design (CAD) are the key component of a process design kit (PDK) and the bridge between design houses and foundries. In this work, a novel substrate model is proposed for accurately characterizing the behaviour of RF-MOSFETs with deep n-wells (DNW). A simple test structure is presented to directly access the substrate parasitics from two-port measurements in DNWs. The most important passive device in RFIC design in CMOS is the spiral inductor. A 1-pi model with a novel substrate network is proposed to characterize the broadband loss mechanisms of spiral inductors. Based on the proposed 1-pi model, a physics-originated fully-scalable 2-pi model and model parameter extraction methodology are also presented for spiral inductors in this work. To test and verify the developed active and passive device models and model parameter extraction methods, a series of RF-MOSFETs and planar on-chip spiral inductors with different geometries manufactured by employing standard RF CMOS processes were considered. Excellent agreement between the measured and the simulated results validate the compact models and modelling technologies developed in this work
A novel design for an RF MEMS resistive switch on PCB substrate
No full textCopyright @ 2008 Stimulation Action on MEM
Self-aligned silicidation of surround gate vertical MOSFETs for low cost RF applications
No full textWe report for the first time a CMOS-compatible silicidation technology for surround-gate vertical MOSFETs. The technology uses a double spacer comprising a polysilicon spacer for the surround gate and a nitride spacer for silicidation and is successfully integrated with a Fillet Local OXidation (FILOX) process, which thereby delivers low overlap capacitance and high drive-current vertical devices. Silicided 80-nm vertical n-channel devices fabricated using 0.5-?m lithography are compared with nonsilicided devices. A source–drain (S/D) activation anneal of 30 s at 1100 ?C is shown to deliver a channel length of 80 nm, and the silicidation gives a 60% improvement in drive current in comparison with nonsilicided devices. The silicided devices exhibit a subthreshold slope (S) of 87 mV/dec and a drain-induced barrier lowering (DIBL) of 80 mV/V, compared with 86 mV/dec and 60 mV/V for nonsilicided devices. S-parameter measurements on the 80-nm vertical nMOS devices give an fT of 20 GHz, which is approximately two times higher than expected for comparable lateral MOSFETs fabricated using the same 0.5-?m lithography. Issues associated with silicidation down the pillar sidewall are investigated by reducing the activation anneal time to bring the silicided region closer to the p-n junction at the top of the pillar. In this situation, nonlinear transistor turn-on is observed in drain-on-top operation and dramatically degraded drive current in source-on-top operation. This behavior is interpreted using mixed-mode simulations, which show that a Schottky contact is formed around the perimeter of the pillar when the silicided contact penetrates too close to the top S/D junction down the side of the pillar
ISMRM Best Practices for Safety Testing of Experimental RF Hardware
No full textThis white paper was authored by the Working Group on Best Practices for Safety Testing of Experimental RF Hardware of the International Society for Magnetic Resonance in Medicine (ISMRM). Its purpose is "to assist experts in MRI scanner hardware with obtaining local research ethics approvals for radio frequency (RF) devices built at the research site". The white paper includes information on risk management and common mitigation strategies used to ensure the safety of site-built RF coils and other RF devices used on research subjects.
This record mirrors the original published on the ISMRM web site in the MR Safety Resources section (https://www.ismrm.org/mr-safety-links/)
Bipolar amplifier bias technique for robust IM3 null tracking independent of internal emitter resistance
No full textBipolar amplifiers can be biased to give a deep null in third order non-linearity, with the potential for high IP3 amplifier stages. This requires maintaining a precise voltage drop across a small resistive emitter degeneration resistance, whose value is related to kT=q. To make such a scheme practical, the bias must not only take into account the change in kT=q with temperature, but must compensate for variations in the degeneration resistance. In this paper we present a bias technique for IM3 null tracking that can take account of temperature and resistance tolerances, and is also insensitive to the value of the internal emitter resistance. Simulations using a 27 GHz BiCMOS technology indicate that the bias of an amplifier can be maintained over temperature, representative element tolerances, and mismatch such that the IP3 performance is maintained within ±9.5 dBV of the optimum null condition. The technique is applicable for a range of bipolar BiCMOS technologies and is attractive for amplifiers where high IP3 is required with moderate noise figure
The outlook on white space utilization policy in Korea: Lessons from the DTV leading countries, namely, the US, the UK, and Japan
No full textSome countries have already finished or are progressing toward a transition to Digital Television (DTV). In particular, the US and UK have conducted technical analyses of white space, and its management strategy is under review. They are also working on determining what kind of service could be used for white space. According to this trend, a special research team led by the Japanese government was formed to study DTV white spaces utilization, and its study was conducted at the end of July 2010 [1]. In Korea, a study was recently begun on Cognitive Radio (CR) that could be applied for white spaces. However, no official research is being conducted to quantify the available spaces and their management strategy depending on the service applications. In this paper, we propose an appropriate spectrum management scheme for white space in Korea considering the results of a survey, Spectrum Requirement According to DTV Transition, and an iconography review based on tentatively assigned DTV channels around three DTV pilot test areas, Uljin, Danyang, and Gangjin. --White space,DTV transition,Spectrum policy,Spectrum demand survey,Iconography review,Spectrum management
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