Search results for "radio frequency"
showing 10 items of 118 documents
An over-the-distance wireless battery charger based on RF energy harvesting
2017
An RF powered receiver silicon IC (integrated circuit) for RF energy harvesting is presented as wireless battery charger. This includes an RF-to-DC energy converter specifically designed with a sensitivity of -18.8 dBm and an energy conversion efficiency of â¼45% at 900 MHz with a transmitting power of 0.5 W in free space. Experimental results concerned with remotely battery charging using a complete prototype working in realistic scenarios will be shown.
Experimental Assessment of the Backoff Behavior of Commercial IEEE 802.11b Network Cards
2007
It has been observed that different IEEE 802.11 commercial cards produced by different vendors experience different performance, either when accessing alone the channel, as well as when competing against each other. These differences persist also when thorough measurement methodologies (such as RF shielding, laptop rotation, etc) are applied, and alignment of the environmental factors (same laptop models, traffic generators, etc) is carried out. This paper provides an extensive experimental characterization of the backoff operation of six commercial NIC cards. It suggests a relevant methodological approach, namely a repeatable, well defined, set of experiments, for such a characterization. …
Analysis of bias-shift effects in free-running and injection-locked negative resistance oscillators
2012
In this paper, the interaction between DC and RF in quasi-sinusoidal free-running and injection-locked oscillators is addressed. To account for and illustrate in a user-friendly manner the bias-shift related effects stemming from such interaction, a frequency-domain method of analysis has been developed for a rather wide class of negative-resistance circuits. Grounding on a first-approximation exact perturbation-refined approach, it permits computationally efficient simulation of the oscillator behavior directly in terms of the DC and RF signals evolutions (dynamical complex envelopes). In fact, it allows the investigation of both steady-state and transient operation of the shifting-bias dr…
An efficient cluster-based outdoor user positioning using LTE and WLAN signal strengths
2015
In this paper we propose a novel cluster-based RF fingerprinting method for outdoor user-equipment (UE) positioning using both LTE and WLAN signals. It uses a simple cost effective agglomerative hierarchical clustering with Davies-Bouldin criterion to select the optimal cluster number. The positioning method does not require training signature formation prior to UE position estimation phase. It is capable of reducing the search space for clustering operation by using LTE cell-ID searching criteria. This enables the method to estimate UE positioning in short time with less computational expense. To validate the cluster-based positioning real-time field measurements were collected using readi…
Design of a configurable multispectral imaging system based on an AOTF.
2011
In this paper, we present a configurable multispectral imaging system based on an acousto-optic tunable filter (AOTF). Typically, AOTFs are used to filter a single wavelength at a time, but thanks to the use of a versatile sweeping frequency generator implemented with a direct digital synthesizer, the imager may capture a configurable spectral range. Experimental results show a good spectral and imaging response of the system for spectral bandwidth up to a 50 nm.
An evaluation of exposure metrics in an epidemiologic study on radio and television broadcast transmitters and the risk of childhood leukemia.
2009
Electric field strength values calculated by wave propagation modeling were applied as an exposure metric in a case–control study conducted in Germany to investigate a possible association between radio frequency electromagnetic fields (RF-EMF) emitted from television and radio broadcast transmitters and the risk of childhood leukemia. To validate this approach it was examined at 850 measurement sites whether calculated RF-EMF are an improvement to an exposure proxy based on distance from the place of residence to a transmitter. Further, the agreement between measured and calculated RF-EMF was explored. For dichotomization at the 90% quantiles of the exposure distributions it was found that…
Construction and commissioning of the S-Band high gradient RF laboratory at IFIC
2018
An S-band High-Gradient (HG) Radio Frequency (RF) laboratory is under construction and commissioning at IFIC. The purpose of the laboratory is to perform investigations of high-gradient phenomena and to develop normal-conducting RF technology, with special focus on RF systems for hadron-therapy. The layout of the facility is derived from the scheme of the Xbox-3 test facility at CERN [1] and uses medium peak-power (7.5 MW) and high repetition rate (400 Hz) klystrons, whose RF output is combined to drive two testing slots to the required power. The design and construction of the various components of the system started in 2016 and has been completed. The installation and commissioning of the…
A Battery-Free Smart Sensor Powered with RF Energy
2018
The development of Internet of Things (IoT) infrastructure and applications is stimulating advanced and innovative ideas and solutions, some of which are pushing the limits of state-of-the-art technology. The increasing demand for Wireless Sensor Network (WSN) that must be capable of collecting and sharing data wirelessly while often positioned in places hard to reach and service, motivates engineers to look for innovative energy harvesting and wireless power transfer solutions to implement battery-free sensor nodes. Due to the pervasiveness of RF (Radio Frequency) energy, RF harvesting that can reach out-of-sight places could be a key technology to wirelessly power IoT sensor devices, whic…
Carotid intima-media thickness measurement through semi-automated detection software and analysis of vascular walls
2013
AIM: The aim of the present study was to compare the semi-automatic measurement of carotid intima thickness (RFQIMT - Esaote, Italy), with the conventional method. METHODS: We enrolle 81 patients, mean age 46 years ±15, with no history of cardio-cerebrovascular events and we assessed the traditional cardiovascular risk factors. We examined the IMT of the common carotid artery with manual and RFQIMT method (based on the "Radio Frequency" signal), according to the ASE protocol. RESULTS: Semi-automatic measurement was on average lower than manual measurement (617 μm ±191 vs. 676 μm ± 222) with a statistically significant difference (P<0.01). In agreement with manual measurements, the values of…
RF fingerprinting for user locationing in LTE/WLAN networks
2016
Location based applications and services have become popular in many wireless communication devices. This thesis study presents a performance evaluation of Radio Frequency (RF) fingerprinting framework in heterogeneous Long Term Evolution (LTE) and Wireless Local Area Networks (WLAN) using Minimization of Drive Testing (MDT) measurements which allow automated construction of extensive RF fingerprint training databases. Utilization of MDT data could create additional opportunities for service provider and application developers. Typical RF fingerprint consist of radio measurements from multiple LTE transceiver stations and WLAN access points. Regardless environmental conditions, received sig…