EP2991159A1 - Feed network for antenna systems - Google Patents

Abstract

The food network according to the invention comprises a waveguide with broad sides and narrow sides, and two microstrip conductors, each containing a conductor loop. The conductor loops each project from one of the narrow sides into the waveguide and are electrically connected to a broad side of the waveguide. On the narrow sides, the waveguide has small openings through which the microstrip conductors are guided without being electrically in contact with the waveguide itself. This results in the possibility of an inductive H-field coupling, which has a low sensitivity to tolerance-induced mechanical displacements of microstrip line relative to the waveguide. By using two conductor loops, it is possible to simultaneously decouple for two signal paths with identical electrical losses, thus reducing the number of power dividers in the waveguide by up to half.

Description

TECHNICAL AREA

The invention relates to feed network with waveguide and two microstrip conductors for antenna systems, in particular for the bidirectional, in the Ka, Ku or X-band operated satellite communication for mobile and aeronautical applications.

BACKGROUND OF THE INVENTION

In order to connect aircraft for the transmission of multimedia data to a satellite network, it requires wireless broadband channels for data transmission at very high data rates. For this purpose, antennas must be installed on the aircraft, which have small dimensions to be installed under a radome and yet for a directed wireless data communication with the satellite (eg in the Ku, Ka or X-band) extreme requirements on the transmission characteristics meet, as a disturbance of adjacent satellites must be reliably excluded.

The antenna continues to be movable below the radome to track the satellite's orientation as the aircraft moves. For this purpose, the antenna must be made compact in order to remain mobile under the radome.

The regulatory requirements for broadcasting arise from international standards. All these regulatory requirements are designed to ensure that in the targeted Transmission mode of a mobile satellite antenna no interference may occur adjacent satellites.

Solutions for compact antennas for the applications show, for example, the WO2014005693 and WO2014005699 , These antennas consist of antenna fields, which are constructed from single radiators and have suitable feed networks. They can be run in any geometry and any length to aspect ratio without sacrificing antenna efficiency. In particular, antenna fields can be realized with low height.

If the horns are densely packed in the antenna fields, then there is another problem that efficient supply networks must be accommodated in the available space behind the Hornstahlerfeld. In the WO2014005699 It is shown that feed networks can be represented by a combination of waveguides and microstrip lines, but the number of power dividers needed is high. Power dividers in the waveguide area of the feed network require installation space that is available only to a limited extent.

In the WO2014005699 shown feed networks allow to distribute a sum signal amplitude and phase correct to the individual emitters in the transmission case or vice versa in the case of reception to correctly add the signals of the individual emitters to a sum signal. The feed network consists of microstrip conductors which combine the first single emitter groups (eg NxN or NxM elements) and a waveguide network to again combine several N * N or N * M groups.

Microstrip conductors have the advantage of a small footprint and thus enable a high integration density. The disadvantage is higher electrical losses compared to waveguides, but which require a much larger volume compared to microstrip conductors.

In order to minimize the weight and rotational volume of an antenna for a given aperture area, ways are sought to minimize the number of waveguide sections or the total volume of the waveguide without sacrificing the electrical performance.

DESCRIPTION OF THE INVENTION

It is an object of the invention to provide a feed network with a coupling between waveguide and microstrip line, which allows a high flexibility of the power coupling and low height.

The object is achieved by a feed network with the features of claim 1 and an antenna with the features of claim 23. Advantageous embodiments of the invention are listed in the further claims.

For this purpose, the feed network includes a waveguide with broad sides and narrow sides, and two microstrip conductors, each containing a conductor loop. The conductor loops each project from one of the narrow sides into the waveguide and are electrically connected to a broad side of the waveguide, i. are shorted to the waveguide on the broad side. On the narrow side, the waveguide has a small opening through which the microstrip conductor is guided without being electrically in contact with the waveguide itself.

This results in the possibility of inductive H-field coupling, which has a low sensitivity to tolerance-induced mechanical displacements of microstrip relative to the waveguide, which different from the usual capacitive E-field couplings. By using two conductor loops one can decouple at identical electrical losses simultaneously for two signal paths and thus reduce the number of power dividers in the waveguide up to half. The number of coupling points of stripline to waveguide can be minimized with the invention. Thus, in turn, reduces the size of the feed network. This simplification of a waveguide feed network formed by the waveguide thus contributes greatly to the reduction in weight and volume of an antenna in which the feed network according to the invention is used.

According to an advantageous embodiment of the invention, the conductor loops protrude from opposite narrow sides into the waveguide. In this way, the microstrip conductors can connect a large number of antenna elements, if necessary via further microstrip power dividers, in the sense of their own feed networks and with low-loss short paths.

The H-field coupling of the waveguide and two microstrip conductors advantageously produces a power divider, the signals arriving via the waveguide. So you get a kind of "hybrid" power divider, which distributes the signal from a waveguide gate on 2 microstrip gates.

According to a further advantageous embodiment of the invention, the conductor loops have an equal length within the waveguide. Thus, the signals on both microstrip lines have the same phase position and in the control of the following antenna elements, no further phase compensation is required.

It is also advantageous to arrange the conductor loops so that they project centrally from the narrow sides into the waveguide. This can provide maximum performance in the microstrip conductors are coupled and the matching at the transition optimized. The arrangement of the microstrip conductors in the waveguide advantageously takes place approximately λ / 4 away from one end of the short-circuited waveguide.

For the expression of asymmetrical power dividers, it is advantageous that the electrical connections between the two conductor loops are differently spaced with the broad side of the waveguide from a center of the broad side. This results in differently sized flooded loop surfaces for both conductor loops. The ratio of the areas of both conductor loops flooded through by the magnetic field determines the divider ratio of the power. Thus, divider ratios of 50:50 to 80:20 can be set in a broad range, as a result of which desired aperture tolerances of the antenna can be easily implemented.

Furthermore, one of the microstrip lines of the feed network can have a phase compensation arc which adapts the length of this microstrip line to the length of the other microstrip line and thus produces an equal microstrip line length and thus equal phase position of the signals of both microstrip lines despite asymmetry in the conductor loop shape. This is particularly advantageous if the phase compensation arc is assigned to the microstrip conductor which is electrically connected to the waveguide at a greater distance from the center of the broadside than the other microstrip conductor.

If the electrical connection of the microstrip lines at different broad sides of the waveguide, then a 180 ° phase shift between the signals of both conductor loops is set without further expenses. This can be used to compensate for geometric mirrored antenna elements or to compensate for possible phase shifts of subsequent waveguide networks.

For impedance matching of the microstrip conductors to the waveguide, the conductor loops are advantageously not straight, but include width jumps and set pieces. By specifying the position and size of stride jumps and set pieces, the reflections are reduced for the desired frequency range.

Advantageously, in the feed network for the microstrip Suspended Strip Line (SSL) are used to keep the losses low. The microstrip conductors consist of a board with a dielectric having a thickness of 0.1 to 1 mm, preferably 0.127 mm, and a copper strip arranged on the board with a thickness of 15 to 50 μm, preferably 17.5 μm. The width of the copper strip is 0.2 to 3 mm, preferably 0.5 mm.

The waveguide or the waveguide network is performed according to an advantageous embodiment of the invention, at least in sections as ridge waveguide. The ridge waveguide allows a wider band frequency range than a "normal" rectangular waveguide, particularly interesting for the Ka band. Furthermore, a ridge waveguide allows more compact designs (reduction of broadside) compared to a "normal" rectangular waveguide at the same cutoff frequency (interesting even at lower frequencies (X-band and Ku-band), in which the waveguide dimensions would otherwise be larger.

The electrical connection of the conductor loops with the broad side of the waveguide is carried out according to advantageous embodiments of the invention galvanic - direct connection of a trace of the microstrip line and the waveguide edge or capacitive. In a capacitive connection, the waveguide includes an opening into which a Board is inserted with the conductor loops. To form a capacitance, the tracks of both sides of the board are connected to each other by means of vias and separated from the waveguide by an insulation. The thickness of the insulation and the area of the tracks insulated from the waveguide determine the capacitance.

For a very compact design, a distance between one end of the waveguide and the microstrip conductor is advantageously only λ / 8 to λ / 12, ie significantly less than λ / 4, for which a maximum of the field strength would exist. It has been shown that with reasonable losses, the size of the feed network can be reduced once again.

The waveguide of the feed network may contain restrictions whereby a ridge waveguide is formed. Advantageously, the electrical connection of the conductor loops with the broad side of the waveguide no restriction, but takes place in a rectilinear section.

Another characteristic of the food network provides an asymmetrical power division, which is achieved in that the conductor loops frame a different area. For an impedance matching, the conductor loop with the larger power output advantageously has the width of the microstrip line larger than in the conductor loop with the lower power output.

According to the invention, it is possible to implement the feed network in the context of an antenna, the antenna comprising a plurality of horn radiators as antenna elements, which are connected via microstrip conductors with a waveguide having broad sides and narrow sides. The microstrip conductors each consist of a conductor loop which protrudes from one of the narrow sides into the waveguide and is electrically connected to a broad side of the waveguide. Horn radiators are very efficient single radiators in Antenna fields are arranged. In addition, horns can be designed broadband.

Thus, the antenna is suitable for bidirectional operation in vehicle-based satellite communication in a frequency band of 7.25-8.4 GHz (X-band), 12-18 GHz (Ku-band) and 27-40 GHz (Ka-band). ,

In addition, other advantages and features of the present invention will become apparent from the following description of preferred embodiments. The features described therein may be implemented alone or in combination with one or more of the features mentioned above insofar as the features are not contradictory. The following description of the preferred embodiments will be made with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1

shows in 3D a waveguide with two coupling microstrip conductors.

FIG. 2

shows the waveguide FIG. 1 with field lines of an H-field.

FIG. 3

shows the cross section of a waveguide with two symmetrical, in-phase microstrip conductors.

FIG. 4

shows the cross section of a waveguide with two symmetrical, antiphase microstrip conductors.

FIG. 5

shows the cross section of a waveguide with two asymmetrical, in-phase microstrip conductors.

FIG. 6

shows a cross section of a ridge waveguide.

FIG. 7

shows an antenna with multiple horns and a feed network.

FIGS. 8 to 13

show feeder networks with different divider ratios and the use of standing waveguides and capacitive short circuits.

Embodiment

FIG. 1 shows a waveguide HL, which is filled with air and has the dimensions 16 x 6 mm for the Ku band or 7 x 2.5 mm for the Ka band. At the in FIG. 1 shown upper side of the waveguide HL this is completed. The termination at the end AB of the waveguide HL is about λ / 4 of a coupling of two microstrip lines MS1, MS2 away. The microstrip conductors MS1, MS2 protrude from a narrow side b1, b2 into the waveguide HL. The microstrip lines MS1, MS2 consist of a Suspended Strip Line (SSL), which consists of a circuit board on which a copper strip, a copper layer, is applied. The board itself consists of a dielectric with a thickness of 0.1 to 1 mm, preferably 0.127 mm. The copper strip thereon has a width of 0.2 to 3 mm, preferably 0.5 mm, and a thickness of 15 to 50 microns, preferably 17.5 microns. So that the microstrip conductors MS1, MS2 can protrude into the waveguide HL, the narrow sides b1, b2 at the level of the coupling have a narrow slot, which is adapted to the shape of the microstrip line MS1 and MS2. The SSL is surrounded by metal, so there are no power losses from radiation out of the structure and through the passage at the slots. By appropriate dimensioning of the slot and the interference on the field of the waveguide HL is negligible.

On a broad side a1 of the waveguide HL, both microstrip conductors MS1, MS2 are electrically connected to the waveguide HL. This connection represents in each case a short circuit 1 of the respective microstrip line MS1, MS2 with the waveguide HL. Thus, a conductor loop 11, 12 forms around both sides of the waveguide HL through the respective microstrip lines MS1, MS2, around which an H field is formed ,

The inductive H-field coupling is in FIG. 2 shown again. On a sectional plane through the coupling can be seen at the locations near the short circuits 1 as the H-field coupled as TE mode from the waveguide HL in the two microstrip lines MS1, MS2 as TEM mode.

This principle of double H-field coupling through two microstrip conductors MS1, MS2 leads to power sharing from the waveguide HL to the microstrip conductors MS1, MS2. In contrast to known couplings and decoupling takes place here already in the transition from waveguide to microstrip power sharing. This reduces the need for further power dividers, which would typically be located in the waveguide feed network.

The feeding network according to the invention, consisting of the two microstrip conductors MS1, MS2 and the waveguide HL, will now be described with reference to FIG FIGS. 3 to 5 further explained.

In FIG. 3 it is shown that the conductor loops 11, 12 within the waveguide HL form two equal loops, which extend from the narrow sides b1 and b2 to the broad side a1. These equal areas of the conductor loops 11, 12 mean a symmetrical power division. The conductor loops 11, 12 further include set pieces and width jumps, which favor the adaptation of the microstrip line MS1 or MS2 to the conditions of the waveguide HL. Here is a conductor piece, which is in each case connected to the broad side a1, narrowest and a conductor loop piece, which represents the transition to the microstrip MS1 or MS2 outside of the waveguide HL, the widest. Size and position of the wide jumps or set pieces are optimized accordingly for the desired frequency band.

The microstrip conductors MS1, MS2 continue after the slot in the narrow side b1, b2 of the waveguide HL and form microstrip conductor networks, with which, as shown later, antenna elements are supplied.

FIG. 4 shows in comparison to FIG. 3 a variant in which a phase shift of the signals between the microstrip conductors MS1, MS2 is effected in that the electrical connection of the conductor loops 11, 12 takes place on opposite broad sides a1 and a2 of the waveguide HL. The positioning of the conductor loops 11 and 12 is here again symmetrical, but with respect to the top and bottom of the waveguide HL mirror image. This means that once again a balanced power line is achieved, but the signals on one microstrip line MS1 are 180 ° out of phase with respect to the other microstrip line MS2.

At the feed network after FIG. 5 a center M of the broad sides of the waveguide is located. Thus it is easier to recognize that in FIG. 5 an asymmetric power divider is realized. The conductor loop 11 on the left side of the waveguide has a larger flooded area than the conductor loop 12 on the right side. Thus, more energy is coupled out in one conductor loop 11 than in the other conductor loop 12. The lengths of the conductor loops 11 and 12 within the waveguide differ therewith. For a phase compensation of the microstrip MS2 with the lower power output an additional phase arc P, the a length compensation of the microstrip line MS2 and an adjustment to the length of the other microstrip line MS1 brings with it.

Due to the asymmetries of the power divider, see FIG. 4 , divider ratios can be set from 50:50 to 80:20. This allows multiple aperture assignments for the antenna driven by the feed network. Due to a set phase shift between the two microstrip lines MS1, MS2, see FIG. 4 , geometrically mirrored antenna elements or possible phase shifts can be compensated by subsequent waveguide networks.

In FIG. 6 is an alternative waveguide shape to the otherwise rectangular waveguide HL as in FIG. 1 , shown. The waveguide HL is provided as a ridge waveguide, each with a restriction RI centered in the broad sides a1, a2. As a result, the waveguide HL broadband.

Furthermore, the web waveguide HL has a width paragraph SP, in which the dimensions of the narrow sides b1, b2 and broad sides a1, a2 change abruptly, and a length of the restriction RI is changed. This is used to minimize the reflections.

These modifications of the waveguide geometry become corresponding FIG. 6 used in the transition to the microstrip lines MS1, MS2 and affect the waveguide space near the short circuits 1 of conductor loops 11, 12 of the microstrip lines MS1, MS2 with the hollow edge HL. However, it is alternatively or additionally possible to use this waveguide geometry in a waveguide network at other sections of the feed network.

The feed network according to the invention is used in particular in antennas having a plurality of horn radiators as antenna elements used. FIG. 7 shows an antenna with 16 antenna elements, a feed network is able to feed 8 antenna elements A1 to A8 alone. A waveguide HL is to centrally located within eight antenna elements A1 to A8 and on both narrow sides of the signals are coupled into two microstrip lines MS1 and MS2. These microstrip conductors MS1, MS2 in turn form microstrip conductor networks, which connect in each case 4 antenna elements A1 to A4 or A5 to A8 to the waveguide HL. The waveguide HL in turn forms the conclusion of a waveguide network. Here, only one waveguide power divider is shown. The waveguide network is in turn connected to a transmitting and receiving device Tx / Rx, which receives corresponding signals from the antenna or sends to the antenna.

The feed network shown here allows the feeding of a large number of antenna elements with a minimum of power dividers in the waveguide network. Thus, lightweight compact antennas are represented, as they are needed in the aircraft-based satellite communication in the X, Ku or Ka band.

Based on FIGS. 8 to 13 show alternative embodiments of the feed networks according to the invention, which except for the embodiment according to FIG. 13 Include climbing ladders with restrictions RI.

FIG. 8 shows a symmetrical power divider (power output 50% / 50%), in which the electrical connection of the conductor loops 11, 12 occurs just to the right and left of the restriction RI of the waveguide HL. Both conductor loops 11, 12 frame the same area and have the same widths of the conductor tracks.

The food network after FIG. 9 is particularly suitable for narrow frequency bands, for example in X-band. One Distance AB1 of one end of the waveguide HL to the microstrip line is only about λ / 10, that is to say significantly less than λ / 4 or half the length A1 of the broad side a1. Thus, the size of the feed network is reduced again.

FIGS. 10 and 11 show asymmetric divisors with a divider ratio of 66.7% / 33.3% and 57% / 43%, respectively, which are set by the fact that the left conductor loop 11 encloses a larger area than the right conductor loop 12. Also in these feed networks, the galvanic electrical connection between conductor loop 11, 12 and waveguide HL without the restriction RI is touched in a rectilinear region of the waveguide HL. In FIG. 9 this is clear. The restriction RI starts from the end of the waveguide AB only shortly after the microstrip MS2. How out FIG. 10 As can be seen, the width D of the left conductor loop 11 with the larger power output is greater than the width of the right conductor loop 12. Thus, the left conductor loop 11 is more low-impedance than the right conductor loop 12 and well fitted.

In addition to the area to be set for the power division - essentially determined by the length of the first line section of the short circuit A and the length of the second line section in the direction of the narrow waveguide side B, which framing the respective line loop 11, 12 are for a reflection-poor adaptation of the microstrip MS1, MS2 after FIG. 12 Also note the other dimensions C, D, E of the conductor loops 11, 12. The width of the first line section C, the width of the second line section D are selected according to the impedance of the conductor loop necessary for a reflection-poor matching. The conductor loop with the greater power output has the designations in FIG. 12 a larger width C, D the microstrip line as the other conductor loop with the lower power output - see FIG. 10 ,

In addition to the previously shown galvanic connection of conductor loop 11, 12 with the waveguide HL and a capacitive connection is possible. For a capacitive connection to FIG. 13 contains the waveguide HL an opening into which a circuit board PL is inserted with the conductor loops forming conductor tracks L on the surface. To form a capacitance, the interconnects L of both sides of the board PL are interconnected by means of vias V. In the inserted state waveguide HL and interconnects L are separated by an insulation I. The insulation I is formed by an electrically insulating coating eg solder resist. The conductor tracks L are made of copper, the waveguide HL is made of aluminum. LIST OF REFERENCE NUMBERS waveguide HL broadside a1, a2 narrow side b1, b2 Microstrip MS1, MS2 conductor loop 11, 12 Center of the broadside M Phase balance sheet P antenna elements A1 .. A8 End of the waveguide FROM Transmitting and receiving equipment Tx / Rx short circuit 1 restriction RI wide sales SP Length of the first line section of the short circuit A Length of the second line section in the direction of the narrow waveguide side B Width of the first line section C Width of the second line section D Distance between the two conductor loops e Length broadside A1 Distance end of the waveguide to microstrip conductor AB1 Via V conductor path L insulation I circuit board PL

Claims (23)

Feed network for antenna systems with a waveguide (HL) having broad sides (al, a2) and narrow sides (b1, b2),
two microstrip conductors (MS1, MS2), each consisting of a conductor loop (11, 12) which protrudes from one of the narrow sides (b1, b2) into the waveguide (HL) and a broad side (al, a2) of the waveguide (HL) electrically connected. Food network according to claim 1, wherein the conductor loops (11, 12) protrude from opposite narrow sides (b1, b2) in the waveguide (HL). Feed network according to one of the preceding claims, in which a coupling of waveguide (HL) and microstrip conductors (MS1, MS2) serves as a power divider of the incoming signals via the waveguide (HL). Feed network according to one of the preceding claims, wherein the conductor loops (11, 12) have an equal length within the waveguide (HL). Feed network according to one of the preceding claims, in which the conductor loops (11, 12) project centrally from the narrow sides (b1, b2) into the waveguide (HL). Feed network according to one of the preceding claims, wherein the electrical connections of the two conductor loops (11, 12) with the broad side (al, a2) of the waveguide (HL) from a center (M) of the broad side (al, a2) are spaced differently. Feed network according to one of the preceding claims, in which at least one microstrip line (MS2) has a phase compensation arc (P) which adjusts the length of this microstrip line (MS2) to the length of the other microstrip line (MS1). Feed network according to the preceding claim, wherein the microstrip line (MS2) with phase compensation arc (P) at a greater distance from the center of the broad side (al, a2) with the waveguide (HL) is electrically connected as the other microstrip line (MS1). Feed network according to one of the preceding claims, wherein the electrical connection of the conductor loops (11, 12) takes place on different broad sides (al, a2) of the waveguide (HL). Feed network according to one of the preceding claims, in which the conductor loops (11, 12) are not exclusively formed straight, but include width jumps and set pieces. Feeder network according to one of the preceding claims, in which the microstrip conductors (MS1, MS2) are in the form of SSL (suspended strip line). Feed network according to the preceding claim, wherein the microstrip line (MS1, MS2) a board made of a dielectric having a thickness of 0.1 to 1 mm, preferably 0.127 mm, and arranged on the board copper strip having a thickness of 15 to 50 microns , preferably 17.5 μm, and a width of 0.2 to 3 mm, preferably 0.5 mm. Feed network according to one of the preceding claims, wherein the microstrip conductors (MS1, MS2) the waveguide (HL) with a plurality of antenna elements (A1 .. A8) connect, wherein the antenna elements A1 .. A8) are horns and the microstrip lines (MS1, MS2) about λ / 4 from one end (AB) of the waveguide (HL) are arranged. Feed network according to one of the preceding claims, wherein the waveguide (HL) is part of a waveguide supply network, which is connected to transmitting and receiving means (Tx / Rx). Feed network according to one of the preceding claims, wherein the waveguide (HL) is at least partially designed as ridge waveguide. Feed network according to one of the preceding claims, wherein the electrical connection of the conductor loops (11, 12) with the broad side (al, a2) of the waveguide (HL) takes place galvanically or capacitively. Feeder network according to Claim 16, in which, for a capacitive connection, the waveguide (HL) contains an opening into which a printed circuit board (PL) is inserted with the conductor loops (11, 12), the conductor loops (11, 12) forming conductor tracks (L ) are connected to one another on both sides of the board (P) by means of vias (V) and are separated from the waveguide (HL) by an insulation (I). Feed network according to one of claims 1 to 12, wherein a distance (AB1) of one end (AB) of the waveguide (HL) to the microstrip line (MS1, MS2) is λ / 8 to λ / 12. Feed network according to one of the preceding claims, wherein the electrical connection of the conductor loops (11, 12) to the broad side (al, a2) of the waveguide (HL) a rectilinear section of the waveguide (HL) takes place and no restriction (RI) touched. Feed network according to one of the preceding claims, in which the conductor loops (11, 12) frame a different area and set an asymmetrical power divider. Feeder network according to claim 20, wherein the conductor loop (11) with the larger power output, the width (D) of the microstrip line (MS1) is greater than in the other conductor loop (12). Antenna with a plurality of horn radiators as antenna elements (A1 .. A8), which are connected via microstrip conductors (MS1, MS2) to a waveguide (HL) having broad sides (al, a2) and narrow sides (b1, b2), the microstrip conductors ( MS1, MS2), each consisting of a conductor loop (11, 12), which protrudes from one of the narrow sides (b1, b2) in the waveguide (HL) and is electrically connected to a broad side (al, a2) of the waveguide (HL) , An antenna according to the preceding claim, bidirectionally operated for vehicle-based satellite communication in an X, Ka or Ku frequency band.

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