Abstract: A system which provides frequency conversion and continuously variable bandwidth control is implemented using first and second filter networks that exhibit a generalised Chebyshev transfer function. The first and second filter networks may comprise a pseudo-high-pass type filter in combination with a pseudo-low-pass type filter, or in a particularly efficient embodiment, a pseudo-high-pass type filter in combination with an elliptic low pass type filter. The effective frequency response overlap of first and second filter networks produces a composite band-pass filter response which is highly selective by nature and is determined only by the steep band edge transition region of the individual filter networks. The maximum pass-band of the first and second filter networks can be tailored to precisely fit the maximum band-pass bandwidth required by a channelised radio communications system.

Abstract: A thermal control film for use in spacecraft having a multi-layer interference filter adapted to exhibit high reflectivity to solar radiation, low absorptivity across the microwave spectrum and high emissivity in the far infra-red. The film is free from metal and extends over the active face of an antenna carried by the spacecraft. Such a film exhibits the desired thermo-optical properties for a thermal control radiator surface and can be used over the active face of a communications or radar antenna without disrupting the RF signal.

Abstract: A phased array antenna for a telecommunications satellite, that is deployable from a retracted condition to a deployed condition when the satellite is on-station, comprising a base member (12) of hexagonal form, and a plurality of deployable antenna panels (14) stacked one on top of the other on the base member (12) in the retracted condition, each antenna panel (14.1-14.6) being connected to a respective side edge region of the base by means of a respective back flap hinge (16.1-16.6), and the hinges having pivot points (18) that are offset relative to one another, such that the antenna panels (14) can be hinged sequentially one after the other from the stick to a position in which each panel is adjacent a respective base side edge region to provide an extended flat two-dimensional area when deployed.

Abstract: A reconfigurable system for the analogue processing of radio frequency signals in a satellite communications system, comprises means for receiving a signal within a pre-selected first intermediate frequency and agile filter means comprising a variable mixer stage and at least one variable filter, adapted to select one or more first frequency channels from the input signal, to amplify and provide automatic gain control of the selected first channel signals and to translate the selected first channels to one or more second frequency channel signals within a pre-selected second intermediate frequency band, wherein the agile filter means is controllable to allow in-orbit reconfiguration of the system. The first and second intermediate frequencies are selected so as to minimize conversion of the uplink and downlink signals.

Abstract: An articulated boom comprises a support arm with a plurality of hingedly-connected joints. The arm is adapted and arranged to carry an antenna reflector so that in use, the reflector can move between a first stowed position in which the reflector is in folded condition and a second deployed position in which the reflector is in deployed condition. A spacecraft incorporates into one or more of its sides a plurality of such articulated booms. The support arms of the booms can be advantageously positioned at the circumference of the associated reflectors when in a stowed position, so as to allow the reflectors to be neatly stacked together within a space defined by the launch vehicle fairing.

Abstract: Projecting elongate stub walls are provided on the planar surfaces of a substrate at positions where bonding of the substrate to a clamping lid or base is to be carried out. On firing of the substrate, the surfaces thereof are mechanically processed but since the stub walls protrude from the substrate, the grinding and polishing tools make contact with the surfaces of these stub walls, rather than with the entire substrate surface. As a result, the area of the substrate to be processed is minimised and problems with dishing and erosion are alleviated. This allows the clamping lid, or frame to be bonded, using conventional conductive adhesive processes, avoiding the cracking and stress problems associated with non-uniformity of the surface of the ceramic substrates.