WO2002060009A1

WO2002060009A1 - Microwave antenna arrangement

Info

Publication number: WO2002060009A1
Application number: PCT/FI2002/000028
Authority: WO
Inventors: Pekka Jakkula; Taavi Hirvonen; Jarmo Karhu; Pekka Moilanen
Original assignee: Pj Microwave Oy
Priority date: 2001-01-25
Filing date: 2002-01-15
Publication date: 2002-08-01
Also published as: WO2002060009A8; FI113589B; FI20010158A; FI20010158A0

Abstract

The invention relates to a microwave antenna arrangement comprising a ground plane (406), radiators (402a, 402b), at least one transmission line (400a) for feeding polarization of a first type to the radiators, at least one transmission line (400b) for feeding polarization of a second type to one or more of the radiators to which polarization of the first type is fed. The invention is characterized in that the radiators (402a, 400b) and the transmission lines (400a, 400b) feeding different types of polarization are positioned alternately in such a way that there is feeding of only one type of polarization between the radiators.

Description

MICROWAVE ANTENNA ARRANGEMENT

FIELD OF THE INVENTION

[0001] An object of the invention is a microwave antenna arrangement comprising a ground plane, radiators, at least one transmission line for feeding polarization of a first type to the radiators, at least one transmission line for feeding polarization of a second type to one or more of the radiators to which polarization of the first type is fed.

[0002] In particular, the invention is applicable to implementing a microwave antenna arrangement carried out with an inverted microstrip structure and fed with dual slant.

BACKGROUND OF THE INVENTION

[0003] Present-day microwave antennas mainly utilize planar antenna types. The antennas are implemented with microstrip circuits, and there are generally two implementation techniques in use. [0004] Simple planar antenna structures are implemented by cutting the radiators and transmission lines out of thin sheet metal and by supporting the structure upon a smooth metal plate functioning as the ground plane by means of plastic support elements. A problem with such sheet metal structures is that they are difficult to apply to antennas with multiple elements because of the complexity of the feed lines. Another problem is that it is difficult to implement narrow transmission lines with this method.

[0005] More complex planar antenna structures are implemented with printed circuit structures. A problem with printed circuit structures is the high price of microwave laminates. Due to great dielectric losses, inexpensive FR4 circuit boards cannot be used as ordinary printed circuit boards in antenna structures at microwave frequencies. One solution to the problem is the inverted structure utilizing an FR4 circuit board, disclosed in US patent 4,697,189, where the electric field mainly proceeds in the air between the ground plane and the transmission line on the inverted FR4 circuit board. Such a structure allows implementation of an inexpensive microwave antenna with little loss.

[0006] Significant problems are related with known antenna solutions, in particular with the coupling of transmission lines feeding different polarization types, i.e. a situation where the signals of adjacent or otherwise closely positioned transmission lines feeding different polarization types are coupled together, which is particularly intensive when the transmission lines are close to each other or positioned high relative to the ground level. The coupling causes a poor cross-polarization ratio when two linear polarizations or two circular polarizations are used.

BRIEF DESCRIPTION OF THE INVENTION

[0007] An object of the invention is to provide an improved microwave antenna arrangement, which decreases problems and disadvantages related to prior art solutions.

[0008] In order to achieve the above object, the antenna arrangement according to the invention is characterized in that the radiators and the transmission lines feeding different types of polarization are positioned alternately in such a way that there is feeding of only one type of polarization between the radiators.

[0009] The invention is based on the idea that the transmission lines and radiators are positioned in a new way relative to each other and that the transmission lines feeding different polarization levels to the radiators are positioned in a new way relative to each other. The transmission lines feeding to the radiators are positioned in such a way that the lines feeding different polarizations are maximally far away from each other, in such a way, however, that not much space needs to be utilized. This is achieved by positioning feed lines feeding one type of polarization in each space remaining vacant between the radiator elements.

[0010] Significant advantages are achieved with the invention, particularly a decrease in the coupling of transmission lines feeding different polarization types.

[0011] By means of preferred embodiments of the invention, some other problems relating to known antenna arrangements can be decreased and alleviated. As regards the antenna, it would be important for the impedance of the transmission lines to be as low as possible, because on a high impedance level, the losses of the transmission line increase when part of the electric field rises to a lossy substrate. The impedance of a transmission line can be lowered by widening the line, but a wide transmission line is unpractical due to the requirement for a large space. Further, the transmission lines can radiate on a high impedance level. In addition, it would be important that conductive patch areas functioning as radiators and formed on the substrate should be sufficiently far from the ground plane in order for the bandwidth of the radiators to be great in a desired way. It is known from publications US 5,444,453 and US 6,121 ,929 to use auxiliary radiators mounted above the actual radiator, but that makes the structure of the antenna more complex and thus also increases the size and price of the antenna. Problems related to the impedance of transmission lines being too high and the bandwidth of radiators being narrow are decreased with a preferred embodiment of the invention, in which the arrangement is such that the impedance of the feed lines of the antenna arrangement is lowered by raising the ground plane at the point of the transmission line. Owing to the low transmission line impedance, the transmission lines do not radiate and are not coupled together, whereby a good cross-polarization attenuation is achieved in a situation where the antenna is fed with two polarizations. The ground plane remains low at the point of the radiating elements, i.e. farther away than at the point of the transmission elements, and thus the bandwidth of the radiators remains great. In this way, a large bandwidth is achieved for the antenna, but if it is desirable to increase the bandwidth, the auxiliary radiators can be mounted on the inner surface of the radome covering the antenna. The auxiliary radiators can thus be separate metal plates, adhesive metal stickers, vaporized metal areas, or areas otherwise metallized.

[0012] Further, some other preferred embodiments of the invention allow a decrease in and alleviation of some other problems relating to known antenna arrangements. In the solutions according to publications US 4,697,189 and US 5,444,453, an additional problem is that feed of the antenna arrangement coaxially is not carried out in a very good way what it comes to production costs, because in said known publications, vias and solder joints must be implemented on a printed circuit board of the antenna arrangement. In order to eliminate above problems, in a preferred embodiment of the invention, the antenna arrangement is connected to the receiver and from the transmitter to the antenna with a particular spring-loaded connector. With this arrangement, no bushing or solder joint is required for an inverted printed circuit board. In this way, a simple antenna structure can be provided that is inexpensive and that can be easily assembled by the manufacturer of the radio apparatus at the production stage without a need for an external antenna supplier. This arrangement is particularly preferable when the backside of the metal cover of a microwave electronic device, i.e. the backside of a radio apparatus cover, functions as the ground plane.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The invention will now be described in more detail in connection with preferred embodiments, with reference to the attached drawings, in which

[0014] Figure 1A shows a top view of a manner of feed of patch antennas according to the prior art. The antenna is implemented with an expensive microwave laminate of little loss, using two polarizations; [0015] Figure 1B shows a side view of the implementation of Figure

1A;

[0016] Figure 2 shows a side view of a manner of feed of antenna elements implemented with an inverted, inexpensive lossy laminate. The top view of the structure is as in Figure 1 A; [0017] Figure 3 shows a side view of a solution provided with a raised ground plane at the point of the feed lines. The top view of the structure is as in Figure 1A,

[0018] Figure 4A shows a top view of a solution provided with a raised ground plane and separated feed lines; [0019] Figure 4B shows a side view of a solution with a raised ground plane and separated feed lines;

[0020] Figure 5 shows the distribution of an electric field with two conductors positioned close to each other when the distance between the ground plane and the transmission lines is long; [0021] Figure 6 shows a corresponding case where the ground plane has been raised below the transmission line;

[0022] Figure 7 shows a feed implementation of a 2X3-element antenna operating with two polarizations in accordance with the invention;

[0023] Figure 8 shows a second way to feed a 2X3-element antenna in accordance with the invention;

[0024] Figure 9A shows a feed implementation of a 4X4-element antenna operating with two polarizations in accordance with the invention;

[0025] Figure 9B shows a feed implementation of a 7-element antenna with vertical and horizontal polarizations; [0026] Figure 10A shows a top view of an inexpensive spring- loaded feed arrangement of an antenna;

[0027] Figure 10B shows a side view of the structure of Figure 10A;

[0028] Figure 11 shows a second spring-loaded manner of connection;

[0029] Figure 12 shows a radio apparatus provided with an integrated antenna according to the invention;

[0030] Figure 13 shows a feed arrangement of an antenna shrunk within a small space.

DETAILED DESCRIPRION OF THE INVENTION

[0031] Let us first briefly study solutions according to the prior art by means of Figures 1 A (an antenna arrangement seen from the top of the circuit board) and 1 B (an antenna arrangement seen from the side of the circuit board). The antenna comprises one or more transmission lines 100 and a radiator 102, which are made on metallization on the substrate 104 of the circuit board. A conductive ground plane 106 is parallel with the radiator 102 and the transmission line 100. The radiator 102 and the ground plane 106 form a resonator, which radiates from the edges of the radiator 102. The signal to be transmitted is brought to the line 100 to that side of the radiator 102 from which radiation is to be detached. Thus, also the opposite side radiates. Two different polarizations can be carried out with a single element by feeding the signals to edges of different directions (being at an angle of 90 degrees). Since the microwave laminates are thin, the transmission lines 100 can be relatively close to each other without microwave power transferring from one line to another. For this reason, great cross-polarization attenuation is achieved with the antenna. On the other hand, since the laminate is thin, the bandwidth of the antenna is extremely narrow. In order to raise the bandwidth, it is known to use auxiliary radiators 108, which are raised above the actual radiator 102 by using a support element 110. The support element can be made of plastic or conductive metal if it is mounted at the mid-point of the radiator, where the electric field is zero.

[0032] Figure 2 shows an implementation corresponding to that of Figure 1 B with an inverted lossy laminate. Seen from the top, the structure in Figure 2 is similar to that in Figure 1 A. This structure has an inverted laminate, whereby the electric field proceeds in a transmission line 200 mainly in the air between the transmission line and the ground with little attenuation. There is such a great air gap 208 between radiators 202 and ground plane 206 that the antenna has a great bandwidth by nature, and therefore, auxiliary radiators 108 shown in Figure 1 B are not needed. A problem with the structure is that the transmission lines 200 are intensively coupled together, whereby the cross- polarization of the antenna is poor.

[0033] With reference to Figure 4, the invention relates to a microwave antenna arrangement comprising a ground plane 406; radiators 402a, 402b, 402c; at least one transmission line 400a for feeding a first type of polarization to the radiators 402a, 402b; and at least one transmission line 400b for feeding a second type of polarization to one or more of those radiators to which the first type of polarization is fed. The transmission lines 400a, 400b and the radiators 402a, 402b, 402c are microstrips formed on a substrate 404, i.e. on an antenna circuit board 404. [0034] It is essential for the invention that the radiators 402a, 402b and the transmission lines 400a, 400b feeding different types of polarization are positioned alternately in such a way that there is feeding of only one type of polarization between the radiators 402a, 402b, i.e. the transmission line 400a. Correspondingly, there is feeding of only one type of polarization between the radiators 402b, 402c, i.e. the transmission line 400b. Several radiators are coupled to the same side of the transmission line, for instance three radiators 402a, and correspondingly three radiators 402b, and correspondingly three radiators 402c, so that these may be called radiator rows R1 , R2, R3. In other words, there are three such rows in the example, each having three radiators. Thus, the transmission lines 400a, 400b are positioned alternately between the radiator rows R1 , R2, R3. In other words, there are radiators in radiator groups R1 , R2, R3 in such a way that each radiator group comprises several radiators and the radiator groups and the transmission lines feeding different polarization levels are positioned alternately in such a way that there is feeding of only one type of polarization between the radiator groups. There is a transmission line 400a between the radiator groups R1 and R2, and a transmission line 400b between the radiator groups R2 and R3. The structure shown in Figures 4A and 4B can be seen as a part of a larger antenna entity. In Figures 4A and 4B, both types of transmission lines 400a, 400b are coupled to the radiators 402b. In Figures 7, 8, 9A and 9B, both types of transmission lines are coupled to all radiators. [0035] In other words, distance has been created between the transmission lines 400a, 400b, and correspondingly between 400b, 400c, feeding different polarizations, because there are radiators between the transmission lines. Since the transmission lines and the radiators are positioned alternately, the distance between the transmission line and the radiators after the second transmission line has increased, which further improves cross-polarization attenuation. This is observed when Figure 4A is compared with Figure 1A.

[0036] In a preferred embodiment, the ground plane 406 comprises a transmission line at the point of a protrusion 410, 412 to make the distance between the ground plane and the transmission line shorter than the distance between the ground plane 406 and the radiator. Consequently, new positioning of transmission lines and a protrusion 410, 412 of the ground plane at the point of the transmission line simultaneously provide an extremely good cross- polarization attenuation and a great bandwidth without elevated auxiliary radiators.

[0037] As shown in Figure 4A, radiators 402a, for instance, are fed to the edges pointing to the same direction at distances of a wavelength, and on the other side of the transmission line, the radiators 402b are fed to the edges pointing to the opposite direction relative said direction at a distance of half a wavelength relative the edges mentioned first. Radiators 402a, 402b are connected to a transmission line, for instance to the transmission line 400a, alternately by both sides of the transmission line. Thus, there is no need to use an excessively long transmission line branch on some side of the transmission line between the transmission line and said radiator 402b, because an excessively long transmission line branch would intensify detrimental coupling between the transmission lines. The problem would be a result of making the transmission line branch excessively long so as to achieve the above- mentioned positioning, i.e. the distance of half a wavelength. Radiators 402a, 402b and correspondingly 402b, 402c are coupled both to one or more transmission lines 400a feeding a first type of polarization and to one or more transmission lines 400b feeding a second type of polarization by both sides of the transmission line 400a, correspondingly 400b.

[0038] In Figure 3, the positioning of the transmission lines 300a, 300b is made in a conventional way, but the coupling of the transmission lines is also reduced by raising the ground plane 306 with a bulge 310 and correspondingly with 312 at the point of the transmission lines 300a, 300b closer to the transmission lines 300a, 300b, whereby the coupling of the transmission lines to each other and to the radiators 302 is intensively reduced. The reason for the reduced coupling is that the electric field is intensively concentrated in a narrow air gap 308 below the transmission line 308. At the same time, the attenuation of the transmission line is reduced, because the electric field does not rise as much into the inside of the lossy laminate 304.

[0039] The raising of the ground plane, i.e. the protrusion, can be carried out with a separate bulge piece 310, or by casting or cutting a protrusion 410 on the ground plane, or by forming a bulge 312, 412 on the ground plane.

[0040] In a preferred embodiment, the protrusion comprised by the ground plane 306, 406 is a protrusion profiled on a conductive plate-like ground plane 312, 412, i.e. a bulge 312, 412 formed on the ground plane. Also such a version can be used in which the protrusion on the ground plane is a coating formed on a protrusion profiled on a non-conductive plate-like or the like planar ground plane substrate, which coating is part of a conductive coating of the ground plane substrate. [0041] In other words, casting or cutting can be applied in such a way that the protrusion on the ground plane 306, 406 is a protrusion 310, correspondingly 410, formed by casting or cutting and being on the ground plane cast or cut of a conductive material. It is also possible that the protrusion 310, 410 on the ground plane 306, 406 is a conductive coating made in a protrusion formed by casting or cutting and being on the ground plane cast or cut of non-conductive material, which coating is part of a conductive coating of the ground plane substrate.

[0042] Figure 5 shows the distribution of the electric field 514 and 516 of a transmission line positioned high relative to the ground plane. The electric field extends to a large area, and the adjacent conductors are coupled together intensively either with an even 516 or an odd 514 waveform. Further, part of the electric field rises to a lossy substrate 504, which increases the attenuation of the lines. The increase in the attenuation along with the increase of the impedance becomes obvious from the following table, which shows losses of the transmission line with different impedances in an inverted transmission line structure. The calculations have been performed with an

Agilent HFSS simulator.

[0043] Table I. Attenuation of an air-insulated inverted microstrip with different impedances. The laminate is FR4 of 0.8 mm.

[0044] Impedance (W) Attenuation (db/200 mm)

[0045] 50 0.24

[0046] 100 0.29

[0047] 150 0.43 [0048] 200 0.65

[0049] A version provided with a raised ground plane is shown in Figure 6. Here, the electπc field 614 is intensively concentrated below the transmission line, whereby the detrimental coupling between the lines is reduced, and in addition, the attenuation of the lines is not increased, since the electric field does not rise to a lossy substrate.

[0050] In Figure 7, the manner of feed according to the invention is applied to a 2X3 radiator group. It becomes obvious from the figure that transmission lines 700 functioning with different polarizations are maximally far from each other. Different polarizations are fed to the transmission lines from points 716 and 718. The antenna arrangement of Figure 7 comprises transmission lines 700a to 700d and radiators 702a to 702c. The transmission lines 700a and 700c feed the same polarization. The transmission lines 700b and 700d feed different polarizations than the transmission lines 700a and 700c. Both polarization types are fed to the radiators 702a to 702c. The radiator groups are denoted by R1 to R3.

[0051] Figure 8 shows a second way to feed a 2X3 radiator group in accordance with the invention. The feed lines are denoted by 816 and 818. In Figure 8, the antenna group comprises transmission lines 800a to 800c and radiators 802a to 802b. The transmission lines 800a and 800b feed the same polarization. The transmission line 800b feeds different polarizations than the transmission lines 800a, 800c. Both polarization types are fed to the radiators. The radiator groups are denoted by R1 and R2.

[0052] Figure 9A shows an example of a feed arrangement of a 4X4-element antenna. The feed points to the transmission lines are at points 916 and 918. The antenna arrangement of Figure 9 comprises transmission lines 900a to 900e and radiators 902a to 902d. The transmission lines 900a, 900c and 900e feed the same polarization to the radiators. The transmission lines 900b and 900d feed different polarization than the transmission lines 900a, 900c and 900e. Both polarization types are fed to the radiators 902a to 902d. The radiator groups are denoted by R1 to R4.

[0053] Figure 9B shows an example of feed of a 7-element radiator group with horizontal and vertical polarization. Also in this example, the feed points are 916 and 918. The antenna arrangement of Figure 9B comprises transmission lines 900a to 900d and radiators 902a to 902c. The transmission lines 900a to 900c feed the same polarization. The transmission lines 900b and 900d feed different polarization than the transmission lines 900a and 900c. Both polarization types are fed to the radiators 902a to 902c. The radiator groups are denoted by R1 to R3.

[0054] A preferred embodiment of the invention in Figures 10 and 11 shows two ways with which there will be no need to make holes or solder joints on the actual substrate, i.e. an antenna circuit board. In both embodiments, the antenna arrangement comprises a spring-loaded, surface- contacted coupling arrangement to couple a signal to a transmission line.

[0055] In Figure 11 , a spring-loaded surface-contacted coupling arrangement comprises a spring-loaded coupling member 1124 coupled to the transmission line with surface contact. Figure 11 utilizes a spring-loaded connecting piece 1124 between a substrate 1104, i.e. an antenna printed circuit board 1104, and a microwave electronic card 1130. The connecting piece is soldered on the electronic card, i.e. on the signal-feeding substrate 1130.

[0056] In Figure 10, a substrate 1004 is provided with a slot 1020 penetrating the substrate to achieve a surface-contacted coupling arrangement, which slot limits a flexible spring-loaded projecting part 1022 on the substrate, the projecting part comprising a conductive area. In a preferred embodiment, the substrate on which the flexible projecting part 1022 is formed is the actual substrate 1004, i.e. the antenna circuit board, on which the transmission lines and radiators are formed. Thus, the solution is such that the flexible projecting part comprising a conductive area is in the area of the transmission line, or at least in a conductive connection with the transmission line, and that a contact member 1024 of a feeding connector 1026 presses the flexible projecting part 1022 it its conductive area, and that a second contact member of the feeding connector is coupled with the ground plane. In other words, also Figure 10 shows a simple and inexpensive way to feed by means of a coaxial connector a microwave signal to an antenna implemented with an inverted printed circuit board. In the figure, a U-shaped slot 1020 is cut on the printed circuit board, which results in a flexible projecting part 1022. The connector 1026 of the coaxial cable is mounted on the ground plane in such a way that the inner conductor 1024 of the connector is pressed against the projecting part 1022 with a force that is determined by the length of the projecting part, the material of the printed circuit and the length of the inner conductor. Thus, a simple connection is formed without a need for bushings or solder joints on the printed circuit board. Both the inner conductor 1024 and the surfaces of a conductor 1000 are at the point of contact coated with an appropriate material, such as gold, to guarantee good, long-term conductivity. Instead of a coaxial cable connector, a rigid connecting pin soldered on the microwave electronic card 1130 below the ground plane can be used.

[0057] Figure 12 shows an assembly of an antenna according to the invention, integrated in a radio apparatus. Here, an antenna printed circuit board 1204 is supported against the ground plane 1206 of a radio apparatus with plastic holding pieces 1234 in such a way that an air gap 1208 remains between the ground plane and the printed circuit board. In order to increase the bandwidth, auxiliary radiators 1238 are added to the antenna radome 1232. Microwave components 1236 are assembled on the printed circuit board 1230 inside a metal casing. The microwave signal is transferred between the printed circuit boards with a spring-loaded coaxial connector 1226. The ground plane has been raised at the point of the feed conductors. This is particularly easy to implement when the backside of a casing 1206, made by casting, functions as the ground plane.

[0058] Figures 7, 8, 9A and 9B show that in a preferred embodiment, the transmission lines arrive alternately from different directions, preferably from opposite directions, in specific, next to and/or between the radiators. In other words, for instance in Figure 9A, the transmission line 900A arrives from the left next to the radiators 902a, and the transmission line 900b feeding different polarization arrives from the right between the radiators 900a, 900b, and the transmission line 900c feeding the same polarization as the transmission line 900a arrives from the left between the radiators 900b, 900c, and so on. Thus, efficient space utilization and good technical properties are achieved for the antenna. Thus also, the feed points 916, 918 are at edges opposite to each other. [0059] Figure 13 shows a feed arrangement of an antenna shrunk within a small space. Here, a feed line 1300 is made in a zigzag form or other winding form, so that the length of half a wave is provided in a shorter space.

Corresponding shrinking can be carried out by applying dielectric material with little loss below the transmission line to increase the effective length.

[0060] It will be obvious to a person skilled in the art that with the advance of technology, the basic idea of the invention can be implemented in a plurality of ways. Thus, the invention and embodiments thereof are not confined to the above-described examples but can vary within the scope of the claims.

Claims

1. A microwave antenna arrangement comprising a ground plane (406), radiators (402a, 402b), at least one transmission line (400a) for feeding polarization of a first type to the radiators, at least one transmission line (400b) for feeding polarization of a second type to one or more of the radiators to which polarization of the first type is fed, characterized in that the radiators (402a, 400b) and the transmission lines (400a, 400b) feeding different types of polarization are positioned alternately in such a way that there is feeding of only one type of polarization between the radiators.

2. An arrangement according to claim 1, characterized in that there are radiators in radiator groups in such a way that a radiator group comprises several radiators, and that the radiator groups and the transmission lines feeding different polarization levels are positioned alternately in such a way that there is feed of only one type of polarization between the radiator groups.

3. An antenna arrangement according to any one of the preceding claims 1 to 2, characterized in that the transmission lines and the radiators are microstrips formed on a substrate.

4. An antenna arrangement according to claim 3, characterized in that radiators are coupled to the transmission line alternately by both sides of the transmission line.

5. An antenna arrangement according to any one of the preceding claims 1 to 4, characterized in that the coupling side of the radiator on a first side of the transmission line to the transmission line is parallel but pointing to the opposite direction relative to the coupling side of the radiator positioned on the other side of the transmission line and coupled to the same transmission line.

6. An antenna arrangement according to any one of the preceding claims 1 to 5, characterized in that the ground plane comprises a protrusion at the point of the transmission line in order for the distance between the ground plane and the transmission line to be shorter than the distance between the ground plane and the radiators.

7. An antenna arrangement according to claim 6, characterized in that the protrusion comprised by the ground plane is a protrusion which is made by casting on the ground plane cast of a conductive material.

8. An antenna arrangement according to claim 6, characterized in that the protrusion comprised by the ground plane is a conductive coating which is formed on a protrusion made by casting and being on the ground plane cast of non-conductive material, the coating being part of the conductive coating of the ground plane.

9. An antenna arrangement according to claim 6, characterized in that the protrusion comprised by the ground plane is a protrusion profiled on a conductive plate-like ground level.

10. An antenna arrangement according to claim 6, characterized in that the protrusion comprised by the ground level is a conductive coating which is formed on a protrusion profiled on a non- conductive plate-like ground plane, the coating being part of the conductive coating of the ground plane.

11. An arrangement according to claim 1, characterized in that the antenna arrangement is integrated in a radio apparatus and that the ground plane of the radio apparatus is used as the ground plane.

12. An antenna arrangement according to claim 1, characterized in that the antenna arrangement comprises a spring- loaded surface-contacted coupling arrangement for coupling a signal to a transmission line.

13. An antenna arrangement according to claim 12, characterized in that the spring-loaded surface-contacted coupling arrangement comprises a spring-loaded coupling member coupled to the transmission line with surface contact.

14. An antenna arrangement according to claim 12, characterized in that the antenna arrangement comprises a substrate, and that in order to provide a spring-loaded contact-surfaced coupling arrangement, a hole penetrating the substrate is made on the substrate, which hole limits a flexible spring-loaded projecting part on the substrate, which projecting part comprises a conductive area (1022).

15. An antenna arrangement according to claim 14, characterized in that the substrate on which the flexible projecting part (1022) is made is the actual substrate on which the transmission lines and radiators are formed, and that the flexible projecting part comprising a conductive area is in the area of the transmission line or in a conductive connection with the transmission line, and that a contact member (1024) in a feeding connector (1026) presses the flexible projecting part (1022) in its conductive area, and that a second contact member of the feeding connector is coupled to the ground plane.

16. An antenna arrangement according to claim 1 or 4, c h a r a c t e r i z e d in that radiators are coupled by both sides of the transmission lines both to one or more transmission lines feeding the first polarization type and to one or more transmission lines feeding the second polarization type.