Antenna feed unit

FIELD: radio engineering, communication.

SUBSTANCE: antenna feed unit (15) includes at least two elongated feed circuits (1, 2) placed next to each other. Each feed circuit is configured to transmit or receive electromagnetic radiation between itself and an antenna (34) along the longitudinal axis (3, 4) of the feed through a transmitting/receiving element (7). The feed circuits (1, 2) are held in a fixed arrangement relative each other by a first support and a second support (5, 6), spaced apart in the axial direction of the feed circuits. The transmitting/receiving elements (7, 8) continue from the first support (5) to the antenna, and the second support (6) is placed on the side of the first support (5) and at a certain distance from the antenna. The first support (5) has a smaller coefficient of thermal expansion in the transverse direction than the second support (6), which reduces translational movement of each transmitting/receiving element (7, 8) in the transverse direction, caused by change in temperature of the unit (15).

EFFECT: avoiding antenna beam alignment error.

15 cl, 12 dwg

The invention relates to nodes of horn antennas, in particular, but not in a restrictive sense to nodes of horn antennas used for satellite communications, and in particular to the errors of pointing the beam of the antenna caused by temperature fluctuations in the node irradiators.

With regard to communication antennas on the satellites, it has long been a difficulty is encountered in attempting to avoid errors pointing the beam of the antenna, caused by temperature fluctuations of the satellite. These temperature fluctuations are caused mainly by the input of the satellite in the solar radiation and the exit from it. A concrete example of this situation are the temperature fluctuations of geostationary satellites. They move in orbits around the Earth and into the solar radiation out as of this movement. Such temperature changes, as a rule, are of the order of hundreds of degrees Celsius and negatively affect all satellites in General, and in particular on any external hinged instruments satellites.

Antenna satellite communications is excited by electromagnetic radiation transmitted by the reflector of the focal plane of the feed contained in the site irradiators. Site irradiators, as a rule, contains a grid of elongated chains of irradiators, which are located next to each other. Each of them will be sent out to the ü electromagnetic radiation, for example microwaves, different from other parts of the antenna, resulting antenna will send a beam of radiation toward a predetermined region of the surface of the Earth, for example, creating a coverage of television broadcasting or mobile phones within a specific country. Each feeder circuit, which transmits and receives signals in dual polarization, typically contains a conical horn feed at the end closest to the reflector, leading to the polarizer waves, and then, at the end most remote from the reflector, oremodules transducer (OMT). Horn the horn is usually located in the form of a lattice horns, grouped close to each other. This arrangement enables obtaining essentially continuous coverage rays, transmitted to Earth from the satellite, that part of the Earth's surface, which is visible from the satellite. Alternatively, you can do to cover the selected discrete region of the surface of the Earth, for example, choosing telecommunication Portugal, not Spain.

In the case of geostationary satellites at a distance of approximately 35000 km from the Earth's surface, even a slight change in the relative position of the mouthpiece relative to the antenna can cause significant movement pattern of the beam incident on the surface of the horn antenna feed. For example the EP, transverse movement of the horn antenna feed due to temperature changes in the node horn irradiators may cause the departure of the beam by 0.01 degrees that can give move the beam position on the Earth's surface 6 kilometers. Thus, it should be recognized that such nodes irradiators can be extremely sensitive to changes in position due to thermal expansion or compression of the supports for the chains of the irradiators.

For reasons of saving weight, chain irradiators often set in the design of aluminum alloy. However, this material has a relatively large coefficient of thermal expansion, and transverse movement of the horn of the horn relative to each other when the host is exposed to large temperature changes, may become unacceptable due to changes in coverage beam. In particular, when the antenna with a single feed per beam (SFB), moving the beam 6 kilometers on the Earth's surface can create a significant difference either in the area of signal coverage at all, or in the field of reception of a signal of sufficient power. For example, this movement could cause part of the big city, signed a contract for coverage of telecommunications, would be outside the coverage of the beam.

When the satellite is subject to requirements of small distortions, support circuits irradiators can be performed Ismael distorting materials, for example, plastics reinforced with carbon fibers (CFRP) or Invar. However, these materials road in the application and in the case of Invar - heavy, as Invar has a specific gravity of 8.0. CFRP can be produced, creating a structure with a very high ratio of strength/stiffness to weight, but it has poor thermal conductivity, which makes the cooling node irradiators. In addition, the production of this material with the surfaces of the section, providing bolt or other mechanical connection can be problematic.

The objective of the invention is to develop a site irradiators for the antenna that overcomes some of the difficulties associated with the prior art.

In accordance with the first aspect of the present invention, a node of the horn antenna comprising at least two circuit irradiators, each of which has a longitudinal axis of the irradiator, with chain irradiators are located next to each other in the transverse direction, with each chain of the irradiator configured to transmit or receive electromagnetic radiation between itself and the antenna reflector along its longitudinal axis irradiator through the transmitting/receiving element, and the circuit irradiators are supported in constant waymores is ulozhenie relative to each other due to the spaced apart in the axial direction of the first and second supports, moreover, the chain of emitters continue in the axial direction from the second support past the first support to the reflector, and transmitting/receiving elements are located between the first support and the reflector, the first bearing has a smaller coefficient of thermal expansion in the transverse direction than the second bearing, thereby reducing the forward movement of each of the transmitting/receiving element in the transverse direction due to temperature change of the node.

It is clear that if the site is exposed to increasing or decreasing temperature, the first bearing will expand or contract, respectively, in a direction mainly perpendicular to the axis of the feed circuit of the irradiator by an amount proportional to its coefficient of thermal expansion. Similarly, the second leg will be extended or compressed to a greater value, because it has a larger coefficient of thermal expansion. Since each circuit irradiator has a rigid construction, any element of the chain feed extending from the first support to the reflector antenna will be forced to move in the above mainly in a perpendicular direction at a lower value than any point on the first support and the second support or between them, due to the geometry of the layout. This geometry is as shown on the Phi is .1 and 2.

Transmitting/receiving elements, as a rule, are of horn irradiators, which are conical in shape, for microwave applications. The horns can be internally stepped or have a composite conical shape and may be internally shaped to optimize the electrical operating characteristics. The portion of the element, the transverse location of which is critical, is usually a aperture bounded by a rim of horn antenna feed. Alternatively, the phase center of the horn feed, usually located at a small distance inwards in the axial direction from the rim of the horn antenna feed can be considered a critical part of the transmitting/receiving element. Thus, the term "transmitting/receiving element should be interpreted as the part of the transmitting/receiving element, for which the transverse location is critical.

The most desirable geometry for the node considered is that in which the critical part of the transmitting/receiving element is not deflected in the transverse direction when the temperature of the node. For this to happen, the relationship between the coefficient (α₁)thermal expansion of the first support and the coefficient (α₂) thermal expansion in the second support is given by the equation

where "a" is the axial distance from the transmitting/receiving element to the first support, and b is the axial gap between the first and second supports.

One bearing, and preferably both of the supports may include a panel, located mainly perpendicular to the axis of feed each circuit of the irradiator, and this panel restricts the aperture through which each circuit irradiator.

It is clear that in accordance with the invention, the panel, forming a first support, will have a coefficient of thermal expansion in the plane of the panel, less than the panel, representing the second support. For convenience, the first bearing may contain titanium, and the second bearing may contain aluminum. The coefficient of thermal expansion of titanium is 8.5×10^-6and the coefficient of thermal expansion of aluminum is 23,0×10^-6. The ratio of these coefficients is 0,370. Thus, the preferred embodiment of the invention, involving the use of titanium panel to the first support and the aluminum panel to the second support, to take advantage of this relationship, could determine the axial distance from the transmitting/receiving element to the first support as constituting a single unit, and the axial gap between the first and second supports - stood as the pillar two units.

Each circuit irradiator, as a rule, will contain a horn feed at one of its end closest to the antenna reflector using, and OMT on the second end, and a horn feed and OMT divided polarizing wave element extending between them.

If the first pillar contains the above-mentioned panel, this bearing may include a flange attached to the chain feed, for example, to the horn circuit of the irradiator, and made with the possibility of contact with the wall bounding the aperture in the panel.

The flange preferably defines a close match with the said wall aperture, which leads to the exact placement of the chain feed into the panel.

If the second pillar contains the above-mentioned panel, it may include a bracket connecting the circuit of the feed to the panel, the bracket provides a limited tolerance in the relative positions of the bars and chains irradiator.

Each bracket may include two orthogonal drilled element for receiving one or more fasteners passing through for fastening chain irradiator to a support.

The node can contain the grid circuits of the horn with horn irradiators located close to each other. Provided any suitable number of circuits irradiators that mo is but to group with each other that way, which will provide space savings.

Axis irradiators respective circuits irradiators may extend parallel to the antenna or can intersect in the field of the reflector antenna.

In accordance with the second aspect of the invention, a node of a communication antenna, for example, the node antenna microwave communication, which includes the site of the horn antenna corresponding to the first aspect of the invention.

In accordance with a third aspect of the invention, a node of a communication antenna that corresponds to the second aspect of the invention, which includes, as a rule, electronic equipment for signal processing uplink communication/downlink designed for satellite communication, for example, with the Earth or another satellite.

In accordance with the fourth aspect of the invention, a communications satellite, which includes a host communication antenna, corresponding to a third aspect of the invention.

Now the invention will be described by example with reference to the accompanying drawings, in which:

figure 1 shows the schematic side view in partial section of the site irradiators containing two chains irradiators, and the first and second supports;

figure 2 shows the geometric arrangement in accordance with the invention;

figure 3 is a schematic diagram directed the spine of the radiation from the circuit irradiator, at which the ray is incident on the reflector antenna having a perfectly designed electrical axis;

figure 4 shows a layout similar to figure 3, but with the circuit of the irradiator, is displaced in the transverse direction and causes the error in the direction of the electrical axis of the antenna.

figure 5 shows a layout similar to figure 4, in which the axis of the feed chain irradiator tilted, but not shifted in the transverse direction;

figure 6 presents a side view in partial section of a circuit irradiator installed on the first and second support;

figure 7 presents a three-dimensional image host irradiators, which shows the horn irradiators first panel and THEN set the second panel;

on Fig presents a three-dimensional image is THEN installed in the second panel;

figure 9 schematically shows the required flexibility of the support chain irradiator in the first and second panels, respectively;

figure 10 schematically shows a layout similar to figure 9, but with hard patch panel supports;

figure 11 schematically shows a layout similar to figure 10, but with a more flexible panel supports; and

on Fig presents a three-dimensional image of a communications satellite, a two node antenna.

The layout shown in figure 1, provides for the presence of node 15 irradiators. Figure 1 shows the neighboring chains 1, 2 the region is of Atala, each of which defines a longitudinal axis 3, 4 irradiator installed in the first support panel 5 and the second support panel 6. Each of the chains irradiators has a horn irradiator 7, 8 and the end of 9, 10 chain irradiator that is closest to the antenna reflector (not shown). Each horn irradiator 7, 8 restricts the rim 11, 12 facing the reflector. Each rim 11, 12 limits contained inside the aperture 13 of the irradiator (see Fig.7). Each horn irradiator 7, 8 also determines the phase center 14. Horn the horn 7, 8 can be used as a transmitting or receiving elements for node 15 depending on, for transmitting or receiving an antenna at this point in time, and transverse or aperture 13 of the irradiator or phase center 14 can be considered critical to the construction site. From figure 1 it can be noted that the axial length of the aperture 13 of the feed from the first support panel 5 is indicated by symbol "a", and the axial distance for the phase center is marked with the symbol"'". Each horn irradiator 7, 8 connected to the polarizing element 16, 17, which, in turn, is connected to the SIP 18, 19.

Details of the supports, on the first and second panels 5, 6, schematically depicted in figure 1 and details shown on Fig.6, 7 and 8. From Fig.6 we can see that the first anchor panel 5 sets made it cranked Aper the ur 20. The flange 21 is attached to the horn irradiator 7 is installed on a tight sliding fit in the crankshaft aperture 20 and secured in place by bolts 22, 23, screwed in the flange 21 through the panel 5. Thus, due to this composition is achieved precise longitudinal and transverse placement of the horn antenna feed axis 3.

In particular, figure 6, 7 and 8 is shown resting on the second support panel 6. Panel 6 similarly defines cranked the aperture 24 (see Fig.6). However, in order to provide relative movement between the chain 1 of the irradiator and the panel 6 when there is a bulk temperature change of the node 15, the support panel 6 are structurally more flexible than the support panel 5. The brackets 25, 26 support the OSP circuit of the feed in the desired position relative to the panel 6. These supports are designed to impart the desired limited flexibility. Each bracket 25, 26 includes mutually perpendicular elements 27, 28, each of which restricts the holes 29 under the bolts. Bolts 30 secure the bracket 25, 26 to the panel 6 and the OSP circuit irradiator, respectively. It is clear that static tolerances can be observed due to the formation of the bolt holes slightly larger than the bolts, and dynamic tolerances, for example, due to temperature changes, can be observed at the expense of flexibility, constructively make the each bracket 25, 26.

It is also clear that support for the first panel 5 can be made more limited flexibility due to the careful choice of material and thickness of the flange 21.

Figures 9, 10 and 11 schematically illustrate different stiffness layout supports circuit irradiator. Figure 9 schematically illustrates the rigidity of 31 joint bolt-flange when the support panel 5 and stiffness 32 in the articulation bolt-bracket when the support panel 6.

Figure 10 illustrates what happens with chain 1 irradiator when the panel 5 is moved in the transverse direction downwards relative to the panel 6, and the stiffness 31, 32 when it is too large. It will be seen that bends itself chain irradiator, and does not bend supports. Figure 11 shows the layout with the supports more suitable stiffness, which allow chain feed to remain straight when the panels 5, 6 are moved in the transverse direction relative to each other.

On Fig shows the 47 satellite communication is a two node 15 irradiators of the type which include one beam irradiator, each of which directs the radiation to one of the two reflectors 45 antenna. Support for antenna reflectors 45 are not shown, but as usual, they are made so as to allow the cover to move between a field position (not shown) in the pantry 48 satellites and the expanded position shown in Fig. 7 podrobnaya one node irradiators, with a grid of 19 chains 1 irradiators, and irradiating the surface 46 of the mounting box 33 knots irradiators. The grating 19 circuits 1 irradiators shown with horn irradiators 7 installed next to each other so that the rim 11 nearly concern for continuity of coverage beam, so that together they occupy minimum space on the satellite. Upon consideration it will be seen that the axis of the irradiators circuits irradiators are not parallel to each other and coincide on or near the surface of the antenna reflector (see Fig). The grid circuits 1 irradiators installed on the first and second panels 5, 6, contained in the mounting box 33.

It should be clear that since the circuit irradiators emit a significant amount of heat when transmit radiation to the reflector or from him, panels 5, 6 should work as heatsinks and remove it from the node 15 irradiators radiant heat by emitting surfaces 46 of the mounting box 33.

The influence of different types of moving horn irradiators 7 relative to the antenna 34 is shown in figure 3, 4 and 5. Figure 3 shows the ideal electric scenario. Horn irradiator 7 directs the radiation along the axis D of the feed to the antenna 34, where it is reflected along the direction of the electric axis 35 of the antenna. There is no transverse movement of the horn antenna feed relative to the desired axis D is irradiated with the La. Thus, the distortion is zero, and the antenna gain is maintained along with the orientation of the antenna. Theoretically this can be achieved through the installation of the panels node set irradiators, made of a material with a zero coefficient of thermal expansion, for example, from Invar or plastics reinforced with carbon fibers. However, such materials can be expensive and problematic, both in terms of manufacturing, and thermal calculation (they have low thermal conductivity and does not always remove heat from the chains of irradiators as effectively as required). In the case of Invar also obtained a significant loss in weight due to its large specific gravity.

Figure 4 shows the layout is similar to figure 3, but with chains of irradiators node irradiators that are installed in one leg, which is the construction of lightweight aluminum alloy, commonly used for such nodes is considered. Due to the effects of the average bulk temperature, the node will always be some transverse movement of the chain feed relative to other circuits irradiators. This transverse movement is depicted in figure 4 and denoted by the symbol δ, having a finite size. It affects the aiming of the antenna, e.g. the, may be error in the pointing of 0.01°. This can reduce the mutual isolation rays and/or reduce coverage for a specific area of the Earth's surface. Figure 4 also shows the resulting error θ of the direction of the electrical axis of the antenna. Shows the layout will give a slightly lower gain antenna on the edge 36 of the coverage area due to transverse translational movement direction of the electric axis of the horn antenna feed.

Figure 5 illustrates the case when the transverse deviation of the horn reflector 7 is absent, and there is only a slight tilt axis 37 D irradiator. This arrangement in accordance with the invention supports the transverse position of the aperture 13 of the horn irradiator 7 relative to the axis D of the horn antenna feed. However, there is some uncertainty guidance horn antenna feed because of the tilt of the electric axis of the horn from the estimated line. This will result in slightly lower gain antenna on the edge 38 of the coverage area due to the tilt direction of the electric axis of the horn. However, it will be seen that the direction of the electrical axis of the antenna is maintained constant, and the angle θ is zero degrees. The error is pointing relative to the direction of the electric axis of the horn, which may be an error of 0.1 degrees, resulting in the th to slightly less gain, mentioned above will be effectively very little effect.

The geometry of a node in accordance with the invention shown in figure 2. Here, chain 1, 2 irradiators shown installed in titanium first support panel 5 and the second support panel 6 of aluminum alloy. Axis 3, 4 irradiators shown together with distorted axes 3', 4' irradiators. Shown centres 39, 40 of the apertures 13 of the horn irradiators. They are zero distortion when the change in bulk temperature of the node causes the expansion of the support panels 5 and 6 in the direction transversely of the axes 3, 4 irradiators. Titanium panel 5 is shown extending approximately one third extension panel 6 of aluminum alloy. If the distance "a" is 100 mm, and the interval "b" between the panels is equal to 200 mm, this leads to zero or almost zero cross distortion in clauses 39 and 40. It is clear that if the circuit 1, 2 irradiators continue at position 39, 40, transverse distortion will be to increase again from zero or nearly zero distortion experienced in clauses 39 and 40. Thus, in positions 41, 42 additional distance of 100 mm from the panel 5 will have the same transverse distortion, which is the axis of irradiation of the panel 5, but this distortion will have the opposite sign. Thus, a critical part of the circuit irradiator, such as and Arturo horn or the phase center of the horn, located somewhere between positions 41, 42 and 43, 44 (where the axis of the irradiators pass through the panel 5)would have less lateral distortion due to temperature changes than the distortion, which is the panel 5 or the panel 6. Therefore, in comparison with the known technical solutions - node according to the invention provides a reduced transverse distortion of critical points at the transmitting/receiving circuit elements of the irradiator, with careful calculation provides a lower transverse distortion to zero. Now mathematical relationship is illustrated in General form in figure 2, will be displayed below with reference to figure 1.

Now, considering that:

panel 1 is subjected to a change in the average bulk temperature δ t₁(when the coefficient of thermal expansion CTE = α₁),

panel 2 is subjected to a change in the average bulk temperature (Delta t₂(KTR = α₂),

we denote the displacement of the front detent (panel 1) from the reference line O-O symbol δ₁

and denote by moving the rear detent (panel 1) from the reference line O-O symbol δ₂.

Therefore,

δ₁=Δ t₁α₁with

δ₂=Δ t₂α₂C.

To move the aperture of the horn (to move the phase center need to replace "a, δ₃" on "and', δ₃'"):

the slope of the chain feed relative to the reference line o-O of the origin

slope - slope

To move the aperture of the horn:

For zero distortion, i.e. δ₃=0:

Δ t₁α₁(ac+cb)=δ t₂α₂ac.

To uniformly increase the temperature of the MFA (the temperature gradients on the site will be considerably less than the daily temperature change) suppose that δ t₁= Δ t₂.

For zero δ₃:

Consider a site where:

b=200 mm,

a=100 mm

Then for minimum distortion are:

Consider the aluminum back panel and titanium front panel:

$$\frac{{\alpha }_{tita}{}_{nium}}{{\alpha }_{alumi}{}_{nium}}=\frac{8.5\times {10}^{-6}}{23.0\times {10}^{-6}}=0.370$$

This is close to the optimal value for this geometry is. The geometry can be optimized to better match the available materials. Alternatively, another material, possible for the front panel is AlBeMet (registered trademark). This material could give the following result.

$$\frac{{\alpha }_{AlBeMet}}{{\alpha }_{alumi}{}_{nium}}=\frac{13.9\times {10}^{-6}}{23.0\times {10}^{-6}}=0.604$$

This gives the benefit for thermoelastic distortion, and depending on the application will result in significant savings in mass and reduce thermal gradients within the supporting structure of the irradiator.

1. Node horn antenna comprising at least two circuit irradiators, each of which has a longitudinal axis of the irradiator, with chain irradiators are located next to each other in the transverse direction, with each chain of the irradiator configured to transmit or receive electromagnetic radiation between itself and the antenna reflector along its lengthwise the axis of the feed through the transmitting/receiving element, when this circuit irradiators are supported in constant relative positions relative to each other by spaced apart in the axial direction of the first and second bearings, and chain emitters continue in the axial direction from the second support past the first support to the reflector, and transmitting/receiving elements are located between the first support and the reflector, the first bearing has a smaller coefficient of thermal expansion in the transverse direction than the second bearing, thereby reducing the forward movement of each of the transmitting/receiving element in the transverse direction due to temperature change of the node.

2. The node according to claim 1, in which the relationship between the coefficient (α₁) thermal expansion of the first support and the coefficient (α₂) thermal expansion of the second support is given by the equation
$$\frac{{\alpha }_1}{{\alpha }_2}=\frac{a}{a+b},$$
where "a" is the axial distance from the transmitting/receiving element to the first support, a "b" - axis between the first and second supports.

3. The node of claim 1, wherein each of the first and second supports includes a panel, located mainly perpendicular to the axis of feed of each chain exposed the El, moreover, this panel restricts the aperture through which each circuit irradiator.

4. The node of claim 1, wherein the first bearing includes titanium, and the second bearing contains aluminum.

5. The node according to claim 4, in which the ratio of the axial distance from the transmitting/receiving element to the first support and the axial gap between the first and second supports is 1:2.

6. The node according to claim 1, in which each circuit irradiator contains horn feed at one of its ends, most closely located to the reflector using, and oremodules transducer (OMT) at the second end, and a polarization wave element extended between the horn and the OMT.

7. The node according to claim 3, in which the first bearing includes a flange attached to the chain feed and executed with a possibility of contact with the said aperture in the panel, included in the first pillar.

8. The node according to claim 7, in which the flange is installed in a tight sliding fit with the wall of the aperture, whereby the circuit irradiator accurately placed in the panel.

9. The node of claim 1, wherein the second support includes a panel and includes at least one bracket, connect the circuit irradiator with the panel, and at least one bracket provides a limited tolerance in the relative positions of the bars and chains irradiator.

10. The node according to claim 6, containing a grid circuits of irradiation is atela, with horn irradiators located close to each other.

11. The node according to claim 1, in which the axis of the irradiators cross each other.

12. The node in claim 11, in which the axis of the irradiators cross each other in the field of the reflector antenna.

13. The node communication antenna, which includes the site of the horn antenna according to any preceding paragraph.

14. The node communication antenna according to item 13, which includes electronic equipment uplink communication/downlink for satellite communications with Earth.

15. Communications satellite that includes the node communication antenna according to item 13.