Inductive power transfer is now a commercially mature technology for short range, localised powering of electronic devices. However, there are many potential applications that would be enabled by a power transfer system tolerant of greater separation between transmitter and receiver. In this paper we consider just such an application and use it to elucidate the design and performance constraints facing poor and variably coupled IPT systems.
A bidirectional ray-tracing algorithm based on the reciprocity theorem is introduced for calculating antenna transfer functions. Ray launching is carried out from both receiver and transmitter antennas. The transfer function is calculated by capturing the rays from both antennas on an interaction surface and by evaluating the reciprocity integral on this surface using a numerical integration technique. Reception spheres, which are utilized in the unidirectional Shooting and Bouncing Rays method, are replaced by the interaction surfaces as they are much more flexible in size and shape. Large geometries, which are cumbersome to simulate with traditional techniques, can be easily and accurately simulated in this way. Additionally, the interaction surfaces can be employed for the calculation of diffraction effects, instead of utilizing the Uniform Theory of Diffraction (UTD). Problems related to the branching in the ray tree can be avoided in this way.
Trajectory of civil aircrafts is typically optimized off-board to optimize fuel consumption, using also information available from weather services. Changes to the set route are decided by the pilot based on METAR and NOTAM updates and unexpected adverse weather conditions detected by the weather radar installed on the nose of the aircraft [1]. Typically, weather radars of most civil aircrafts are single-polarization X-band systems (only larger airplanes use C-band) with 3° beam-width flat antenna, following the specifications set by the ARINC 708A standard. Notoriously, attenuation due to propagation through a precipitation filled medium is not negligible at X-band and in the presence of cluster of convective cells, the nearer cells masks or weakens returns from farther cells, ultimately determining a wrong input to the pilot's decision on optimal trajectory. Unfortunately, attenuation correction techniques applicable to single polarization radar are notoriously unreliable and strongly affected by radar calibration bias. Conversely, dual polarization technologies in ground based weather radar have demonstrated the capability of mitigating X-band attenuation based on differential phase shift measurements [2] and therefore could be successfully exploited for civil aviation weather radars. Current systems show to the pilot precipitation returns according to a few levels of reflectivity (the correspondence between colors and levels of reflectivity is not shown) and, within a shorter range, also information on turbulence detected from radar Doppler spectrum width. Meteorological interpretation of such images is largely left to the pilot's experience. Dual polarization radar provides more information arising from the sensitivity their measurements to microphysical properties of particles exploited in hydrometeor classification products [3]. On the other hand, dealing with more information yields increased workload for pilot and therefore, to keep simple and effective the information shown to the pilot, an automated software to process dual-polarization measurements along with trajectory information to support the pilot in decision making is essential. The European Union, through the Clean Sky framework funded several projects to improve airborne weather radars and to optimally use them to optimize flight route. The project KLEAN aimed at using output of the Selex ES Weather Radar Post-Processor software (WRPP) inside an EFB (Electronic Flight Bag) to produce weather classification maps and related binary risk maps as the final radar product to be shown to the pilots or to be used by a trajectory optimizer.
This paper represents a low cost printed Vivaldi antenna at 3–10 GHz bandwidth for Radio telescope Feed system. The idea of this design is to minimize the number of telescope receivers for Square Kilometre Array (SKA) [1]. A minimized tapered slot antenna with a balun feed for receiver systems is proposed. The Vivaldi antenna is design on a relatively low dielectric constant substrate which operates at Ultra-Wideband (UWB). A typical tapered slot antenna is a combination of a wideband balun and a radiator with different tapering shapes such as linear, constant width, exponential and dual exponential. Two feeding configurations are used such as coplanar waveguide (CPW) to slot line transition and microstrip line to slotline transition [2–5]. The antenna modeling is analyzed using two different electromagnetic simulators such as HFSS and CST Microwave Studio. The results are shown that the antenna operates over a wide bandwidth extending from 3.1 to 10.6 GHz with a maximum gain of 7.3 dBi. Stable radiation patterns are observed across the operational bandwidth, with cross-polarization levels below −20 dB. The realized antenna structure occupies a volume of 45 × 45 × 0.5 mm 3 , and possesses the essential time domain fidelity needed for UWB Radio telescope Feed system applications. A prototype Vivaldi antenna is constructed and measured for validation. The Voltage Standing Wave Ratio (VSWR) of the proposed antenna is verified against the simulated data results, the measured and simulated results are found to be in good agreement. In particular, a good impedance bandwidth matching and stable directional radiation patterns were achieved across the operating frequency range. The combination of design aims and outcomes described in the paper indicates that the proposed antenna can be a suitable candidate for portable RF systems, or possible sensor element in an UWB antenna array application.
In this paper, the performance of massive multiuser multiple-input-multiple-output (MIMO) transmit beamforming techniques and antenna selection is analyzed. Transmit antenna selection is used to reduce the number of radio frequency units, system complexity and system cost, making massive MIMO more applicable. Special attention is given to study the effect of the number of available antennae and radio frequency units on the performance of the system. Three types of transmit beamforming techniques are considered, namely, maximum ratio transmission beamforming, zero forcing beamforming, and minimum mean square error beamforming. The numerical results of the paper clearly show that transmit antenna selection affects the performance of massive MIMO systems for all considered types of transmit beamforming. In particular, it is shown that lower bit error rate can be achieved with small number of selected antennae from a large group of actual transmit antennae. This is of course in addition to the great advantage from the system complexity perspectives.
In this paper, efficient techniques for the classification of chaotic codes are presented. Four different clustering techniques, namely, k-mean clustering, hierarchical clustering, fuzzy c mean clustering, and subtractive clustering are used for classification. Higher order statistics features obtained from some different types of wavelet transform are utilized. The codes to be classified are assumed to be generated by two different methods. The first method is generating different chaotic codes using different chaotic maps with the same initial values. Two types of chaotic maps are considered, namely the logistic map and bended-up-down map. The second method of code generation is to use the same chaotic map with different initial values.
This paper performs an assessment of available architectures and techniques for Wireless Power Transfer (WPT) transmitter blocks. In the transmitting segment of the WPT chain one of the driving components is the power amplification block, because it generally defines the capability of the system in terms of the range for the WPT link to be established, as well as, limiting or not the amount of information that can be exchanged. These facts are quite important because it is common to have WPT links that provide not only energy to the battery-less devices, but also allowing information to be exchanged between the WPT transmitter and several receivers. A practical example of a power amplifier to be integrated in a WPT transmitter for the 5.8GHz band is presented, along with some conclusions on the topic.
Nano antennas recently became popular due to their ability to localize incident electromagnetic fields in sub-wavelength volumes. In this paper, a beam antenna is proposed for THz application, which is based on a switchable high-impedance surface (HIS) using a single-layer graphene. The use of graphene as reflection surface to enhancement the reflection power of the Nano antennas' system due to its unique electronic and optical properties which lead to a complex surface conductivity at THz frequencies. We report the configuration of a graphene patch array antenna based on grapheme surface deposited by Sio2/Si substrate.
This paper describes the design, calibration, and measurements with a personal, distributed exposimeter (PDE) for the on-body detection of radio frequency (RF) electromagnetic fields due to Wireless Fidelity (WiFi) networks. Numerical simulations show that using a combination of two RF nodes placed on the front and back of the body reduces the 50% prediction interval (PI50) on the incident free-space electric-field strength E-RMS(free). Median reductions of 10 dB and 9.1 dB are obtained compared to the PI50 of a single antenna placed on the body using a weighted arithmetic and geometric average, respectively. Therefore, a simple PDE topology based on two nodes, which are deployed on opposite sides of the human torso, is applied for calibration and measurements. The PDE is constructed using flexible, dual-polarized textile antennas and wearable electronics, which communicate wirelessly with a Universal Serial Bus (USB) connected receiver and can be unobtrusively integrated into a garment. The calibration of the PDE in an anechoic chamber proves that the PI50 of the measured E-RMS(free) is reduced to 3.2 dB. To demonstrate the real-life usability of the wireless device, a subject was equipped with the PDE during a walk in the city of Ghent, Belgium. Using a sample frequency of 2 Hz, an average incident power density of 59 nW m(-2) was registered in the WiFi frequency band during this walk.
This paper investigates the effect of mutual coupling between two graphene patch antennas designed for THz systems. In particular, a reduction of more than 22 dB in the level of mutual coupling between the two antennas is obtained with the proper choice of the voltage applied to the graphene sheets. As a result, a wider bandwidth is obtained with a better reflection coefficient level.
To study instabilities caused by inhomogeneities of the electric field and plasma density in the auroral zone, numerical algorithms are developed and computational modeling are performed for different conditions in the background plasma. It is shown that the dispersion relation has unstable solutions in a wide range of frequencies and wavenumbers. These solutions manifest themselves in satellite observations as a broadband spectrum of electrostatic perturbations. In addition to inhomogeneous energy-density-driven waves of ion-cyclotron type, ionospheric structures are capable of destabilizing oblique ion acoustic waves modified by a shear in the parallel drift of ions.
Information plays a key role in natural disaster crisis management and relief. We discussed in previous contributions how lightweight Unmanned Aerial Vehicles (UAVs) or (micro-)drones can effectively assist rescuers in order to improve the situational awareness and assessment (Aprvrille et. al, 2014) and (Tanzi et al., 2014). The paper discusses how SysML-Sec/TTool can be efficiently used for formally verifying the safety and security of an autonomous drone mission and flight. More specifically, we consider the architecture of the system that we have used in the scope of the drone4u project. A Parrot platform is used to capture videos of its surroundings. Those videos are transmitted by the UAV to a remote computer, which autonomously controls the drone according to its mission. We have modeled the UAV embedded system (properly speaking the drone capturing the videos, connecting to a WIFI network, and applying remote orders), as well as the communication itself, and the processing performed by the remote control computer.
Ionospheric propagation is harmful for the electromagnetic signals broadcast by Global Navigation Satellite System (GNSS) satellites, mainly because of the presence of electron density anomalies. GNSS receivers are indeed of primary importance in scintillation and Total Electron Content (TEC) monitoring, especially at low and high latitudes, where scintillations are more frequent. Professional dual frequency custom hardware Global Positioning System (GPS) receivers have been successfully exploited since years as measurement tools able to provide post-correlation data that are then used for modeling the atmospheric phenomena. Recent trends in scientific GPS receivers implementation consider Software Defined Radio (SDR) as a valuable technology that enables access to intermediate and low level receiver processing stages. With respect to commercial hardware tools, they provide a larger subset of observables related to the signal processing stages, as well as a high grade of flexibility and re-configurability, depending on the user needs. Such features enable the design and test of innovative ionosphere monitoring techniques.
This article gives an overview of the German research and development initiative FAST, a project cluster aiming at a technological and economic breakthrough by means of real-time capabilities. The FAST project cluster consists of around 80 partners from industry and academia, with a strong participation of small innovative companies. FAST comprises around 20 projects and is scheduled from 2014 to 2020.
Application of OAM waves in radiofrequency bands presents very interesting perspectives in communication and radar domains [1] [2]. These applications are based on the orthogonality property between the different topological charges of the received wave. In free space, this property can be conserved along the propagation path, but in a real environment, multipath effects can degrade the orthogonality between OAM modes, in particular due to the reflection on surfaces (ground, buildings ...) or objects, and the interference between waves.
This paper presents the results from a field trial that was performed during a four-year period on a 5.5 km long radio link path operating at 26 GHz in Prague. The purpose was to investigate the amount of attenuation due to precipitation and its yearly variations. The attenuation of the radio link signal as well as the rain rate were measured. The measured attenuation results are compared to the models given by the International Telecommunication Union (ITU). The propagation measurements show large yearly variations due to variability in rain rate from one year to another. These variations represent a risk that must be taken into consideration in the planning of radio links. The measured results are in agreement with the ITU long-term statistical rain attenuation model if the measured rain rate for the individual year is used. For the worst year the number of fades, the fade duration, the fade speed, the worst month statistics, and the polarization correlation are presented. The measurements presented will add to the current knowledge of fading due to precipitation, and some of the results, such as the fade duration distributions, are new knowledge.
In this paper, we present our study on the shielding effectiveness (SE) of a metallic rectangular enclosure with various aperture shapes and numbers. We calculate the SE value for various apertures such as rectangle, square, pentagon, hexagon and circle. The best SE value is obtained with the pentagon shaped aperture. We have calculated the SE value of the enclosure with multiple apertures to observe the variation of SE with the number of apertures. We also present the SE value of an enclosure with apertures including inductive iris. Preliminary results reported here look very promising for future studies. We use CST Microwave Studio and transmission line method in the calculations.
Summary form only given. Low-frequency, wide-field radio telescopes such as the Murchison Widefield Array (MWA) enable the dense spatial sampling of the ionosphere and plasmasphere on regional scales. For a physically compact array such as the MWA, the refractive shifts in the positions of celestial sources in the synthesised radio images are proportional to spatial gradients in the total electron content (TEC) transverse to the line of sight. By measuring the angular position shifts of celestial radio sources, one can probe waves and disturbances in the intervening plasma. Radio telescopes differ fundamentally from other techniques for measuring plasma fluctuations in that they are sensitive to TEC gradients/differences rather than absolute TEC. This makes them sensitive specifically to fluctuations about the ambient density, and therefore powerful probes of plasma density waves and irregularities. The authors present the results of an analysis of plasma fluctuations detected by the MWA, which can measure TEC gradients to a precision of ~1 mTECU/km at observing frequencies of ~150MHz. Around 2000-3000 point sources are visible instantaneously to the MWA, each functioning as a measurement point for the TEC gradient across the field-of-view (FoV). The spatial sampling completeness achieved by the MWA is unparalleled among interferometer observations of the ionosphere/plasmasphere to date, which have been limited both to smaller fields of view and at most several tens of measurement points (e.g. J. F. Helmboldt, W. M. Lane & W. D. Cotton, 2012, Radio Sci., 47, RS5008). This ~100-fold improvement in sampling completeness has permitted the first detailed imaging of the near-Earth plasma by a radio telescope.
We report multi-frequency radio continuum observations of few Wolf Rayet galaxies Mrk 8, Mrk 1089, Mrk 33, Mrk 1236 and NGC 3049 using the Giant Meter-wave Radio Telescope (GMRT). It is remarked that these galaxies have not so far been detected and studied at much lower frequencies. Our investigations reveal that many of these galaxies are detected at frequencies <;1 GHz. We estimate synchrotron spectral index after separating the thermal free-free emission and obtain α nt = 1 to -0.4. The radio morphology of the galaxies resembles the UV emission seen by GALEX with and extent similar to the NIR emission from 2MASS.
Electromagnetic waves are widely used for the assessment of architectural structures, like walls, wood beams, stone, and concrete. Ultrasound, Ground Penetrating Radar, and impedance tomography are commercially available and largely used for deep investigation, but the resolution on the first range of 10-20 cm is not particularly effective. The interest of authors is the development of a robust and user-friendly non-destructive measurement system to diagnose the materials used in masonry until 20 cm in depth, with a resolution less than 2cm. A similar system could be crucial to diagnose hidden defects within the material in order to prevent damages and to properly design remedial intervention.
