Passive wireless tags for tongue controlled assistive technology interfaces

Tongue control with low profile, passive mouth tags is demonstrated as a human–device interface by communicating values of tongue-tag separation over a wireless link. Confusion matrices are provided to demonstrate user accuracy in targeting by tongue position. Accuracy is found to increase dramatically after short training sequences with errors falling close to 1% in magnitude with zero missed targets. The rate at which users are able to learn accurate targeting with high accuracy indicates that this is an intuitive device to operate. The significance of the work is that innovative very unobtrusive, wireless tags can be used to provide intuitive human–computer interfaces based on low cost and disposable mouth mounted technology. With the development of an appropriate reading system, control of assistive devices such as computer mice or wheelchairs could be possible for tetraplegics and others who retain fine motor control capability of their tongues. The tags contain no battery and are intended to fit directly on the hard palate, detecting tongue position in the mouth with no need for tongue piercings

Male antene: postupci smanjivanja izmjera i primjene

The paper presents research results in the field of small antennas obtained at the Department of Wireless Communications, Faculty of Electrical Engineering and Computing, University of Zagreb. A study comparing the application of several miniaturization techniques on a shorted patch antenna is presented. Single and dual band shorted patch antennas with notches and/or slot are introduced. A PIFA designed for application in mobile GSM terminals is described. The application of stacked shorted patches as array elements for a mobile communication base station as well as for electromagnetic field sensor is presented. The design of single and dual band folded monopoles is described. Prototypes of the presented antennas have been manufactured and their characteristics were verified by measurements.U radu su prikazani rezultati istraživanja u području malih antena ostvareni na Zavodu za Radiokomunikacije, Sveučilišta u Zagrebu Fakulteta elektrotehnike i računarstva. Prikazana je primjena više postupaka za smanjivanje izmjera skraćene mikrotrakaste antene. Opisane su izvedbe skraćenih mikrotrakastih antena s urezima i prorezom za rad u jednom i u dva frekvencijska područja. Prikazana je izvedba planarne invertirane F-antene (PIFA) za primjenu u ručnim terminalima sustava pokretnih komunikacija GSM. Višeslojne skraćene mikrotrakaste antene uporabljene su za izvedbu antenskog niza za baznu postaju sustava pokretnih komunikacija te kao elementi osjetila za mjerenje jakosti elektromagnetskog polja. Prikazana je izvedba savijenih monopolnih antena za rad u jednom te u dva frekvencijska pojasa. Izrađeni su prototipovi opisanih antena i mjerenjima su ispitane njihove osobine

CHANNEL MODELING FOR FIFTH GENERATION CELLULAR NETWORKS AND WIRELESS SENSOR NETWORKS

In view of exponential growth in data traffic demand, the wireless communications industry has aimed to increase the capacity of existing networks by 1000 times over the next 20 years. A combination of extreme cell densification, more bandwidth, and higher spectral efficiency is needed to support the data traffic requirements for fifth generation (5G) cellular communications. In this research, the potential improvements achieved by using three major 5G enabling technologies (i.e., small cells, millimeter-wave spectrum, and massive MIMO) in rural and urban environments are investigated. This work develops SPM and KA-based ray models to investigate the impact of geometrical parameters on terrain-based multiuser MIMO channel characteristic. Moreover, a new directional 3D channel model is developed for urban millimeter-wave (mmW) small cells. Path-loss, spatial correlation, coverage distance, and coherence length are studied in urban areas. Exploiting physical optics (PO) and geometric optics (GO) solutions, closed form expressions are derived for spatial correlation. Achievable spatial diversity is evaluated using horizontal and vertical linear arrays as well as planar 2D arrays. In another study, a versatile near-ground field prediction model is proposed to facilitate accurate wireless sensor network (WSN) simulations. Monte Carlo simulations are used to investigate the effects of antenna height, frequency of operation, polarization, and terrain dielectric and roughness properties on WSNs performance

Interference sources in congested environments and its effects in UHF-RFID systems : a review

In scenario where radio frequency identification (RFID) readers become increasingly common in hand held devices, the radios are prone to several interferences not only from external radio sources but also from the plurality of portable devices that may become more common over time. For that reason it is of interest to well understand how these radio interferences may be influencing a UHF-RFID transceiver working according to EPCglobal Class-1 Gen-2. In particular, in this paper, the combination of interference coming from the self-radio, from other radio systems, such as mobile phone or other RFID reader, is analyzed, and such effects are combined with the appearance of multiple tag antennas interfering each other. A method based on simulation using tag antenna design is presented to evaluate inter-tag interference in a variety of cases. For a better understanding analytic examples are presented to compute such interference interactions within the RFID system

Diffraction Analysis with UWB Validation for ToA Ranging in the Proximity of Human Body and Metallic Objects

The time-of-arrival (ToA)-based localization technique performs superior in line-of-sight (LoS) conditions, and its accuracy degrades drastically in proximity of micro-metals and human body, when LoS conditions are not met. This calls for modeling and formulation of Direct Path (DP) to help with mitigation of ranging error. However, the current propagation tools and models are mainly designed for telecommunication applications via focus on delay spread of wireless channel profile, whereas ToA-based localization strive for modeling of DP component. This thesis provides a mitigation to the limitation of existing propagation tools and models to computationally capture the effects of micro-metals and human body on ToA-based indoor localization. Solutions for each computational technique are validated by empirical measurements using Ultra-Wide-Band (UWB) signals. Finite- Difference-Time-Domain (FDTD) numerical method is used to estimate the ranging errors, and a combination of Uniform-Theory-of-Diffraction (UTD) ray theory and geometrical ray optics properties are utilized to model the path-loss and the ToA of the DP obstructed by micro- metals. Analytical UTD ray theory and geometrical ray optics properties are exploited to model the path-loss and the ToA of the first path obstructed by the human body for the scattering scenarios. The proposed scattering solution expanded to analytically model the path-loss and ToA of the DP obstructed by human body in angular motion for the radiation scenarios

Design of a compact, fully-autonomous 433 MHz tunable antenna for wearable wireless sensor applications

The authors present the design of a tunable 433 MHz antenna that is tailored for wearable wireless sensor applications. This study first presents a detailed analysis of the measured impedance characteristics of a chosen antenna under test (AUT) in varying proximity to a human test subject. Instead of limiting the analysis to the head and hand only, this analysis measures the AUT impedance at varying distances from 11 different body positions. A novel antenna equivalent circuit model is then developed that enables both the free-space and total on-body AUT impedance variation to be rapidly computed using a circuit simulator instead of the requirement for computationally intensive finite-element methods for example. The design and characterisation of a tunable matching network that enables AUT impedance matching for 11 different positions on the human body is then outlined. Finally, a fully-autonomous 433 MHz tunable antenna is demonstrated. The antenna occupies a small printed circuit board area of 51 × 28 mm and is printed on standard FR-4 material with the tuner completely integrated into the antenna itself. Prototype measurements show an improvement of 3.9 dB in power delivery to the antenna for a load voltage standing wave ratio of 17:1, with a maximum matching loss of 0.84 dB and S11 (−10 dB) ≥ 18 MHz for all load conditions

A new configuration of patch antenna array for rectenna array applications

The performance and advantages of microstrip patch antennas made them a field of interest for wireless power transmission applications, especially for rectenna systems where the choice of the antenna is a crucial step.  In this paper, a 5.8 GHz circularly polarized patch antenna has been designed and fabricated, then mounted by using 4 elements to achieve an antenna array to enhance the captured power to be converted by the rectifier circuit. The antenna array is well matched at 5.8 GHz in terms of reflection coefficient and has a directivity of 11dB and a gain of 6 dB. Results have been confirmed by fabrication

Measured adaptive matching performance of a MIMO terminal with user effects

Absorption and impedance mismatch due to the proximity of a user as well as certain propagation channel characteristics can severely degrade the multiple-input multiple-output (MIMO) performance of multi-antenna terminals in real usage scenarios. In this context, we investigated the potential of adaptive impedance matching (AIM) to mitigate performance degradation from these effects based on channel measurements involving a terminal prototype in three user scenarios and two propagation environments. First, optimal AIM state for the terminal in a given user-channel setup was found by post-processing the measured channels. The optimal state was then experimentally verified with two Maury Microwave mechanical tuners. The results show that by employing AIM instead of 50Ω termination, the average capacity is increased by up to 25%. Moreover, the observed capacity gains can be partly explained by physical mechanisms underlying the propagation conditions. Furthermore, the achieved gains with real tuners are only marginally affected by the tuners’ actual insertion losses, estimated to be 0.1-0.7 dB. Therefore, we conclude that AIM can be a viable solution to enhance MIMO terminal performance