Abstract
An antenna feeding network for a multi-radiator antenna. The feeding network comprises at least one substantially air filled coaxial line, each comprising a central inner conductor, an elongated outer conductor surrounding the central inner conductor and an elongated rail element slidably movably arranged inside the outer conductor. The rail element is longitudinally movable in relation to at least the outer conductor.
Claims
1. An antenna feeding network for a multi-radiator antenna, said feeding network comprising a first inner conductor; a first outer conductor formed by the walls defining a first elongated compartment filled essentially by air; a rail element arranged inside the walls of the first elongated compartment; and and at least one dielectric element attached to the rail element and longitudinally movable within the first elongated compartment.
2. The antenna feeding network according to claim 1, wherein the walls are made in a conductive material.
3. The antenna feeding network according to claim 1, further comprising a second inner conductor; a second outer conductor formed by the walls defining a second elongated compartment filled essentially by air; and a connector device indirectly interconnecting the first and second inner conductors.
4. The antenna feeding network according to claim 3 wherein the indirect interconnection provided by the connector device is a capacitive coupling.
5. The antenna feeding network according to claim 3 wherein the indirect interconnection provided by the connector device is an inductive coupling.
6. The antenna feeding network according to claim 3 wherein the indirect interconnection provided by the connector device is a combination of capacitive and inductive coupling.
7. A multi radiator antenna comprising: an electrically conductive reflector, at least one radiating element arranged on said reflector and an antenna feeding network, said radiating elements being connected to said antenna feeding network, and said antenna feeding network comprising: a first inner conductor; a first outer conductor formed by the walls defining a first elongated compartment filled essentially by air; a rail element arranged inside the walls of the first elongated compartment; and and at least one dielectric element attached to the rail element and longitudinally movable within the first elongated compartment.
8. The multi radiator antenna of claim 7 wherein the walls are made in a conductive material.
9. The multi radiator antenna of claim 7, wherein said antenna feeding network further comprises: a second inner conductor; a second outer conductor formed by the walls defining a second elongated compartment filled essentially by air; and a connector device indirectly interconnecting the first and second inner conductors.
10. The multi radiator antenna of claim 9 wherein the indirect interconnection provided by the connector device is a capacitive coupling.
11. The multi radiator antenna of claim 9 wherein the indirect interconnection provided by the connector device is an inductive coupling.
12. The multi radiator antenna of claim 9 wherein the indirect interconnection provided by the connector device is a combination of capacitive and inductive coupling.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) These and other aspects of the present invention will now be described in more detail with reference to the appended drawings, which show presently preferred embodiments of the invention, wherein:
(2) FIG. 1 shows a schematic view of an antenna feeding network for a multi radiator antenna;
(3) FIG. 2 shows a cross section view of a prior art coaxial line;
(4) FIG. 3 shows a schematic cross section view of a prior art multi-radiator antenna, where the outer conductors of the coaxial lines combine to form a reflector for the radiators;
(5) FIG. 4 shows a detail view of an antenna feeding network according to an embodiment of the first aspect of the invention;
(6) FIG. 5 shows a view of a multi radiator antenna according to an embodiment of the second aspect of the invention;
(7) FIG. 6 shows parts of an antenna feeding network according to an embodiment of the first aspect of the invention;
(8) FIG. 7 shows a cross section view of an antenna feeding network according to an embodiment of the first aspect of the invention;
(9) FIG. 8 shows means for moving two rail elements in an antenna feeding network according to an embodiment of the first aspect of the invention in a partial cross section view from the side;
(10) FIG. 9 shows a schematic view of an antenna feeding network according to an embodiment of the first aspect of the invention; and
(11) FIG. 10 schematically illustrates a perspective view of an embodiment of an antenna feeding network according to the fourth aspect of the invention;
(12) FIG. 11 schematically illustrates another perspective view of parts of an embodiment of an antenna feeding network according to the fourth aspect of the invention;
(13) FIG. 12 schematically illustrates a front view into two neighbouring coaxial lines of an embodiment of an antenna feeding network according to the fourth aspect of the invention;
(14) FIG. 13 schematically illustrates parts of another embodiment of an antenna feeding network according to the fourth aspect of the invention;
(15) FIG. 14 schematically illustrates parts of yet another embodiment of an antenna feeding network according to the fourth aspect of the invention;
(16) FIG. 15 schematically illustrates an embodiment of an antenna arrangement according to the seventh aspect of the invention, showing a perspective view onto a cross section cut through the middle of one of the radiating elements along a coaxial line;
(17) FIG. 16 schematically illustrates an embodiment of an antenna arrangement according to the seventh aspect of the invention, showing another perspective cross sectional view of the connection between the radiating element and the inner conductor, the cross section being cut perpendicular to the coaxial line;
(18) FIG. 17 schematically illustrates a view of a coupling element and an inner conductor of an embodiment of an antenna arrangement according to the seventh aspect of the invention;
(19) FIG. 18 schematically illustrates a cross section view of parts of an embodiment of an antenna arrangement according to the seventh aspect of the invention, which is provided with a snap-on mechanism; and
(20) FIG. 19 schematically illustrates a view of a coupling element and an inner conductor of an alternative embodiment of an antenna arrangement according to the seventh aspect of the invention.
DETAILED DESCRIPTION
(21) FIG. 1 schematically illustrates an antenna arrangement 1 comprising an antenna feeding network 90, an electrically conductive reflector 17, which is shown schematically in FIG. 1, and a plurality of radiating elements 14. The radiating elements 14 may be dipoles. The antenna feeding network 90 connects a coaxial connector 15 to the plurality of radiating elements 14 via a plurality of lines 91, 92 which may be coaxial lines, which are schematically illustrated in FIG. 1. The signal to/from the connector 15 is split/combined using, in this example, three stages of splitters/combiners 16.
(22) FIG. 2 shows a cross section view of a prior art coaxial line 3″, where the outer conductor 5″ is formed as a square cross section tube, and the inner conductor 4″ is supported by dielectric support means 7″.
(23) FIG. 3 shows a schematic cross section view of a prior art multi-radiator antenna, having an antenna feeding network comprising a plurality of coaxial lines, each having an outer conductor with a substantially square cross section and an inner conductor 4′″ arranged in the outer conductor. The antenna feeding network is of the open type, i.e. each of the coaxial lines is provided with a longitudinally extending opening 18 along one side of the outer conductor, in this case along the bottom of the outer conductor. The antenna further comprises a reflector 17′″ which is formed by upper outer surfaces of the outer conductors of the coaxial lines, and radiators/dipoles 14′″ arranged in parallel (only one is seen in the figure) on the reflector. The antenna feeding network and the reflector form a self-supporting structure.
(24) FIG. 4 shows a detail view of an antenna feeding network according to an embodiment of the first aspect of the invention. The feeding network comprises a plurality of parallel coaxial lines. The figure shows two coaxial lines 3a, 3b which each comprise a central inner conductor 4a, 4b, an elongated outer conductor 5a, 5b forming a cavity or compartment around the central inner conductor, and an elongated rail element 6a, 6b slidably arranged inside the outer conductor. The outer conductors 5a, 5b have square cross sections and are formed integrally and in parallel to form a self-supporting structure. The wall which separates the coaxial lines 3a, 3b constitute vertical parts of the outer conductors 5a, 5b of both lines. The rail elements 6a, 6b are longitudinally movable relative the outer conductors. In the figure is illustrated a support element 7 which is arranged between the rail element 6b and the inner conductor 4b, and also between the inner and outer conductors. Furthermore, the coaxial line 3a is provided with a dielectric element 8 which is attached to the elongated rail element 6a and is configured to co-operate with the coaxial line 3a. The dielectric element 8 has a U-shaped cross section and is arranged around the inner conductor 4a such that it partially surrounds the inner conductor from below and fills most of the cavity between the conductors. Arranging the dielectric element 8 in the cavity between the inner and outer conductor forms a phase shifting device arranged to adjust the phase of signals in coaxial line 3a. Since the dielectric element 8 is attached to the rail element 6a, the phase may be adjusted by moving or sliding the rail element longitudinally until the desired position and phase shift is achieved.
(25) FIG. 5 shows a view of a multi radiator antenna according to an embodiment of the second aspect of the invention. The antenna 1 comprises an antenna feeding network 90, a reflector 17 and three radiating elements or dipoles 14a-c arranged on the reflector. The antenna feeding network is provided with coaxial lines 3a, 3b having central inner conductors 4a, 4b and outer conductors 5a, 5b. The description above with reference to FIG. 4 also applies to this feeding network, although no rail elements are shown in FIG. 5. In this figure, it is illustrated how the coaxial lines are integrally formed with the reflector in the sense that the reflector 17 is formed by the upper walls of the outer conductors. Each outer conductor is formed by the walls defining an elongated compartment, the walls being made in a conductive material such as aluminum. The inner conductors and the rail elements are thus arranged in elongated compartments. Although only two of the compartments are provided with inner conductors in FIG. 5, it is realized that one or a plurality of the shown compartments may also be provided with inner conductors to form coaxial lines. It is further realized that the number of inner conductors (two) and number of radiators (three) shown are only for illustrative purposes, and that further inner conductors may be used to provide a splitting/combing antenna feeding network of the type shown in FIG. 1. Outer conductors of the antenna feeding network 90 are provided with openings 22. The openings 22 have an elongated shape in the lateral direction and are solely provided to allow electrical interconnection between inner conductors. The openings are thus of quite short extension in the longitudinal direction. The outer conductors thus substantially surround the inner conductors, and the antenna feeding network may be described as a substantially closed type of antenna feeding network.
(26) FIG. 6 shows parts of the antenna feeding network shown in FIG. 4. The support element 7 may be held in the desired axial position by being arranged in a circumferential recess or groove (not shown) of the inner conductor 4b. The support element has a circular through hole provided with a side opening, and is made from a flexible plastic material such that the inner conductor may be inserted into the through hole via the side opening, such that the inner conductor and the support element is engaged with each other as shown in the figure. The elongated dielectric element 8 on the other hand is attached to the rail element 6b (and thereby axially fixated). Thus, the support element(s) is axially fixated relative to the inner conductor, while the dielectric element(s) is axially fixated to the rail element. Prior to inserting the inner conductors, rail elements, support element(s) and dielectric element(s) into the outer conductors, the inner conductors and the support element are placed on top of the rail element, for example as illustrated in FIG. 6. Thereafter, the inner conductors, rail elements, support element(s) and dielectric element(s) are pushed into corresponding outer conductors as a single unit. Since the support element 7 is axially fixated to the inner conductor 4b, their relative positions are maintained after having been inserted into the corresponding outer conductor. After the inner conductors, rail elements, support element(s) and dielectric element(s) have been inserted into the outer conductors, each inner conductor is advantageously attached or fixated to the corresponding outer conductor, for example by means of at least one holding element. After the inner conductors have been attached or fixated, the rail elements may be moved back and forth independently of the inner conductors. It is understood that only axial portions of the inner conductors and rails are shown, and that at least one support element corresponding to that of inner conductor 4b may also be attached to inner conductor 4a, and that at least one rail dielectric element corresponding to element 8 may also be attached to the rail element 6a.
(27) The connector device 19 and the inner conductors 4a, 4b together form a splitter/combiner. When operating as a splitter, the inner conductor 4b is part of the incoming line, and the two ends of the inner conductor 4a are the two outputs of the splitter. The dielectric element 8 can be moved along the inner conductor 4a, which forms first and second coaxial output lines on opposite sides of the connector device 19 (together with an outer conductor which is not shown). The dielectric element thus has various positions along those coaxial output lines.
(28) We first consider the case when the dielectric element 8 is placed in a central position, equally filling the first and second output coaxial lines. When a signal is entered at the input coaxial line 4b, it will be divided between the first output coaxial line and the second output coaxial line, and the signals coming from the two output coaxial lines will be equal in phase. If the dielectric element 8 is moved in such a way that the first output coaxial line will be more filled with dielectric material than the second output coaxial line, the phase shift from the input to the first output will increase. At the same time the second output coaxial line will be less filled with dielectric, and the phase shift from the input to the second output will decrease. Hence, the phase at the first output will lag the phase at the second output. If the dielectric part is moved in the opposite direction, the phase of the first output will lead the phase of the second output. The splitter/combiner may thus be described as a differential phase shifter.
(29) FIG. 7 shows a detailed cross section view of the antenna feeding network shown in FIG. 4. In FIG. 7, it is clearly illustrated how the outer conductor is provided with guiding means configured to guide the rail element inside the outer conductor. The guiding means comprises one longitudinally extending protrusion or ridge 9a, 9b on each inner side wall of the outer conductor arranged at a distance from the bottom surface of the outer conductor corresponding to the thickness of the rail element 6b. The ridges extend in parallel along the whole or essentially the whole length of the outer conductor (in the depth direction as shown in the figure), such that the rail element is guided from below by the bottom surface 20 and from above by the ridges 9a, 9b.
(30) FIG. 8 shows means for moving two rail elements in an antenna feeding network according to an embodiment of the first aspect of the invention. The means for moving the two rail elements of the coaxial lines is configured to move the rail elements simultaneously at different speeds. The means for moving comprises a longitudinally extending rod 10 and at least first and second connecting elements 11, 12, each connecting element being provided with an internally threaded portion 11a, 12a, the internally threaded portions being configured to co-operate with corresponding (externally) threaded segments or portions 10a, 10b of the rod 10, wherein the threaded segment or portion 10a of the rod has a greater pitch than the other threaded segment or portion 10b, such that the first connecting element 11 moves at a greater speed than the second connecting element 12 when the rod is rotated. The connecting elements 11, 12 are connectable to respective rail elements (not shown in the figure) through elongated slots in the outer conductors. The rod may be rotated manually or using electric motors controlled by a controlling device such as micro-controller. When using electric motors, the rails, and hence the downtilt of the antenna, can be controlled remotely. The remote control can be achieved e.g. by connecting the motor and micro-controller to a cellular base station, or some other means for control. The means for moving two rail elements illustrated in FIG. 8 may be combined with two or more splitter/combiners of the differential phase shifting type illustrated in FIG. 6. Thus, the means for moving may be configured to move a rail element 6b and dielectric element 8 of a first splitter/combiner simultaneously and at a different speed than a rail element and dielectric of a second splitter/combiner. Such a combination including a plurality of differential phase shifters may be used in an antenna arrangement to provide a variable electrical tilt angle.
(31) FIG. 9 shows a schematic cross section view of an antenna feeding network. The feeding network comprises eight coaxial lines. The figure shows four compartments 105a-105d formed in parallel in an integral self-supporting structure. The walls which separate the compartments constitute vertical parts of the outer conductors. In each of the first and second compartments 105a, 105b, a single inner conductor 104a, 104b is arranged, forming first and second coaxial lines together with the walls defining the compartment. In the compartment 105c, two inner conductors 104c1, 104c2 are arranged spaced apart from each other as seen in the longitudinal direction forming third and fourth coaxial lines using the walls defining compartment 105c as outer conductors. In the fourth compartment 105d, four inner conductors 104d1-104d4 are arranged spaced apart from each other as seen in the longitudinal direction forming fifth-eighth coaxial lines using the walls defining compartment 105d as outer conductors.
(32) The inner conductor 104a forms part of an incoming line 115. The inner conductor 104a of the first coaxial line is interconnected to the inner conductor 104b of the second coaxial line by means of a connector device 119a. Opposite ends of the inner conductor 104b of the second coaxial line are interconnected to the inner conductors 104c1 and 104c2, respectively, by means of connector devices 119b1 and 119b2. Opposite ends of the inner conductor 104c1 of the third coaxial line are interconnected to the inner conductors 104d1 and 104d2, respectively, by means of connector devices 119c1 and 119c2. The inner conductor 104c2 is connected to the inner conductors 104d3 and 104d4 by means of connector device 119c3 and 119c4 in the same manner. The connector devices 119a, 119b1-b2, 119c1-c3 may be of the same type shown in FIG. 6 and described above. Each of the inner conductors 104b, 104c and 104d may be considered to be a part of separate coaxial output lines on opposite sides of the corresponding connector device together with the outer conductors formed by the walls defining the respective surrounding compartment.
(33) The second, third and fourth compartments 105b-d are each provided with an elongated rail element 106b-d slidably arranged inside the corresponding compartment. The rail elements are longitudinally movable in the compartment. The rail element 106b in the second compartment is provided with a dielectric element 108b which is attached thereto such that the first and second coaxial lines form a splitter/combiner with differential phase shift as described above with reference to FIG. 6. The rail element 106c in the third compartment is provided with two dielectric elements 108c1, 108c2 which are attached thereto in a longitudinally spaced apart manner. The dielectric elements 108c1, 108c2 are configured to co-operate with a respective coaxial line formed with inner conductor 104c1, 104c2, such that the second coaxial line together with the third and fourth coaxial lines form two splitters/combiners with differential phase shift. In the same manner, the rail element 106d in the fourth compartment is provided with four dielectric elements 108d1-d4 which are attached thereto in a longitudinally spaced apart manner. The dielectric elements 108d1-d4 are configured to co-operate with a coaxial line formed with respective inner conductor 104d1-d4, such that the third and fourth coaxial lines together with the fifth-eighth coaxial lines form four splitters/combiners with differential phase shift. In other embodiments, the dielectric elements in the fourth compartment are omitted. The dielectric elements may be of the same type shown in FIG. 6 and described above.
(34) As shown schematically in the figure, the ends of the fourth-eighth coaxial lines are each connectable to a corresponding radiator/dipole, thus forming a multi radiator antenna. The upper side of the outer conductors (not visible in the shown cross section view) may form a reflector on which the radiators are arranged in the same manner as shown in FIG. 5 and described above.
(35) The embodiments shown in FIGS. 8 and 9 are advantageously combined to provide an antenna with electrically adjustable tilt. In such an embodiment, the means for moving are preferably configured to move the rail 106c (and the dielectric elements 108c1-c2) twice as fast/long as the rail 106d (and the dielectric elements 108d1-d4), and to move the rail 106b (and the dielectric element 108b) twice as fast/long as the rail 106c, i.e. four times as fast/long as the rail 106d.
(36) The text above describes one possible, but not limiting, embodiment of the invention. Other embodiments are possible, e.g. with other numbers of radiators such as 2, 4, 6, 10, 12, 14, 16, 18 etc. Embodiments with odd numbers of radiators are also possible. In such other implementations, the movement of the different rails will not be exactly twice or four times compared to that of the slowest moving rail.
(37) Returning to FIG. 5, which illustrates a multi-radiator antenna 1 in a perspective view, the antenna 1 comprises the electrically conductive reflector 17 and radiating elements 14a-c.
(38) The electrically conductive reflector 17 comprises a front side 93, where the radiating elements 14a-c are mounted and a back side 95.
(39) FIG. 5 shows a first coaxial line 3a which comprises a first central inner conductor 4a, an elongated outer conductor 5a forming a cavity or compartment around the central inner conductor, and a corresponding second coaxial line 3b having a second inner conductor 4b and an elongated outer conductor 5b. The outer conductors 5a, 5b have square cross sections and are formed integrally and in parallel to form a self-supporting structure. The wall which separates the coaxial lines 3a, 3b constitute vertical parts of the outer conductors 5a, 5b of both lines. The first and second outer conductors 5a, 5b are formed integrally with the reflector 17 in the sense that the upper and lower walls of the outer conductors are formed by the front side 93 and the back side 95 of the reflector, respectively.
(40) Although the first and second inner conductors 4a, 4b are illustrated as neighbouring inner conductors they may actually be further apart thus having one or more coaxial lines, or empty cavities or compartments, in between.
(41) In FIG. 5 not all longitudinal channels or outer conductors are illustrated with inner conductors. It is however clear that they may comprise such inner conductors.
(42) Each of the radiating elements 14 is configured to be electrically connected to at least one of the inner conductors 4 via a coupling element 24 (c.f. FIG. 15).
(43) The front side 93 of the reflector comprises at least one opening 22 for the installation of the connector device 19. The opening 22 extends over the two neighbouring coaxial lines 3a, 3b so that the connector device 19 can engage the first and second inner conductors 4a, 4b.
(44) Although the invention is illustrated with two neighbouring inner conductors 4a, 4b it falls within the scope to have an opening (not shown) that extends across more than two coaxial lines 3a, 3b and to provide a connector device 19 than can bridge two or even more inner conductors. Such a connector device (not shown) may thus be designed so that it extends over a plurality of coaxial lines between two inner conductors or over empty cavities or compartments. Such a connector device (not shown) may also be used to connect three or more inner conductors.
(45) In FIG. 10, an enlarged view of the opening 22 and the connector device 19 arranged therein is illustrated. The connector device 19 is clipped or snapped onto the first inner conductor 4a and the second inner conductor 4b. The connection between the first inner conductor 4a and the second inner conductor 4b is electrically indirect, which means that it is either capacitive, inductive or a combination thereof. This is achieved by providing a thin insulating layer of a polymer material or some other insulating material (e.g. a non-conducting oxide) on the connector device 19. The insulating layer may have a thickness of 1 μm to 20 μm, such as from 5 μm to 15 μm, such as from 8 μm to 12 μm, or may have a thickness of 1 μm to 5 μm. The insulating layer may cover the entire outer surface of the connector device 19, or at least the portions 30, 30′ of the connector device 19 that engage the first and second inner conductors 4a, 4b.
(46) The connector device 19 comprises a bridge portion 32 and two pairs of snap on fingers 30, 30′. One of the two pairs of snap on fingers 30′ is arranged close to one end of the bridge portion 32 and the other of the two pairs of snap on fingers 30 is arranged close to the other end of the bridge portion 32. The two pairs of snap on fingers 30, 30′ may be connected to the bridge portion 32 via connecting portions configured such that the bridge portion 32 is distanced from the first and second inner conductors 4a, 4b. In other embodiments, the snap on fingers 30, 30′ are connected directly to the bridge portion 32. The connecting portions, as well as the other portions of the connector device, are shaped to optimize the impedance matching of the splitter/combiner formed by the connector device and the coaxial lines. The shape, or preferably the diameter of the connecting inner conductors may also contribute to the matching of the splitter/combiner.
(47) As can be seen from FIG. 10, the vertical separating wall portion 94 is cut down to about two-thirds to three-quarters of its original height in the area of the opening 22 so that the connector device 19 does not protrude over the front side 93 of the electrically conductive reflector 17. In other embodiments, the wall portion 94 is cut down all the way to the floor of the outer conductors. The remaining height of the wall portion is adapted together with the other components, such as the connector device to optimize the impedance match.
(48) It may be possible (not shown in the figures) to provide only one pair of snap on fingers, for example the pair of snap on fingers 30′ engaging the first inner conductor 4a providing an indirect connection, and to let the other end of the bridge portion 32 contact the second inner conductor 4b directly without insulating layer or coating. This direct connection can be provided by connecting the bridge portion 32 to inner conductor 4b by means of a screw connection, or by means of soldering, or by making the bridge portion an integral part of inner conductor 4b, or by some other means providing a direct connection.
(49) FIG. 11 shows another view of parts of an embodiment of the antenna feeding network. The connector device 19 engages the first and second inner conductors 4a, 4b. The connector device 19 and the inner conductors 4a, 4b together form a splitter/combiner. When operating as a splitter, the inner conductor 4a is part of the incoming line, and the two ends of the inner conductor 4b are the two outputs of the splitter. The U-shaped dielectric element 8 can be moved along the inner conductor 4b, which, together with an outer conductor (not shown), forms first and second coaxial output lines on opposite sides of the connector device 19. The dielectric element thus has various positions along those coaxial output lines.
(50) We first consider the case when the dielectric element 8 is placed in a central position, equally filling the first and second output coaxial lines. When a signal is entered at the input coaxial line 4a, it will be divided between the first output coaxial line and the second output coaxial line, and the signals coming from the two output coaxial lines will be equal in phase. If the dielectric element 8 is moved in such a way that the first output coaxial line will be more filled with dielectric material than the second output coaxial line, the phase shift from the input to the first output will increase. At the same time the second output coaxial line will be less filled with dielectric, and the phase shift from the input to the second output will decrease. Hence, the phase at the first output will lag the phase at the second output. If the dielectric element is moved in the opposite direction, the phase of the first output will lead the phase of the second output. The splitter/combiner may thus be described as a differential phase shifter.
(51) FIG. 11 illustrates how the connector device 19 engages the first and second inner conductors 4a, 4b in circumferential recessed areas or grooves 42 of the first and second inner conductors 4a, 4b. These grooves may be used to position the connector device 19 correctly along the longitudinal direction of the inner conductors 4a, 4b.
(52) FIG. 12 illustrates a view into the first and second coaxial lines 3a, 3b where the connector device 19, bridging the first inner conductor 4a and the second inner conductor 4b is visible. The snap on fingers 30, 30′ are not so well visible since the snap on fingers 30, 30′ engage the first and second inner conductors 4a, 4b in areas with a smaller diameter than the rest of the first and second inner conductors 4a, 4b. FIG. 12 further illustrates that the bridge portion 32 is not extending beyond the front side 93 of the electrically conductive reflector.
(53) The embodiment of the connector device 19 has been described having a thin insulating layer on the connector device 19. It may however be possible to provide the first and second inner conductors 4a, 4b respectively with a very thin insulating layer of a polymer material and provide the connector device without any insulating layer. The insulating layer may cover the entire outer surface of the first and second inner conductors 4a, 4b, or at least the portions where snap on fingers 30, 30′ of the connector device 19 engage the first and second inner conductors 4a, 4b. In other embodiments, an isolating material in the form of a thin foil is placed between the snap-on fingers 30, 30′ and the inner conductor 4.
(54) Further, the connector device 19 has been described illustrating a first and a second inner conductor 4a, 4b in the antenna arrangement 1. The antenna arrangement 1 may however comprise more than one connector device 19 and a plurality of inner conductors 4a, 4b.
(55) FIG. 13 schematically illustrates parts of another embodiment of an antenna feeding network according to the fourth aspect of the invention. In FIG. 13, a cross section view is shown of a first inner conductor 4a′ and a second inner conductor 4b′. The first inner conductor 4a′ comprises a cavity 50 extending axially into one of its ends. The second inner conductor 4b′ comprises a rod-shaped protrusion 51 extending axially from one of its ends. The protrusion 51 is adapted to extend into the cavity 50 of the first inner conductor. An insulating layer 52 is provided in and around the cavity to provide an indirect electrical connection between the conductors. In other embodiments, the insulating layer may be provided on the protrusion 51, or as a separate insulating film between the conductors. The insulating layer may be provided as a polymer material or some other insulating material (e.g. a non-conducting oxide) on either or both inner conductors 4a′ or 4b′, completely or partially covering inner conductors 4a′ or 4b′, or it may be provided as a thin insulating foil inserted between inner conductors 4a′ and 4b′.
(56) FIG. 14 schematically illustrates parts of yet another embodiment of an antenna feeding network according to the fourth aspect of the invention. In FIG. 14, a cross section view is shown of three inner conductors 4a″, 4b″ and 4c″ and a three legged h-shaped connector device 19′. Each leg of the connector device 19′ is provided with a cavity 50a-c extending axially into their respective ends. The inner conductors 4a″-c″ each comprises a rod-shaped protrusion 51a-c extending axially from one of its ends. The protrusions 51a-c extend into corresponding cavities 50a-c of the connector device. Insulating layers 52a-c are provided in and around the cavities to provide an indirect electrical connection between the conductors. In other embodiments, the insulating layers may be provided on the protrusions, or as separate insulating films between the conductors and the connector device. The h-shaped connector device 19′ may be mounted in a similar manner as the connector device 19, i.e. by cutting down a separating wall between two adjacent outer conductors. In other embodiments, the connector device 19′ is provided with protrusions, and the inner conductors 4″-c″ are provided with cavities.
(57) FIG. 15 illustrates a perspective view onto a cross section cut through the middle of one of the radiating elements 14 in longitudinal direction of antenna arrangement. FIG. 15 also illustrates how the radiating element 14 is connected to one of the inner conductors 4. The radiating element 14 comprises a coupling element 24 having a conductor line portion 46 and a free end portion 48 at an end of the conductor line portion 46. The coupling conductor element 24 extends through the at least one opening 28 in the electrically conductive reflector 17 into a cavity or through hole 36 formed in the inner conductor 4.
(58) The cavity or through hole 36 and the free end portion 48 of the coupling conductor element 24 are both conically shaped having corresponding diameter and rise to achieve a tight fit. The cavity or through hole 36 extends through the entire inner conductor 4 but may in other embodiments only extend partially into the inner conductor 4.
(59) The coupling between the coupling element 24 and the inner conductor 4 is either capacitive, inductive or a combination therefore. This is achieved by providing a thin insulating layer on at least the free end portion 48 of the coupling element. In other embodiments, the cavity or through hole 36 comprises a thin insulating layer, while the free end portion does not. The insulating layer may have thickness of less than 50 μm, such as from 1 μm to 20 μm, such as from 5 μm to 15 μm, such as from 8 μm to 12 μm. In other embodiments, both the free end portion 48 and the cavity or through hole 36 comprise a thin insulating layer. The thin insulating layer could be provided by applying a thin layer of a polymer material, or by having a thin oxide layer, or by some other provisions applying an isolating layer.
(60) The radiating elements 14 each comprise four identical radiating parts 85a-d forming a dipole. The radiating parts extend essentially in a plane parallel with the antenna reflector. The radiating parts are fed using a balanced-unbalanced transformer 85e, also called a balun, which also forms a mechanical support for the radiating parts. As is further illustrated in FIG. 15, the balun comprises a body part 85e′ and the coupling element 24 which is positioned in the centre of a cylindrical hole in the body part. The body part 85e′ is connected to the outer conductor and to the antenna reflector.
(61) FIG. 16 illustrates another perspective cross sectional view of the connection between the radiating element 14 and the inner conductor 4. The cross section is cut through the connection. The coupling element 24 and its enlarged free end portion 48 are shown. The free end portion 48 is conically inverted shaped and comprises a step 35 between the free end portion 48 and the conductor line portion 46. The free end portion 48 has a greater diameter than the conductor line portion 46.
(62) Although the free end portion 48 has a conically inverted shaped it is conceivable that it has another shape such as cylindrical, cubical, etc. The shape of the cavity or through hole 36 may be adapted accordingly.
(63) FIG. 17 schematically illustrates the inner conductor 4 and the coupling conductor element 24 engaged in the cavity or through hole 36. As can be seen, the inner conductor 4 has a slightly greater diameter where the cavity or through hole 36 is shaped. This may be done for example for improved stability and/or a higher capacity of the indirect electric connection. The step 35 formed between the conductor line 46 and the enlarged free end portion 48 is also shown.
(64) FIG. 18 schematically illustrates a cross section view of parts of an antenna arrangement which comprise a snap on mechanism. The snap on mechanism has a snap on portion in the form of the step 35, which is integrally arranged on the coupling element 24 (only partially shown in the figure), above the free end portion 48, and a complementary snap on portion 49 arranged on the inner conductor 4. The complementary snap on portion 49 is formed as an edge of a dielectric support element 50 that is used to engage with and hold the inner conductor 4 in position within the outer conductor. The support element 50 is made from a plastic material which is slightly flexible which causes the opening in the spacer to widen slightly when the coupling element is pushed into the cavity or through hole of the inner conductor. After the coupling element has been pushed down, the edge/snap on portion 49 prevents it from accidentally leaving the cavity or through hole. In other embodiments, the complementary snap on portion is formed on a separate component which is not a dielectric support element.
(65) FIG. 19 schematically illustrates parts of an alternative embodiment of an antenna arrangement according to the seventh aspect of the invention. The figure shows an inner conductor 114 and a coupling conductor element 124 engaged with the inner conductor. The coupling element 124 is provided with a conductor line portion 146, wherein the free end portion is formed at an end of the conductor line portion, wherein a snap on portion is provided at the free end portion of the coupling element as a pair of snap on fingers 151 (only one is visible in the figure). The complementary snap on portion is provided in the form of a recessed portion 152 of the envelope surface of said inner conductor. The recessed portion has a smaller diameter than the adjacent portions of the envelope surface and has a length (in the longitudinal direction) which corresponds to that of the snap on fingers 151. The snap on fingers 151 may be described as a pair of protrusions configured to engage around the inner conductor, which fingers or protrusions may be configured to be flexible to allow the coupling element to be removably connectable to the inner conductor.
(66) The coupling between the coupling element 124 and the inner conductor 114 is either capacitive, inductive or a combination therefore. This is achieved by providing a thin insulating layer on at least the surface portions of the snap on fingers 151 which are in abutment with the inner conductor, or on the whole coupling element or snap on finger portion thereof. In other embodiments, the inner conductor 114, or at least the recessed portion 152 thereof, comprises a thin insulating layer, while the snap on fingers do not. The insulating layer may have thickness of less than 50 μm, such as from 1 μm to 20 μm, such as from 5 μm to 15 μm, such as from 8 μm to 12 μm. In other embodiments, both the snap on fingers and the recessed portion comprise a thin insulating layer. The thin insulating layer could be provided by applying a thin layer of a polymer material, or by having a thin oxide layer, or by some other provisions applying an isolating layer.
(67) It is understood that the alternative embodiment shown in FIG. 19 and described above only differs in the above described details relating to the interconnection between the coupling element and the inner conductor. Apart from this, the description above relating to FIGS. 5 and 15-16 applies analogously to this embodiment.
(68) The description above and the appended drawings are to be considered as non-limiting examples of the invention. The person skilled in the art realizes that several changes and modifications may be made within the scope of the invention. For example, the number of coaxial lines may be varied, the number of radiators or dipoles may be varied, the number of coaxial lines provided with rail elements may be varied, the number of coaxial lines provided with dielectric elements and/or support elements may be varied, and the shape of the support element(s) and dielectric element(s) may be varied. Furthermore, the reflector does not necessarily need to be formed integrally with the coaxial lines, but may on the contrary be a separate element. The scope of protection is determined by the appended patent claims.
