Dual-polarized antenna

• US 6,531,984 B1
• Filed: 10/27/2000
• Issued: 03/11/2003
• Est. Priority Date: 10/29/1999
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Derneryd, Anders, Johansson, Martin, Johannisson, Björn
• Primary Examiner(s): Wong, Don
• Assistant Examiner(s): Clinger, James
• Application Number:
  US09/696,944
• Time in Patent Office: 865 Days
• Field of Search: 343/700.MS, 343/848, 343/846, 343/830
• US Class Current: 343/700.0MS
• CPC Class Codes: H01Q 1/38 formed by a conductive layer on an insulating support patch antennas H01Q9/0407; microstrip dipole antennas H01Q9/065; microstrip slot antennas H01Q13/106; transmission line microstrip antennas H01Q13/206; manufacturing reflecting surfaces using insulating material for supporting the reflecting surface H01Q15/142
• CPC Class Codes: H01Q 9/0435 using two feed points

Abstract

A dual-polarized antenna (10) with good isolation between feed ports (13a, 13b) and high similarity with respect to the radiation patterns is provided. An antenna (10) includes a patch (11), four symmetrically arranged feed structures (12a-12d, 15), two feed ports (13, 13b) and a feed network (14). Radiation pattern similarity is obtained by the pair-wise symmetrical, orthogonal layout of the feed structures (12a-12d, 15). Good isolation between feed ports (13a, 13b) is achieved through a feed network (14) divided into two network parts (14a, 14b) where each network part (14a, 14b) is designed so that each coupling between a network part (14a, 14b) and a feed structure (12a12d, 15) belonging to the other polarization is cancelled by a mirrored coupling with the other feed structure (12a-12d, 15) belonging to the polarization. In addition, a network part (14a, 14b) is laid out so that its corresponding feed structures (12a-12d, 15) are fed with supporting signals of equal magnitude.

Claims

1. A dual-polarised antenna element (10) comprising:

a patch (11),

a ground plane (9),

four feed structures (12a-12d, 15),

two feed ports (13a, 13b), and

a feed network (14), where the feed network (14) is divided into two separate network parts (14a, 14b) connected to a feed port (13a, 13b) each, where the four feed structures (12a-12d, 15) are symmetrically arranged, one pair for each polarisation, where the first of said two network parts (14a, 14b) is connected to one pair of said feed structures (12a-12d, 15) and the second of said two network parts (14a, 14b) is connected to the other one pair of said feed structures (12a-12d, 15), and where all network parts (14) reside in a single plane.

2. A dual-polarised antenna element (10) according to claim 1, where the feed structures (12a-12d, 15) are placed on two perpendicular lines passing through the projected centre of the patch (11).

3. A dual-polarised antenna element (10) according to claim 2, where each feed structure (12a-12d, 15) is located the same distance from said centre of the patch (11).

4. A dual-polarised antenna element (10) according to claim 2, where each feed structure pair (12a-12d, 15) is symmetrically placed with regard to any patch symmetry line.

5. A dual-polarised antenna element (10) according to claim 2, where at least part of each feed structure (12a-12d, 15) is in contact with the patch (11).

6. A dual-polarised antenna element (10) according to claim 1, where the patch (11) is a microstrip patch.

7. A dual-polarised antenna element (10) according to claim 1, where the patch (11) is planar.

8. A dual-polarised antenna element (10) according to claim 1, where the patch (11) is non-planar.

9. A dual-polarised antenna element (10) according to claim 1, where the patch (11) has at least two orthogonal symmetry planes.

10. A dual-polarised antenna element (10) according to claim 9, where the patch (11) is circular.

11. A dual-polarised antenna element (10) according to claim 9 where the patch (11) is square.

12. A dual-polarised antenna element (10) according to claim 1, where the feed structures (12a-12d, 15) are slots (12a-12d) in a ground plane (9).

13. A dual-polarised antenna element (10) according to claim 12, where the width of the slots (12a-12d) is non-uniform.

14. A dual-polarised antenna element (10) according to claim 12, where a geometry of the slots (12a-12d) conforms with the current distribution on the patch (11).

15. A dual-polarised antenna element (10) according to claim 1, where the feed structures (12a-12d, 15) are probes (15) feeding through a ground plane (9).

16. A dual-polarised antenna element (10) according to claim 15, where the probes (15) are galvanically connected to the patch (11).

17. A dual-polarised antenna element (10) according to claim 15, where the probes (15) are capacitivally connected to the patch (11).

18. A dual-polarised antenna element (10) according to claim 1, where a first and second network part (14a, 14b) is structured so as to affect the pair of feed structures (12a-12d, 15) it is connected to, while its effect on the feed structures (12a-12d, 15) belonging to the other polarisation is cancelled.

19. A dual-polarised antenna element (10) according to claim 18, where the branches (14b1, 14b2) of a first network part (14b) are laid out so that they together are symmetrical around a projection of the line intersecting the middle of the feed structures (12a-12d, 15) belonging to the other polarisation, and that the difference in electric length between a point on a shorter branch (14b2) and its mirror point on a longer branch (14b1) is a minimum of 180 degrees from the point where said branch (14b2) enters the projection of the patch (11) onward, and where at least the major part of the second network part (14a) and the feed port (13a) feeding it are laid out symmetrically around a projection of the line on which the feed structures (12a-12d, 15) belonging to its own polarisation are arranged, and the feed port (13a), the straight lines in contact with the feed structures (12a-12d, 15), and the stretch of the branches (14a1-14a3) comprising the lines leading from the connection to the feed port (13a) to the lines leading into the patch (11), and where, in said second network part (14a), the electric distance between a point and its mirror point is zero degrees, while the feed structures (12a-12d, 15) are fed effectively in-phase such that the fields from both feed structures (12a-12d, 15) have the same magnitude and phase.

20. A dual-polarised antenna element (10) according to claim 19, where said second network part is arranged with symmetry, as a first branch (14a3) runs straight from the connection to the feed port (13a) to the nearest feed structure (12d, 15) or across the nearest feed structure, while the second and third branches (14a1, 14a2) run as mirror images of each other essentially orthogonal to said first branch (14a3) until they enter a projection of the patch (11) on a pair of radial lines between the nearest feed structure (12d, 15) and neighboring feed structures (12a, 12c, 15), continuing on said radial lines until they intersect in the centre of said projection of the patch (11) whereafter they run as a single line straight to the second feed structure (12b, 15) belonging to the polarisation.

21. A dual-polarised antenna element (10) according to claim 20, where the difference in electrical length between a point on the first branch (14a3) and a point on the other branches (14a1, 14a2) is 360 degrees where the two last branches (14a1, 14a2) have intersected and where the distances between above-said points and the feeding structures (12b, 12d, 15) are equal.

22. A dual-polarised antenna element (10) according to claim 20, where said radial lines are arranged so that the distances between a radial line and the nearest feed structures (12a-12d, 15) are equal.

23. A dual-polarised antenna element (10) according to claim 19, where a first branch (14a2) runs orthogonally with respect the symmetry line, until it turns to enter a projection of the patch (11) on a radial line between above-mentioned feed structure (12d, 15) and one of its neighbours (12a, 12c, 15), continuing to the centre of said projection, where said branch (14a2) turns to run straight to, and possibly across, the farther feed structure (12b, 15) belonging to the polarisation, while the second branch (14a1) mirrores the first branch (14a2) until said second branch has entered said projection of the patch (11) and has passed the point where the nearest feed structures (12a, 12d, 15) are closest to each other to a point roughly halfway between the point where the branch (14a1) entered the projection of the patch (11) and the middle of said projection where said branch (14a1) turns in order to, further on, run to, and possibly across, the closer feed structure (12d, 15) belonging to the polarisation.

24. A dual-polarised antenna element (10) according to claim 23, where said radial line is arranged so that the distances between the radial line and the nearest feed structures (12a-12d, 15) are equal.

25. A method of feeding current to two orthogonal polarisations in a dual-polarised antenna element (10) comprising:

feeding through four feed structures (12a-12d, 15), two for each polarisation, through a first and second network part (14a, 14b) so that the the current corresponding to one polarisation has no net effect on the feed current and the radiation pattern corresponding to the other polarisation, wherein all network parts (14) reside in a single plane.

26. A method for obtaining a dual-polarised antenna element (10) comprising a patch (11), four feed structures (12a-2d, 15), two feed ports (13a, 13b) and a feed network (14), where the feed network (14) is divided into two separate network parts (14a, 14b) connected to a feed port (13a, 13b) each, comprising the steps of:

arranging the four feed structures (12a-12d, 15) symmetrically, one pair for each polarisation, and

connecting the first of said two network parts (14a, 14b) to one pair of said feed structures (12a-12d, 15) and connecting the second of said two network parts (14a, 14b) to the other one pair of said feed structures (12a-12d, 15), where all network parts reside in a single plane.

27. A method for obtaining a dual-polarised antenna element (10) according to claim 26, comprising the further step of placing the feed structures (12a-12d, 15) on two perpendicular lines passing through the projected centre of the patch (11).

28. A method for obtaining a dual-polarised antenna element (10) according to claim 27, comprising the further step of locating each feed structure (12a-12d, 15) the same distance from the projected centre of the patch (11).

29. A method for obtaining a dual-polarised antenna element (10) according to claim 27, comprising the further step of placing each feed structure pair (12a-12d, 15) symmetrically with regard to any patch symmetry line.

30. A method for obtaining a dual-polarised antenna element (10) according to claim 27, comprising the further step of placing at least part of each feed structure (12a-12d, 15) in contact with the patch (11).

31. A method for obtaining a dual-polarised antenna element (10) according to claim 26, comprising the further step of constructing feed structures (12a-12d, 15) by making slots (12a-12d) in a ground plane (9).

32. A method for obtaining a dual-polarised antenna element (10) according to claim 31, where the width of the slots (12a-12d) is non-uniform.

33. A method for obtaining a dual-polarised antenna element (10) according to claim 31, comprising the further step of matching the geometry of the slots (12a-12d) to the current distribution on the patch (11).

34. A method for obtaining a dual-polarised antenna element (10) according to claim 26, comprising the further step of constructing the feed structures (12a-12d, 15) with probes (15) feeding through a ground plane (9).

35. A method for obtaining a dual-polarised antenna element (10) according to claim 26, comprising the further step of structuring a first and second network part (14a, 14b) so as to affect the pair of feed structures (12a-12d, 15) it is connected to, while its effect on the feed structures (12a-12d, 15) belonging to the other polarisation is cancelled.