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The application of digital signal generation for a Radar Wind Profiler (RWP) utilising Frequency Modulated Continuous Wave (FMCW) operation is described, and the progress of the design to Technology Readiness Level 3 (TRL 3) is demonstrated. The technology and the methods for the TRL assessment are described, and results of the TRL assessment are presented. Conclusion and outlook complete this contribution.

Approaches to the geolocation of radio emitters typically involves the down-conversion, digitisation and subsequent signal processing of signals impinging on an antenna array. For geolocation using angle-of-arrival (AoA), a variety of different super-resolution algorithms have been proposed. Although these vary in performance and assumptions, they often present a significant computational burden, requiring the determination of covariance matrices, subsequent eigen-decomposition and analysis. This has a significant impact on ultimate power consumption. In this paper we consider the AoA accuracy of an approach using a low-power array based on steerable sum/difference beamforming. We evaluate its use and accuracy in an application for the identification of Global Positioning System (GPS) jammers in vehicles. It is shown that this relatively simple approach performs well when the signal to noise ratio is sufficiently high.

Models for the scattering of leaves is a key input into the current ITU-R recommendation P.833-9 for attenuation in vegetation. This paper examines the variability of scattering from leaves due to uncertainties in various parameters including leaf size, shape, curvature, inhomogeneity and moisture content. The resulting scattering amplitudes have been determined using numerical methods at frequencies of 1.9 and 26 GHz. The modelling assumptions made in current literature, backed up by measurements are reasonable up to around 10 GHz. However, at 20 GHz and beyond it is shown that some of these assumptions begin to breakdown.

Clinics with limited resources rely on paper patient records because they are easy to use, reliable, and can be supported by the clinics' financial and technical resources. Electronic health record (EHR) systems provide benefits in patient information management and reporting; however, they often require financial and technical resources that exceed those available to the clinics. This paper hypothesizes that limited-resource clinics could successfully install and sustain a patient-record automation system if it did not require resources beyond the reach of those clinics—if such a system was available. Because no system was found, the piClinic Console was developed to test this hypothesis. The piClinic Console is a Raspberry-Pi-based, patient-record automation system that provides essential patient-record automation functions and runs on hardware that costs less than $300 USD per clinic. This paper describes the features that provide the most benefit to the clinics and that run on a low-cost system as determined through end-user observation, participatory design, and iterative user testing. Preliminary testing shows that the piClinic Console can provide immediate benefits to clinic information processing and can prepare the clinic for a smoother transition to more complete EHR system when the resources to sustain one become available. The piClinic Console system is in its early stages of field testing and this paper describes the design and development process, the results of performance and user testing, and the plans for future research and development.

This experience report describes how two technical communication professors from Mercer University use focused, independent-study courses to help students advance beyond the general coverage of the technical communication curriculum to gain additional expertise in specific areas of technical communication. Specifically, we focus on the usability curriculum and how it is enhanced with such independent studies. We describe our experience with several substantive projects including work with the US Department of Homeland Security in the basic course and independent studies with Go Baby Go, visual-acuity simulations, and the development of a patient-information console. Each of these projects has provided undergraduate research opportunities and enhanced usability experiences for our students.

Unlike AM and PM systems, FM systems do not necessarily require the use of a dual I/Q receiver for unambiguous phase measurement. In this paper we describe this phenomenon in detail and work out the conditions when single-channel phase measurements can be used for the reliable measurement of the phase and the Doppler frequency of targets in FMCW radars systems. The developed theory is applied to surveillance and automotive radar systems to determine the velocity bounds for the unambiguous measurement of phase. The influence of phase noise in the same context is discussed. Results of coherent averaging on the data acquired using a single-channel radar system are presented to validate the theory.

In this work we present a unified Brownian motion-based model for the dispersion in the RF spectrum of oscillators due to the phase and frequency noise processes. A novel analysis of the spectral dispersion due to random-walk frequency noise will be presented that shows the possibility of the existence of satellite peaks around the mainlobe of the RF spectrum, along with time-varying spectral broadening. Fourier Transform based models will be used for the even-order phase noise process, and fractional calculus based models will be used for the odd-order flicker phase and frequency processes. The generalised Gaussian function (GGF) is shown to be an appropriate model for the RF autocorrelation function in all cases.

A novel source localization approach suitable for urban environments is proposed. The reliability against noise and other practical issues are investigated via simulation. A fingerprint database of transmitter and receiver candidate locations is obtained using an efficient ray launching simulator developed in earlier work. Following a pre-described path, a UAV (unmanned aerial vehicle) equipped with a radio receiver is simulated to generate time series of observations such as signal strength and angle-of-arrival for all possible transmitter candidate locations. The localisation algorithm uses an approach based on the DFT (discrete Fourier transform) and dynamic time warping (DTW). Using the fingerprint database and the measured time-series the best matching transmitter location is found. The algorithm is found to be robust to significant measurement errors and also to signification deviations in the actual path flown by the UAV.

Mercer University's Department of Technical Communication has continuously moved away from established currents to create new ones that aid in making learning most effective. This paper presents three approaches to continuous innovation: innovations in teaching freshman writing as a general education course located in engineering, improving teaming strategies through strategic metacommunication, and incorporating open-source software development methods and tools into the curriculum.

The performance of GPS (Global Positioning System) in densely built urban areas is greatly undermined due to multipath propagation. Many attempt alternative means for urban navigation, of which the ‘fingerprinting’ method has drawn much attention recently. However, the labor of site surveys and a constantly changing environment prevents ‘fingerprinting’ from being an eificient solution. Therefore, we propose a propagation model which is used to obtain location fingerprints with the aid of modern computers thanks to their growing processing power. At the heart of the technique is the use of a ray-launching model from which a database is generated containing propagation parameters such as received signal strength, time of arrival and angle of arrival as a function of source and receiver location. These are then mapped with physical locations using an artificial neural network. Besides, a sequence based tracking tool is proposed to assist navigation with minimal communication required between mobile device and database. This paper details the generation of a database for real world geometries read from OpenStreetMap and the development of a localisation algorithm.

Best practices provide convenient, but general, guidelines for authoring web content; however, as general guidelines, they cannot possibly provide the best advice for every context. Testing is required to know if their application works in a specific context. However, testing web content is challenging, especially content that does not support the funnel-shaped interactions typically found in commerce-oriented web sites. This paper presents the case of an experiment that tested how varying two common best practices for web content— content minimalism and visual navigational affordances—affected software developers' perceptions and task performance. Applying these best practices improved some metrics as expected, but also reduced or had no measurable effect on others. The experience from this case study revealed opportunities for innovation in web-content authoring: (1) describing best practices to include the contexts in which they are most effective and the factors they might improve, (2) developing methods for modeling audience requirements and goals as they relate to the effective use of information concepts and visual design, and (3) improving the tools and methods used to measure web content and integrate such measurements into the authoring process.

In many contemporary electronic systems, phase noise sets the bound on the achievable performance. Radar systems are no exception, with the actual radar signals carrying significant amounts of phase noise due to the high transmit frequencies. In coherent radars, some of the phase noise sidebands on the received signal are cancelled due to mixing in the receiver. The sampling clock used to sample the intermediate frequency (IF) signals also introduces phase noise/jitter. This paper focuses on the contribution of the sampling clock's phase noise to the overall phase noise in the sampled signal in coherent homodyne FMCW radar systems. We develop a model relating the phase noise in the sampled signal to the phase noise in the radar signals and the jitter in the sampling clock. We apply our analysis to example FMCW radar systems. The derived model can be used to work out the phase noise requirement on the sampling clock for a given phase noise level in radar signals.

The localisation of interference sources in radio systems is a long standing problem. This topic has been recently seen considerable interest in the context of jammers used to deny GNSS (Global Navigation Satellite Systems) reception on the ground. Such jammers are used (illegally) as privacy protection devices or more seriously to defeat tracking systems in order to commit crime. The growing reliance on GNSS systems such as GPS (Global Positioning System) means that there is also potential for considerably more dire consequences. Critical infrastructure such as telecommunications and electrical power systems can often be reliant upon GNSS for timing. In this paper we present a novel approach to source localisation based on a technique of radio “fingerprinting”. The key objective is to exploit knowledge of the radio propagation environment so as to determine the location of a radio source from as few measurements as possible. At the heart of the technique is the use of a ray-tracing model from which a database is generated containing propagation parameters such as received signal strength and angle of arrival as a function of source and receiver location. These are then used as constraints against which measured data can be inverted to yield the source location. This paper details the planned approach and progress made towards the development of a suitable ray-tracing method and discusses the generation of a database and inversion methods.

Phase noise in radar transmitters is known to raise the noise floor around large targets, making impossible the detection & tracking of small targets nearby. This paper presents phase-noise modelling techniques, with a focus on homodyne FMCW radars, to accurately predict the level of phase noise expected in the radar display. Phase noise models of the sub-systems inside a typical radar are presented. We also discuss the cancellation of phase noise in coherent radar systems for short-ranges and analyse the situation for longer ranges. Practical measurements from a millimetre-wave radar system are presented to validate the theoretical modelling.

The electromagnetic environment of the Earth was recently explored with networks of radio receivers which are distributed over spatial scales from ∼1×1–10×10 km⁁2 (Mezentsev and Fullekrug, JGR, 2013, Fullekrug et al., SGeo, 2013). These networks were operated in an interferometric configuration to measure the ground and sky waves of 100 kHz radio waves from radio transmitters and lightning discharges. The key parameter for the interferometric signal processing is the frequency dependent slowness of the radio waves within the Earth's atmosphere with respect to the speed of light in vacuum. Here we extend this interferometric signal processing into the Very-Low Frequency (VLF) range to actually measure the slowness of radio waves from submarine communication transmitters operating around ∼20 kHz. The measured values are in good agreement with previously reported results. However, a more detailed analysis shows that the remaining residuals have a significant information content which enables an application of VLF radio tomography. Possible interpretations of the observed distortions of the radio wavefront will be discussed in light of the compelling measurements.

One of the most significant factors affecting signals propagating through the electrically neutral lower atmosphere such as troposphere is the atmospheric refractivity. Atmospheric refractivity from water vapour introduces path delay error for signals propagating through this environment. This paper provides an insight into understanding the effects and variability of atmospheric refractivity from water vapour on the path delay. A two dimensional ray tracing algorithm is developed and implemented to incorporate different sensor data to measure the propagation path delay in the troposphere. Statistical analysis has been performed to show the relative dependence and relation between the atmospheric refractivity and path delay. Furthermore path delay comparison of yearly and monthly analysis of the data has been observed.

The demand for wireless internet access continues to grow. A large number of services, irrespective of their application, are now moving to internet protocol. Furthermore there is growing expectation that these be accessible on the move which places huge demand on the main subscriber networks. Networks based on IEEE 802.22 operating in white space spectrum have been put forward as a means for easing the load. This paper builds on our previous work which has constructed a highly detailed white space geolocation database for the UK. Using the database a simulation study was performed to determine the potential data throughput of a television white space system network. In this paper we will present results to indicate how the throughput of such systems varies as function of the availability threshold.

Software developers use application-programming interface (API) documentation to learn how to use the features of software libraries. How quickly software developers learn to use a library's features determines how quickly they can apply those features in a software application. Recent studies have shown that API documentation is, unfortunately, not always as helpful to software developers as they need it to be. This paper studies the prototype of a tool and a method that are being developed to help technical writers identify the elements of API reference documentation that help software developers complete programming tasks. The tool and method described in this paper use a remote user-assessment platform, which enables researchers and technical writers to study the effect that document design variations have on a large and diverse audience. Such an approach can help technical writers identify new best practices for writing effective API documentation.

High-resolution numerical weather models require fine-scale (1–5 km) measurements of moisture fields over large areas (>20,000 km2). Existing techniques such as GPS are not able to meet these requirements. This paper discusses the feasibility of a novel method for measuring atmospheric refractivity by the opportunistic reception and processing of digital radio and television signals. This technique is step towards the realization of a wide-area water vapor sensor network made possible by the widespread availability of digital broadcast signals. This paper presents the background and some preliminary results.

White space radio networks have achieved acceptance in principal by radio regulators across the world. The challenges associated with accurately sensing the availability of the channel without knowing the details of the current shadowing environment have lead to a tendency toward requiring a geo-location database approach for determining available bands as was required by Ofcom [1]. This provides regulators with a central point of control from which they can ensure primary users are protected. However to provide the initial database a reliable and verifiable dataset for an entire country is required, at a high resolution (100m cells is recommended in the UK [1]). In this paper such a model, based on the Parabolic Equation Model, is presented and the results of field trials to confirm the model validity are discussed.

Availability of television white space is of interest for developing new data networks which operate between licensed users. The practical sensing and computational modelling of this band has been the focus of study in this and a preceding paper. In this paper a high spatial resolution was used to look at the areas that a single channel was available in moderately rough terrain in the UK. The size of areas which shared available frequencies was found to be small and potential problems with spot measurements were highlighted. The practical validation of the software model with a measurement campaign has been started, the early results of this show the model to be reasonably accurate in exposed areas with little building but at portable equipment heights in streets the model shows significant variation from measured results.

TV white space is a general term for the geographical redundancies in the TV broadcast bands. The re-use of TV white space is of current interest due to the change to digital transmission in many parts of the world. This has led to the biggest re-structuring of the TV bands since their creation. The bands represent a prime section of spectrum, which currently has some geographical white space. This paper attempts to quantify the number of bands available in the south-west of the UK where digital switch over is now complete. It is shown that, in high and flat terrain, there is little spectrum free. This suggests that limiting access to this spectrum to large scale protocols, such as IEEE 802.22, would be inefficient in the UK. In areas of more complex terrain the number of bands increases significantly allowing short-range, local links.

Technical writers who want to be more involved in the earlier stages of software product development must often find ways to demonstrate how their skills can benefit the initial design process. This case study describes how the application of technical communication skills and tools helped improve the usability and clarity of a new application program interface (API) by performing a text analysis of the API elements. The case study presents the theory upon which this approach is grounded and describes how the theory was applied to analyze a specific API. The paper concludes with a review of how this analysis method could be transferred to other projects and how the tools used in this analysis can be applied to benefit the design, development, and documentation processes of APIs.

The large number of millimetre and microwave terrestrial links that are in operation has lead to the belief that it may be possible to estimate two-dimensional rainfall rate fields. This paper outlines a reconstruction algorithm that can be used to estimate the rainfall field from a number of measurements of path attenuation on terrestrial links. In this paper we adopt a different approach to the regular-ization of this inverse problem. The main focus of the paper is a description of the retrieval algorithm which is demonstrated through simulation. The approach has been shown to be robust and relatively insensitive to errors and quantisation in the link measurements.

A TEM half-horn antenna has been designed and constructed for the detection impulsive noise. The particular application of interest is the recording of partial discharge and/or sferic radiation in a 400 kV electricity transmission substation. The characteristics and performance of the half-horn are presented. Laboratory verification of the antenna's utility for the detection partial discharge has been carried out using a partial discharge simulator.

A laboratory test to assess the impact of impulsive noise on the performance of WLAN equipment is described. The test is put in the context of a larger programme of work to assess the performance and reliability of wireless equipment subject to partial discharge noise in high voltage electricity supply substations. The character of partial discharge and WLAN technology are briefly reviewed. The laboratory test methodology is reported and some preliminary results are presented. A related forthcoming field-trial for tests of WLAN equipment in a 275/400 kV air-insulated substation is briefly described.

A study to assess the impact of partial discharge on the performance of ZigBee equipment in high voltage electricity supply substations is described. The character of partial discharge and ZigBee technology are both briefly reviewed. A field trial system developed for deployment in a 400 kV air insulted substation is described in detail and some preliminary proof-of-system results are presented.

For communication systems operating at EHF and SHF frequencies, propagation impairments caused by meteorological phenomena (such as cloud, rain, etc.) become significant. As a result, there is considerable interest in developing fade mitigation techniques. The test and development of these techniques requires simulation tools, particularly attenuation time-series generators. We present a method for the generation of attenuation time series using estimates of the meteorological environment from numerical weather prediction (NWP) systems. We also make use of precipitation estimates derived from weather radar. Fractal downscaling of rain fields can also be performed in order to improve the spatio-temporal resolution of estimates by introducing a stochastic small-scale structure. Time series exhibit the correct first and second order characteristics, as well as the correct spatial correlation, and compare well to the ITU-R recommendations. There are two novelties to this approach: any number of time-coincident time series can be created for different locations; the process is directly applicable for the real-time prediction of propagation conditions. The latter offers the potential to aid in the management of radio resources, where knowledge of forthcoming fades, their depth and duration could be advantageous.

An expert system is a type of program designed to model human knowledge and expertise. This work describes the design, implementation, and testing of an onboard expert system developed for the dual spacecraft Emerald small satellite mission. This system takes advantage of Emerald's distributed computing architecture and is currently being used for on-board fault detection. The distributed computing architecture is composed of a network of PICmicro and Atmel microcontrollers linked together by an I/sup 2/C serial data communication bus which also supports sensor and component integration via Dallas 1-wire and RS232 standards. The expert system software is executed by an Atmel microcontroller within Emerald's expert subsystem hardware. The human knowledge and expertise that the system simulates is contained within software "rules" that can be easily modified from the ground. The flexibility offered by this system allows the ground operator to add, modify, or remove logical operations on-orbit and overcomes the limitations imposed by hardwired systems. While expert systems have been used on spacecraft in the past, its role on Emerald for on-board fault-detection using threat integrals and persistence counters further demonstrates the power and versatility of such systems. Results include experimental data verifying the expert system's performance and its ability to distinguish threat levels posed by out-of-limit sensor readings. This paper describes the technical design of the aforementioned features and its use as part of the Emerald satellite mission.

In this paper, a method for deriving time-series of attenuation on fixed satellite or terrestrial links is described. The method uses meteorological model forecast data and radar data and hence permits time coincident derivations for multiple sites that include the spatial correlation properties inherent in weather systems. The success of the technique depends upon insertion of the short interval temporal properties (varying typically over 1 second to 15 minutes) that are statistically independent between stations. The technique has immediate application to simulation of the performance of multi-media satellite to earth links and has longer-term significance in terms of operational real-time performance prediction.

Thermo-mechanical modeling has indicated the desirability of using 'brush' structures (clusters of small filaments or rods) for armor in plasma facing components as a means of reducing stresses at the joint with the heat sink. Fabrication challenges have prevented use of this armor configuration to date. Development work in the US has resulted in methods for fabricating tungsten (W) brush structures suitable for scale-up on the ITER targets and dome. Methods developed use 1.6 mm and 3.2 mm diameter W welding electrode as stock for the armor, and welded metallic honeycomb for fixturing. Three approaches to fabricating said structures are: (1) Cu or Cu/W functionally gradient materials (FGMs) are plasma sprayed to the W brushes followed by diffusion bonding to the Cu alloy heat sink, (2) Cu is cast to the tips of the W brushes followed by diffusion bonding to the Cu alloy heat sink, and (3) W rods are coated with a bonding aid and are directly pressed into and diffusion bonded to the Cu alloy heat sink. All three methods utilize low temperature Cu/Cu diffusion bonding techniques also developed in the US under ITER. The honeycomb core may be left in place to provide indications of armor wear.

Plasma-spray technology is under investigation as a method for producing high thermal conductivity beryllium coatings for use in magnetic fusion applications. Recent investigations have focused on optimizing the plasma-spray process for depositing beryllium coatings on damaged beryllium surfaces. Of particular interest has been optimizing the processing parameters to maximize the through-thickness thermal conductivity of the beryllium coatings. Experimental results will be reported on the use of secondary H/sub 2/ gas additions to improve the melting of the beryllium powder and negative transferred-arc cleaning to prepare beryllium surfaces prior to depositing beryllium. Information will also be presented on thermal fatigue tests which were performed on beryllium coated ISX-B beryllium limiter tiles using 10 sec cycle times with 60 sec cooldowns and an International Thermonuclear Experimental Reactor (ITER) relevant divertor heat flux slightly in excess of 5 MW/ml.

A novel technique has been used to test the relative low cycle thermal fatigue resistance of different grades of US and Russian beryllium, which is proposed as plasma facing armor for fusion reactor first wall, limiter, and divertor components. The 30 kW electron beam test system at Sandia National Laboratories was used to sweep the beam spot along one direction at 1 Hz. This produces a localized temperature "spike" of 750/spl deg/C for each pass of the beam. Large thermal stresses in excess of the yield strength are generated due to very high spot heat flux, 250 MW/m/sup 2/. Cyclic plastic strains of the order of 0.6% produced visible cracking on the heated surface in less than 3000 cycles. An in-vacuo fiber optic borescope was used to visually inspect the beryllium surfaces for crack initiation. Grades of US beryllium tested included: S-65C, S-65H, S-200F, S-200F-H, SR-200, I-400, extruded high purity, HLP'd spherical powder, porous beryllium (94% and 98% dense), Be/30% BeO, Be/60% BeO, and TiBe/sub 12/. Russian grades included: TGP-56, TShGT, DShG-200, and TShG-56. Both the number of cycles to crack initiation, and the depth of crack propagation, were measured. The most fatigue resistant grades were S-65C, DShG-200, TShGT, and TShG-56. Rolled sheet Be (SR-200) showed excellent crack propagation resistance in the plane of rolling, despite early formation of delamination cracks. Only one sample showed no evidence of surface melting, Extruded (T). Metallographic and chemical analyses are provided. Good agreement was found between the measured depth of cracks and a 2-D elastic-plastic finite element stress analysis.

In an off-normal event, water-cooled copper divertor plates in the International Thermonuclear Experimental Reactor (ITER) may either experience heat loads beyond their design basis, or the normal heat lends may be accompanied by low coolant pressure and velocity. The purpose of this experiment was to illustrate that during one-sided heating, as in ITER, a copper divertor plate with the proper side wall thickness, at low system pressure and velocity can absorb without failing an incident heat flux, q/sub i/, that significantly exceed the value, q/sub i//sup CHF/, which is associated with local CHF at the wall of the coolant channel. The experiment was performed using a 30 kW electron beam test system for heating of a square cross-section divertor heat sink with a smooth circular channel of 7.6 mm diameter. The heated width, length, and wall thickness were 16, 40, and 3 mm, respectively. Stable surface temperatures were observed at incident heat fluxes greater than the local CHF point, presumably due to circumferential conduction around the thick tube walls when q/sub i//sup CHF/ was exceeded. The Post-CHF tube walls when enhancement factor, /spl eta/, is defined as the ratio of the incident burnout heat flux, q/sub i//sup BO/, to q/sub i//sup CHF/. For this experiment with water at inlet conditions of 70/spl deg/C, 1 m/s, and 1 MPa, q/sub 1//sup CHF/ and q/sub i//sup BO/ were 600 and 1 100 W/cm/sup 2/, respectively, which gave an /spl eta/ 1.8.

The Loss of Flow Accident (LOFA) is a serious safety concern for the International Thermonuclear Experimental Reactor (ITER) as it has been suggested that greater than 100 seconds are necessary to safely shutdown the plasma when ITER is operating at full power. In this experiment, the thermal response of a prototypical ITER divertor tube during a simulated LOFA was studied. The divertor tube was fabricated from oxygen-free high-conductivity copper to have a square geometry with a circular coolant channel. The coolant channel inner diameter was 0.77 cm, the heated length was 4.0 cm, and the heated width was 1.6 cm. The mockup did not feature any flow enhancement techniques, i.e., swirl tape, helical coils, or internal fins. One-sided surface heating of the mockup was accomplished through the use of the 30 kW Sandia Electron Beam Test System. Alter reaching steady state temperatures in the mockup, as determined by two Type-K thermocouples installed 0.5 mm beneath the heated surface, the coolant pump was manually tripped off and the coolant flow allowed to naturally coast down. Electron beam heating continued after the pump trip until the divertor tube's heated surface exhibited the high temperature transient normally indicative of rapidly approaching "burnout". Experimental data showed that time-to-burnout increases proportionally with increasing inlet velocity and decreases proportionally with increasing incident heat flux.