Antenna and antenna system

Abstract

An antenna for a vehicle. The antenna has an omni-directional radiation pattern and is configured for V2X communication. An x-y plane is defined as the horizontal plane in relation to the vehicle, an x-z plane is defined as a plane that is parallel to a side of the vehicle to which the antenna is positioned, and a y-z plane is defined as an elevation plane in relation to the vehicle. The antenna includes a first patch antenna and a second patch antenna and a reflector, and a feed network and power divider. The first patch antenna is aimed in a first direction along the x-axis. The second patch antenna is aimed in a second and opposite direction along the x-axis, and the reflector is positioned in a plane that is parallel to the x-z plane.

Claims

1. An antenna for a vehicle, the antenna having an omni-directional radiation pattern and being configured for V2X communication, an x-y plane being defined as the horizontal plane in relation to the vehicle, an x-z plane being defined as a plane that is parallel to a side of the vehicle to which the antenna is positioned, a y-z plane being defined as an elevation plane in relation to the vehicle, the antenna comprising: a first patch antenna, the first patch antenna being aimed in a first direction along the x-axis; a feed network and power divider; and a second patch antenna and a reflector, the second patch antenna being aimed in a second and opposite direction along the x-axis, and the reflector being positioned in a plane that is parallel to the x-z plane.

2. The antenna according to claim 1, wherein the reflector is configured to control the radiation pattern orientations for the first and second patch antenna, and thus for the antenna as a whole.

3. The antenna according to claim 1, wherein the first and second patch antenna is a direct probe feed patch antenna.

4. The antenna according to claim 1, wherein a first electrically conductive structure is used to form the patch antennas and wherein a second electrically conductive structure is used to form the feed network and power divider.

5. The antenna according to claim 4, wherein at least one of the first and the second electrically conductive structure is a sheet metal.

6. The antenna according to claim 4, wherein at least one of the first and the second electrically conductive structure is a printed circuit board (PCB).

7. The antenna according to claim 6, wherein the antenna is formed in a multi layered PCB, wherein: a first patch radiator belonging to the first patch antenna is formed in a first electrically conductive layer in the multi layered PCB; a first ground plane belonging to the first patch antenna is formed in a second electrically conductive layer in the multi layered PCB; the feed network and power divider is formed in a third electrically conductive layer in the multi layered PCB; a second ground plane belonging to the second patch antenna is formed in a fourth electrically conductive layer in the multi layered PCB; a second patch radiator belonging to the second patch antenna is formed in a fifth electrically conductive layer in the multi layered PCB; and each electrically conductive layer is separated by a substrate in the multi layered PCB.

8. The antenna according to claim 4, wherein the second electrically conductive structure with the feed network is positioned parallel to and between the first and second patch antenna, and wherein the power divider is a 3 dB in-phase microstrip power divider configured to combine the first and second patch antenna.

9. The antenna according to claim 8, wherein a low loss dielectric material with a thickness adapted to its DK value is used as a substrate for at least one of the feed network and the patch antennas.

10. The antenna according to claim 1, wherein a first electrically conductive structure is used to form the patch antennas, wherein a second electrically conductive structure is used to form the feed network, and wherein discrete components are used to form the power divider.

11. The antenna according to claim 1, wherein: the first and second patch antenna has a circular patch radiator with a rectangular ground plane; the size of the ground plane is substantially /2/20.76 mm; the metal reflector has a diameter of substantially 0.65 to substantially 0.75; the reflector is positioned at a distance of 0.3 to 0.4 from the edge of the first and second patch antenna; the antenna feed of the first patch antenna is placed on the y axis; and the antenna feed of the second patch antenna is placed on the +y axis.

12. The antenna according to claim 1, wherein the patch antenna has a feed structure, the feed structure being one of a co-planar strip, proximity-coupled and aperture-coupled.

13. The antenna according to claim 1, wherein the patch antenna is one of an antenna array and a stacked patch antenna.

14. The antenna according to claim 1, wherein parameters regarding design of the antenna, including at least of: antenna feed probe location(s); divider dimensions; antenna distance to feed network locations; and reflector size and distance to antenna element(s); are selected to eliminate mismatching and phase errors.

15. The antenna according to claim 1, wherein the antenna is configured to function in the frequency range of 5850 to 5925 MHz.

16. The antenna according to claim 1, wherein the antenna is configured to provide an antenna gain in the range of 2 dBi to 5 dBi with an average of 3.5 dBi in the horizontal plane and VSWR: <2.0:1.

17. An antenna system for a vehicle, the system being configured for V2X communication, the antenna system comprising at least one first and one second antenna, each of the at least one first and one second antenna having: an omni-directional radiation pattern and being configured for V2X communication, an x-y plane being defined as the horizontal plane in relation to the vehicle, an x-z plane being defined as a plane that is parallel to a side of the vehicle to which the antenna is positioned, a y-z plane being defined as an elevation plane in relation to the vehicle, the antenna comprising: a first patch antenna, the first patch antenna being aimed in a first direction along the x-axis; a feed network and power divider; and a second patch antenna and a reflector, the second patch antenna being aimed in a second and opposite direction along the x-axis, and the reflector being positioned in a plane that is parallel to the x-z plane; and the first antenna being positioned at an opposite position to the second antenna on the vehicle, the y-axis of the first antenna being directed in a first direction, and the y-axis of the second antenna being directed in a second direction opposite to the first direction.

18. The antenna system according to claim 17, wherein the first and second antennas are positioned on the sides of the vehicle, wherein the first direction of respective first patch antenna is the forward direction of the vehicle, and wherein the second direction of respective second patch antenna is the backward direction of the vehicle.

19. The antenna system according to claim 18, wherein the antenna system comprises at least one third antenna, wherein the third antenna is positioned in the front of the vehicle, wherein the first direction of the first patch antenna belonging to the third antenna is the right direction of the vehicle, and wherein the second direction of the second patch antenna belonging to the third antenna is the left direction of the vehicle.

20. The antenna system according to claim 18, wherein the antenna system comprises at least one fourth antenna, wherein the fourth antenna is positioned in the back of the vehicle, wherein the first direction of the first patch antenna belonging to the fourth antenna is the right direction of the vehicle, and wherein the second direction of the second patch antenna belonging to the fourth antenna is the left direction of the vehicle.

21. The antenna system according to claim 17, wherein the first and second antennas are positioned in the front and back of the vehicle, wherein the first direction of respective first patch antenna is the right direction of the vehicle, and wherein the second direction of respective second patch antenna is the left direction of the vehicle.

22. The antenna system according to claim 17, wherein the antenna system comprises mechanical support for at least one antenna, and wherein the mechanical support extends from the vehicle to position the supported antenna to provide clear light-of-sight from the vehicle to other objects or vehicles around the vehicle.

23. The antenna system according to claim 17, wherein the antenna system comprises a radome for at least one antenna configured to protect and enclose the at least one antenna.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) An antenna and an antenna system having the properties associated with the present invention will now be described in more detail for the purpose of exemplifying the invention, reference being made to the accompanying drawing, wherein:

(2) FIGS. 1a and 1b shows schematically and very simplified an antenna, its position on a vehicle, and the radiation pattern of the antenna positioned on the vehicle, where FIG. 1a shows a top view of the vehicle and FIG. 1b shows a front view of the vehicle,

(3) FIG. 2 shows an exploded view of an inventive antenna,

(4) FIGS. 3a and 3b are graphs showing the radiation pattern of an inventive antenna,

(5) FIG. 4 shows a schematic and simplified side view of an antenna formed in a multi layered PCB,

(6) FIG. 5 is a graph showing the Voltage Standing Wave Ration of an inventive antenna,

(7) FIGS. 6 to 11 are schematic and simplified illustrations of different antenna systems where antennas are placed in different positions on a vehicle,

(8) FIG. 12 is an exploded view of an antenna with a radome, and

(9) FIG. 13 is an illustration of an antenna in its radome positioned on a mechanical support.

DETAILED DESCRIPTION

(10) The present invention will be described with a reference to FIGS. 1a and 1b showing an antenna A for a vehicle B, where FIG. 1a is a top view of the vehicle and FIG. 1b is a front view of the vehicle. The antenna A has an omni-directional radiation pattern Ar and is adapted to V2X communication.

(11) FIG. 2 shows an exploded view of the antenna A which comprises a first patch antenna 1, a feed network and power divider 21, a second patch antenna 3 and a reflector 4.

(12) An x-y plane is defined as the horizontal plane in relation to the vehicle, an x-z plane is defined as a plane that is parallel to a side of the vehicle to which the antenna A is positioned, and an y-z plane is defined as an elevation plane in relation to the vehicle.

(13) FIG. 2 shows that the first patch antenna 1 is aimed in a first direction along the x-axis, that the second patch antenna 3 is aimed in a second and opposite direction b along the x-axis, and that the reflector 4 is positioned in a plane that is parallel to the x-z plane, whereby the antenna A provides a radiation pattern of substantially a half circle in the horizontal plane, as schematically shown in FIG. 1a and as shown in FIG. 3a, and a radiation pattern of substantially a sector in the elevation plane, as schematically shown in FIG. 1b and as shown in FIG. 3b, of the vehicle B.

(14) FIGS. 3a and 3b shows radiation patterns of an exemplified inventive antenna, where FIG. 3a is a graph showing a 2D cut in the horizontal plane of Fairfield Gain Abs (Phi=90) in the frequency of 5,8875 GHz and a main lobe magnitude of 4.4 dB, and where FIG. 3b is a graph showing a 2D cut in the vertical plane of Fairfield Gain Abs (Theta=90) in the frequency of 5,8875 GHz and a main lobe magnitude of 3.6 dB.

(15) The reflector 4 is adapted to control the radiation pattern orientations for the first and second patch antenna 1, 3, and thus for the antenna A as a whole. It is proposed that the first and second patch antenna 1, 3 is a direct probe feed patch antenna.

(16) A first electrically conductive structure can be used to form the patch antennas 1, 3 and a second electrically conductive structure can be used to form the feed network and power divider 21. The material for the first and second electrically conductive structure can be chosen independently from each other.

(17) Examples of possible conductive structures are sheet metal and PCB. There are many other ways of forming a conductive structure, such as forming a structure through injection molding which is metalized to form desired conductive structure.

(18) It is also possible that discrete components can be used to form the power divider regardless of what structure that is used to form the feed network.

(19) For the sake of simplicity, a PCB 2 will be used in the following description to illustrate both the first and second electrically conductive structure. If the materials sheet metal and/or PCB are chosen, then it is clear that: sheet metal can be used for both the first and second electrically conductive structure, PCB can be used for both the first and second electrically conductive structure, sheet metal can be used for the first electrically conductive structure and PCB can be used for the second electrically conductive structure, or sheet metal can be used for the first electrically conductive structure and PCB can be used for the second electrically conductive structure.

(20) FIG. 4 shows one proposed embodiment where an inventive antenna A is formed in a multi layered PCB 2, where: a first patch radiator 11 belonging to said first patch antenna 1 is formed in a first electrically conductive layer 2a in said multi layered PCB 2, a first ground plane 12 belonging to said first patch antenna 1 is formed in a second electrically conductive layer 2b in said multi layered PCB 2, said feed network and power divider 21 is formed in a third electrically conductive layer 2c in said multi layered PCB 2, a second ground plane 32 belonging to said second patch antenna 3 is formed in a fourth electrically conductive layer 2d in said multi layered PCB 2, a second patch radiator 31 belonging to said second patch antenna 3 is formed in a fifth electrically conductive layer 2e in said multi layered PCB 2, and each electrically conductive layer 2a, 2b, 2c, 2d, 2e is separated by a substrate layers 2f, 2g, 2h, 2i in said multi layered PCB 2.

(21) The antenna feed 13 from the feed network and power divider 21 is led from the feed network and power divider 21 in the third electrically conductive layer 2c through the substrate layer 2g separating the third electrically conductive layer 2c from the second electrically conductive layer 2b, through the first ground plane 12 in the second electrically conductive layer 2b, and through the substrate layer 2f separating the first electrically conductive layer 2a from the second electrically conductive layer 2b, and into contact with the first patch radiator 11 in the first electrically conductive layer 2a.

(22) In the same way, the other antenna feed 33 from the feed network and power divider 21 is led from the feed network and power divider 21 in the third electrically conductive layer 2c through the substrate layer 2h separating the third electrically conductive layer 2c from the fourth electrically conductive layer 2d, through the second ground plane 32 in the fourth electrically conductive layer 2d, and through the substrate layer 2i separating the fourth electrically conductive layer 2d from the fifth electrically conductive layer 2e, and into contact with the second patch radiator 31 in the fifth electrically conductive layer 2e.

(23) It should be understood that FIG. 4 shows only a schematic illustration of an inventive antenna and that the different thicknesses of the different electrically conductive layers and substrate layers are individually adapted to the antenna design of respective patch antenna and to the antenna as a whole in a real implementation of the invention.

(24) As shown in FIGS. 2 and 3, the PCB 2 with its feed network 21 is positioned parallel to and between the first and second patch antenna 1, 3, and it is proposed that the power divider is a 3 dB in-phase micro strip power divider designed to combine the first and second patch antenna 1, 3.

(25) A proposed embodiment of the present invention teaches that a low loss dielectric material with a thickness adapted to its DK value, such as Rogers RO4350 with DK=3,656, DF=0.0037 and thickness of 0.76 mm, is used as a substrate for the feed network and patch antennas 1, 3.

(26) Proposed material properties are only one example of a PCB that can be used, where the thickness of 0.76 mm is a standard thickness for PCB, and it should be understood that a PCB with another thickness, DK and DF can be used.

(27) The components of a patch antenna according to the present invention can be dimensioned and shaped in different ways. The distance and size of the reflector place a big role on the antenna radiation directivities. Which plane the reflector is placed, which in our case is the x-y plane, is also important, since the x-y plane define the horizon plane related to the antenna placed on the vehicle B. According to one exemplifying embodiment, where calculated dimensions are based on that the frequency to which the antenna is adapted is 5.8 GHz, it is proposed that the first and second patch antenna 1, 3 has a circular patch radiator 11 with a rectangular ground plane 12, 32, that the size of the ground plane 12, 32 is typically /2/20.76 mm, which in this example would result in approximately 25 mm25 mm0.76 mm, that the metal reflector 4 has a diameter of typically 0.65 to 0.75, which would result in approximately 40 mm, that the reflector is positioned at a distance d of 0.3 to 0.4 from the edge of the patch antennas 1, 3, which would result in approximately 20 mm, that the antenna feed 13 of the first patch antenna 1 is placed on the y axis, and that the antenna feed 33 of the second patch antenna 3 is placed on the +y axis,
in order to provide patch antennas in phase on the Phi=90 plane, and so that the reflector positioned in the x-z plane will not affect the phase.

(28) It should be understood that illustrated embodiment is only an example of a possible antenna design. The shape of the patch, ground plane or reflector can be chosen differently from what is proposed in this embodiment, where these shapes can be circular, rectangular or oval depending on design, and the invention is not limited to shapes and dimensions shown in this proposed embodiment.

(29) It is also proposed that the patch antenna 1, 3 has a feed structure such as a co-planar strip, proximity-coupled or aperture-coupled.

(30) It is possible to use different ways of enhancing the capacity of the antenna, such as using an antenna array or a stacked patch antenna based on the inventive patch antenna.

(31) With the purpose of eliminating any kind of mismatching and phase errors from the antenna it is proposed that parameters regarding design of the antenna, such as antenna feed probe location(s), divider dimensions, antenna distance to feed network locations, reflector size and distance to antenna element(s),
are carefully designed.

(32) The antenna can be designed and optimized to function for different frequency ranges and the exemplifying embodiment shows an antenna that is adapted to function in the frequency range of 5850 to 5925 MHz in order to match the antenna to the licensed ITS band of 5.9 GHz (5.85-5.925 GHz) according to the ITS-G5 standard. It is however obvious that the antenna design can be optimized for other systems and frequencies such 2.4 GHz or 5 GHz for WiFi, or 868/915 MHz.

(33) It is also proposed that the antenna is adapted to provide an antenna gain in the range of 2 dBi to 5 dBi with an average of 3.5 dBi in the horizontal plane or bi-omni directions, and a Voltage Standing Wave Ratio (VSWR): <2.0:1. FIG. 5 shows a graph of the antenna performance VSWR for an antenna according to this design.

(34) The present invention also relates to an antenna system for a vehicle, which system is adapted to V2X communication. The system will be illustrated in FIG. 6, where it is shown that the system comprises at least one first antenna A1 and one second antenna A2 according to any exemplifying embodiment of the above mentioned inventive antenna A.

(35) FIGS. 6 to 10 shows schematically the top view of a vehicle B where the direction of the vehicle B is indicated by an arrow on the vehicle.

(36) FIG. 6 illustrate that the first antenna A1 is positioned at an opposite position to the second antenna A2 on the vehicle B, that the y-axis of the first antenna A1 is directed in a first direction c1, and that the y-axis of the second antenna A2 is directed in a second direction c2 opposite to the first direction c1.

(37) FIG. 6 illustrates an embodiment where the first and second antenna A1, A2 are positioned on the sides of the vehicle B, in which case the first direction a1 of the first patch antenna belonging to the first antenna A1 is the forward direction of the vehicle B, the second direction b1 of the second patch antenna belonging to the first antenna A1 is the backward direction of the vehicle B, and in which case the first direction a2 of the first patch antenna belonging to the second antenna A2 is the forward direction of the vehicle B, the second direction b2 of the second patch antenna belonging to the second antenna A2 is the backward direction of the vehicle B.

(38) FIG. 7 illustrates a proposed embodiment showing that with antennas A1, A2 on the sides of the vehicle B it is also possible to include at least one third antenna A3 in the antenna system, which third antenna A3 is positioned in the front of the vehicle B, where the first direction a3 of the first patch antenna belonging to the third antenna A3 is the right direction of the vehicle B, and the second direction d3 of the second patch antenna belonging to the third antenna A3 is the left direction of the vehicle B.

(39) FIG. 8 shows that in the same way it is also possible to have at least one fourth antenna A4, which is positioned in the back of the vehicle B, where the first direction a4 of the first patch antenna belonging to the fourth antenna A4 is the right direction of the vehicle B, and that the second direction b4 of the second patch antenna belonging to the fourth antenna A4 is the left direction of the vehicle B. These first, second, third and fourth antennas A1, A2, A3, A4 will provide a possibility to have a system radiation pattern that covers the full 360 degrees around the vehicle, even with vehicles of very complex shape and form.

(40) FIG. 9 illustrates a possible embodiment with only two antennas A1, A2, where a first antenna A1 is positioned in the front of the vehicle B and the second antenna A2 is positioned in the back of the vehicle B, in which case the first direction a1 of the first patch antenna belonging to the first antenna A1 is the right direction of the vehicle B, the second direction b1 of the second patch antenna belonging to the first antenna A1 is the left direction of the vehicle B, and in which case the first direction a2 of the first patch antenna belonging to the second antenna A2 is the right direction of the vehicle B, the second direction b2 of the second patch antenna belonging to the second antenna A2 is the left direction of the vehicle B.

(41) FIG. 10 illustrate a proposed embodiment where several antennas have been positioned on a vehicle B and a trailer B1 belonging to the vehicle. A trailer or something else connected to the vehicle B, will provide possibilities to position antennas on other places than the actual vehicle itself. Here it can be seen that the vehicle B has three antennas, A11, A21 and A3, while the trailer B1 has 5 antennas A12, A13, A22, A23 and A4 in different directions around the trailer B1. Antennas positioned on a trailer can be connected to the vehicle through any connection device that provides signal transmission between the vehicle B and the trailer B1.

(42) FIG. 11 shows an alternative embodiment where a first antenna A1 and a second antenna A2 have been positioned on top of a vehicle B. In FIG. 11 the direction of the vehicle B is indicated by an arrow on the vehicle trailer B1 behind the vehicle B. One of the problems that is solved by the present invention is to provide an antenna on a vehicle where it is not possible to place the antenna on top of the vehicle. The present invention provides an antenna that will solve this problem. However, this does not prevent that an inventive antenna can be positioned on top of a vehicle when this position is possible and available, as illustrated in FIG. 11.

(43) FIG. 12 shows that the antenna system may provide mechanical and environmental protection to an antenna A through a radome 5 for each antenna that require such protection to protect and enclose such antenna, which radome 5 also is shown in FIGS. 3a and 3b.

(44) Each antenna in the system require a clear light-of-sight from the vehicle to other objects or vehicles around the vehicle. This can be achieved if it is possible to position the antenna on parts of the vehicle that extends out from the vehicle, such as a rear view mirror on the vehicle or if possible on top of the vehicle.

(45) There might be situations where there are no such parts on the vehicle, and FIG. 13 shows an embodiment where the antenna system comprises mechanical support 6 for an antenna, which mechanical support extends from the vehicle to position the supported antenna in a position with clear light-of-sight from the vehicle to other objects or vehicles around the vehicle.

(46) The length extension of a support 6 varies depending on how far out from the vehicle the antenna needs to be positioned, and some antennas in the system might not require any such support but can be mounted directly on the vehicle.

(47) The skilled person understand that antennas according to the invention can be combined into an antenna system according to the invention in many different ways, where proposed embodiments discloses some of these possible antenna configurations, thus it is clear that the invention is not limited to the embodiments given above as examples but may be subjected to modifications within the scope of the general idea of to the invention as defined and shown in the subsequent claims.