AN ANTENNA MEANS, A RADIO COMMUNICATION SYSTEM AND A METHOD FOR MANUFACTURING A RADIATING STRUCTURE

Abstract: An antenna means for transmitting and/or receiving RF signals, a radio communication system and a method for manufacturing a radiating structure. The antenna means comprises a conductive structure (10) extending between first and second opposite edges (11, 12), and a feed portion. The conductive structure (10) is formed to a radiating structure (1) partially enclosing a volume, and the first and second edges (11, 12) are located at a distance from each other forming a radiating first slit (21), which has a first and a second open end. Hereby an antenna means, which can be made compact, and can operate in more than one frequency band is obtained. A second slit can be arranged to improve the operation in a higher frequency band. The radio communication system comprises transmitting/receiving circuits connected to an such antenna means.

Description: AN ANTENNA MEANS, A RADIO COMMUNICATION SYSTEM AND A METHOD FOR MANUFACTURING A RADIATING STRUCTURE FIELD AND BACKGROUND OF THE INVENTION The invention relates to an antenna means for transmitting and/or receiving RF signals, comprising a conductive structure extending between first and second opposite edges and a feed portion. Specifically, it relates to an antenna means for a mobile radio communication device, and is especially suitable as a vehicle antenna. It also relates to a radio communication system including such an antenna means and to a method for manufacturing a radiating structure included in the antenna means . BACKGROUND OF THE INVENTION AND RELATED ART Many vehicles are equipped with antennas protruding from the vehicle body. Such antennas are for example whip, wire or blade antennas. To overcome problems with elements protruding from the vehicle body, there is a demand for antennas concealed or arranged m the vehicle. US-A- 5,682,168 discloses an example of such antennas, where a dipole antenna is submerged beneath a cover over a roof supporting member of a motor vehicle or hidden behind or as a part of the front grill. In US-A-5 , 402 , 134 a planar antenna for installation under a dielectric cover of a vehicle is disclosed. Antennas concealed m a piece such as a spoiler rack are disclosed m US-A-5 , 629 , 712 and US-A-5 , 812 , 095. Those antennas are complicated to manufacture and to mount. Further, operation in more than one frequency band requires special arrangements. They are also dependent of a ground plane or sensitive to conductive parts m the vicinity. Further, US-A-5 , 177 , 494 discloses a vehicular slot antenna system, m which a plurality of slot antenna units are installed on the vehicle. Each antenna unit is U-shaped and is provided with a closed opening or slot . Such an antenna unit is intended for operation m one frequency band only. Further, an antenna unit of this kind radiates from both sides of a plane of the plate portion m which the slot is arranged. SUMMARY OF THE INVENTION The main objects of the invention are to provide an antenna means for transmitting and/or receiving RF signals, which antenna means can be manufactured m a simple and cost- effective way, is simple to mount and requires a relatively small space. Another object of the invention is to provide an antenna means, which, does not require a separate ground plane and can be mounted to have relatively low sensitivity to adjacent conductive parts. These and other objects are attained by an antenna means according to the appended claims . By the features of claim 1 an antenna means, which can operate m more than one frequency band, is achieved. By the features of claim 1 an antenna means navmg good antenna performance and directional radiation characteristics is further achieved. The arrangement of the radiating structure as a closed structure has the effect that a mam portion of the radiation is directed from the slit portion m a lobe away from the radiating structure. Mounted m a vehicle with the slit facing a glass pane, thus a major portion of the radiation will exit through the window m directions from the vehicle . The antenna means of claim 1, which does not require a separate ground plane and can be mounted to have relatively low sensitivity to adjacent conductive parts, is very suitable for mounting m a vehicle with the slit covered by a glass pane, and the radiating structure adjacent to, or far from conductive parts. By providing the slit with open ends the operation m plural bands is remarkably improved, and surprisingly it also makes it possible to decrease the dimensions of the antenna means without significant decrease m antenna performance. By the features of claim 1 an antenna means which is simple to match, and m which the matching can be done directly m the radiating structure, is also achieved. By the arrangement of a capacitance between the edges of a slit, the electrical lengths m the radiating structure are increased, and therefore the dimensions of the antenna means can be reduced. By forming the capacitance by portions of the conductive structure, a well defined capacitance, which can be formed m a simple and efficient way is achieved. By the arrangement of a second slit, the antenna characteristics m a higher frequency band can be further improved . By the arrangement of a dielectric material covering the slit, the electrical lengths in the radiating structure are increased, and therefore the dimensions of the antenna means can be reduced. By further arranging the antenna means having a dielectric material covering the slit to be covered by a second dielectric material having different dielectric constant, such as a window, the electromagnetic waves transmitted/received by the antenna means can be refracted and the antenna lobe can hereby be controlled. By including a conductive layer carried by a dielectric substrate or carrier in the conductive or radiating structure, an antenna device is obtained, which is simple to manufacture with simple, suitable and accurate methods for obtaining the slit. By dividing the conductive or radiating structure into at least two constructional portions, whereof one portion includes a conductive layer carried by a dielectric substrate or carrier, an antenna device is obtained, which is simple to manufacture and to adapt to different frequency bands and operation conditions. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a view of an antenna means according to a first embodiment of the invention. Figure 2 is a side view of the antenna means of Figure 1. Figure 3 is a top view of the antenna means of Figure 1. Figure 4 is a view of an antenna means according to a second embodiment of the invention. Figure 5 is a side view of the antenna means of Figure 4. Figure 6 is a top view of the antenna means of Figure 4. Figures 7 is a view of an antenna means according to a third embodiment of the invention. Figure 8 is a side view of the antenna means of Figure 7. Figure 9 is a view of an antenna means according to a fourth embodiment of the invention. Figure 10 is a side view of the antenna means of Figure 9. Figure 11 is a view of an antenna means according to a fifth embodiment of the invention. Figure 12 is a side view of the antenna means of Figure 11. Figure 13 is a view of an antenna means according to a sixth embodiment of the invention. Figure 14 is a side view of the antenna means of Figure 13. Figures 15 and 16 show the radiating structure with different shapes of the sections forming the capacitance over the slit. Figure 17 and 18 show the radiating structure with different shapes of the slit. Figure 19a and 19 b show the radiating structure with curved shape . Figure 20 is a diagrammatic view of an antenna means according to invention mounted to a glass pane of an automobile. Figure 21 shows an antenna device according to the invention provided with a slit, which is short circuited m one end. Figure 22 is a view of a variation of an antenna means according to the invention, where a conductive layer, carried by a substrate or carrier, is included m the conductive or radiating structure. Figure 23 is a side view of the antenna means of Figure 22. Figure 24 is a top view of the antenna means of Figure 22. Figure 25 is a top view of a variation of the conductive layer, carried by a substrate or carrier m the antenna means of Figure 22. Figure 26 is a view of a further variation of an antenna means according to the invention, where a conductive layer, carried by a substrate or carrier, is included m the conductive or radiating structure. DESCRIPTION OF PREFERRED EMBODIMENTS It should be noted that similar or corresponding parts have been given the same reference numerals throughout the drawings . With reference to Figure 1, 2 and 3, an antenna means for transmitting and/or receiving RF signals according to a first embodiment of the invention is shown m different views. A radiating structure 1 is formed of a conductive structure in the form of a conductive plate 10, which has curved portions so as to form a structure partially enclosing a dielectric volume, such as air. The plate 10 has first and second edges 11, 12, and the structure is formed so that the edges are essentially parallel. The edges are separated by a distance d, so as to form a radiating slit 21. Further, the plate has third and fourth edges 13, 14 which are curved and limit the radiating structure m a longitudinal direction. As seen, the radiating structure 1 is open at the ends defined by the third and fourth edges 13, 14, and the slit 21 has open ends m the regions of the third and fourth edges 13, 14. Sideways, the radiating structure 1 is limited by a first 101 and a second 102 wall section. The radiating structure 1 has m this embodiment the form of a profile with constant cross section. The wall section 103 is inclined m order to adapt the radiating structure 1 to an available space. The radiating structure 1 can alternatively have a rectangular or other cross section and can easily be adapted to an available space. The portions of the plate surrounding the slit 21 are preferably arranged m the same plane and the portions adjacent to the first and second edges 11, 12 are preferably folded down to form two essentially parallel sections 15, 16. Between these sections a capacitance is formed. The folded down sections could be omitted so that the edges 11, 12 face each other and are located m the same plane the portions of the plate surrounding the slit 21. In such a case capacitances can be arranged by other means or left out. The radiating structure 1 is fed by a feeding line 3, e.g. by a coaxial cable as shown m the figure. The feed line can however be of any other suitable kind, e.g. a part of a pattern of a printed circuit board. The ground conductor of the feed line 3 is connected to the plate 10 at or close to the section 16 and close to the edge 13. The signal conductor (hot wire) of the feed line 3 is connected to the plate 10 on the other side of the slit 21 at or close to the section 15 and close to the edge 13. Even if it is preferred that the feed line is connected at the edge 13 or close thereto, it can be connected at a distance therefrom, e.g. up to about 20 mm (for radio telephone communication bands) . The feeding line 3 can for example enter into the radiating structure 1 through a hole m a wall portion of the conductive structure or plate 10, as shown, or enter from an open side of the structure. It can of course enter the radiating structure 1 from the opposite side to the shown, and tnen the hot wire is to be connected to the section 16, and ground is connected to section 15, or m the vicinity thereof, as mentioned above. If the sections 15 and 16 are omitted the connection points or feed portions will be located on the plate 10 m portions adjacent to the locations described above. In order to obtain good performance the distance between the third and fourth edges 13, 14 should generally be approximately λ/2, where λ is the wavelength of signals of the center frequency f cι of the (first) frequency band, m which the antenna means is to transmit/receive. If the antenna operates m more than one frequency band, λ is the wavelength of signals of the center frequency of the lower frequency band. Moreover, the circumference of the radiating structure 1 (the slit excluded) m a direction perpendicular to the slit 21 should preferably also be approximately λ/2. The radiating structure is thus resonant for the frequency f cl . However, by the arrangement of the slit with open ends and the possible arrangementof the capacitance (s) , the electrical lengths m the radiating structure 1 are increased. Therefore, the physical lengths can be decreased to the same extent. However it has been shown that good antenna performance of the antenna means according to the invention can still be obtained if the dimensions are further decreased. Especially, the length 1 of the slit (distance between edges 13 and 14) can be decreased to approximately λ/3 without significant decrease m performance . As an example, the slit has a width (between the edges 11, 12) being about 5-7 mm, for operation m radio telephone communication bands (approximately m the range 0.8- 2.2 MHz) . The width of the sections 15, 16 forming the capacitance is preferably also m the range 5-7 mm for the same frequency bands . Figure 4, 5 and 6 show an antenna means for transmitting and/or receiving RF signals according to a second embodiment of the invention m different views. This embodiment is very similar to the first embodiment. However, a second slit 22 has been arranged essentially parallel with the first slit 21, m order to obtain improved operation m the second (higher) frequency band, having the center frequency f 2 . The second slit 22 has an open end surrounded by the third edge 13, and continues towards the fourth edge 14 up to its closed second end 17, which preferably is located at a distance m the range λ/2-λ/3 from the open end, where λ is the wavelength for signals of the frequency f 2 . A section 18 of the plate can be folded down to be parallel with the sections 15 and 16 to form a second capacitance together with section 15. The capacitance can however be left out, as m the first embodiment. Even m this embodiment it is preferred that the signal conductor (hot wire) of the feed line 3 is connected to the plate 10 at or close to the section 15 and close to the edge 13, although other connection points can be possible, as mentioned above. By the arrangement of the second slit 22, the operation of the antenna means m a second frequency band having a center frequency f c2 is improved, when f cl < f c2 . The improvement is a result of that the second slit assists m directing the radiation of the higher frequency band. With the second slit 22 improved antenna operation can be obtained m for example the 900 MHz and 1800 MHz bands. In the Figures 7 and 8, an antenna means for transmitting and/or receiving RF signals according to a third embodiment of the invention is shown m different views. This embodiment is also very similar to the first embodiment. However, a dielectric plate 4 is arranged on, and m contact with plate 10 on the side where the slit is located. The plate covers the whole side, but could be smaller so as to cover at least the slit. The arrangement of the dielectric plate has the effect that the electrical lengths m the radiating structure are increased. Hereby the dimensions of the radiating structure 1 can be decreased. Figures 9 and 10, show an antenna means for transmitting and/or receiving RF signals according to a fourth embodiment of the invention m different views. In this embodiment a dielectric plate 4 is arranged m the same way as m the third embodiment but on a radiating structure 1 as described m connection to the second embodiment, i.e. with two slits 21, 22. A fifth embodiment of an antenna means for transmitting and/or receiving RF signals according to the invention is shown m Figures 11 and 12 m different views. This embodiment is similar to the third embodiment, but differs from that m that the radiating structure 1 has a different cross section m a plane perpendicular to the slit 21. Alternatively to what is shown, the radiating structure 1 can have two slits and/or have the dielectric plate 4 left out. Figures 13 and 14 shows m different views an antenna means for transmitting and/or receiving RF signals according to a sixth embodiment of the invention. This embodiment is similar to the third embodiment, but differs from that m that the radiating structure 1 has a circular cross section m a plane perpendicular to the slit 21, and that the dielectric plate has the shape of a portion of a tube. Alternatively to what is shown, the radiating structure 1 can have two slits and/or have the dielectric plate 4 left out . Even if a major portion of the electromagnetic radiation is transmitted/received from/in the slit, the whole radiating structure 1 takes part m the transmission/reception, m embodiments of the invention. The antenna means can be seen as including two radiation sources m the same structure. One radiates as an electric dipole across the slit, due to the electric field over the slit and the proximity to the first 101 and second 102 wall sections. The other radiates as a magnetic dipole, due to the currents m the plate. In a cross section perpendicular to the extension of the slit the plate can be seen as a current loop radiating as a magnetic dipole with its dipole axis perpendicular to and through the center of the loop, due to the currents circulating m the radiating structure 1. The electric field radiating from the magnetic dipole co-operates with the radiation from the slit directed out from the structure, and counteracts the radiation from the slit directed m to the structure. The operation m reception is the reverse to that of transmission, by the law of reciprocity. In the open slit arrangement the voltage over the slit is constant along its extension between the free ends. Due to this fact, the length 1 of the slit can be decreased to a great extent without significant decrease m antenna performance. In a slot with closed ends the voltage over the slot varies along its extension between the closed ends, where it is zero at the ends and has a maximum m the center between the ends. This implies that a slit (with open ends) can be made substantially shorter than a slot having closed ends, for equal radiation properties. A variation of an antenna means according to the invention, is shown m Figures 22, 23 and 24. Here a conductive layer 104 105', carried by a substrate or carrier 109', is included m the conductive or radiating structure 10', 1' . The antenna means is divided nto two constructional portions, whereof one, the bottom portion 110' m the figures, is a conductive portion having a generally U-shaped cross section. Portion 110' can be made from a plate, which is bent or by extruding the suitable profile. Alternatively it could be made m any suitable way to obtain a conductive structure, e.g. as a conductive layer on a dielectric carrier or flexfilm. The top portion comprises a dielectric substrate or carrier 109', on which a conductive layer 104', 105' is applied. The layer is divided into two separate portions 104', 105' by the slit 21'. The top portion 109', 104', 105' is preferably made as a PCB (printed circuit board) with suitable manufacturing methods . At the two edges of the top portion, parallel with the slit, the conductive portions 104', 105' of the top portion are connected to the bottom portion 110' . The bottom portion 110' is therefore provided with conductive pins or protrusions which pass through holes m the substrate or carrier 109' and the conductive layers 104', 105' . The pins or protrusions are connected, conductively and mechanically to the conductive layer, e.g. by soldering at spots 108' . The conductive and mechanical connections between the top and bottom portions can be obtained by other methods. For example the bottom portion can be provided with grooves e.g. oy providing ridges. The top portion is then pushed into position guided by the grooves. The top portion can be retained m position by means of friction or other suitable means as soldering, gluing or mechanical fastening devices. The conductive connection s preferably obtained by the same means as the retaining function. The radiating structure 1' is fed by a feeding or transmission line 3' , e.g. by a coaxial cable as shown m the figure. The feeding line can however be of any other suitable kind, e.g. a part of a pattern of a printed circuit board or a pattern on the substrate 109', e.g. on the side opposite to that of the conductive layer 104', 105' . When a part of the feeding line 3' is located inside the radiating structure 1', it is advantageous that conductive pins or conductors extend through holes m the substrate or carrier 109' and the conductive layers 104', 105' . The pins or conductors are connected to the conductive layer, e.g. by soldering at spots 106', 107' . The ground conductor of the feed line 3' is connected to the portion 105' close to the edge 12' and close to the edge 13' . The signal conductor (hot wire) of the feed line 3' is connected to the portion 104' on the other side of the slit 21' close to the edge 11' and close to the edge 13' . Even if it is preferred that the feed line is connected at the edge 13' or close thereto, it can be connected at a distance therefrom, e.g. up to about 20 mm (for radio telephone communication bands) . The feeding line 3' can for example enter into the radiating structure 1' through a hole m a wall portion of the structure 10' , as shown, or enter from an open side of the structure. It can of course enter the radiating structure 1' from the opposite side to the shown, and then the hot wire is to be connected to the portion 105', and ground is connected to portion 104', or m the vicinity thereof, as mentioned above. In the figures, the conductive layer 104', 105' is provided on one side of the substrate or carrier 109'. However, both sides of the substrate or carrier 109' can carry the conductive layer 104', 105' . For example, the portion 104' can be provided on one side and portion 105' on the other side of the substrate or carrier 109'. Otherwise, the function, ways of operation, and possibilities of this variation of the antenna means are similar to those of the embodiments described above, with one important exeption. The capacitances formed by folded down portions m the slit region are not present here. Instead, the impedances are adjusted/matched by the width and the length of the slit 21' and "channels" or slits 111', 112' formed m the conductive layer 104', 105'. The channel/slit 112 is an example on adjusting the impedance/matching m the higher frequency band ( f o2 ) • Figure 25 is a top view of a variation of the conductive layer 104', 105', carried by the substrate or carrier 109' m the antenna means of Figure 22. Here, channel 111', which is formed m portion 105' and connected to slit 21', forms an impedance as mentioned above. Channel 112' is provided m order to further improve the higher frequency band (f c2 ) • Figure 26 is a view of a further variation of an antenna means according to the invention, where a conductive layer, carried by a substrate or carrier, is included m the conductive or radiating structure. The substrate or carrier 109'' is tubular and can be a flexible substrate. The conductive structure 10'' is arranged on the tubular substrate or carrier 109'' so as to exhibit slit 21'' . Further, the conductive structure do not have to be continuous, as long as there is an electrical connection between edges 12'' and 11' A Furthermore the conductive structure 10'' can be provided with a dielectric cover or insulation. The function, ways of operation, and possibilities of this variation of the antenna means are similar to those of the previous described variation. In all embodiments the matching can be done directly m the radiating structure 1. This is done by adjusting the size of the slit (length and width) , the size of the radiating structure 1, and/or the capacitance over the slit. The capacitance can be adjusted and adapted to the different frequency bands by different shapings of the sections 15, 16, whereof some examples, which can be used m the previous embodiments, are shown m Figures 15 and 16. In Figure 15 it is shown how the widths of the sections 15, 16 varies stepwise, and m Figure 16 it is shown how the widths of the sections 15, 16 varies continuously. In connection to the matching, the slit can be short-circuited by means of a conductive tape, plate or other conductor 23 arranged at the end of the slit, which is opposite to the end which is close to the feed portion. This is illustrated m Figure 21. By this arrangement the antenna means can be tuned to e.g. λ/4. Such an antenna means will be longer and operable m narrower frequency band(s) . Also the slit can have other forms than the parallel shape and perpendicular extension over the conductive structure. Figure 17 and 18 show the radiating structure 1 with examples of different shapes of the slit (s) , which can be used m the previous embodiments. Figure 17 shows a slit navmg a curved shape and Figure 18 shows a slit having a distance between the edges 11, 12, which varies along the slit. The radiating structure 1 can further be given a curved shape. In Figures 19a and 19b a radiating structure 1 having a such shape is shown. In this embodiment the first 101 and second 102 wall sections are parallel and parallel to the slit, which is preferable but not necessary. In the antenna means of this embodiment of the invention the radiating structure 1 can further be provided with two slits and/or be provided with a dielectric plate, as m previous embodiments. The curved shape has the advantage that a greater freedom m locating the antenna means with preserved antenna performance is obtained. The mounting m a vehicle of an antenna device according to the invention is schematically shown m Figure 20, where 51 is a conductive part of the vehicle, e.g. the roof, and 52 is a glass pane, e.g. the wind shield. The radiating structure 1 is located so that slit 21 and slit 22, if present, are covered by the glass pane, preferably with a non-metallized portion thereof. If the antenna means 1 is provided with a dielectric plate, the dielectric material is preferably selected to have a dielectric constant different from that of the glass pane, the electromagnetic waves transmitted/received by the antenna means can then be refracted and the antenna lobe can hereby be controlled. When the dielectric constant of the dielectric plate 4 is lower (e.g. ε r »;2.5) than dielectric constant of the glass pane (e.g. ε r «4-5) the radiation lobe will be directed more downwards or to a more horizontal direction. As mentioned, the antenna means 1 does not require a special ground plane, and the reason is the closed structure. It can further be mounted to have very low sensitivity to adjacent conductive parts. If the radiating structure 1 is looked at without the conductive part 51 m Fig. 20, the electric fields passes the slit and has circular forms m a plane perpendicular to the slit (m fact two circular formations m each direction from the slit) . If a conductive plate is introduced m the field and essentially forms a radius or a portion thereof to the circular field lines, the field lines will be incident essentially perpendicular to the plate, which leads to a very low influence from the conductive plate. In the case of Figure 20 the conductive part 51 is present. Then it is essential that there is no galvanic or conductive connection between the radiating structure 1 and the conductive part 51. When the dielectric plate 4 is present there will be a sufficient insulation therebetween. Alternatively or m combination an inner lining, edging or similar, made of plastic, rubber or some other dielectric material can be used as insulation. A capacitive coupling will then appear between the radiating structure 1 and the conductive part 51, which can be calculated or measured and compensated for if desired. The antenna means is preferably protected, when mounted, by a cover or housing of plastic or an other suitable dielectric material . Possibly the antenna means is attached to a housing which is mounted on the vehicle. The antenna means is mounted by means of snapping means, screwing, gluing or other suitable method. It should preferably be mounted with a small spacing (,or none) from the glass pane, e.g. about 0-10. Of course other locations on a vehicle then the shown and described are possible and suitable. It is then favorable if the slit is not covered by any conductive material . Some of the radiating structures 1 or portions thereof described above are suitable to be manufactured by extrusion and subsequent cutting into suitable lengths. Alternatively stamping or cutting from a plate, and subsequent bending operations can be used. Thus, a profile according to some of the embodiments above can be manufactured from one conductive plate . Although the invention is described by means of the above examples, naturally, many variations are possible withm the scope of the invention. For example, the embodiments with their dimensions and measures have been described for radio telephone communication bands, but for operation m other frequency bands the dimensions and measures should be adjusted.

Claims: CLAIMS 1. An antenna means for transmitting and/or receiving RF signals, comprising: - a conductive structure (10) extending between first and second opposite edges (11, 12) , and a feed portion, c h a r a c t e r i s e d i n that the conductive structure (10) is a radiating structure (1) partially enclosing a volume, and the first and second edges (11, 12) are located at a first distance from each other forming an open radiating first slit (21) , having at least one open end. 2. The antenna means according to claim 1, wherein the conductive structure (10) comprises a conductive plate (10) extending between the first and second edges. 3. The antenna means according to claim 1 or 2 , wherein - said slit (21) has first and second open ends. 4. The antenna means according to any preceding claim, wherein the conductive structure (10) further has third and fourth opposite edges (13, 14) , and - the first slit (21) extends between the third and fourth edges (13, 14) . 5. The antenna means according to any preceding claim, wherein additional capacitance means is provided between the first and second edges (11, 12) . 6. The antenna means according to claim 5, wherein the capacitance is formed by a first section (15) and a second section (16) of the conductive structure m connection with the first and second edges (11, 12) , respectively, and - the first and second sections (15, 16) are arranged to be essentially parallel. 7. The antenna means according to any preceding claim, wherein the conductive structure (10) has a second slit (22) at a second distance from the first slit (21) , and the second slit (22) having at least one portion essentially parallel with the first slit (21) . 8. The antenna means according to claim 7, wherein - the second slit (22) has a first and a second end (17) , whereof the first end is open and the second end (17) is closed. 9. The antenna means according to claim 7 or 8 , wherein - the second slit (22) has two opposite sides between which a capacitance is arranged. 10. The antenna means according to any preceding claim, wherein - the radiating structure (10) has a shape being box-like. 11. The antenna means according to any preceding claim, wherein the conductive structure (10) extends in one plane m regions surrounding said slιt(s) (21, 22) . 12. The antenna means according to any preceding claim, wherein the radiating structure (1) has a circumference being essentially in the range λ/2-λ/4, and a length (1) being essentially the range λ/2-λ/3, in a direction perpendicular to said circumference, where λ is the wavelength, of a signal of the center frequency of a frequency band, being the lower frequency band which the antenna means is to be operating. 13. The antenna means according to any preceding claim, wherein the radiating structure (1) has a circumference being essentially λ/2, and a length (1) being essentially λ/2, in a direction perpendicular to said circumference, where λ is the wavelength, of a signal of the center frequency of a frequency band, being the lower frequency band in which the antenna means is to be operating. 14. The antenna means according to any preceding claim, wherein a first dielectric material (4) is arranged to cover at least the slιt(s) . 15. The antenna means according to any preceding claim, wherein - a first dielectric material (4) is arranged to cover the slit(s) and regions around the slιt(s) . 16. The antenna means according to claim 14 or 15, wherein said antenna means is adapted to be mounted on one side of a window having a dielectric constant different to that of the first dielectric material (4) . 17. The antenna means according to claim 14 or 15, wherein the antenna means is adapted to be mounted on a vehicle, on one side of a glass pane (52) having a dielectric constant different to that of the first dielectric material (4) . 18. The antenna means according to claim 16 or 17, wherein the dielectric constant of the first dielectric material (4) is lower than the dielectric constant of the glass pane (52) . 19. The antenna means according any preceding claim, wherein the antenna means is adapted to be mounted on a vehicle, on one side of a glass pane (52) , possibly close to a conductive part of the vehicle. 20 The antenna means according any preceding claim, wherein said first distance is constant along the slit (21) . 21. The antenna means according to any preceding claim, wherein said first distance increases linearly along the slit (21 ) . 22. The antenna means according to any preceding claim, wherein the radiating structure includes a conductive layer carried by a dielectric substrate which layer said first slit is arranged, forming two portions of the conductive layer. 23. The antenna means according to any of claims 1-21, wherein conductive portions are arranged on opposite surfaces of said dielectric substrate and where said slit is formed between adjacent edges on opposite surfaces of said conductive portions. 24. The antenna means according to claim 23, c h a r a c t e r i s e d i n that a first conductive portion on a first side of said dielectric substrate is at least partly overlapping a second conductive portion on a second side of said dielectric substrate. 25. The antenna means according to claim 23, c h a r a c t e r i s e d that a first conductive portion on a first side of said dielectric substrate is laterally displaced from a second conductive portion on a second side of said dielectric substrate, thereby, forming parts of said opposite surfaces arranged on top of each other including no conductive material . 26. The antenna means according to any preceding claim, wherein the radiating structure includes a conductive layer carried by a dielectric substrate m which layer said first and second slits are arranged. 27. The antenna means according to any preceding claims, wherein at least one channel the conductive layer is connected to the slιt(s) forming an impedance the conductive layer. 28. The antenna means according to any preceding claims, wherein at least two channels m the conductive layer are connected to the slιt(s) whereof a first channel is adapted for matching/tuning the antenna means for a higher frequency band and whereof a second channel is adapted for matching/tuning the antenna means for a lower frequency band. 29. The antenna means according to any preceding claims, wherein the radiating structure is divided into at least two constructional portions, whereof a first portion includes said dielectric substrate carrying said conductive layer (s) and exhibits fifth and sixth edges, said first slit being located between the fifth and sixth edges, and a second portion exhibits seventh and eighth edges, being conductively connected to the fifth and sixth edges, respectively. 30. A radio communication system comprising transmitting/ receiving circuits connected to an antenna means, c h a r a c t e r i s e d i n that it includes an antenna means according to any preceding claim. 31. The radio communication system according to claim 30, wnerein the transmitting/ receiving circuits operate m two or more frequency bands. 32. A method for manufacturing a radiating structure of an antenna means according to claim 1, c h a r a c t e r i s e d i n that at least a portion of the radiating structure is extruded.

Inventors: GRAHAM ROBERT, HELLGREN MATTIAS, GRAHAM, ROBERT, HELLGREN, MATTIAS
Applicants: GRAHAM ROBERT, HELLGREN MATTIAS, SMARTEQ AB, GRAHAM, ROBERT, HELLGREN, MATTIAS
Application year: 2000
Main classification: H01Q1
IPC codes: H01Q1, H01Q5, H01Q13