27,680 research outputs found
Experiments for Ka-band mobile applications: The ACTS mobile terminal
To explore the potential of Ka-band to support mobile satellite services, the Jet Propulsion Laboratory (JPL) has initiated the design and development of a Ka-band land-mobile terminal to be used with the Advanced Communications Technology Satellite (ACTS). The planned experimental setup with ACTS is described. Brief functional descriptions of the mobile and fixed terminals are provided. The inputs required from the propagation community to support the design activities and the planned experiments are also discussed
Ka band propagation experiments on the Australian low earth orbit microsatellite 'FedSat'
University of Technology, Sydney. Faculty of Engineering.The emergence of the 20/30 GHz Ka band in satellite communications in recent
decades has seen systems designers faced with the problem of severe signal
attenuation though atmospheric effects, especially rain. Previous experimental
missions, such as ACTS and OLYMPUS, have succeeded in collecting large
amounts of propagation data, which has led to the development of various
semi-empirical models for link design. However, all these experiments were
carried out over geostationary satellites, and with a recent tendency towards
constellations of low-earth orbit satellites for true global coverage and increased
system capacity for real-time services, these models are in need of adaptation
for variable elevation angles and the effects of rapid satellite movement.
The work contained in this largely experimental thesis presents the Australian
‘FedSat’ LEO microsatellite, carrying a Ka band beacon and a bent-pipe mode
transponder, as an ideal research platform for such investigations. The inhouse
design, deployment and operation of a very low-cost, fast-tracking earth
station is examined in-depth, and particular attention is paid to systems design
aspects involving numerous hardware and software technologies, which interact
with each other in a highly complex manner, for example Doppler frequency
tracking, pointing accuracy control and precise signal power measurements.
Prior to and during the operational phase, several crucial design improvements
are discussed, implemented and verified. Successful and reliable tracking by
using pointing coordinates derived from two-line elements, as opposed to GPS
data, is experimentally proven.
The design of the earth station prototype is validated by the collection of
Ka band propagation data in both beacon and bent pipe modes. After postprocessing
of the data, attenuation results for various weather conditions and
down to elevation angles well below 10 degrees are illustrated and interpreted in conjunction
with the prevailing weather conditions. While a comparison with the
measurements from geostationary satellites widely confirms the validity of the
results, other interesting phenomena are unveiled that require further investigation.
In particular, the extent of low-angle scintillation appears to be wider
band than previously reported in published literature, which is a potentially
important finding.
Finally, the experience gathered during the late-stage design and the operation
of the earth station gives rise to several recommendations for further design
improvements and operational strategies, which may be helpful for future research
groups in this field wishing to conduct similar LEO Ka band propagation
experiments on a low budget
Satellite system performance assessment for in-flight entertainment and air traffic control
Concurrent satellite systems have been proposed for IFE (In-Flight Entertainment) communications, thus demonstrating the capability of satellites to provide multimedia access to users in aircraft cabin. At the same time, an increasing interest in the use of satellite communications for ATC (Air Traffic Control) has been motivated by the increasing load of traditional radio links mainly in the VHF band, and uses the extended capacities the satellite may provide. However, the development of a dedicated satellite system for ATS (Air Traffic Services) and AOC (Airline Operational Communications) seems to be a long-term perspective. The objective of the presented system design is to provide both passenger application traffic access (Internet, GSM) and a high-reliability channel for aeronautical applications using the same satellite links. Due to the constraints in capacity and radio bandwidth allocation, very high frequencies (above 20 GHz) are considered here. The corresponding design implications for the air interface are taken into account and access performances are derived using a dedicated simulation model. Some preliminary results are shown in this paper to demonstrate the technical feasibility of such system design with increased capacity. More details and the open issues will be studied in the future of this research work
Olympus propagation studies in the US: Propagation terminal hardware and experiments
Virginia Tech is performing a comprehensive set of propagation measurements using the Olympus satellite beacons at 12.5, 20, and 30 GHz. These data will be used to characterize propagation conditions on small earth terminal (VSAT)-type networks for next generation small aperture Ka-band systems. The European Space Agency (ESA) satellite Olympus was launched July 12, 1989. The spacecraft contains a sophisticated package of propagation beacons operating at 12.5, 19.77, and 29.66 GHz (referred to as 12.5, 20, and 30 beacons). These beacons cover the east coast of the United States with sufficient power for attenuation measurements. The Virginia Satellite Communications Group is completing the hardware construction phase and will begin formal data collection in June
Assessing radiative transfer models trained by numerical weather forecasts using sun-tracking radiometric measurements for satellite link characterization up to W band
Radio communications, and in particular Earth-to-satellite
links, are worldwide used for delivering digital services.
The bandwidth demand of such services is increasing
accordingly to the advent of more advanced applications
(e.g., multimedia services, deep-space explorations, etc.)
thus pushing the scientific community toward the
investigation of channel carriers at higher frequencies.
When using carrier frequencies above X band, the main
drawback is how to tackle the impact of tropospheric
processes (i.e., rain, cloud, water vapor). This work
assesses the joint use of weather forecast models, radiative
transfer models and Sun-tracking radiometric
measurements to explore their potential benefits in
predicting path attenuation and sky noise temperature for
slant paths at frequencies between K and W band, thus
paving the way to the optimization of satellite link-budgets
Ultra-low-loss CMOS-Compatible Waveguide Crossing Arrays Based on Multimode Bloch Waves and Imaginary Coupling
We experimentally demonstrate broadband waveguide crossing arrays showing
ultra low loss down to dB/crossing (), matching theory, and
crosstalk suppression over dB, in a CMOS-compatible geometry. The
principle of operation is the tailored excitation of a low-loss spatial Bloch
wave formed by matching the periodicity of the crossing array to the difference
in propagation constants of the 1- and 3-order TE-like
modes of a multimode silicon waveguide. Radiative scattering at the crossing
points acts like a periodic imaginary-permittivity perturbation that couples
two supermodes, which results in imaginary (radiative) propagation-constant
splitting and gives rise to a low-loss, unidirectional breathing Bloch wave.
This type of crossing array provides a robust implementation of a key component
enabling dense photonic integration
Characterization and Commissioning of a Ka-Band Ground Station for Cognitive Algorithm Development
In 2018, the Cognitive Communications and Propagation projects completed installation and checkout testing of a new Ka-Band ground station at the NASA Glenn Research Center in Cleveland, Ohio. The Cognitive Algorithms Demonstration Testbed (CADeT) was developed to provide a fully characterized and controllable dynamic link environment to researchers looking to demonstrate hardware and software aligned with atmospheric sensing and cognitive algorithms. CADeT integrates a host of precision control and measurement systems in addition to repurposing a 5.5 meter beam-waveguide dish platform previously used with the Advanced Communications Technology Satellite (ACTS). This paper will discuss the laboratory testing of ground station components with a emphasis on elements vital to achieving link budget requirements including characterization of the new Gallium Nitride (GaN) Solid State Power Amplifier (SSPA) and far-field measurements of the new antenna feed. Finally, the paper discusses in-situ tests conducted with CADeT and the Tracking and Data Relay Satellite System (TDRSS) to validate laboratory results and make necessary link budget adjustments before reviewing the lessons learned
Experiments applications guide: Advanced Communications Technology Satellite (ACTS)
This applications guide first surveys the capabilities of the Advanced Communication Technology Satellite (ACTS) system (both the flight and ground segments). This overview is followed by a description of the baseband processor (BBP) and microwave switch matrix (MSM) operating modes. Terminals operating with the baseband processor are referred to as low burst rate (LBR); and those operating with the microwave switch matrix, as high burst rate (HBR). Three very small-aperture terminals (VSATs), LBR-1, LBR-2, and HBR, are described for various ACTS operating modes. Also described is the NASA Lewis link evaluation terminal. A section on ACTS experiment opportunities introduces a wide spectrum of network control, telecommunications, system, and scientific experiments. The performance of the VSATs is discussed in detail. This guide is intended as a catalyst to encourage participation by the telecommunications, business, and science communities in a broad spectrum of experiments
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