EP0856908B1 - Antenna beamforming device for channel multiplex systems - Google Patents

Description

The present invention relates generally to a beam forming unit which carries a plurality frequency multiplexed channel signals. The unit multiplex, or combine, spatially in the same beam this plurality of channel signals.

According to one embodiment, this training unit for beam belongs to a repeater output stage of a satellite. The satellite is for example a satellite of broadcast television signals and produce a beam of emission covering an area on the ground.

Typically, according to the prior art, this stage output includes a plurality of amplifiers each intended to amplify a respective channel signal as well than an output "multiplexer". The various channel signals are each amplified by a respective amplifier in order to minimize the distortions resulting from the non-linearity of the amplifiers used. The output "multiplexer", or OMUX (Output MUltipleXer), provided at the output of amplifiers, is as described in the book "Satellite Communications Systems ", G. Maral and M. Bousquet, Edition WILEY, Second Edition, pages 411 and following. This multiplexer includes filters and a common guide which is intended to combine the channels after their amplification and individual filtering.

To achieve reduced loss coupling between the filters and the common guide, we usually plan to mount the filters directly on the common guide without use circulators which have the disadvantage of inducing high power losses. Filters and guide common are in the form of cavities and the coupling between each filter and the common guide is made through a iris, or cleft. One end of the common guide is short-circuited, the other delivers a combined signal conveying all multiplexed channel signals. This combined signal is issued by an antenna.

The losses induced by such a training unit prior art beam in the portion between the outputs of the amplifiers and the antenna remain relatively high, typically close to 2dB for high frequencies, for example in Ka band. In in addition, such an OMUX has a relatively high weight.

The closest state of the art is shown by the document. EP-A-0638956. There is described an antenna active "offset" comprising a network of sources and a radio lens having a first network of sources said collector. This collector receives and receives a beam concentrate reflected by a first reflector, from the beam emitted by said network of elementary sources.

However, such an antenna does not guarantee to receive at the collector the different radiated waves of optimally.

Thus, a first objective of the invention is to provide a beam forming unit, or combination of channel signals to be transmitted in the same beam, whose power losses are reduced compared to the prior art. Another goal of the invention is to provide a combination unit of channel signals to be transmitted in the same weight beam reduced compared to the aforementioned realization of the prior art.

To this end, a unit for combining N signals radio frequencies, N being an integer, said numbers N channel signals being produced by N wave sources respective respective radiating waves, said radiating waves being focused on collector network means of the unit capable of multiplexing said waves, is characterized according to the invention in that said network means collector are capable of receiving the N channel signals in respective directions defined by lobes of radiation produced by said network means manifold.

To transmit the signals thus combined, it can be provided that the collector network means are coupled to transmission network means which transmit the N signals of channel that are combined.

In addition, a dish arranged in a mounting offset from the transmission network means can be used. This parable reflects, in the form of a beam, the N channel signals which are combined.

Advantageously, the unit further comprises focusing means for focusing the N respectively channel signals on the collector network means, respectively in said directions.

According to one embodiment, the focusing means are in the form of substantially reflective elements concaves each associated with a respective one of the signals of channel.

According to a first variant, these elements reflectors are carried by a portion of arc parabolic.

According to a second variant, these elements reflectors are carried by a surface portion of paraboloid.

• la figure 1 est un bloc-diagramme d'une unité selon l'invention de combinaison de signaux de canal à émettre dans un même faisceau;
• la figure 2 est une représentation d'un réseau de sources pour expliquer l'invention;
• la figure 3 est une vue de dessus d'éléments réfléchissants formant partie de l'unité selon une variante de l'invention;
• les figures 4 et 5 montrent respectivement une partie de l'unité selon l'invention et un tube de champ pour expliquer le dimensionnement de l'unité selon l'invention; et
• la figure 6 montre une pluralité de courbes isoniveaux telles qu'obtenues selon l'invention.

Other characteristics and advantages of the present invention will appear more clearly on reading the following description, with reference to the corresponding appended drawings, in which:

• FIG. 1 is a block diagram of a unit according to the invention for combining channel signals to be transmitted in the same beam;
• Figure 2 is a representation of a network of sources to explain the invention;
• Figure 3 is a top view of reflective elements forming part of the unit according to a variant of the invention;
• Figures 4 and 5 respectively show part of the unit according to the invention and a field tube to explain the dimensioning of the unit according to the invention; and
• Figure 6 shows a plurality of isonevel curves as obtained according to the invention.

Referring to Figure 1, a training unit for beam according to the invention is supplied by N sources respective separate 30, 31 and 32, in number N equal to 3 in Figure 1. Each source 30, 31 and 32 is for example composed of a cone, typically small. Of in known manner, a horn comprises a guide portion access, or entry, and a radiating section opening gradually increasing. Upstream of each respective N sources 30, 31 and 32 are provided in cascade one power amplifier 10, 11 and 12 and a filter strip 20, 21 and 22.

The N = 3 channel signals S0, S1 and S2 to be sent in the same beam are centered on respective frequencies f0, f1 and f2. For example, the frequencies f0, f1 and f2 are located in the frequency band 11.5 GHz-12.5 GHz radio frequencies. Each signal S0, S1 and S2 is applied to an input of a respective amplifier 10, 11 and 12 to be amplified at high power. Each amplified signal resulting and transmitted through a guide waveform at an input of the corresponding band filter 20, 21 and 22. Each filter is in the form of a cavity and filters the signal in the frequency band f0, f1 and f2 of the signal S0, S1 and S2 it receives. Filters 20, 21 and 22 have outputs which are respectively coupled to entrances of the horns 30, 31 and 32 through slots. The horns 30, 31 and 32 radiate respective waves R0, R1 and R2.

Advantageously, these waves R0, R1 and R2 are directed towards respective focusing means 40, 41 and 42 which are, in the illustrated embodiment, in the form reflective elements, or mirrors, substantially concave. These reflective elements 40, 41 and 42, having a metallic surface, reflect waves R0, R1 and R2 to a collector network 50. The concave shape reflective elements 40, 41 and 42 guarantees a focusing the energy of the different waves R0, R1 and R2 on the collector network 50.

According to the variant illustrated in FIG. 1, the reflective elements 40, 41 and 42, in number equal to N = 3, are carried for example by an imaginary parabolic arc C whose focal length f coincides with the collector network 50. According to another variant shown diagrammatically in FIG. 3, the sources are in number equal to N = 5 and arranged in a cross. In this case, the reflective elements 40, 41, 42, 43 and 44 are carried by an imaginary paraboloid surface. This is reflected in the fact that the centers of the different reflective elements 40, 41, 42 (and possibly 43 and 44) coincide with points of the same parabolic arc imaginary C (or an imaginary paraboloid surface) whose the focal length f coincides with the collector network 50.

Each wave R0, R1 and R2 is reflected, being focused, towards the collector network 50 according to a particular direction thanks to positioning and appropriate convergence of the reflecting element 40, 41 and 42 which reflects this wave R0, R1 and R2. It is to highlight that waves R0, R1 and R2 could be focused on the collector network 50 through a lens, without reflection.

The respective specific directions according to which waves R0, R1 and R2 are emitted according to the invention, after reflection, towards the collector network 50 will now be explained with reference to FIG. 2.

In known manner, a one-dimensional source network, of the type shown in FIG. 2, comprising (M + 1) sources S0, S1, S2, ... and SM supplied in phase, produces a radiation diagram whose maximums are defined by angles  such as: (2.π.d / λ) .sin () = 2.m.π, is sin () = (m.λ) / d

d being the distance between two adjacent sources, λ the radiation wavelength,  the angle between the normal to S0-SM source plan and direction considered, and m a zero integer, positive or negative.

The condition for no network lobe to appear is given by: d <λ.

Conversely, if d> λ, there are appearance of lobes of network, and the radiation pattern can include several maximums if the alignment consists of several sources S0-SM. It is the periodic nature of network of sources which brings up these network lobes in the radiation diagram.

Returning to FIG. 1, the collector network 50 is in the form of a network of elements operating in reception. For example, this collector network 50 is consisting of (5 x 5) cones arranged in a matrix. Typically, the collector network 50 is mesh rectangular or triangular. The geometric structure "periodic" of the collector network 50 is such that the network has the characteristics of a network of sources, to say that it is capable, on transmission, of generating several maximums, preferably of substantially amplitudes identical, in respective respective directions. These directions correspond to the directions of radiation of waves R0, R1 and R2 after their reflection respectively on the reflective elements 40, 41 and 42.

In our case, the collector network operates in reception, but taking into account the "reciprocity" of operations of the collector network 50 in transmission and in reception, this results in the fact that on reception, the collector network 50 guarantees mixing, or multiplexing, without high loss between the different radiated waves, or channel signals R0, R1 and R2. It must therefore be remembered that the collector network 50 receives the channel signals R0, R1 and R2 along respective directions defined by lobes theoretical network transmission of these network means collector 50.

In the entry guide or access portions, horns of the collector network 50, the various signals of channel R0, R1 and R2 are channeled without high loss. The portion of access guide for each horn in the network collector 50 is coupled with an access guide portion of a cornet corresponding to a transmission network 51. This transmission network 51 is for example made up of (5 × 5) cones arranged in a matrix. It produces the N = 3 signals R0, R1 and R2 channels combined.

According to the illustrated embodiment, the channel signals handsets transmitted by the transmission network 51 are reflected by a portion of a dish 6. The transmission network 51 is arranged in an "offset" arrangement relative to the parabola 6 according to an assembly known to those skilled in the art so that the beam of F channel signals reflected by the portion of parabola is not directed towards the constituent elements of unity.

Although in the part of the above description, we limited ourselves to N = 3 sources 30, 31 and 32, the invention can be extended to a higher number of sources. For that, or the different radiated waves directed towards the collector network 50 can be worn according to axes of the same plane, or the different radiated waves directed to the collector network 50 can be carried by axes belonging to a volume delimited by a cone. This last point results from the fact that for a network of sources of the non-monodimensional type as presented in Figure 2 but two-dimensional, the results obtained with regard to the lobes of network are reproduced in the two dimensions.

It should be noted that efficient operation of the unit according to the invention is all the more guaranteed as the frequencies f0, f1 and f2 of channel signals R0, R1 and R2 are close and located in a frequency band high.

Referring to Figure 4, will now be specified the dimensioning relationships of the unit according to the invention. Specifically, regarding each source to horn, such as 30, for a given focal task spreading W0 on the collector network 50, are going to be define the relationship between the distances d0 'and d0 (d0' being the source distance 30-reflecting element 40 and d0 the distance between the reflecting element 40 and the collector network 50), and the convergence of the associated radiating element, here 40. The focal spot on the collector network 50 must have a substantially flat equiphase surface as shown in Figure 5. It is shown that the operation of the unit can be approximated completely appropriate by a wave model of the Gaussian optical type.

Each source, here 30, is in the form of a cornet which is defined by spreading the field W1 over the opening cornet and a length of cornet L.

With reference to FIG. 5, for a field tube, the radius of curvature R and the spread W of the field distribution varies throughout the beam, and an equiphase field zone can be defined at any point by the couple (W, R), with the following relationships: R = d (1 + ρ 2 ), with ρ = (2.R / kW 2 ) and W 2 = (1 + ρ 2 ) .W0 2 , where W0 denotes the minimum spread of the field.

For an equiphase field, therefore of infinite radius of curvature, and spreading W0 on the collector network 50, it can then be shown that the spreading W (d0) on the reflecting element is given by: W (d0) = W0. 1+ ( 2. d 0 kW 0 2 ) 2 , and that the radius of curvature R1 (d0) of the wave in the vicinity of the reflecting element 40 in the direction of the collector network 50 is given by R1 (d0) = k. (W0 2 /2.d0) 2 . [1 + (2.d0 / k.W0 2 ) 2 ] taking as reference d = 0 on the collector network 50, and d = d0 on the reflecting element 40.

The Gaussian wave at the opening of the horn is characterized by the couple (W1, L). By writing that this wave, after propagation over the path of length d0 'source 30-radiating element 40, must have as parameter (W (d0), R1 (d0)), d0' can be expressed as a function of d0: d0 '(d0) = [k.W1. ( (d0) - ψ)] / [2. (1 + ψ 2 )] with  (d0) = (1 + ψ 2 ) ( W ( d 0) W 1 ) 2 -1 , and ψ = k.W1 2 /2.L

Furthermore, the convergence C of the reflecting element 40 is given by: C = 1 / R1 (d0) + 1 / R2 (d0 ')

R2 (d0) being the radius of curvature of the wave in the vicinity of the reflecting element 40 coming from the source 30, and being defined by: R2 (d0) = k. (W (d0)) 2 /2.(d0).

In the above, the sign of each radius of curvature must respect the rule that said sign is positive if the wave diverges and is negative if the wave converges.

The operation of the unit described above has been simulated for the realization that the collecting network 50 comprises 5 rows of 5 horns. The (5x5) cones are arranged in a matrix and the section of the flaring end of each horn is a side square of length equal to 26.2 mm. The sources 30, 31, 32, etc. are in number equal to N = 5 and arranged in a cross. In this case, as shown in FIG. 3, the reflective elements 40, 41, 42, 43 and 44 are carried by an imaginary paraboloid surface whose focal length f coincides with the collector network 50. The transmission network 51 comprises 5 × 5 horns, each supplied by a respective corresponding horn of the collector network 50. For each source, the radiation diagram is modeled by a cos ^τ () diagram.

Below are given 4 coupling "matrices". Each of them defines, for a given source, the coupling coefficients of each of the (5x5) horns of the collector network 50. Each coefficient is given in amplitude (dB) and in phase (°) in the form of a couple ( X (dB); Y (°)). FIRST MATRIX ASSOCIATED WITH THE SOURCE ILLUMINATING THE MIRROR 42 (FIG.3). (28.6; 59.5) (18.9; 55.07) (17.7; 55) (18.9; 55) (28.6; 59.5) (21.7; 50) (12.5; 44.9) (-9.9; 41) (12.5; 44.9) (21.7; 50.4) (19.6; 47.1) (-9.4; 49.4) (6.8; 51.5) (-9.4; 49.4) (19.6; 47.1) (22.2; 43.6) (-12.2; 52) (-9.9; 56) (-12.2; 52) (22.2; 43.6) (29.5; 35.8) (19.7; 44.1) (17.6; 48.2) (19.7; 44.1) (29.5; 35.8) SECOND MATRIX ASSOCIATED WITH THE MIRROR ILLUMINATING SOURCE 41 (FIG.3). (-25.2, 140.9) (-21.2; 141) (-20.8, 132.8) (-21,2,141) (-25.2, 140.9) (-21.3, 131.3) (-12.7, 119.7) (-10.2, 120.4) (-12.7, 119.7) (-21.3, 131.3) (-18.5, 120.6) (8.9; 126.9) (6.8; 132.1) (8.9; 126.9) (-18.5, 120.6) (-21.2, 109.5) (-12; 123) (-10.1, 128.9) (-12; 123) (-21.2, 109.5) (-31.2, 75.2) (-21, 97.1) (-19.1, 103.9) (-21, 97.1) (-31.2, 75.2) THIRD MATRIX ASSOCIATED WITH THE SOURCE ILLUMINATING THE MIRROR 40 (FIG.3). (-23.6, 100.8) (-19.2, 134.9) (-17.7, 127.9) (-19.2, 134.9) (-23.6, 147.8) (-20.8, 144.4) (-13.4, 137.8) (-11.5, 138.2) (-13.4, 137.8) (-20.8, 144.4) (-18.7, 137.1) (10.4; 145) (8.6; 149.3) (10.4; 145) (-18.7, 137.1) (-19.1, 123.6) (-10.9, 142.1) (-9.32, 148.8) (-10.9, 142.1) (-19.1, 123.6) (22.4; 93.7) (-14.6, 120.7) (-13.1, 129.3) (-14.6, 120.7) (22.4; 93.7) THIRD MATRIX ASSOCIATED WITH THE TWO SOURCES ILLUMINATING RESPECTIVELY MIRRORS 43 and 44 (FIG.3). (-27.5, 100.8) (-22.6, 106.9) (-18.6, 122.3) (-31; 166.3) (23.7; 177) (-17.5, 115.6) (-14.4, 129.8) (7.3; 120.8) (-13.8, 101.4) (-24.3, 101.7) (-16.1, 140.6) (-15.2, 155.1) (5.6; 134.1) (-11.1, 115.8) (-15.4, 102.8) (-19.2, 134.1) (-18.1, 143.4) (8.4; 130.6) (-13.5, 120.7) (-16.7, 112.8) (27.9; 115) (-28.4, 120.6) (17.9; 104) (22.8; 94.2) (24.5; 84.3)

The two matrices associated with the sources illuminating the mirrors 43 and 44 are identical due to the layout symmetrical of these two sources with respect to the network collector 50.

These matrices show the good constancy of the phase for each of the horns of the network, which guarantees the proper functioning of the unit according to the invention.
In Figure 6, are shown the isoniveaux lines of the fields corresponding to the 4 matrices which show that spots formed by the unit of the invention are substantially concentric.

Claims (9)

1. Unit for combining N radio channel signals (R0, R1, R2), where N is an integer, said N channel signals (R0, R1, R2) being produced by N respective separate sources of radiating waves (30, 31, 32), said radiating waves being focussed on collector array means of the unit adapted to multiplex said waves, characterized in that said collector array means (50) are adapted to receive said N channel signals (R0, R1, R2) in respective directions defined by radiation lobes produced by said collector array means (50).
2. A unit according to claim 1 characterized in that said collector array means (50) are coupled to transmit array means (51) that transmit said combined N channel signals (R1, R2, R3).
3. A unit according to claim 2 characterized in that said collector array means (50) and said transmit array means (51) are in the form of horns, each horn of the collector array (50) being coupled to a respective horn of the transmit array (51) via I/O waveguides.
4. A unit according to either claim 2 or claim 3 characterized in that it includes parabola means (6) disposed in an offset arrangement relative to said transmit array means (51), said parabola means reflecting said combined N channel signals (R1, R2, R3) in the form of a beam (F).
5. A unit according to any preceding claim characterized in that said unit includes focusing means (40, 41, 42) for focusing said N channel signals onto said respective collector array means (50) in said respective directions.
6. A unit according to claim 5 characterized in that said focusing means (40, 41, 42) are in the form of substantially concave reflective members each receiving a respective channel signal.
7. A unit according to claim 6 characterized in that said reflective members (40, 41, 42) are carried by a parabola arc portion (C).
8. A unit according to claim 6 characterized in that said reflective members (40, 41, 42, 43, 44) are carried by a paraboloid surface portion.
9. A satellite including a unit according to any preceding claim.

Images