Theoretical and experimental satellite channel characterisation

The proliferation of very high throughput satellite systems offering Terabit/s of system capacities, puts a large strain on the gateway feeder link requirements. This is leading to the exploitation and use of communication link systems using higher frequencies for data transmission, as it offers a larger bandwidth than the traditional Ka-band channels. Even with the exploitation of the Q/V-band (40/50 GHz), the number of required gateways may be such that the cost of the ground segment exceeds the cost of the satellite. The use of W-band (70/80 GHz) as an additional feeder link frequency band in future very high throughput satellite systems could significantly reduce the cost of the ground segment. This would also offer an opportunity for the user links to migrate to higher frequencies, improving their capacity and helping into decongesting the current occupied channels. Atmospheric impairments, including sky noise, play a major role towards the design of future satellite systems and their mitigation techniques as higher bands magnify these impairments. Within this thesis, an overview of the current communication satellite systems, propagation campaign heritage and current atmospheric impairment models is shown. Furthermore, the design and development of a geostationary beacon payload for propagation measurements premiering W-band is shown. Ground receivers are also significant towards the collection of propagation measurements. The design, development and implementation of such a receiver at Ka-band is shown. Moreover, beacon measurements at Ka- and Q-band using the Aldo Paraboni payload are processed to reflect excess and total atmospheric fading respectively. Concurrent recordings of the sky noise enable radiometric measurements from the implemented receiver terminals, which can enable sky monitoring. Calibration of the noise channel at Q-band and validation of the fading with that from a beacon power measurement is also shown.Heriot-Watt University DTP scholarship funded by the Engineering and Physical Sciences Research Council (EPSRC)

Tropospheric scintillation and attenuation on satellite-to-Earth links at Ka and Q band: modeling, validation and experimental applications

Link budget is a crucial step during the design of every communication system. For this reason it is fundamental to identify and estimate the effects of the atmosphere on the electromagnetic signal along the path from the source to the sink. Troposphere represent the bigger source of attenuation and scintillation for signals in the microwave and upper frequency spectrum. During last years we have participated in the European Space Agency “AlphaSat Aldo Paraboni” experimental campaigns to acquire up to date propagation data at two frequencies of interest for future communication systems. We realized two high performance low-noise receiver located in Rome, one at Ka and one at Q band (19.701 and 39.402 GHz) to detect the two signal beacons sent from the AlphaSat geostationary satellite to a wide area over Europe. Collected data from Rome receiving station have been analysed to measure excess attenuation and scintillation along the path. Such statistics collected in a database together with data from other experimenter will be in the near future a useful instrument, giving professionals updated data for their custom application design. Classical link budget techniques rely on climatological atmospheric statistics based on different time-scales, usually data collected for several years. In the background of the European Space Agency “STEAM” project, we proposed the use of high resolution 3D weather forecast models (up to 166m pixel resolution) for the calculation of excess attenuation and tropospheric scintillation for satellite to earth link. As a result, the estimation of these electromagnetic parameters to use in link budgets could be given no more as a statistical analysis of past events as in the case of Internation Telecommunication Union recommendation but as time-series forecast specific for the selected receiving station and along the slant path of the transmitted signal. Case studies for the use of this technique have been deeply analysed and results compared with data from the AlphaSat measurement campaign for the Rome and Spino d’Adda receiving station, confirming the validity even in different geographical regions. In everyday situations, propagation models based on statistics are often replaced by the use of easier to apply parametric models. Those have the advantage of the simplicity and the need of less input parameter to be applied. In particular, for what concerning the tropospheric scintillation, the Hufnagel-Valley refractive index structure constant (C2n ) parametric model is actually the most used, due to the simplicity and the relative accuracy. We here propose a new Cn2 polynomial parametric model (CPP) based just on the altitude z and a function C2 n0(to,RH0) that allow to calculate the ground refractive index structure constant just using the ground temperature (T0) and the relative humidity (RH0). In this work CPP and Hufnagel-Valley models are applied to different location around the globe to prove their accuracy. The obtained model could be also used in the future to realize a simulator able to generate random C2n vertical profiles specific for the receiver site

Aldo paraboni mission how technology demonstrators and scientific activities pave the way for commercial SatCom Q/V band missions

The Q/V band technology demonstration mission on board the Alphasat satellite has been operational for four and a half years, since January 2014. The mission was conceived by Professor Aldo Paraboni’s, who proposed to investigate through a low scale demonstration mission the characteristics of propagation impairments and satellite communication systems at Q/V band frequencies. ASI supported the mission and its implementation, space and Italian ground mission segments, were undertaken respectively under ESA’s ARTES Programme and ASI’s national research programme. In addition, a ground segment in Austria has been implemented, thanks to the support of the Austrian delegation to ESA, under ESA’s ARTES Programme. The Aldo Paraboni Mission has also enabled a number of R&D projects in the framework of ESA ARTES 5.1, TRP, and PECS programs. A number of national space organisations, including CNES and NASA, are also actively involved in the wide propagation campaign carried out over Europe. The scientific coordination between experimenters is performed by a group of Alphasat Aldo Paraboni Propagation Experimenters (ASAPE) promoted by ESA and ASI. The Aldo Paraboni mission is paving the way towards the development of fully dimensioned missions operating at Q/V band. The Aldo Paraboni payload is composed by two payloads, a propagation payload consisting of two beacon transmitters. And a communication payload that enables two simultaneous communication channels at Q/V band. Aldo Paraboni’s propagation mission complements the research on propagation impairments over satellite communication systems, which were initiated in the 90’s through missions like Olympus and Italsat at high frequency bands. The support of the scientific community is paramount to the success of the mission gathering propagation data from multiple locations over Europe at Ka and Q bands. The data obtained over the planned mission lifetime, i.e. 6 years, can lead to accurate propagation models that will be used on the design of communication systems at these frequency bands, with particular regard to the spatial-temporal model of the radio channel over Europe for multi-beam reconfigurable satellite systems. The results of these activities are intended to be submitted to ITU-R Study Group 3 “Radiowave Propagation” to contribute to International Radio Regulations for Fixed Satellite Services. The Aldo Paraboni Communication mission covers a broad range of tests using the Q/V band communication payload on board Alphasat, which aim at optimizing the operation of the communication systems at these frequency bands. The utilization of propagation impairment mitigation techniques, like adaptive coding and modulation, power adaptation or space diversity techniques will greatly contribute to the optimization of the design of the payloads and ground segment elements of fully dimensioned systems that will operate at these frequencies. This paper aims at presenting how the Aldo Paraboni mission, with the actual technologies and results from scientific and communication experiments, contributes to the characterization and design of future operational satellite communication systems at Q/V band

1-D broadside-radiating leaky-wave antenna based on a numerically synthesized impedance surface

A newly-developed deterministic numerical technique for the automated design of metasurface antennas is applied here for the first time to the design of a 1-D printed Leaky-Wave Antenna (LWA) for broadside radiation. The surface impedance synthesis process does not require any a priori knowledge on the impedance pattern, and starts from a mask constraint on the desired far-field and practical bounds on the unit cell impedance values. The designed reactance surface for broadside radiation exhibits a non conventional patterning; this highlights the merit of using an automated design process for a design well known to be challenging for analytical methods. The antenna is physically implemented with an array of metal strips with varying gap widths and simulation results show very good agreement with the predicted performance

Beam scanning by liquid-crystal biasing in a modified SIW structure

A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium

Validation of ground infrastructure in the framework of the ASI Q/V-band program

The Q/V Band program of ASI involves two main elements: the Space Segment and the Mission Segment. The Space Segment is represented by the Technology Demonstration Payload TDP#5, the Aldo Paraboni P/L. Financed by Italy through the ARTES-8 Program, it has been developed by the European Space Agency and implemented by italian space industries. It has been embarked as hosted payload on Alphasat satellite, and successfully launched on July 25th 2013. Alphasat is an INMARSAT Commercial Telecommunications Geosynchronous satellite, which uses the ESA developed Alphabus Platform and embarks four Technology Demonstration Payloads (TDPs). Among these TDPs, TDP#5 is devoted to the exploitation and the investigation of Q/V band communications. In conjunction with the Mission Segment (MS) the TDP#5 allows to carry out communications experiments (Propagation Impairment Mitigation Techniques - PIMT) at 40/50 GHz (Q/V-band) and propagation experiments at both 20 GHz (Ka-band) and 40 GHz (Q-band). The MS has been developed by ASI and consists of two transmitting/receiving Ground Stations (GS) and three control centers, for the execution of experiments in accordance with the requirements defined by the two Principal Investigators, appointed by ASI for the communication and propagation experiments. After the integration of all the elements composing the MS, the system test campaign started with the scope to demonstrate the correct operations through functional and performance tests. In particular, in addition to the propagation experiment verification, the campaign allows to test the Q/V band communication functions in the two payload configurations (i.e. in loopback mode and in cross mode)

The propagation and telecom experiments of the Alphasat Aldo payload (TDP5 Q/V band experiment)

The utilization of millimetric waves in satellite communications requires the use of advanced transmission techniques known as Propagation Impairments Mitigation Techniques (PIMT) to counteract severe atmospheric phenomena without excessive power expenditures. Among these PIMTs we remind Adaptive Code Modulation (ACM), reconfigurable antenna pattern, site diversity, up/down link power control and others. The possibility to exploit profitably this concept is based on the knowledge coming from the propagation science, i.e. on accurate models for the space- and time-distribution of impairments such as rain attenuation and to allow their experimental validation through measurements. The TDP5 Q/V Band Propagation Payload, which has been renamed as Alphasat Aldo payload to the memory of Prof. Aldo Paraboni, who conceived and greatly contributed to its realization, will allow in the near future further propagation and telecom measurements across Europe. The mission will allow a direct assessment of the advantages obtainable from PIMTs like the ACM or reconfigurable on-board antenna. The payload has been supported by the Italian Space Agency (ASI) as in-kind contribution to the Alphasat project which is executed by the European Space Agency (ESA) in the framework of the ARTES 8 Telecom programme. Alphasat will be launched in 2013. The Aldo payload will permit simultaneous measurements of attenuation and depolarisation at 20 and 40 GHz during a long period (some years) all over Europe. In addition the Aldo payload will enable telecom Q/V experiments at the stations located within the 3 narrow spot beams covering Austria, North and South Italy. As for the ground segment, ASI assumed directly the commitment to realize the deployment and realization of the Earth terminals in Italy with the support of Politecnico di Milano and Univ. Tor Vergata as Principal Investigators for the propagation and telecommunication experiments, respectively. One of these terminals will be placed at the experimental station of Spino d'Adda (near Milan, North of Italy); another one will be installed in Tito Scalo (South of Italy). A third Earth Terminal for the telecom experiment is being developed by Joanneum Research (in the framework of an ESA ARTES 8 activity with the support of the Austrian Aeronautics and Space Agency) and it will be installed in Graz, Austria. As well, in order to enlarge the significance of this experiment, the development of additional propagation ground terminals for Alphasat has been assigned by ESA within the ARTES-5 programme for Telecom technology development to Joanneum Research and Graz University of Technology. In the frame of this contract a propagation terminal will be placed in Graz to perform joint measurements with the Telecom station. In this contribution the status and the planning of the Alphasat TDP5 experiments will be presented with particular regard to the ground segment and the planning for scientific activities

The Propagation and Telecom Experiments of the Alphasat Aldo Payload (TDP5 Q/V Band Experiment)

The utilization of millimetric waves in satellite communications requires the use of advanced transmission techniques known as Propagation Impairments Mitigation Techniques (PIMT) to counteract severe atmospheric phenomena without excessive power expenditures. Among these PIMTs we remind Adaptive Code Modulation (ACM), reconfigurable antenna pattern, site diversity, up/down link power control and others. The possibility to exploit profitably this concept is based on the knowledge coming from the propagation science, i.e. on accurate models for the space- and time-distribution of impairments such as rain attenuation and to allow their experimental validation through measurements. The TDP5 Q/V Band Propagation Payload, which has been renamed as Alphasat Aldo payload to the memory of Prof. Aldo Paraboni, who conceived and greatly contributed to its realization, will allow in the near future further propagation and \ud telecom measurements across Europe. The mission will allow a direct assessment of the advantages obtainable from PIMTs like the ACM or reconfigurable on-board antenna. The payload has been supported by the Italian Space Agency (ASI) as in-kind contribution to the Alphasat project which is executed by the European Space Agency (ESA) in the framework of the ARTES 8 Telecom programme. Alphasat will be launched in 2013. The Aldo payload will permit simultaneous measurements of attenuation and depolarisation at 20 and 40 GHz during a long period (some years) all over Europe. In addition the Aldo payload will enable telecom Q/V experiments at the stations located within the 3 narrow spot beams covering Austria, North and South Italy. As for the ground segment, ASI assumed directly the commitment to realize the deployment and realization of the Earth terminals in Italy with the support of Politecnico di Milano and Univ. Tor Vergata as Principal Investigators for the propagation and telecommunication experiments, respectively. One of these terminals will be placed at the experimental station of Spino d'Adda (near Milan, North of Italy); another one will be installed in Tito Scalo (South of Italy). A third Earth Terminal for the telecom experiment is being developed by Joanneum Research (in the framework of an ESA ARTES 8 activity with the support of the Austrian Aeronautics and Space Agency) and it will be installed in Graz, Austria. As well, in order to enlarge the significance of this experiment, the development of additional propagation ground terminals for Alphasat has been assigned by ESA within the ARTES-5 programme for Telecom technology development to Joanneum Research and Graz University of Technology. In the frame of this contract a propagation terminal will be placed in Graz to perform joint measurements with the Telecom station. In this contribution the status and the planning of the Alphasat TDP5 experiments will be presented with particular regard to the ground segment and the planning for scientific activities