Astrium Gmbh

Agence Spatiale Europeenne

British Aerospace Plc

Simon John Stirland

Antoine G Roederer

Antony Duncan Craig

Ronald W Young

David Robson

A satellite antenna arrangement for a satellite communication system comprising: a reflector for producing a far field pattern with near-zero field strength at a predetermined location to reject unwanted signals from said predetermined location or minimize signal power transmitted to said predetermined location, the reflector having a surface comprising a stepped profile arranged to generate the near-zero field strength in the predetermined location. The stepped profile may comprise a radial step. The location of the near-zero field strength can be steered by moving the reflector or by adjusting the amplitude and phase of an additional beam that covers substantially the same region as the main beam reflected by the reflector.

Reflector

A phased array antenna for providing a radiation pattern having at least one communication beam, includes a plurality of antenna elements, each with an antenna element signal having a phase relationship and an amplitude relationship to the other element signals; a digital signal processing arrangement providing a digital beamforming network; and an analog beamforming network arranged to reduce exposure of the digital signal processing arrangement to an interfering signal. Analog beamforming weights are selected to generate a null in the radiation pattern in a direction corresponding to the interfering signal.

Antenna

A telecommunications satellite having a phased array antenna, wherein the beam-forming function within the phased array is simplified by partitioning it into two stages, in which the sub-array stage relates to a fixed, or infrequently changed, set of overlapping sub-arrays and the main stage provides the main pattern reconfiguration, typically in the form of multiple reconfigurable spot beams within a defined coverage region. The key advantage lies in the significant reduction in number of second stage beam-forming control points (at which independent amplitude and phase is applied) when compared with a conventional phased array (where amplitude and phase control is applied for each element of the array). The sub-array stage beam-forming may be implemented in analogue technology. The main beam-former may be implemented in digital technology, where the key processing functions of A/D or D/A conversion, frequency (de)multiplexing and digital beam-forming all scale with the number of control points.

System for simplification of reconfigurable beam-forming network processing within a phased array antenna for a telecommunications satellite

The invention relates to a feed device for a multisource semiactive antenna with multiple beams, including: a) a nonorthogonal beam shaper device (65) splitting Nb beam input signals and combining them to form Na output signals, b) Na amplifier modules (64), c) an orthogonal output power splitter (63) arranged between the Na amplifier modules (64) and Ne radiating elements (61). According to the invention, Nb.ltoreq.Na.ltoreq.Ne, and the orthogonal transfer function of the splitter (63) permits change between, on the one hand, Nb distributions at the input of the splitter (63), in which the amplitude of the Na signals is equal for each of the Nb beams, and in which the phase satisfied the condition of equality of the scalar products, taken in pairs, of the Nb excitation vectors at the input of the splitter (63), and of the scalar products, taken in pairs, of the Nb corresponding output excitation vectors and, on the other hand, Nb predetermined output distributions. Appended FIG. 6.

Feed device for a multisource and multibeam antenna

Measurement of flux density at the edges of the footprint of an RF transmission from a spacecraft with a view to determining the spacecraft antenna pointing error is difficult because of atmospheric fading local to the measuring station. Previous proposals to permit determination of pointing error in the face of such effects involve additional hardware on board the craft. Herein, it is proposed to induce a relatively small repetitive scanning motion of the spacecraft hence producing an oscillatory flux density variation at peripheral ground stations and then measuring the oscillatory component relative to the average flux density--frequency analysis equipment operable to discriminate the known frequency of the variation over a plurality of wavelengths can be used giving substantial accuracy improvement. A series of measurements enable the diurnal pointing error pattern to be determined and hence a spacecraft attitude correction command program to be produced.

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Hitchin, United Kingdom

Simon John Stirland