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1. WO2010074618 - DUAL FREQUENCY ANTENNA APERTURE

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CLAIMS

1. An antenna structure comprising at least two stacked antenna apertures, a first antenna aperture (101, 420) with first antenna elements (102, 423) and at least a second antenna aperture (200, 421) with second antenna elements (201, 410), cha racterized in that the antenna structure is arranged for operation in at least a high and a low frequency band with the first antenna elements (102, 423) being arranged for operation in the high frequency band and said second antenna elements (201, 410) for operation in the low frequency band, the first antenna elements (102, 423) being arranged to have a polarization substantially perpendicular to the polarization of the second antenna elements (201, 410) and in that the second antenna elements are arranged in at least one group and each of said group, comprising a number of second antenna elements coupled in series, are arranged to have a common feeding point (205) on a straight feeding structure (206, 301, 404), one feeding structure being located adjacent to each group of second antenna elements, the direction of the feeding structure being substantially perpendicular to the polarization of the first antenna elements (102, 423).

2. An antenna structure according to claim 1, ch a racterized in that the second antenna elements (201, 410) are dipoles and in that each of said group is arranged in a column (202) of second antenna elements, the columns being substantially in parallel.

3. An antenna structure according to claim 1 or 2, ch aracterized in that the first antenna elements (102, 423) are slots in parallel waveguides (103), the waveguides being parallel to the columns (202) of the second antenna elements and the slots being arranged in a lattice.

4. An antenna structure according to any one of claims 1 - 3, ch a racterized in that the columns (202) of the second antenna elements are arranged in between the columns (105) of the first antenna elements.

5. An antenna structure according to any one of claims 1 - 4, ch a racterized in that the second antenna aperture (200, 421) is located above or in front of the first antenna aperture and having a vertical projection towards the first antenna aperture (101, 420) being mainly within the area of the first antenna aperture.

6. An antenna structure according to any one of claims 1 - 5, ch a racterized in that first parasitic dipole elements (411 ) on a third antenna aperture (422) are located above or in front of a second side (425) of the second antenna aperture (421).

7. An antenna structure according to any one of claims 1 - 6, ch a racterized in that the columns (105) of the first antenna elements are arranged along a centre line (106) of each waveguide (103), every second slot being off-centred to one side of the centre line (106) and the slots in between being off-centred to the opposite side of the centre line and in that there is a substantially constant first distance (107) between the centre lines of adjacent waveguides and a substantially constant second distance (108) between neighbouring slots in the column (105) of the first antenna elements.

8. An antenna structure according to any one of claims 1 - 7, ch a racterized in that the columns (202) of the second antenna elements are placed between and in parallel with two columns (105) of the first antenna elements, the parallel displacement being about half of the first distance (107), a third distance (203) between neighboring columns of the second antenna elements and a fourth distance (204) between neighboring second antenna elements in a column (202) of the second antenna elements being substantially constant.

9. An antenna structure according to any one of claims 1 - 8, ch a racterized in that the ground plane (304) of the feeding structure (206, 301, 404) comprises a conductive structure located some distance above or in front of the first antenna aperture.

10. An antenna structure according to any one of claims 1 - 9, ch a racterized in that:

• the first antenna aperture is a conductive surface comprising the first antenna elements (423),

• the ground plane (304, 412) comprising a conductive structure is integrated into a first laminate (401) and located substantially in parallel with the first antenna aperture (420) at a distance (426),

• the feeding structure (404) with its gaps (405) is applied to a second laminate (403),

• the second antenna elements (410) are applied to a third laminate (407) and

• the optional first parasitic antenna elements (411) are applied to a fourth laminate (409).

11. An antenna structure according to claim 10, ch a racterized in that:

• a first foam structure (402) is located between the first and second laminate and • a second foam structure (406) is located between the second and third laminate and a third foam structure (408) is located between the third and fourth laminate.

12. An antenna structure according to claim 10 or 11, ch aracterized in that the ground plane (304, 412), the feeding structure (404), the first foam structure (402), the optional first parasitic antenna element (411) and the second foam structure (406) are integrated in a radome covering the first antenna aperture (101, 420).

13. An antenna structure according to any one of claims 1 - 9, c h a ra cte ri ze d in that the second antenna aperture (200, 421) and the feeding structure with its ground plane (304) is integrated in a radome covering the first antenna aperture (101, 420).

14. An antenna structure according to any one of claims 1 - 8, c h a ra cte ri ze d in that the ground plane (304) of the feeding structure

(301, 404) comprises the conductive surface (104) of the first antenna aperture (101, 420).

15. An antenna structure according to any one of claims 1 - 14, c h a ra cte ri ze d in that the antenna apertures (101, 420, 200, 421 ) are plane or curved in a third dimension.

16. An antenna structure according to any one of claims 1 - 15, c h a ra cte ri ze d in that the elongated feeding structure (206, 301 , 404) is applied to a non conductive second laminate (403) located between the first and second antenna apertures, the feeding structure having one gap (302, 405) for each second antenna element (201, 410) with a vertical projection of the second antenna element towards the feeding structure covering at least part of the gap and further in that the feeding structure has the common RF-feeding point (205) located at one endpoint of the feeding structure.

17. An antenna structure according to claim 16, c h a ra cte ri ze d in that the second antenna elements (201, 410) are dipoles and that a midpoint of the dipole is centred above the gap (302, 405).

18. An antenna structure according to any one of claims 1 - 17, c h a ra cte ri ze d in that the first distance (107) is about a half wavelength or less of a centre frequency in the frequency band of the first antenna aperture and that the third distance (203) is about a half wavelength or less of a centre frequency in the frequency band of the second antenna aperture for the antenna structure to be electronically scannable.

19. An antenna structure according to any one of claims 1 - 18, c h a ra cte ri ze d in that the amount of off-centring of the slots and the length of the slots can be slightly varied from slot to slot to achieve a tapering effect.

20. An antenna structure according to any one of claims 1 - 19, c h a ra cte ri ze d in that the length and width of a dipole can vary slightly from dipole to dipole in order to achieve a tapering effect.

21. An antenna structure according to any one of claims 1 - 20, c h a ra cte ri ze d in that further parasitic dipole elements are stacked above or in front of the first parasitic dipole elements (411 ).

22. An antenna structure according to any one of claims 1 - 21, c h a ra cte ri ze d in that the second antenna elements (201, 410) are proximity coupled or galvanically coupled to the feeding structure (206, 301, 404).

23. An antenna structure according to any one of claims 1 - 22, c h a ra cte ri ze d in that the first and second antenna elements can be electronically scanned.

24. A radar system comprising an antenna structure according to anyone of claims 1-23.

25. A method for arranging an antenna structure comprising at least two stacked antenna apertures, a first antenna aperture (101 , 420) with first antenna elements (102, 423) and at least a second antenna aperture (200, 421 ) with second antenna elements (201 , 410), c h a r a c t e r i z e d in that the antenna structure is arranged for operation in at least a high and a low frequency band with the first antenna elements (102, 423) being arranged for operation in the high frequency band and said second antenna elements (201 , 410) for operation in the low frequency band, the first antenna elements (102, 423) have a polarization substantially perpendicular to the polarization of the second antenna elements (201 , 410) and in that the second antenna elements are arranged in at least one group and each of said group, comprising a number of second antenna elements coupled in series, having a common feeding point (205) on a straight feeding structure (206, 301 , 404), one feeding structure being located adjacent to each group of second antenna elements, the direction of the feeding structure being substantially perpendicular to the polarization of the first antenna elements (102, 423).