This invention relates to improved antenna and particularly to antennae for transmitting or receiving electromagnetic signals from satellite orbiting the earth.

A number of types of satellite dish antennae presently exist, e. g. the prime-focus type, the offset type and the flat plate type. All of these suffer from problems such as being awkward and expensive to install and have in some cases become a danger due to high wind-loading.

EP 0643876B describes an improved antenna in which the dish is replaced by an elongate member of a dielectric material extending from a horn, the elongate member being surrounded by a plurality of plastic rods. A sheath is mounted over the elongate member and the surrounding rods.

Whilst this antenna provides significant advantages over satellite dish antennae, further improvements, especially in the operation of the antenna in wet conditions may be achieved.

The present invention aims to provide an improved antenna which produces a more stable signal, particularly in wet conditions which may, in relation to known antenna, cause interruption or distortion of the satellite signal.

According to one aspect of the present invention there is provided an antenna for receiving and/or transmitting signals from or to a satellite, the antenna comprising a housing, an elongate member extending from the housing and at least one strip of dielectric material provided over

the free end of the elongate member remote from the housing.

Preferably a plurality of strips of dielectric material are provided, each extending over the free end of the elongate member.

Advantageously, the ends of the or each strip of material is anchored to the housing and extends axially adjacent to the elongate member from the housing to the free end of the elongate member.

Conveniently, a free space is maintained between the elongate member and the or each strip.

Preferably, the elongate member is retained within the housing. The elongate member may be received in the housing in a push-fit arrangement.

Advantageously the housing is adapted to be mounted to a suitable surface. Mounting means may be provided on the housing to enable the housing to be mounted to a wall or roof of a building. The mounting means may comprise a bracket.

Advantageously also, a housing may comprise a sheath provided over the elongate member. Preferably the sheath may be provided with one or more channels to receive the one or more strips of dielectric material therein.

Preferably, the housing may be provided in the form of a horn, the elongate member extending from the open mouth of the horn.

Advantageously, a cover is provided over the antenna. The cover provides protection for the elongate member from precipitation and prevents water ingress into the housing of the antenna.

Advantageously, the width of the cover tapers outwardly from the housing to the free end of the elongate member.

Preferably also, the cover may be provided in the shape of an aerofoil around the elongate member.

Preferably also, a gasket may be provided around the open end of the horn to seal the boundary between the cover and the housing.

Embodiments of the present invention will now be described by way of example only, with reference to the accompanying drawings, which are: Fig 1 shows a schematic side view of an antenna according to the present invention; Fig 2 shows an end view along direction B of the antenna of Fig. 1; and Fig 3 shows end views of various modifications to the antenna of Fig 2.

Referring to Figs 1 and 2, there is illustrated a satellite antenna according to one aspect of the present invention, generally designated 5. The antenna 5 comprises an elongate member in the form of a hollow rod 10, and a horn 15. The rod 10 may be made from any suitable dielectric material, for example, P. V. C. having a dielectric constant, r-3. 0 to 3.5. The horn 15 comprises a front-most frusto-conical portion 20 and a rearmost portion 25 integrally connected thereto. The

rearmost portion 25 comprises first, second and third cylindrical portions 30,35 of decreasing diameter, the first portion 30 extending from a narrow end 40 of the frusto-conical portion 20.

The shape of the horn 15 determines the overall signal gain. It also defines the signal frequency. The horn 15 can be made from stamped, spun or diecast metal as long as the internal dimensions are accurate and the surface is relatively smooth.

The rod 10 is the main collector or transmitter of the electro magnetic signal and utilises its surface wave properties. Signal strength and frequency is controlled by rod diameter, type of plastic rod used and rod length.

The first and second cylindrical portions 30,35 are likewise integrally connected by a second frusto-conical portion 50.

A first end 60 of the rod 10 is rigidly retained within a narrow end 61 of the horn 15 provided by the second cylindrical portion 35 the internal diameter of which is a close fit with the outer diameter of the rod 10.

Further, provided on an outer surface 62 of the second cylindrical portion 35 are connection means comprising a threaded portion 65, the threaded portion 65 allowing connection of the antenna 5 to a conventional low noise blocker (LNB) 115, as is known in the art, used when the antenna is receiving signals. As an alternative, a push fit connection between the horn and the LNB may be provided.

The antenna 5 also comprises an elongate sheath 70 having an elongate space 75, such that the sheath 70 is capable of being received on the elongate member 10. The

sheath is made from an expanded polystyrene. Various industrial grades of polystyrene are available, however, it has been found that good results are obtained from grades in the low-middle range.

The sheath 70 provides a first open end 80 suitably shaped so as to snugly fit within the frusto-conical portion 20 of the horn 15. Preferably, a main elongate portion 85 of the sheath 70 can be round or elliptical in cross section. Further, the sheath 70 is open ended and the elongate rod 10 extends slightly beyond the end of the sheath 70. The elongate rod 10 is fluted at this end which extends beyond the end of the sheath.

Alternatively, the sheath 70 could have a closed end extending over the free end of the elongate rod.

The sheath 70 of this embodiment is provided with two opposing elongate channels 95 at or near an outer surface thereof and surrounding the rod 10. The channels extend along the length of the sheath and terminate at the free end 90 of the sheath. An elongate strip 100 of plastics material is provided within the channels, the strip extends from the channels and passes over the end of the free end of the elongate member when the sheath is mounted in operational position. The strip is generally rectangular in cross section as shown in Figs 2 and 3 (a) to (d). The channels 95 are shaped so as to suit the shape of the strip. On the outermost surface of the sheath there is provided a waterproof (weatherproof) cover 105. The strip is attached to the inner surface of the sheath within the front-most frusto-conical portion 20 of the horn. Attachment means such as adhesive may be applied to the ends of the strip to hold them in position.

One or more elongate strips 100 are used to excite the rod 10 and increase the signal strength in the horn 15 prior to it entering the chosen LNB. They also assist in containing the signal within the antenna. Again, strip

length, thickness, type of plastic strip used and spacing from the rod 10 all have an effect on the signal strength available to the LNB.

It has been found that by providing at least one strip adjacent to the elongate member and extending the strip over the free end of the elongate member ensures that the signal strength and quality emitted from or received by the antenna, particularly during adverse weather conditions such as rain or snow is maintained to a greater degree than with known satellite antennae.

Further, the antenna 5 is mounted on a wall bracket 110 such that the orientation of the antenna 5 can be adjusted. The bracket 110 comprises a plate 120 from which extends downwardly an L-shaped rod 125 which is inserted into a jaw clamp bracket 130 and secured using fasteners 135. The jaw clamp bracket 130 is attached to a clamp 140 which is mounted on a surface of the cylindrical portion 30 where it is fastened securely to this surface using the clamp fasteners 145.

While the rod 10 and strips 100 described above may be made from a solid plastics material, the cover may for example be made from an extruded plastics material.

Referring to Figs. 3 (a) to (d) there are illustrated various embodiments of antenna 5a to d having a variety of cross sections of sheath 70a to d and a variety of elongate strips 100a to d.

In use, the antenna 5 may be suitably mounted on a building by means of brackets or the like, as previously described, the threaded portion 65 connected to the transmitter or receiver and the orientation of the antenna 5 adjusted until the end 90 of the sheath 70 points substantially in the direction of the satellite. The precise direction of orientation of the antenna may then

be finely adjusted until a suitable level of signal is either received, and converted by the LNB 115, or transmitted, by the antenna 5.

Where the antenna is mounted on the outside of a building, a weatherproof protection shield may be mounted over the antenna to deflect precipitation away from the antenna.

Alternatively, the antenna may be mounted within a building such as within a house or garage adjacent a window which provides a line of sight from the antenna to the satellite for receipt of or transmission of signals.

The embodiments of the present invention hereinbefore described are given by way of example only and are not meant to limit the scope of the invention in any way.