Choosing threshold levels for electromagnetic hazards

The concept of electromagnetic hazards is today frequently taken to refer to direct effects on biological tissue. However, several other effects are possible and have been the subject of a substantial amount of research in earlier decades. One of these is the hazard of ignition of flammable gas/vapor mixtures due to sparks resulting from radiofrequency currents flowing in metallic structures. Although the physics of the mechanism linking power from a radio transmitter to ignition of a flammable mixture is relatively straightforward, compared with bioelectromagnetic effects, there are many uncertainties and poorly-understood steps in the process, leading to considerable difficulties for committees tasked with setting safety limits. The author has experience of such committees, notably that concerned with British Standard 6656, and the way in which these difficulties were addressed may give useful insights for the regulation of other hazards

Design considerations of MIMO antennas for mobile phones

YesThe paper presents a new modeling and design concept of antennas using polar- ization diversity of 2 £ 2 and 3 £ 3 Multiple Input Multiple Outputs (MIMO) system that is proposed for future mobile handsets. The channel capacity is investigated and discussed over Raleigh fading channel and compared to a linear/planner antenna array MIMO channel. The capacity is also discussed over three types of power azimuth spectrums. The results are compared to the constraints capacity limits in which the maximum capacity observed

Bandwidth Enhancement of Balanced Folded Loop Antenna Design for Mobile Handsets Using Genetic Algorithms

YesIn this paper, a simple folded loop antenna (FLA) for handsets with relatively wide- band impedance, designed and optimized using genetic algorithms (GA). The FLA dimensions were optimized and evaluated using GA in collaboration with NEC-2 source code. Configuration of optimal FLA with excellent VSWR covering entirely the required GSM1800 frequency bands was found within the maximum generation. A prototype antenna was tested to verify and validate the GA-optimized antenna structure. The measured data have shown good agreement with predicted ones. Moreover, the capabilities of GA are shown as an e±cient optimisation tool for selecting globally optimal parameters to be used in simulations with an electromagnetic antenna design code, seeking convergence to designated specifications

Design of controlled RF switch for beam steering antenna array

YesA printed dipole antenna integrated with a duplex RF switch used for mobile base station antenna beam steering is presented. A coplanar waveguide to coplanar strip transition was adopted to feed the printed dipole. A novel RF switch circuit, used to control the RF signal fed to the dipole antenna and placed directly before the dipole, was proposed. Simulated and measured data for the CWP-to-CPS balun as well as the measured performance of the RF switch are shown. It has demonstrated the switch capability to control the beam in the design of beam steering antenna array for mobile base station applications

Evaluating the REF2014 Results in Art and Design

In the UK, periodic assessment of research in universities has taken place since 1986. The most recent took place during 2014 with the results being published at the end of the year. This evaluation is concerned with art and design though all disciplines were included in the assessment. The method used for assessing research quality is outlined and the results summarised. The lessons drawn from the evaluation by REF2014 are detailed. A number of issues are identified and discussed. These include the staff selected for submission, the method of evaluation, and a cost-benefit analysis of the process

Compact superconducting dual-log spiral resonator with high Q-factor and low power dependence

A new dual-log spiral geometry is proposed for microstrip resonators, offering substantial advantages in performance and size reduction at subgigahertz frequencies when realized in superconducting materials. The spiral is logarithmic in line spacing and width such that the width of the spiral line increases smoothly with the increase of the current density, reaching its maximum where the current density is maximum (in its center for 2 resonators). Preliminary results of such a logarithmic ten-turn (2 5 turns) spiral, realized with double-sided YBCO thin film, showed a -factor seven times higher than that of a single ten-turn uniform spiral made of YBCO thin film and 64 times higher than a copper counterpart. The insertion loss of the YBCO dual log-spiral has a high degree of independence of the input power in comparison with a uniform Archimedian spiral, increasing by only 2.5% for a 30-dBm increase of the input power, compared with nearly 31% for the uniform spiral. A simple approximate method, developed for prediction of the resonant frequency of the new resonators, shows a good agreement with the test results

Performance Evaluation of The Split Transmission in Multihop Wireless Networks

Multimedia applications in multihop wireless networks have great market potential. Multiple channels and multiple radios are commonly used to explore multimedia transmissions in multihop wireless networks. Split transmission allows multiple channels attached to different radios to be used simultaneously, and so to achieve a fundamentally improved transmission capacity. The goal of this paper is to present a theoretical background to justify the improved performance of split transmission. We theoretically study and derive formulae to study the improvement in worst-case delay, average throughput and average delay jitter when using split transmission as opposed to non-split transmission. We believe that this is the first attempt to consider split transmission in theory

A Simple Algorithm for Sidelobe Cancellation in a Partially Adaptive Linear Array

The far-field lobes of the edge elements of a uniformly excited linear array are nearly equal in width to the sidelobes of the array itself, and hence the edge elements are ideal for cancellation of specific sidelobes of the pattern. This supports the concept of partial adaptivity using only the edge elements. This technique is suitable for real-time implementation because only the edge elements require direct control whereas the inner elements are controlled by PROM’s. Other advantages are that the nulls produced specifically by control of the edge elements are deep and wide. Also the main beam gain is not much affected by the sidelobe cancellation