EP0561675A1 - Receiving antenna with a single pointing direction for reception from several satellites of different orbiting positions - Google Patents

Abstract

The receiving antenna with single pointing direction, for several satellites with different orbital positions, includes a multi-sector reflector including a central sector (2) and at least one outer sector (1) in an annulus about the central sector. The sectors of the reflector are formed from portions of parabaloids with different axes defining the receiving directions (D1, D2) corresponding to the various orbital positions, the sectors focusing the radiation which they receive in a common focusing zone (F). A multi-polarisation broadband source (S) is placed in the zone (F), the source being coupled to an electronic processing channel for selecting the useful signals. Application, in particular, to satellite reception in private stations. <IMAGE>

Description

The invention relates to satellite reception equipment available in the form of individual reception stations and more particularly relates to a reception antenna with single pointing for several satellites with different orbital positions.

• d'une antenne équipée d'une monture équatoriale motorisée,
• d'une source large bande associée à un ou plusieurs démodulateurs faible bruit,
• d'un dispositif de commande et d'un dispositif de mémorisation des coordonnées des satellites choisis.

When several satellites placed on different orbital positions are to be received at the same location, at least the following is currently available:

• an antenna fitted with a motorized equatorial mount,
• a broadband source associated with one or more low noise demodulators,
• a control device and a device for memorizing the coordinates of the selected satellites.

The transition from the reception of a satellite on a first orbital position to the reception of a satellite on another orbital position requires several seconds or even tens of seconds.

When, moreover, several satellites thus placed in different orbital positions must be received simultaneously for reasons of service, the problem becomes much more complex. An obvious solution is to target the satellites with as many antennas as there are orbital positions.

There are several reasons why this solution cannot be applied on a large scale. First of all there are economic reasons: the cost of the installation is multiplied by the number of antennas and the installation is complex and expensive. There are also aesthetic reasons: in addition to the size of a field of two or three parabolas, a set of parabolas is difficult to integrate into the rectilinear architectures of current constructions. Finally, there are also regulatory reasons because, in many countries, only one parable is tolerated by building; moreover the taking of the antennas in the wind can be a source of insecurity, not tolerated.

A new need therefore appears for a single antenna making it possible to receive several satellites located at different orbital positions simultaneously or sequentially, without modifying the pointing of the antenna so as to avoid motorized equipment and the corresponding commands, and to save time by minimizing service interruptions during changes.

French patent n ° 89 14287 filed on October 31, 1989 describes a multifocal reception antenna with single pointing direction for several satellites located on the same orbital position. For this, the reflector is multi-sector, the different sectors of the reflector focusing the radiation they receive from the targeted direction towards sources placed in different positions corresponding to the focal points of the different sectors. With the antenna described in this request, reception can therefore take place on several satellites with a predefined orbital position, either simultaneously or sequentially depending on the equipment of the antenna (one or more microwave heads); but the satellites received are always located on the same orbital position, and their selection is made by a choice of polarization and. frequency, due to a spatial separation of polarizations, the antenna being multifocal.

The object of the invention is to meet the need for an antenna capable of receiving simultaneously or sequentially several satellites located in different orbital positions by a single pointing, and a single electronic assembly. For this, the antenna reflector is multi-sector, each sector being adapted to the reception of a satellite, and these sectors have focal points which coincide spatially; a broadband and multipolarization source transmits the various signals received to the electronic assembly which separates them.

The present invention relates to an antenna capable, by a single pointing, of receiving several satellites of different orbital positions, and comprising for this a multi-sector reflector whose sectors are formed by portions of paraboloids with the same focus and different focal axes corresponding to the directions of reception of the different satellites.

• la figure 1 illustre, en coupe, une antenne de réception à pointage unique, selon l'invention, pour plusieurs satellites situés sur des positions orbitales différentes dans un premier mode de réalisation ;
• la figure 2 illustre un second mode de réalisation en coupe de l'antenne suivant l'invention ayant une forme "plate", pour la réception de deux satellites ;
• la figure 3 représente en coupe un autre mode de réalisation d'une antenne plate selon l'imvention, pour la réception de trois satellites ;
• la figure 4 représente en plan un troisième mode de réalisation de l'antenne.

Other objects and characteristics of the invention will appear from the following description with reference to the appended figures which represent:

• FIG. 1 illustrates, in section, a reception antenna with single pointing, according to the invention, for several satellites located on different orbital positions in a first embodiment;
• FIG. 2 illustrates a second embodiment in section of the antenna according to the invention having a "flat" shape, for the reception of two satellites;
• Figure 3 shows in section another embodiment of a flat antenna according to the invention, for the reception of three satellites;
• Figure 4 shows in plan a third embodiment of the antenna.

The antennas which will be described comprise sectors of paraboloids whose characteristics are such that they focus radiation originating from different directions at the same point.

FIG. 1 schematically represents an antenna for the reception of two satellites: two sectors of paraboloids 1 and 2 connected by a truncated cone 3, focus the radiation coming from the directions D₁ and D₂ respectively in the same focal point F. The two sectors 1 and 2 therefore have different focal axes, Fx₁ and Fx₂ angularly offset by the difference between the orbital positions of the two satellites to be targeted. The shape of the reflector with its two sectors 1 and 2 as illustrated in FIG. 1 can be used. But there is an advantage in using a reflector producing the same result, but whose size is reduced.

For this, the second embodiment of the antenna shown in FIG. 2 is such that the external paraboloid sector 1 is in fact constituted by several portions of different paraboloids whose virtual vertices on the focal axis Fx₁ are offset by a whole number of half wavelengths, and which are connected by truncated cones, each of these paraboloid portions focusing the received radiation in the same direction D₁ as previously, at the focal point F. This structure makes it possible to minimize the bulk and makes it possible to obtain a quasi-planar structure formed, for the external sector, of a set of "rings" which are portions of paraboloids. The central sector 2, the dimension of which is relatively small if it is chosen for the reception of the satellite having the highest effective radiated power, integrates well into the antenna, forming with the reflector 1 an almost planar structure for the receiver.

The main advantage of the flatness of the antenna due to this ring group structure is to reduce the cost per unit of volume, in particular for all that concerns the packaging prior to installation. To further facilitate the procedures prior to installation, in particular the packaging for transport from the place of manufacture to the place of installation, the external sector 1 in rings can be cut to form a rectangular or square structure which makes it possible to optimize the receiving surface compared to traditional means of packaging and storage. This embodiment is shown in plan in Figure 3. The central sector 2 'hatched is also in rings on its outer part, and is associated with satellites with high apparent radiated power TDF1 for example, and the outer sector 1' cut into square is associated with lower radiated power satellites EUTELSAT 2, for example. The sectors 1 'and 2' can rotate relative to each other to allow their relative positions to be adjusted. For this an axis of rotation Y'Y, allows to precisely define the angle between the two pointing directions.

FIG. 4 illustrates a structure in which the reflector enables the radiation from three different directions to be focused in the same focus F. For this, the central part consists of a portion of paraboloid focusing in F the radiation in the direction D₃; an intermediate part is formed of concentric rings formed by sectors of paraboloids and trunks of cones and focuses in F the radiation coming from the direction D₂. This middle part is joined to the central part towards the inside and joined with a second external ring structure intended to always focus in F the radiation coming from the direction D₁. In the same way as described with reference to FIG. 2, the rings of sectors 1 and 2 of the reflector are formed by portions of paraboloids whose vertices are offset by an integer number of times the half wavelength of the received radiation, on the focal axes Fx₁ and Fx₂ respectively, the focal axis Fx₃ parallel to D₃ being the axis of the central sector 3.

All of these embodiments allow movement of the reflector, therefore with a single pointing direction, to receive in the different predetermined directions. At the focal point F is placed a multipolarization and multiband or broadband source. This source receives signals from different satellites, for example signals from telecommunications satellites, FSS band, either 10.7 to 11.7 GHz or 12.5 to 12.75 GHz, or signals from large broadcast satellites. audience in the BSS band, i.e. 11.7 to 12.5 GHz. These satellites are at different orbital positions and transmit at different frequencies in the bands mentioned according to different polarizations (right circular, left circular, horizontal or vertical). The multipolarization source can be a printed multipolarization plane network equipped with electronic switching means for selecting one or the other of the polarizations. The source can be produced in particular according to the structures described by M. DUBOST in an article entitled "Dual polarized flat folded dipoles application to an array in KU Band" published in "Asia-Pacific Microwave conference (A6MC 1990), TOKYO. it is of course necessary to provide a polarization splitter or switch to select the required signal (s).

Figures 5 and 6 illustrate the channels required in the electronic assembly associated with the antenna so that the satellites transmitting in directions D₁ and D₂ can be received. FIG. 5 illustrates the case where it is desired to receive radiation from two satellites only sequentially. A single microwave head 10 is necessary. It is preceded by a polarization switch (or separator) 11 suitable for the selection of one of the four types of polarization mentioned (right circular, left circular, horizontal and vertical) whose input is connected to the broadband source. multipolarization S.

FIG. 6 illustrates the case where it is desired to receive radiation from two satellites simultaneously. Two microwave heads 20 and 30 are then required. They each include a low noise amplifier and a frequency converter. Each of these microwave heads or "LNB" (for "Low Noise Block" according to English terminology) is preceded by a polarization switch, respectively 21 and 31. If the microwave heads 20 and 30 are assigned to signal processing transmitted respectively in circular polarization and in linear polarization, the polarization switch 21 selects the polarized radiation in right or left circular and the polarization switch 31 selects the linearly polarized radiation either vertically or horizontally. The inputs of the switches are connected to the multi-polarization broadband source.

These structures have a large number of advantages: the reception assembly sees its cost decrease due to the presence of a single reflector, a single source and a set of common electronic circuits for the reception of several satellites . Even if the electronic circuits must provide, as indicated above, switching and separation means, the assembly obtained is of course of lower cost than a juxtaposition of systems specialized in the reception of the various satellites.

Another advantage of such a structure is the simplicity of its installation since by a single adjustment of the position of the antenna reflector several directions of reception are obtained.

In addition, the system is versatile since it is suitable for the reception of several types of satellites applied to different fields such as telecommunications and television. These two types of information can even be received simultaneously provided that the electronic reception circuits, particularly low noise converter, are doubled and that ad-hoc separation means are available.

Finally, another not insignificant advantage is the aesthetics of the system which makes it possible, with a single reflector possibly of square section and almost planar, to minimize the drawbacks of these structures arranged on buildings, these structures being more easily integrated into the architecture of cities .

The invention is not limited to the embodiments described and shown. Indeed, it was indicated above that the sectors of the reflector could either consist of a single sector of paraboloid receiving the radiation coming from a direction D to focus it in F or of several portions of paraboloids always receiving in the same direction D and focusing the radiation at the same point F. The number of sectors with different directions 2 or 3 in the examples shown can obviously be adapted provided that each sector has a sufficient surface to ensure reception of the satellite for which it is intended, with its given effective radiated power. The limit is therefore fixed by the power received from the different satellites on the different parts of the reflectors. Finally, any combination of satellites capable of being received in the same place is possible, the radiation from each being defined by its direction, frequency and polarization, provided that the radiation from these satellites placed on positions different orbitals do not transmit at the same time on the same frequency and with the same polarization.

Claims (6)

Receiving antenna comprising a source and a multi-sector reflector, this reflector comprising a central sector (2) and n, with n integer greater than zero, external sectors (1) forming successive rings around the central sector, the sectors of the reflector being formed by portions of praboloids with focal axes (Fx₁, Fx₂, Fx₃) and given focal points (F), characterized in that, so as to be single pointing, for n + 1 satellites with different orbital positions determining, in a place, different directions of reception, the given axes are distinct from each other and the given foci combined, in that the given axes make between them angles corresponding to the angles between the directions of reception (D₁, D₂, D₃) different and in that the source is a broadband multipolarization source (S) placed at the foci (F). Antenna according to claim 1, characterized in that, in order to constitute a quasi-planar antenna, the n sectors are each formed by several portions of paraboloids of the same axis with the same focus and of vertices offset by an integer half the length of the working wavelengths of that of the n sectors considered. Antenna according to one of claims 1 and 2, characterized in that the projection of the reflector, on a plane orthogonal to the axis relative to that of the n sectors farthest from the central sector, is a rectangle. Antenna according to one of claims 1 to 3 with n = 1, characterized in that, for the reception of two satellites respectively at high and low effective radiated power, the central sector (2) is intended for the reception of the satellite at low effective radiated power, and the outside sector (1) on reception of the satellite with high effective radiated power. Antenna according to one of claims 1 to 3, characterized in that, for a sequential reception of the satellites, it comprises an electronic processing channel coupled to the source with in series a polarization selector (11) and a microwave reception head (10) having means for frequency conversion and low noise amplification. Antenna according to one of claims 1 to 3, characterized in that, for simultaneous reception of m, with m integer greater than 1 and less than n + 2, satellites, it comprises m electronic processing channels coupled to the source with each a polarization selector (21, 31) connected to a microwave reception head (20, 30) having means for frequency conversion and low noise amplification.

Images