James A. Flint

Study of the Effects of SEU-Induced Faults on a Pipeline Protected Microprocessor

This paper presents a detailed analysis of the behavior of a novel fault-tolerant 32-bit embedded CPU as compared to a default (non-fault-tolerant) implementation of the same processor during a fault injection campaign of single and double faults. The fault-tolerant processor tested is characterized by per-cycle voting of microarchitectural and the flop-based architectural states, redundancy at the pipeline level, and a distributed voting scheme. Its fault-tolerant behavior is characterized for three different workloads from the automotive application domain. The study proposes statistical methods for both the single and dual fault injection campaigns and demonstrates the fault-tolerant capability of both processors in terms of fault latencies, the probability of fault manifestation, and the behavior of latent faults.

Insect attraction to wind turbines: does colour play a role?

The phenomenon of wildlife mortality at wind turbine installations has been generating increasing concern, both for the continued development of the wind industry and for local ecology. While an increase in aerial insectivore activity in the vicinity resulting from insect attraction to turbines remains a strong possibility, little research exists on the possible causes for such events. In this paper, the relative attraction of a selection of specific turbine colours and other hues is assessed in order to determine if turbine paint colour could be influencing insect numbers at these installations. The common turbine colours ‘pure white’ (RAL 9010) and ‘light grey’ (RAL 7035) were among those found to attract significantly more insects than other colours tested, suggesting colour may well have a role to play in potential mitigation.

Planar Electromagnetic Bandgap Structures Based on Polar Curves and Mapping Functions

A type of electromagnetic bandgap structure is described that is easily parameterized and can produce a range of square and spiral geometries. Individual electromagnetic bandgap (EBG) geometries are defined on a cell-by-cell basis in terms of their convolution factor k, which defines the extent to which the elements are interleaved and controls the coupling slot length between adjacent elements. Polar equations are used to define the slot locus which also incorporate a transformation which ensures the slot extends into the corners of the square unit cell and hence extends the maximum slot length achievable. The electromagnetic properties of the so-called polar EBG are evaluated by means of numerical simulation and measurements and dispersion diagrams are presented. Finally, the performance is compared with other similar miniaturized EBG cell geometries. It is shown that the polar EBG has better angular stability than the equivalent square patch design and is comparable in terms of performance to other low frequency EBG elements. At the same time it retains the ability to fine tune the response by adjusting k.

A biomimetic antenna in the shape of a bat's ear

This letter presents a novel antenna that physically resembles the ear of a bat. The device consists of a circular ground plane with a central monopole element. An equilateral triangular conducting plate is curved around the ground so that the base of the triangle is electrically connected to the perimeter of the circle and is of the same length. The input characteristic is similar to the monopole above ground, providing there are a sufficient number of modes in the triangular plate at the frequency of interest. Certain frequencies yield a high gain and a radiation pattern with low side lobes.

Wind turbines and bat mortality: Doppler shift profiles and ultrasonic bat-like pulse reflection from moving turbine blades

Bat mortality resulting from actual or near-collision with operational wind turbine rotors is a phenomenon that is widespread but not well understood. Because bats rely on information contained in high-frequency echoes to determine the nature and movement of a target, it is important to consider how ultrasonic pulses similar to those used by bats for echolocation may be interacting with operational turbine rotor blades. By assessing the characteristics of reflected ultrasonic echoes, moving turbine blades operating under low wind speed conditions (<6 m s(-1)) were found to produce distinct Doppler shift profiles at different angles to the rotor. Frequency shifts of up to ±700-800 Hz were produced, which may not be perceptible by some bat species. Monte Carlo simulation of bat-like sampling by echolocation revealed that over 50 rotor echoes could be required by species such as Pipistrellus pipistrellus for accurate interpretation of blade movement, which may not be achieved in the bats approach time-window. In summary, it was found that echoes returned from moving blades had features which could render them attractive to bats or which might make it difficult for the bat to accurately detect and locate blades in sufficient time to avoid a collision.

Design of a multi-band frequency reconfigurable planar monopole antenna using truncated ground plane for Wi-Fi, WLAN and WiMAX applications

Reconfigurable or switchable antennas are potential candidates for modern wireless and portable devices to operate at more than one frequency bands, polarizations and scanning radiation patterns in accordance with user requirements. This paper describes the design of multi-band frequency reconfigurable 7-shaped planar monopole antenna, employing 1.6 mm thicker FR4 as a substrate material and a truncated metal ground plane. The antenna operates in single as well as dual-band frequency modes depending on the state of the switch used. The proposed antenna operate in the dual frequency mode (Wi-Fi at 2.45 GHz and WLAN at 5.4 GHz) and single frequency mode (WiMAX at 3.5 GHz) when the optical switch is in ON and OFF states respectively. The bandwidths achieved are 20, 39 and 9.3% centered at 2.4, 3.5 and 5.4 GHz, frequencies respectively. The antenna is impedance matched (i.e. input impedance=51~54 Ω) resulting in VSWR<; 1.3 for the three frequency bands. Satisfactory gains of 1.92, 2.41 and 3.02 dBi and efficiencies of 86.5, 85 and 74.6% are attained at 2.45, 3.5 and 5.4 GHz frequencies respectively. Printed monopole reconfigured antennas are small, low profile and light-weight which can be used in portable electronics (mobile phones, iPads, PDAs and laptops) and wearable applications (safety and rescue operations). The antenna scattering and far-field parameters are evaluated using a numerical Finite Integration Technique (FIT) and Finite Element Method (FEM) employed in CST MWS and HFSS, respectively.

Efficient protection of the pipeline core for safety-critical processor-based systems

The increasing number of safety-critical commercial applications has generated a need for components with high levels of reliability. As CMOS process sizes continue to shrink, the reliability of ICs is negatively affected since they become more sensitive to transient faults. New circuit designs must take this fact into consideration, and incorporate adequate protection against the effects of transient faults. This paper presents a novel method for protecting the pipelined execution unit of an embedded processor. It is based on a self-configured architecture with hybrid redundancy that can mask single and multiple errors, which can occur on storage elements due to transient or permanent faults. This concept can be easily applied to any processing architecture of this nature with a high safety integrity level. Results from error-injection experiments are also reported that show that this design can maintain a non-interrupted and failure-free operation under single and double errors with a probability that exceeds 99.4%.

Polarisation dependent EBG surface with an inclined sheet via

This paper presents a novel polarisation dependent EBG (PDEBG) surface which makes use of sheet vias. The performance of the surface is analysed whilst varying the length, thickness and inclination of the vias. It is observed that the phase difference between the x-polarised and y-polarised component of the reflected wave can be controlled by varying these parameters. Furthermore, the surface exhibits a polarisation conversion property with potential use in a variety of antennas.

Design and SAR Analysis of Wearable Antenna on Various Parts of Human Body, Using Conventional and Artificial Ground Planes

This paper presents design and specific absorption rate analysis of a 2.4 GHz wearable patch antenna on a conventional and electromagnetic bandgap (EBG) ground planes, under normal and bent conditions. Wearable materials are used in the design of the antenna and EBG surfaces. A woven fabric (Zelt) is used as a conductive material and a 3 mm thicker Wash Cotton is used as a substrate. The dielectric constant and tangent loss of the substrate are 1.51 and 0.02 respectively. The volume of the proposed antenna is 113×96.4×3 mm3. The metamaterial surface is used as a high impedance surface which shields the body from the hazards of electromagnetic radiations to reduce the Specific Absorption Rate (SAR). For on-body analysis a three layer model (containing skin, fats and muscles) of human arm is used. Antenna employing the EBG ground plane gives safe value of SAR (i.e. 1.77W/kg 2W/kg). The efficiency of the EBG based antenna is improved from 52 to 74%, relative to the conventional counterpart. The proposed antenna can be used in wearable electronics and smart clothing.

Electro-textile based wearable patch antenna on biodegradable poly lactic acid (PLA) plastic substrate for 2.45 GHz, ISM band applications

Biodegradable polymers and plastics are environment friendly because they decrease environmental pollution, conserve resources and reduce non-recyclable waste. Poly lactic acid (PLA) is a biodegradable plant derived polymer. Their properties are improved by copolymerization, blending, plasticization, polymer alloy technology and by development of composites techniques. These polymers can be used in computers, mobile phones, housing, textiles, optical, packaging films and bags. In this paper the feasibility of 1.7 and 3 mm thicker PLA as a substrate in wearable patch antenna is investigated. For comparison patch antenna on identically thicker (1.7 and 3 mm) FR-4 substrate is also simulated under the same conditions in CST Microwave Studio. The return loss, gain, directivity and efficiency of both antennas were compared on operating frequency of 2.45GHz. The proposed antenna employing PLA substrates give return losses of -21 and -22dB, gain of 6 and 6.14 dBi, directivity of 7.58 and 7.54dBi and efficiency of 59 and 70% on 1.7and 3mm thicker substrates respectively, while reference antenna using FR4 substrates results in return losses of -19 and -19.3dB, gain of 2.7 and 3.45dBi, directivity of 7.02 and 6.92 dBi and efficiency of 35and 43% for 1.7 and 3 mm thicker FR4 substrates.