A3TB: Adaptive Antenna Array Test-Bed for Tracking LEO Satellites Based on Software-Defined Radio

Paper number

IAC-08.B2.4.3

Author

Dr. Ramón Martínez Rodríguez-Osorio, Universidad Politécnica de Madrid, Spain

Coauthor

Mr. Miguel Alejandro Salas Natera, Universidad Politécnica de Madrid, Spain

Coauthor

Mr. Alberto Antón, Universidad Politécnica de Madrid, Spain

Coauthor

Ms. Isabel García-Rojo López, INSA, Ingeniería y Servicios Aeroespaciales, S.A., Spain

Coauthor

Mr. Luis Cuéllar, Universidad Politécnica de Madrid, Spain

Year

2008

Abstract

Nowadays, earth stations for downloading data from LEO (Low Earth Orbit) satellites use large reflector antennas. These antennas pose a number of impairments regarding their mechanical complexity, lower flexibility, network efficiency and higher cost. Furthermore, reflector antennas can track only one satellite at a time, so the efficiency of the earth segment is reduced. In order to improve the performance of traditional earth stations, the feasibility of other antenna technologies such as antenna arraying must be evaluated. In this contribution the A3TB (Adaptive Antenna Array Test-Bed) prototype for tracking of meteorological LEO satellites is presented. 

The A3TB testbed is based on a Software-Defined Radio (SDR) architecture and has been implemented in a BenADC® hardware platform from Nallatech, that can process signals from four antennas. A3TB downconverts and decimates the received signals in the antenna array, and produces an array output according to the selected beamforming weight computation. The array output is transferred to a WXtoImg software to verify the reception of Earth images.

The aims of the testbed are to prove the advantages of antenna array processing compared to single-antenna schemes and compare the performance of different beamforming and calibration algorithms in a real scenario. Although the current implementation of A3TB processes the signals transmitted by NOAA satellites in the APT channel (137 MHz), it can process any satellite signal transmitted in the VHF band thanks to its SDR scheme.

In a satellite scenario, where the position of the satellite in its orbit is known, the most suitable beamforming algorithms are those based on a spatial reference. The performance of a beamformer based on spatial information relies on the operation of the calibration algorithm, that compensates for the possible mispointing of the array due to the temperature drift of the components, mutual coupling phenomena and unbalanced radiofrequency stages. Both beamforming and calibration can be implemented either in the FPGA (real time) or in the PC (offline), and thanks to the flexibility of the implementation, updated versions of the algorithm can be tested.

In the final version of the paper, performance results in terms of time of visibility and pointing accuracy will be compared for different beamforming and calibration algorithms. In particular, the time of visibility for a LEO satellite will be measured using one antenna and using the antenna array in order to show the increase in the capacity to download data from the satellite.

Abstract document

IAC-08.B2.4.3.pdf

Manuscript document

IAC-08.B2.4.3.pdf (🔒 authorized access only).

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