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Objectives
The need for wider frequency bandwidths in multimedia applications pushes payload design toward higher frequencies. Recently, a significant frequency bandwidth has been allocated by the International Telecommunication Union (ITU) in the Q/V band for Fixed-Satellite Services (FSS), making these frequencies the most promising candidates for the near future broadband systems. From on-going studies investigating next-generation high-capacity satellite architectures, it is anticipated that a first step would be a GEO mission making use of Q/V band for the feeder link, while the user link remains in Ka band.
Within this frame, and under the ARTES 5.1 initiative, the European Space Agency has contracted to the team composed by HPS GmbH (as prime contractor), INVENT GmbH and TESAT GmbH (as sub-contractors), Cobham CTS Limited and other partners the development of an earth-deck antenna for feeder link applications in Q/V band (Frequency band Tx: 37.5-40.5 GHz, Rx: 47.2-50.2 GHz) to be embarked on a GEO communication satellite mission with high capacity requirements.
One of the objectives of the activity was to perform an antenna architecture trade-off to identify the most suitable antenna geometry for such an application taking into account RF and thermo-mechanical aspects.
As best antenna configuration a Gregorian offset geometry has been selected and validated with an EM (Engineering Model), including a representative feed chain.
Figure 1: FLANT EM model during the RF test campaign (HPS GmbH)
Challenges
From an RF point of view high isolation between all beams and low scan degradation for widely scanned beams had to be realized in a fairly compact antenna configuration.
From a mechanical point of view the high frequency band of the FLANT antenna requires very challenging tolerances of all the RF components (Feed chain, main and sub reflector). The design of the antenna, the processes adopted for the manufacturing, the assembly procedures, the measurement during the alignment phase have all required special care in order to achieve the very good performances measured on the RF test campaign.
Plan
The project was organized as follows:
- Task 1 had to consolidate the proposed mission using a Q/V-band feeder link antenna sub-system and the corresponding feeder link antenna requirements.
- Task 2, running in parallel to task 1, had to provide an overview of the state-of-the-art of Earth deck antennas and Q/V-band technology.
- Task 3 had to perform an antenna configuration trade-off and selection of most promising candidate and derive requirements at sub-system level.
- Task 4 had to provide the analysis at feed and antenna level and define the antenna EM to be manufactured.
- Task 5 is related to the hardware manufacturing.
- Task 6 covers the antenna EM RF testing.
Task 7 had to perform a review of achievement based on the measurement results and conclude on the feasibility of an Earth deck antenna suited for Q/V-band feeder link applications.
Current Status
All the tasks have been completed.
The measurement of the EM model of the antenna has shown the compliance with margins to the requirements and an excellent agreement with the RF analysis performed taking into account the contour measurement of the reflectors and the alignment data (see Figure 5). This confirms the robustness of the mechanical and RF antenna design and validates the MAIT (Manufacturing Assembly Integration and Test) processes and procedures adopted by HPS GmbH and its partners for Q/V band antennas.
Figure 5: FLANT EM antenna, comparison of the measured and predicted co-polarization contours @37.5GHz (top), @40GHz (center) and @50.2GHz (bottom)
