Telecommunication Satellites Research Articles

When Teleconferencing was the Future: The 1970 ‘Medizin Interkontinental’ Transmission and West German Medicine in the Space Age

Abstract In March 1970, the first ever medical teleconference connected U.S. aeromedical experts in Houston and San Antonio to an audience of 25,000 physicians in congress centres in West Germany, Austria, and Switzerland. As this article shows, the ‘Medizin Interkontinental’ transmission was a costly demonstration of the latest developments in satellite telecommunications and projection technology as well as a stage for space-age visions of the future of medicine in the aftermath of the moon landing. Audio-visual and space technology became, at one at the same time, the medium and the message of medical futurity. As I argue, the teleconference was an audio-visual techno-spectacle that marked the culmination of the German medical community’s infatuation with futurology at the end of the 1960s, but it was also contingent on the concrete interests of the parties involved, which included the German Medical Association, medical futurologists, nasa, the U.S. Air Force, and the Swiss pharmaceutical company Ciba. Decades before teleconferences and telemedicine entered day-to-day medicine, the convergence of new medical and media technology, changes in medical education, Cold War geopolitics, and pharmaceutical sponsorship created a brief glimpse of a technology-based future of medicine that fell apart once these constellations changed in the early 1970s.

Multibeam Antennas With Reflector for High Throughput Satellite Applications

Telecommunication satellites have been developing toward broadband and high throughput systems. Compared with conventional telecommunication satellites, high throughput satellites (HTSs) have been able to provide broadband system capacity with the maximum value exceeding 200 Gbit/second, and are more cost-effective with less expense per bit/second. To satisfy the demand of HTS, multibeam antennas with narrow beams and frequency or polarization reuse scheme will be applied. This article reviews the derivation of multibeam antennas on satellites and the principle of obtaining beams with various beamwidth. This article describes single feed per beam and multiple feeds per beam schemes with various number of reflectors. Some multibeam HTS missions over the past two decades are listed and presented. New technologies about HTS are presented.

Ka-Band Reconfigurable Reflectarrays Using Varactor Technology for Space Applications: A proposed design

In this article, Ka-band reconfigurable reflectarray antennas based on varactor diodes are investigated. Varactor diodes enable high radiation pattern flexibility while maintaining acceptable costs. The design of a dual-band reconfigurable reflectarray based on varactor technology is described in detail. The antenna, considered for a fixed or mobile ground station for satellite telecommunications systems, could be used for several other applications. To demonstrate and validate experimentally the proposed concept, the design of a reduced-sized antenna is presented. The manufacturing and testing of its reconfigurable reflecting surface are then described and discussed. This antenna design could also be considered as a baseline for a data downlink antenna employed on a satellite.

ESTIMATION OF FEM AND FDTD METHODS FOR SIMULATION OF ELECTROMAGNETIC CHARACTERISTICS OF POLARIZATION TRANSFORMING DEVICES WITH DIAPHRAGMS

Context. Today, there is a rapid expansion of the range of modern branches of science and technology, which actively use satellite telecommunication systems to receive, process and transmit various information. These radioelectronic systems quite often require an increase of the volumes of information, which they are processing and transmitting. Increase of the volumes of transmitted information in two times can be achieved by using dual-polarization antenna systems and devices. Nowadays, most part of the specialists, who are engaged in the development of various modern polarization-processing microwave devices, carry out their numerical modeling and optimization using variational techniques, methods of integral equations, method of fields matching in partial regions. The methods with division of the internal region of the device into elementary cells are applied most actively. Among them in the time domain the most often used approach is finite difference method with the decomposition at hexagonal mesh, while and in the frequency domain the finite elements method with the adaptive tetrahedral mesh is applied. Therefore, the estimation of the speed and accuracy of these methods with the purpose of determination of more effective among them is a relevant problem. Objective. The goal of the research is comparison of speed and accuracy of the calculations of electromagnetic characteristics of waveguide polarizers using FEM and FDTD methods, as well as the comparison of the convergence of these methods for the analysis of polarization-processing microwave devices with diaphragms. Method. For the calculations and analysis of electromagnetic characteristics in the article we used the method of finite differences in the time domain (FDTD) and the method of finite elements in the frequency domain (FEM). In FEM the volume is split into the tetrahedral mesh cells. In FDTD the computational domain is divided into hexagonal mesh cells. Results. It was found that the convergence of voltage standing wave ratio for the waveguide polarizer is fast for both methods. It was obtained that the convergence of the characteristics of differential phase shift, axial ratio, and crosspolar discrimination of the developed microwave device turned out to be much more sensitive to the number of mesh cells used. Moreover, in the research it was obtained by calculations that the computation time by the finite elements method in the frequency domain is more than 2 times less than the corresponding time required for calculations by the finite difference time domain method. When using the finite elements method in the frequency domain the corresponding number of tetrahedral mesh cells is 10 times less than the number of hexagonal mesh cells, which are used in the finite difference time domain method. Conclusions. Performed investigations have shown that FEM in the frequency domain, which applies an adaptive tetrahedral mesh, is more efficient than the FDTD method for the calculations of phase and polarization characteristics of modern waveguide polarizers and other microwave devices for various applications.

Design and optimization of a self-deployable composite structure

Self-deployable composite structures are attractive for space applications as they provide lightweight, low cost and simple solutions that can replace mechanical systems. These structures can be folded and use the stored strain energy to promote a self-deployment event. However, these structures present design, manufacture and optimize challenges. This article describes the process of designing and optimizing an elastic-hinge, for a telecommunication satellite considering both structural and frequency requirements using finite element analysis, manufacturing and experimental testing. Furthermore, the paper details the sequence of optimization algorithms that were used to produce a solution capable of meeting the original design specifications. The structural assessment consists of the elastic-hinge numerical modelling during the folding process, by means of an explicit formulation. This model correlates well to the experimental test data and was used to evaluate the damage installed in the hinge using a pletfora of damage criteria. The frequency analysis considers the numerical modelling of a system constituted by the elastic-hinge and a telecommunication satellite antenna. This model was used to estimate the natural frequency of the system. Results show that a design methodology which uses a genetic algorithm (GA) for a global search, followed by a particle swarm optimization (PSO) method for a local search provides a good approach to the optimization problem. It is also shown that the efficiency of these algorithms can be maximized by tailoring their architecture and internal parameters.

Quantum Chemical Computations of an Efficient Push-Pull NLO Chromophore 3-[4-Nitrophenyl Azo]- 9H- Carbazole-9-Ethanol

Electric-optic (EO) materials are being explored for applications ranging from fiber and satellite telecommunications, optical gyroscopes, to photonic detection of radar etc. Dipolar push-pull Organic chromophores that exhibit extended π-conjugation, in particular, show enhanced second order NLO properties. The present investigation reports the quantum chemical computations of the high efficiency push-pull NLO molecule 3-[(4-Nitrophenyl Azo)] - 9H-Carbazole-9-Ethanol (NPACE). The organic push-pull molecule is optimized in gaseous and in various solvent condition using Exchange correlation function (B3LYP/MP2). Molecular electrostatic potential, thermal properties and NBO analysis have also been performed in detail. The effective electron cloud moment in the molecule is mainly governed by the physical process termed intramolecular Charge Transfer (ICT).

Диаграммообразующие схемы многолучевой антенной решетки

The work is devoted to the study of multibeam phased array beam forming networks, based on Butler matrix and Rotman lens. The study was made with similar conditions of the same telecommunications satellite service area. The microstrip circuit pattern was developed, the amplitude and phase frequency response were investigated, arrays directional patterns for beam forming variants were calculated. Evaluation of adjacent ray overlay inside service area boundary was carried out. Conclusions about acceptability of the proposed beam forming networks were made.

Conceptual Design Process for LEO Satellite Constellations Based on System Engineering Disciplines

Satellite design process is an interdisciplinary subject in which the need for collaboration among various science and engineering disciplines is evident. Meanwhile, finding an optimal process for conceptual design of a satellite, which can optimize time and cost, is still an important issue. In this paper, based on system engineering approach, an optimal design process is proposed for LEO satellite constellations. In the proposed method, design process, design sequences, and data flow are established. In this regard, the conceptual design process is divided into two levels of mission (or constellation) and system (or satellite) as well as 15 main activities based on the mission profile, previous experiences of the authors, and existing literature. Then, the relationships between these activities have been determined by considering the importance of relationships according to their priority. Finally, these relations are optimized based on design structure matrix (DSM). By utilizing this approach, system design process of a telecommunication satellite constellation in LEO is formulated in conceptual design phase. Performance and capability of the proposed approach in optimal design process of the satellite constellation are investigated by comparing the outcome with existing results in the literature.

Phased array beamforming networks

The work is devoted to studying multibeam phased array beamforming networks based on the Butler matrix and Rotman lens. The study was performed under conditions similar to those in the telecommunication satellite service area. The microstrip circuit pattern was developed; the amplitude and phase frequency responses were investigated taking into account losses in materials. Array directional patterns for beamforming variants were calculated. Evaluation of adjacent ray overlay within the service area was carried out. Conclusions about acceptability of the proposed beamforming networks were made. Keywords: beamforming network, antenna array, Butler matrix, Rotman lens.

Simulation of the influence of negative internal factors on performance indicators of the synchronization system of a coherent demodulator of satellite telecommunications in permanent and transient modes of carrier frequency estimation

The subject of study in the article is the system of phase synchronization of radio technical devices of communication technology. The purpose of the article is theoretical research in the direction of development, analysis and improvement of known and synthesis of new phase synchronization schemes, which are characterized by high interference resistance, accuracy and speed of operation with a simple design. The problem to be solved is to investigate the possibilities of closed and combined synchronization systems in terms of operation in conditions of internal noise and disturbances against the background of external additive Gaussian noise and Doppler frequency shift. The article presents a model that allows you to investigate the influence of negative internal factors on the performance indicators of the synchronization system of the coherent demodulator of satellite telecommunications in stable and transient modes of carrier frequency estimation. With its help, the article analyzes closed-type synchronization systems when operating under the influence of negative internal factors and shows its inconsistency in minimizing the dispersion of the phase error and increasing the dynamics during tracking of the carrier frequency. The process of synthesis of open communication in the combined synchronization system has been clarified and analytical dependencies have been proposed, which allow to clarify the methodology of synthesis of open communication for the combined synchronization system, taking into account the influence of internal negative factors. It was established that under the influence of negative internal factors for the combined synchronization system, by selecting the parameters of the proportionalintegrating filter, it is possible to achieve an expansion of the noise bandwidth of the input signal and thereby ensure the necessary dynamics of the system and achieve the preservation of the optimal value of the dispersion of the phase error in it.

Predicting Joint Effects on CubeSats to Enhance Internet of Things in GCC Region Using Artificial Neural Network

Satellite telecommunication systems promise to bridge digital gaps and deliver wireless communication services to any corner of the world. However, despite satellites’ global connectivity and wide footprint, still atmospheric and dust impairments are open challenges that face satellite systems, especially at high-frequency bands in arid and semiarid regions. Therefore, this paper aims to predict joint effects of atmospheric and dust attenuations in Gulf Cooperation Council (GCC) countries on CubeSat communications using Artificial Neural Network (ANN). The prediction model has been carried out using a massive Multiple-Input Multiple-Output (MIMO) antenna payload at K-frequency Bands. Consider these joint effects have positive relations in calculating satellites link margin, which leads to obtaining efficient communication system, delivering better quality of service (QoS), and enhancing Internet of Things (IoT) connectivity, or even Internet of Space Things (IoST). Predicated results infer that the ANN attenuation predictions, along with the 5G MIMO antenna on-board the CubeSat, offer much promise channel model for satellite communications, which in turn leads to not only supporting IoT connectivity but also reducing power consumption, thus enhancing lifetime of CubeSat. Also, this study can provide a reference for CubeSat engineers to guarantee large-capacity communication.

Optimization of the Return Link Carrier Planning for a Constant Coding and Modulation Satellite Network

In this paper, we propose an approach to optimize the frequency plan and associated bandwidth allocation in the return link of a broadband satellite network, by exploring several design techniques for carrier allocation plans. Since bandwidth is a limited resource in satellite telecommunications, the minimization of bandwidth usage is a core issue that satellite communication service providers must solve, in particular for networks using a constant coding and modulation plan, which lacks the flexibility found in newer satellite communication products and can be subject to hardware constraints. This problematic led us to raise the following question: how can the long term bandwidth requirement of the network be minimized, given a set of ground terminals, of Modulations and Codings, and of discrete bandwidths. In this document we formally define the long-term carrier allocation problem and analyze current practical solutions. We subsequently investigate two other potential solutions, found to be more bandwidth-efficient: one based on heuristics and another based on integer linear programming. Finally, we look at the impact of several parameters on the performance of those three methods. Overall we observed marginal reductions in bandwidth, however significant gains were reached for networks with small return links with low committed information rate, a case in which some constant coding and modulation networks could fall. We concluded that those networks could benefit from our methods and see a significant reduction in bandwidth, and subsequently operational costs, at low implementation costs.

Prominence of Terahertz Acoustic Surface Plasmon Excitation in Gas–Surface Interaction with Metals

The current understanding of the dynamics of gas-surface interactions is that all of the energy lost in the collision is transferred to vibrations of the target. Electronic excitations were shown to play a marginal role except for cases in which the impinging particles have energies of several electronvolts. Here we show that this picture does not hold for metal surfaces supporting acoustic surface plasmons. Such loss, dressed with a vibronic structure, is shown to make up a prominent energy transfer route down to the terahertz region for Ne atoms scattering off Cu(111) and is expected to dominate for most metals. This mechanism determines, e.g., the drag force acting on telecommunication satellites, which are typically gold-plated to reduce overheating by sunshine. The electronic excitations can be unambiguously discerned from the vibrational ones under mild hyperthermal impact conditions.

A Multi-Spectral Approach to Fuzzy Quantum Modelling of Nonlinear Systems

In this work, we explore multi-input multi-output (MIMO) nonlinear control systems design by generalizing concepts from radio link analysis. We demonstrate practical applications of multidimensional sampling and reconstruction to reducing computational overhead in nonlinear systems analysis. Using multi-spectral analysis, we show that (de)fuzzification in control systems and (de)modulation in communication systems are analogous. Finally, we explore the values of fuzzy submodels as quantum mechanics objects for stability analysis and feedback controller synthesis of nonlinear mechanical systems. The effectiveness of the proposed approach is confirmed by simulating the attitude model a telecommunications satellite.

Design of a large bandwidth 2 × 2 interferometric switching cell based on a sub-wavelength grating

In the last few decades, increasing research effort has focused on the design of telecommunication payload systems with advanced features and lower costs in space applications. In this context, photonic solutions have already proven the potential to achieve additional functionalities, such as multiplexing or switching of RF or microwave signals, with consequent additional benefits in terms of size and mass reduction. In this paper, we report on the design of a 2 × 2 switching cell based on a thermo-optic interferometric configuration, whose key element is a sub-wavelength grating. We have theoretically demonstrated a broadband operation, with better performance in terms of operating wavelength range and compactness with respect to the existing interferometric cells. The switching cell shows a worst extinction ratio of about 13 dB, insertion loss of less than 2 dB, crosstalk of 12 dB, over a bandwidth of 150 nm, within a footprint as small as 240 µm × 9 µm. To demonstrate its potential use as a routing fabric in flexible telecommunication satellite payloads, as an example, the designed switching cell has been used as a building block of an 8 × 8 dilated Banyan matrix, where large bandwidth (150 nm), low crosstalk (−38 dB), small footprint (≈1620 µm × 576 µm) and relatively low power consumption (276 mW) have been achieved.

The cis-lunar ecosystem — A systems model and scenarios of the resource industry and its impact

Lunar resources is one of the many new putative business models that may transform space logistics. Yet it competes with Earth-based resources, in a complex trade-off involving both tech development & socioeconomic dynamics. This study models the size vs. time of a future resource ecosystem focused on water for exploration and satellite refueling, in cis-lunar space. We use a recently-developed multi-methodology concept based on System Dynamics and scenario planning, characterizing uncertainties. Top critical uncertainties include the accessibility of resource finds, and government investment into lunar resources, demarcating 2 particularly illustrative scenarios: Moonopolis and Apollo 2.0 — a rosy and a low-resources future. Concurrently, a System Dynamics model with 7 interacting systems is developed: exploration, production, demand, satellite industry, R&D, natural resources, and government. It is based on models of other industries (e.g. oil) and can express the scenarios. Uncertainties in 25 variables are estimated, and sensitivity analysis of ecosystem size is performed globally using variance-based measures, including interaction effects. These show (a) systems are tightly coupled, (b) variable importance is sensitive to the baseline. Three variables are crucial: government support to production development, production firms’ re-investment, and growth of the GEO telecom satellite industry. A lunar resources ecosystem with $32B economic impact after 20 years is plausible, given excellent government support to production capacity, high growth in GEO satellites, early demand and large initial resource discoveries. The main contributions are a novel holistic model of the dynamics of a space resources industry showing how to mix technical & socioeconomic parts, and a first case study of the methodology.

Pure and Linear Frequency-Conversion Temporal Metasurface

Metasurfaces are ultrathin structures which are constituted by an array of subwavelength scatterers with designable scattering responses. They have opened up unprecedented exciting opportunities for extraordinary wave engineering processes. On the other hand, frequency converters have drawn wide attention due to their vital applications in telecommunication systems, health care devices, radio astronomy, military radars and biological sensing systems. Here, we show that a spurious-free and linear frequency converter metasurface can be realized by leveraging unique properties of engineered transmissive temporal supercells. Such a metasurface is formed by time-modulated supercells; themselves are composed of temporal and static patch resonators and phase shifters. This represents the first frequency converter metasurface possessing large frequency conversion ratio with controllable frequency bands and transmission magnitude. In contrast to conventional nonlinear mixers, the proposed temporal frequency converter offers a linear response. In addition, by taking advantage of the proposed surface-interconnector-phaser-surface (SIPS) architecture, a spurious-free and linear frequency conversion is achievable, where all undesired mixing products are strongly suppressed. The proposed metasurface may be digitally controlled and programmed through a field programmable gate array. This makes the spurious-free and linear frequency converter metasurface a prominent solution for wireless and satellite telecommunication systems, as well as invisibility cloaks and radars. This study opens a way to realize more complicated and enhanced-efficiency spectrum-changing metasurface.

Why do MNEs both make and coopete for innovation?

While multinational enterprises (MNEs) possess the resources and knowledge to develop innovation projects internally with their own international subsidiaries, they sometimes prefer to develop innovation projects with their competitors. We investigate the circumstances under which MNEs prefer to “make” or “coopete” for certain specific innovation projects, which has not previously been addressed in the literature. Based on a case study of Airbus Defence and Space, we study two telecommunication satellite innovation projects (one developed internally and the other with a competitor). We show that both make and coopete strategies lead to short- and long-term benefits as well as risks. More precisely, we underscore that coopete decisions provide more short-term benefits than make decisions. By contrast, in the longer term, make decisions are more beneficial than coopete decisions. Therefore, we emphasize that for a given project, managers weight the options for and against each choice based on specific time frames, keeping in mind the necessity of both making and coopeting at the corporate level.

SIMULATION OF COMPACT POLARIZERS FOR SATELLITE TELECOMMUNICATION SYSTEMS WITH THE ACCOUNT OF THICKNESS OF IRISES

Background. One of the main problems in modern satellite telecommunication systems is to increase the volume of information transmission with simultaneous preservation of its quality. Key element of such systems is antenna systems with polarization processing, which is carried out using polarizers. Therefore, development of new polarizers and simple techniques for their analysis and optimization are important problems. The most simple, effective, technological and actual for analysis are polarizers based on waveguides with irises. Objective. The purpose of the paper is to create a mathematical model of the polarizer based on a square waveguide with irises, which allows analyzing the influence of polarizer’s design parameters on its electromagnetic characteristics. Methods. A mathematical model of the waveguide polarizer with irises is created by decomposition technique using transfer and scattering wave matrices. To take into account the irises’ thickness their equivalent T- and Π-shaped circuits were used. Results. We have developed mathematical model of the waveguide polarizer with irises, which takes into account their thickness and is based on the complete scattering wave matrix of the waveguide polarizer. The matrix has been obtained using the microwave circuit theory. The main characteristics of the waveguide polarizer were defined using matrix elements. The optimization of characteristics of a polarizer was carried out in the operating Ku-band 10.7–12.8 GHz. Conclusions. Suggested mathematical model of a waveguide polarizer with irises provides the account of heights of irises, distances between them and their thickness. The results obtained show that this model is simpler and faster for the calculation of electromagnetic characteristics compared to finite elements method, which is often used for analysis of microwave devices for various applications.

An EnKF-based method to produce rainfall maps from simulated satellite-to-ground MW-link signal attenuation.

Measuring rainfall is complex, due to the high temporal and spatial variability of precipitation, especially in a changing climate, but it is of great importance for all the scientific and operational disciplines dealing with rainfall effects on the environment, human activities, and economy. Microwave (MW) telecommunication links carry information on rainfall rates along their path, through signal attenuation caused by raindrops, and can become measurements of opportunity, offering inexpensive chances to augment information without deploying additional infrastructures, at the cost of some smart processing. Processing satellite telecom signals bring some specific complexities related to the effects of rainfall boundaries, melting layer, and non-weather attenuations, but with the potential to provide worldwide precipitation data with high temporal and spatial samplings. These measurements have to be processed according to the probabilistic nature of the information they carry. An EnKF-based (Ensemble Kalman Filter) method has been developed to dynamically retrieve rainfall fields in gridded domains, which manages such probabilistic information and exploits the high sampling rate of measurements. The paper presents the EnKF method with some representative tests from synthetic 3D experiments. Ancillary data are assumed as from worldwide-available operational meteorological satellites and models, for advection, initial and boundary conditions, rain height. The method reproduces rainfall structures and quantities in a correct way, and also manages possible link outages. It results computationally viable also for operational implementation and applicable to different link observation geometries and characteristics.