Analysis of distortion in pulse modulation converters for switching radio frequency power amplifiers

High-efficiency linear radio frequency (RF) power amplifiers are needed for today’s wireless communication systems. Switch mode techniques have the potential for high efficiency but require a pulse drive signal. The generation of pulse width modulated signals and pulse position modulated signals by sigma delta modulators can introduce unwanted spectral components. Third order and image components are the dominant distortions generated in the pulse position modulation circuit. The authors identify the cause of distortion and mathematically quantify its amplitude and frequency. In a single carrier environment, an increase in offset frequency increases the unwanted spectral components. Calculations, simulations and measurements show that offsets less than 1% of the carrier frequency are required to keep unwanted components 40 dB below the signal level. Simulations and measurements show that the effect on a multichannel orthogonal frequency division multiplexing (OFDM) system is less detrimental. Nonetheless, unacceptable noise increases of up to 20 dB are observed in odd harmonic channels when the transmission is not centred on the nominal carrier frequency

Analysing Transportation Data with Open Source Big Data Analytic Tools

Big data analytics allows a vast amount of structured and unstructured data to be effectively processed so that correlations, hidden patterns, and other useful information can be mined from the data. Several open source big data analytic tools that can perform tasks such as dimensionality reduction, feature extraction, transformation, optimization, are now available. One interesting area where such tools can provide effective solutions is transportation. Big data analytics can be used to efficiently manage transport infrastructure assets such as roads, airports, bus stations or ports. In this paper an overview of two open source big data analytic tools is first provided followed by a simple demonstration of application of these tools on transport dataset

A digital up-conversion architecture for future high efficiency wireless base stations

Over the past few years, there has been a growing need for wireless communications with higher data rates and ubiquitous coverage, and these must be achieved at reduced cost and with a lower carbon footprint. This evolution in wireless demand places a big burden on transmitter architectures. The need for higher efficiency has stimulated research into the potential replacement of current linear power amplifiers (PAs) by switch mode power amplifiers (SMPAs) at cellular frequencies. The radio frequency (RF) PA currently accounts for a significant part of the cost, and most of the power requirements of a typical wireless base station. This research is focused on the modulation and up-conversion circuits for generating the SMPA drive signals. The switched (‘on’/‘off’) nature of the amplifier drive signal creates an opportunity for an all-digital solution removing traditional analog components such as the digital to analog converters, reconstruction filters, quadrature modulator and local oscillators. Digital signal processing techniques used for signal modulation are extended to digital up-conversion to generate suitable drive signals for the SMPA. In this thesis, a sigma-delta (ΣΔ) based technique is used to embed a complex modulation scheme such as OFDM into a single ‘on’-‘off’ bit stream

Applicability of Federated Learning for Securing Critical Energy Infrastructures

Energy grids are becoming more intelligent due to the use of a vast array of technologies, including the Internet of Things and Intelligent Systems. These Critical Energy Infrastructures, which are essentially cyber-physical systems, are particularly vulnerable to cyber threats. Machine Learning (ML) techniques have been increasingly used in security applications, and the energy domain is no exception. One approach, in particular, Federated Learning (FL), employs a distributed architecture and has potential in security applications, as it counters the issue of having a centralized data warehouse. In this work, a review of FL and its applications in security and privacy are presented. Moreover, a demonstration case involving a simulated model of FL for enhancing the security of systems is implemented and discussed. This demonstration case has provided added insight into potential issues and challenges as well as mitigation strategies

A framework for safer driving in Mauritius

According to the National Transport Authority (NTA), there were 493,081 registered vehicles in Mauritius in April 2016, which represents a 1.4% annual increase compared to 2015. Despite the sensitization campaigns and the series of measures setup by the Minister of Public Infrastructure and Land Transport, the number of road accidents continues to rise. The three main elements that contribute to accidents are: road infrastructure, vehicle and driver. The driver has the highest contribution in collisions. If the driver is given the right information (e.g. driving behaviour, accident-prone areas and vehicle status) at the right time, he/she can make better driving decisions and react promptly to critical situations. This paper proposes a framework for safer driving in Mauritius that uses an on-board car diagnostic module (OBDII) to collect data such as vehicle average speed, engine revolution and acceleration. This module relays the data to a cloud environment where an adaptive algorithm analyses the data and predicts driver behaviour in real-time. Based on driving behaviour, mobile alerts can be sent to the driver in the form of messages, voice commands or beeps. A survey was also carried out to evaluate the acceptance rate of such a framework by people of different age groups in Mauritius

Guiana Shield diamonds, the sub-cratonic lithosphere, and kimberlite emplacement in the upper crust.

The origin of diamonds from Guyana have remained an enigma despite being mined for nearly 150 years within the Guiana Shield. These gemstones are an undescribed diamond suite within an understudied portion of the Amazonian Craton. Our study confirms they are likely eroding as paleo-placers from Roraima Supergroup rocks, but may have been primarily derived from older ultramafic rocks (≥ 2 Ga) with a high H2O/CO2 volatile budget. These ancient diamonds also contain inclusions that preserve high Cr, Al, Mg, and low Ca, suggesting a harzburgitic paragenesis. Forsterite with elevated Mn, and chromite with low Fe3+/Fe2+ ratios suggest metasomatic alteration within low oxygen fugacity conditions (log ƒO2 (ΔFMQ) -1.6±1.1). Raman thermobarometry suggests entrapment at 5 – 7 GPa within cratonic roots. Low OH active infrared absorbances indicate low ppm H2O contents of forsterite inclusions, from which we were able to estimate high viscosities of 1023.7±2.1 Pa∙s within the cratonic root which incidentally resists delamination through geologic time. We applied similar mineralogical and spectroscopic techniques to diamonds from the Prairie Creek lamproite in Arkansas, USA. Coesite and forsterite inclusions record entrapment conditions of 4.8±0.5 GPa, typical of cratonic settings. However, Arkansas diamonds preserve brown body colors and one example of purple luminescence suggesting vacancy clusters and a distorted cubic lattice. In a highly viscous and turbulent upper mantle of an edge-driven convection cell, as inferred for Arkansas lamproite magma genesis, diamonds may be subjected to extreme forces which distort the atomic lattice. Finally we conducted high temperature (300 – 900 °C) and cold seal experiments at 100-200 MPa on hypabyssal kimberlite from the Jericho kimberlite (Northwest Territories, Canada) to examine sub-solidus reactions that occur syn- to post- emplacement. We observe that olivine in the presence of calcite is unstable and monticellite is precipitated, within the span of hours, suggesting at least rapid syn-emplacement This decarbonation reaction is directly proportional to temperature and indirectly proportional to available fluid CO2, where +12 wt.% CO2 increases calcite stability by 100 °C. Additionally, calcite preservation in hypabyssal kimberlite provides an observational constraint that diamond grade has not been diminished by post-emplacement conditions

Sigma Delta Digital Drive Signals for Switchmode Power Amplifiers

A novel all-digital approach to generate a pulse train to drive switch-mode power amplifiers is proposed. Sigma-delta (ΣΔ) techniques are used to shape time quantisation noise away from the band of interest. The proposed architecture promises greater than 10-dB improvement in adjacent channel power over an existing scheme. The key contribution is to quantise in the polar domain while performing the ΣΔ filtering in the Cartesian domain

The 9 Mile Deposit of the Barama-Mazaruni Greenstone Belt of the Guiana Shield: geochemistry, geochronology and regional significance

ABSTRACT: The granitoid and greenstone-hosted 9 Mile Deposit, located in the Paleoproterozoic Barama-Mazaruni Greenstone Belt of the Guiana Shield, is one of a series of gold deposits within the NW-SE trending Makapa-Kuribrong Shear Zone (MKSZ), which extends from Venezuela, through Guyana, and French Guiana. The 9 Mile Deposit is underlain by the upper section of a shallowly-dipping meta-rhyolite rock, which was intruded by a host granodiorite and subsequently intruded by of a series of mafic dykes. Auriferous quartz veins are associated with the NE-SW thrust which was crosscut by a steep E-W shear zone, at least 12 km in length. Field relationships and lithogeochemical data suggest that the granodiorite was crustally derived and emplaced in a volcanic arc or syn- to late-collisional setting. U-Pb (SHRIMP II) dating of zircons indicates the granodiorite intruded at approximately 2.15, Ga suggesting it is a local representative of a regional suite of syn- to late-tectonic granitoid plutons emplaced during the main phase of Trans-Amazonian Orogeny

Performance analysis of dedicated short range communications technology and overview of the practicability for developing countries

Vehicular communication is a widely researched field and aims at developing technologies that may complement systems such as the advanced driver assistance systems. It is therefore important to analyse and infer on the performance of vehicular technologies for different driving and on-road criteria. This study considers the dedicated short range communications technology and more precisely the IEEE 802.11p standard for a performance and practicability analysis. There is also the proposal of a new classification scheme for typical driving conditions, which includes the main categories of Emergency and Safety scenarios while sub-classifications of Critical and Preventive Safety also exist. The scheme is used to build up scenarios as well as related equations relevant to developing countries for practical network simulation. The results obtained indicate that the relative speed of nodes is a determining factor in the overall performance and effectiveness of wireless vehicular communication systems. Moreover, delay values of low order were observed while an effective communication range of about 800 m was calculated for highway scenarios. The research thus indicates suitability of the system for an active use in collision avoidance even though independent factors such as climatic conditions and driver behaviour may affect its effectiveness in critical situations