180 research outputs found
Investigation of RIS integration in satellite systems guided by ITU-R VSAT radiation diagram
No full textProperties of array factor of reconfigurable intelligent surfaces for radio communications
No full textPredicting the power output of distributed renewable energy resources within a broad geographical region
No full textIn recent years, estimating the power output of inherently intermittent and potentially distributed renewable energy sources has become a major scientific and societal concern. In this paper, we provide an algorithmic framework, along with an interactive web-based tool, to enable short-to-middle term forecasts of photovoltaic (PV) systems and wind generators output. Importantly, we propose a generic PV output estimation method, the backbone of which is a solar irradiance approximation model that incorporates free-to-use, readily available meteorological data coming from online weather stations. The model utilizes non-linear approximation components for turning cloud-coverage into radiation forecasts, such as an MLP neural network with one hidden layer. We present a thorough evaluation of the proposed techniques, and show that they can be successfully employed within a broad geographical region (the Mediterranean belt) and come with specific performance guarantees. Crucially, our methods do not rely on complex and expensive weather models and data, and our web-based tool can be of immediate use to the community as a simulation data acquisition platform.<br/
AdaHeat: A general adaptive intelligent agent for domestic heating control
No full textCopyright © 2015, International Foundation for Autonomous Agents and Multiagent Systems (www.ifaamas.org). All rights reserved.Improving the energy efficiency of domestic heating systems can lead to a major reduction in energy consumption and the corresponding CO2 emissions. To this end, intelligent domestic heating agents (IDHAs) aim to operate domestic heating systems more efficiently with minimum user input. In this work, we propose a new general IDHA that balances heating cost and thermal discomfort in an infinite horizon optimization manner, learns an adaptive thermal model of the system under control on-line and plans a heating schedule that fully exploits the probabilistic occupancy estimates. Importantly, our agent adapts to the user preferences in balancing heating cost and thermal discomfort, as it relies on a single parametrization variable that is learned on-line, and is able to consider a wide range of heating systems typically employed in domestic settings. The backbone of our IDHA is an adaptive model predictive control approach along with a new general planning algorithm that utilizes dynamic programming. We present a thorough evaluation of our approach, and show its effectiveness in terms of Pareto efficiency and usability criteria against state-of-the-art IDHAs. By so doing, we also conduct a comprehensive characterization of existing IDHAs to provide significant insights about their performance in different operational settings
An Inline V-Band WR-15 Transition Using Antipodal Dipole Antenna as RF Energy Launcher @ 60 GHz for Satellite Applications
No full textThis article demonstrates the design and development of WR-15 transition using an antipodal microstrip dipole antenna at a frequency of 60 GHz for space applications. An inline microstrip line to rectangular waveguide (MS-to-RWG) transition is proposed for the V-band (50–75 GHz) functioning. The RF energy is coupled and launched through an antipodal dipole microstrip antenna. Impedance matching and mode matching between the MS line and dipole are achieved by a quarter wave impedance transformer. This results in the better performance of transitions in terms of insertion loss (IL > −0.50 dB) and return loss (RL < −10 dB) for a 40.76% relative bandwidth from 55.57 GHz to 65.76 GHz. The lowest values of IL and RL at 60 GHz are −0.09 dB and −32.05 dB, respectively. A 50 μm thick double-sided etched InP substrate material is used for microstrip antipodal dipole antenna design. A back-to-back designed transition has IL > −0.70 dB and RL < −10 dB from 54.29 GHz to 64.07 GHz. The inline transition design is simple in structure, easy to fabricate, robust, compact, and economic; occupies less space because the transition size is exactly equal to the WR-15 length; and is prepared using an InP substrate with high permittivity of 12.4 and thickness of 50 μm. Thus, the devices have the lowest insertion loss value and lowest return loss (RL) value, of <−31 dB, as compared to earlier designs in the literature. Therefore, the proposed design has the lowest radiation loss (because of thickness) and highest transmission (about 97% power). Easy impedance matching using only a single-step quarter-wave transformer between the antipodal dipole antenna and 50 Ω microstrip line (avoiding the multi-sections’ demand and microstrip line’s tedious complexity) is needed. Since, when the InP dielectric substrate is inserted in WR-15, the waveguide becomes a dielectric-filled waveguide (DFWG), and its characteristics impedance reduces to 143 Ω from 505 Ω at an operating frequency of 60 GHz. In the proposed transition, no ridge waveguide or waveguide back-short is utilized in WR-15. The microstrip line did not contain any via, fence, window, screw, galvanic structure, post, etc. Hence, the transition is suitable for high-data-rate 5G communications, satellite remote sensing, missile navigation, MIC/MMIC circuits’ characterization, and mm-wave applications. The electrical equivalent model of the proposed design has been generated and validated using an RF circuit simulator and was found to have excellent matching
Capacity Statistics Evaluation for Next Generation Broadband MEO Satellite Systems
No full textIn this paper, the performance of a reference medium earth orbit (MEO) satellite constellation system operating at Ka-band and employing single links to ground is compared with next generation advanced systems in higher RF or optical bands employing multiple diversity links. The fill rate of existing MEO constellations offering broadband and trunking services in Ka-band is growing fast, rendering the search for additional spectrum of vital importance. Therefore, this paper reports on the results of a system study investigating the option of using Q/V-band, or even optical wavelengths, instead of Ka-band, to deliver substantially higher system capacity. The system study takes a holistic approach covering from atmospheric channel impairments to waveform optimization and system analysis for realistic assumptions. After proposing a sophisticated channel model to generate spatio-temporal time series of atmospheric attenuation, an optimization of the performance at physical layer is performed to derive the inputs necessary to the system analysis. Five different advanced high frequency RF and optical systems are compared in terms of outage capacity and availability for various locations of single ground stations, multiple ground stations (site diversity) and from multiple satellites (orbital diversity). For maximizing the realism of the comparison, similar on board satellite resources (mass, power) are assumed for all scenarios
Assessment of seasonal asia monsoon rain impact on the earth-space propagation in Equatorial Kuala Lumpur
No full textFuture satellite communication systems are moving towards high operational frequencies, typically in the Ka band (18 to 30 GHz) to deliver wider bandwidths and higher data rates in response to the increasing demand for broadband communication services and the congestion of Ku band (11 to 18 GHz). As well known, signal degradation due to rain can be a main limiting factor in this frequency band, especially in tropical and equatorial regions [1]. Equatorial regions are characterized by wet months throughout the whole year and there is no alternation of summer and winter as in temperate regions. However, the climate in South East Asia, where Kuala Lumpur is located, is strongly seasonal because of the different monsoons caused by the changes in the direction and speed of airstreams [2]. Hence, it is worthwhile to further assess the impact of this monsoon variation on the Earth-space propagation in this specific equatorial location
Propagation Phenomena and Modeling for Fixed Satellite Systems Evaluation of Fade Mitigation Techniques
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