TEC-EEA Final Presentation Day: Recent Communication Satellite Antenna Developments

Wednesday 23 Mar 2016, 09:15 → 16:15 Europe/Amsterdam

Escape Dance Room (ESA/Estec)

Nelson Fonseca (European Space Agency), Peter de Maagt (ESTEC)

You are cordially invited to attend the Final Presentation Day organized by the Antenna and Sub-Millimetre Wave Section on the subject of “Recent Antenna and RF materials Developments”. This Final Presentation Day will be held on the 23^rd of December 2016 at ESA/ESTEC, Noordwijk, The Netherlands (Escape Dance room).

The full day programme starting at 9:15 is detailed in the 'timetable' section. Each presentation will last about 60 minutes, including questions. A brief summary for each activity and associated time slot can be downloaded by clicking on 'Programme' here below. Feel free to forward this invitation to colleagues that may be interested in these developments.

Please fill in the registration form to confirm your attendance and enable non-ESA attendees to access the site.

09:15 Introduction

1 Active multibeam sparse array demonstrator - Space Engineering (IT) and CNIT (IT)

The scope of this Artes 5.1 activity is to design a Transmit reconfigurable direct radiating array based on a sparse layout and to validate the design with a representative antenna demonstrator. Sparse arrays, based on non-regular lattices, are a valid alternative to periodic arrays because they are able to generate an equivalent tapering by adjusting the element positions. They also allow reducing the number of elements, and increasing the DC to RF overall efficiency of the antenna. In this activity the optimization of the irregular array layout has been done in such a way to satisfy the required radiative performance keeping at the same time a simplified beam forming network and cooling system (e.g. heat-pipe). During the project several challenges have been faced and solved adopting state of the art solutions like: • design, manufacturing and testing of an innovative Active Feed Module composed by a square horn, integrating two SSPAs, mounted directly on the Heat Pipes so improving the cooling management; • design, manufacturing and testing of a modular box BFN able to feed an 8 Active Feed Module providing the re-configurable network for multi-beams (i.e. 4 beams per polarization) based on multi-layer PCB technology and high MMICs integration.

2 Overlapping Ka-band multiple spot beam based on single aperture antenna - Space Engineering (IT)

The future generation of communication satellites will use multi-beam antennas providing wide-band two-ways communication applications. Active discrete lens antennas generate a multibeam coverage adopting only a single Tx/Rx aperture or two separated apertures instead of the current solutions based on multi-reflector systems. Reduced volume and maximum EIRP flexibility over the service area are the main advantages of this antenna. The activity has been divided in two phases. Phase 1 included trade-off between several discrete lens architectures, selection of the overall antenna architecture and preliminary design of the demonstrator. Phase 2 concerned the detailed analysis and design of the Tx on-board antenna together with the manufacturing, integration and testing of a small Tx demonstrator with 28 active elements radiating both opposite circular polarizations. During the activity a Tx active lens for a Ka-band Inmarsat-like multibeam application with 1.75° spot beams and with a DC power consumption of 4 kW has been designed. The system uses a four colour reuse scheme and is able to radiate 13 active beams, with an EIRP of 55 dBW, selected between 121 spot beams of the Earth global coverage. The active lens has 218 active elements radiating both circular polarization by means of two GaN SSPAs. The front and the back array are aperiodic to simplify the RF chain inside the discrete lens. A thermal control system with 27 heat pipes and 4 loop heat pipes has been designed to dissipate the heat power dissipated by the SSPAs.

11:30 Coffee break

3 Dual-Gridded Carbon Fibre Reinforced Plastic Reflector - HPS GmbH (DE)

The objective of the activity was the development of a very lightweight linear polarisation sensitive dual gridded antenna for future Ku‐band missions (KuDGR). The applied technology was based on HPS’s patented KaDGR‐Technology (patent N° 10711326.8‐1959/2406855) in which the reflective surface is realised by a high number of thin CFRP rods stabilized and connected with a small number of perpendicular non‐conductive rods. For the KuDGR‐activity the front and rear reflector had to be shaped, both grids had been designed out of CFRP rods. The selected reference mission scenario was a co‐polar coverage split into three areas over north Africa. The most difficult task was the development of manufacturing processes for the single shaped rods. A breadboard was built in order to check the manufacturability in advance. Finally an engineering model has been manufactured and tested: thermal vacuum cycling, thermal distortion test and an extensive RF test. The results have been correlated with the models. The KuDGR project demonstrated that the principal design for a • shaped DGR with a completely new concept (see above) • without any dielectrical shells • with grids being manufactured as CFRP rods and • with structural parts also made of pure CFRP is working well w.r.t. structural/thermal design and also for the RF properties. This new design is thermally extremely stable and does not need any thermal protection in the assumed configuration as Earth-deck antenna. It also results in clearly reduced mass of just 4.2 kg “as built”. In relation of the available budget of the activity the results can be rated as very successful.

12:45 Lunch Break

4 Tx/Rx Feed Assembly with Flexible Polarisation - RYMSA ESPACIO SAU (ES)

Although telecommunication satellites are designed to have long life time to maximize operators´ revenue, they also need to have some in-orbit flexibility to react to short-term market changes. This development addressed the need for polarization flexibility (converting from Circular to Linear polarization) at feed assembly level, which could be necessary to comply with regional regulations when changing the service area and orbit position of a given GEO satellite. The purpose of this activity was to achieve such a functionality without duplication of hardware (feed assemblies) and minimizing the number of actuated parts to maintain high reliability. This activity started with a consolidation of the mission needs to identify possible missions/frequency bands benefiting the most from polarization flexibility. Requirements at feed level were derived from the selected mission and combined with a state-of-the-art review to select the most promising feed assembly concept. A representative Engineering Model was then developed and tested, with polarization flexibility both in Tx and Rx. RF measurement results were in line with expectations, demonstrating the potential of the proposed solution.

5 Thermal Blanket with Low RF Reflectivity - HPS Lda (PT)

One of the problems of traditional Multi-Layer Insulation (MLI) blankets is the reflection of radio (particularly microwave) frequencies in its metallized surface. Such reflection equates to the one of a perfect electric conductor, and can pose a significant problem to the communication branch of the mission – it can generate sidelobes in unwanted angles and cross polarisation in circular polarised applications. In this study HPS developed an MLI which is able to manage such reflections, and minimize them to an insignificant level. The project objectives were to design, manufacture and characterize a MLI blanket that is capable of dealing with the high RF reflectivity of traditional MLI and thus reduce the coupling between antennas and multipath effects. This novel MLI blanket is still able to: 1. maintain its primary thermal-optical functionality, 2. withstand the harsh space environment, 3. Be characterised with respected to their thermal-optical and electrical properties. The key challenges of the project were to make use of available space qualified materials (with known outgassing, cleanliness, solvent compatibility proprieties and preferably ITAR free), using a technology to enable RF absorption in either C-band, Ku-band and/or Ka-band. In addition, the blanket shall perform, as good as a traditional MLI, withstanding temperatures up to 200 ºC. Best practices were also applied in order to be PIM-free, while including all grounding and venting requirements. The results obtained at breadboard level will also be presented.

16:00 Closure