Slim Multi-Band Antenna Array For Cellular Base Stations

• US 20080062062A1
• Filed: 08/31/2005
• Published: 03/13/2008
• Est. Priority Date: 08/31/2004
• Status: Active Grant

• Current Assignee: CommScope Technologies, LLC (CommScope Holding Company, Inc.)
• Original Assignee: Fractus SA
• Inventors: Borau, Carmen, Baliarda, Carles, Kirchhofer, James, Teillet, Anthony
• Granted Patent: US 7,868,843 B2
• Time in Patent Office: Days
• US Class Current: 343/844
• CPC Class Codes: H01Q 1/246 specially adapted for base stations
• CPC Class Codes: H01Q 1/523 between antennas of an array
• CPC Class Codes: H01Q 21/065 Patch antenna array
• CPC Class Codes: H01Q 21/205 providing an omnidirectional coverage turnstile aerials H01Q21/26
• CPC Class Codes: H01Q 5/42 using two or more imbricated arrays H01Q5/49 takes precedence

Abstract

This invention is in the field of base station antennas for wireless communications. The present invention refers to a slim multi-band antenna array for cellular base stations, which provides a reduced width of the base station antenna and minimizes the environmental and visual impact of a network of cellular base station antennas, in particular in mobile telephony and wireless service networks. A multiband antenna array comprises a first set of radiating elements operating at a first frequency band and a second set of radiating elements operating at a second frequency band, said radiating elements being smaller than λ/2 or smaller than λ/3, being (λ) the longest operating wavelength. The ratio between the largest and the smaller of said frequency bands is smaller than 2.

Claims

1. - A multiband antenna system for cellular base stations, comprising at least one multiband antenna array, wherein each antenna array comprises a first set of radiating elements operating at a first frequency band and a second set of radiating elements operating at a second frequency band, wherein the radiating elements are smaller than λ

/2 or smaller than λ

/3, being (λ

) the longest operating wavelength, and wherein the ratio between the largest and the smallest frequency of said frequency bands is smaller than 2

2. - Antenna system according to claim 1 wherein the antenna arrays are radially spaced from a central axis of the antenna system, and wherein each antenna array is longitudinally placed within an angular sector defined around said central axis.

3. - Antenna system according to claim 2 wherein an angular spacing is defined between said angular sectors.

4. - Antenna system according to claim 3 wherein it includes three antenna arrays and wherein the angular spacing defined between said angular sectors is within the range 0°

to 30°

.

5. - Antenna system according to any of the preceding claims wherein at least a portion of at least one radiating element features a shape selected from the group comprising:

space-filling curve, grid-dimension curve, multilevel, or fractal.

7. - Antenna system according to any of the preceding claims wherein in each antenna array the first and the second set of radiating elements are arranged in two substantially parallel columns and in several substantially parallel rows, wherein in each column at least some elements of the first and second set of radiating elements are interlaced, so that each radiating element is vertically and horizontally adjacent to respective radiating elements of the other set of radiating elements.

8. - Antenna system according any of the claims 1 to 6 wherein the first and the second set of radiating elements of each antenna array are aligned in a single column, wherein the radiating elements of the first and the second set are grouped together forming respectively a first and a second sub arrays one on top of each other in a stacked arrangement, such that the distance between the center to center of each sub array is larger than one operating wavelength.

9. - Antenna system according to any of the preceding claims wherein each antenna array comprises at least one phase-shifter device providing an adjustable electrical downtilt for each frequency band, the phase shifter having an electrical path of variable length.

10. - Antenna system according to claim 9 wherein the phase-shifter comprises a first transmission line electrically connected and slideably mounted on a second transmission line.

11. - Antenna system according to any of the preceding claims wherein the antenna includes a substantially cylindrical radome of a dielectric material, said dielectric material being substantially transparent within the 1700-2700 MHz frequency range, the antenna arrays being housed within said radome.

12. - Antenna system according to any of the preceding claims wherein it is mounted on an elongated support of adjustable height.

6. - Antenna system wherein each radiating element is a patch antenna having a perimeter of the element structure shaped with a curve of at least 5 segments, being said segments smaller than the longest operating wavelength (λ

) divided by 5.

13. - Antenna system wherein the support is formed by one or more modular support sections axially coupled.

14. - Antenna system wherein the support comprises hinge, folding or retracting means, so that the support can be retracted or folded.

15. - A multiband antenna array for cellular base station antennas, said antenna array operating at a first and a second frequency bands within the 1700 MHz-2700 MHz frequency range, the ratio between the largest and the smaller of said frequency bands being smaller than 1.28, said antenna array featuring a width smaller than one and a half times the longer operating wavelength, said array including a set of small radiating elements, said elements being smaller one half of the longest operating wavelength, wherein said set of elements include a first subset of elements, a first subset operating at the first frequency band, the second subset operating at the second frequency band, wherein the elements of the first and second frequency bands are spatially interlaced such that the spacing between them is between ½

and ⅓

of the operating wavelength, and wherein at least a portion of the radiating elements feature a shape selected from the following group;

space-filling curve, grid-dimension curve, multilevel, fractal.

16. - A method for reducing the environmental and visual impact of a network of cellular or wireless base station antennas, consisting on combining one or more of the narrow width multiband antenna arrays described in claim 15.

17. - A method for reducing the environmental and visual impact of a network of cellular or wireless base station antennas, comprising the step of combining one or more of the narrow width multiband antenna arrays described in claim 15.

18. - A multiband antenna array for cellular base station, said antenna array adapted to operate at a first frequency band and at a second frequency band, the ratio between the largest and the smaller of said frequency bands being smaller than 2, said antenna array including a first set of radiating elements operating at said first frequency band and a second set of radiating elements operating at said second frequency band, said radiating elements being smaller than half a wavelength (λ

/2) or smaller than λ

/3 of the longest operating wavelength.

19. - Antenna array according to claim 18 wherein the ratio between the largest and the smaller of said frequency bands is smaller than 1.5 or smaller than 1.28.

20. - Antenna array according to claims 18 or 19 wherein the radiating elements of the first and second set of radiating elements are arranged in two parallel columns wherein the said radiating elements are spatially interlaced.

21. - Antenna array according to claim 20 wherein a horizontal spacing is defined between the radiating elements of the first and second set of frequency bands, wherein said spacing is between ½

and ⅓

of the operating wavelength (λ

).

22. - Antenna array according to any of the claims 18 to 21 wherein at least a portion of said radiating elements feature a shape selected from the group comprising:

a space-filling curve, a grid-dimension curve, a multilevel or fractal.

23. - Antenna array according to any of the claims 18 to 22 wherein each radiating element is a patch antenna or a dipole antenna, having a perimeter or at least a portion of the structure shaped with a curve of at least five segments, being said segments smaller than the longest operating wavelength divided by 5.

24. - Antenna array according to any of the claims 18 to 23 wherein at least a portion of the antenna is defined by a curve having a box-counting dimension or grid dimension larger than 1.1, or 1.2, or 1.3.

25. - Antenna array according to any of the claims 18 to 24 wherein it comprises at least one phase-shifter providing a variable down-tilt for at least one frequency band.

26. - Antenna array according to any of the claims 18 to 25 wherein the phase-shifter comprises a first transmission line slideably mounted on a second transmission line.

27. - Antenna array according to any of the claims 18 to 26 wherein the phase-shifter comprises a first transmission line on a first substrate, and a second transmission line on a second substrate, being the said first substrate mounted onto the said second substrate so that there is a region in which at least a portion of the said first transmission line is in the projection of at least a portion of the said second transmission line, and wherein the said first substrate can slide along a direction contained in the plane defined by the said second substrate so that the extension of said region is varied.

28. - Antenna array according to any of the claims 18 to 26 wherein the vertical spacing between radiating elements is less than one wavelength λ

, or less than ¾

of λ

, or less than ⅔

of λ

at all frequencies of operation.

29. - Antenna array according to any of the claims 18 to 28 wherein at least one of the radiating elements is housed within a box-like ground plane.

30. - Antenna array according to any of the claims 18 to 29 wherein at least one row of radiating elements has a discontinued ground-plane.

31. - Antenna array according to any of the claims 18 to 30 wherein a first and a second frequency bands are within the 1700 MHz-2700 MHz frequency range.

32. - Antenna array according to any of the claims 18 to 31 wherein said antenna array features a width smaller than two wavelengths, or one and a half times the longer operating wavelength, or 1.4λ

, or 1.3λ

. or less than 1λ

for any of the operating bands.

33. - An antenna system comprising three antenna arrays according to any of the claims 18 to 32, wherein the three antennas arrays are housed within a cylindrical radome.

34. - Antenna system according to claim 33 wherein three equal circular sectors are defined within said cylindrical radome, and wherein each antenna array is longitudinal placed within one of said circular sector, the angular spacing between sectors is approximately 20°

.

35. - Antenna system according to claim 33 wherein three equal circular sectors are defined within said cylindrical radome, and wherein each antenna array is longitudinal placed within one of said circular sectors, and wherein there is approximately no angular spacing between sectors.

36. - Antenna system according to any of the claims 34 to 35 wherein each antenna array comprises a ground plane, the ground plane defines an horizontal central portion and two side flanges, wherein each flange defines an angle approximately equal to α

, wherein α

=30+A/2, and wherein A is the angular spacing between two adjacent circular sectors.

37. - A dual-band dual-polarized radiating system for a cellular base station, said radiating system including three antenna arrays radially displaced from a common mounting structure, wherein said three antenna arrays are symmetrically placed within three 120°

angular sectors around said common mounting structure, wherein an angular spacing between antennas is provided such as to allow independent azimutal mechanical tilt for each sector, wherein each of said three arrays is composed by at least two sub-arrays operating at a first and at a second frequency band respectively, wherein said first and a second frequency bands within are selected within the 1700 MHz-2700 MHz frequency range, the ratio between the largest and the smaller of said frequency bands being smaller than 1.28, wherein said at least two subarrays operating at two different frequency bands are colinearly aligned one on top of each other in a stacked arrangement such that the distance between the center to center of each sub array is larger than one operating wavelength,

wherein each of said three antenna array features a width smaller than one and a half times the longest operating wavelength, and a thickness smaller than half times the longer operating wavelength, wherein each of said three arrays includes a set of compact radiating elements, wherein said elements are smaller than one half of the longest operating wavelength,

wherein at least one of said sub-arrays operating at different frequencies includes a set of compact phase shifters for featuring variable electrical downtilt, wherein at least one phase shifter feeds two radiating elements together through a power splitter network,

wherein the whole radiating system is covered by a cylindrical radome of a dielectric material, said dielectric material being substantially transparent within the 1700-2700 MHz frequency range.

38. - A dual-band polarized radiating system according to claim 37 wherein at least a portion of at least one radiating element features a shape selected from the following group:

space-filling curve, grid-dimension curve, multilevel, fractal.

39. - A radiating system according to claim 37, wherein the three antenna arrays are spaced in azimuth by an angle spacing ranging from 0°

to 30°

.

40. - A radiating system according to claim 37, wherein said system is supported by a set multiple modular sections, said sections being mounted in a colinearly stacked fashion to form a longer tower section.

41. - A radiating system according to claims 37, 38, 39, or 40 wherein the tower supporting the radiating system includes a hinge at its base, such that the whole tower can be bent to install, upgrade or repare such a radiating system.

42. - A mobile telecommunication network including one or more radiating systems according to claim 37, said network co-allocating multiple services operating at least at two different frequency bands within the 1700 to 2700 MHz frequency range, wherein the coverage and capacity of the network is independently adjusted at each of said at least two frequency bands by means of adjusting the phase shifters included in the sub-arrays of said radiating system.

43. - A method for reducing the deployment and maintenance cost of a mobile telecommunication network consisting on deploying a substantial part of the sites of the network with the radiating systems according to claims 37 through 42.

44. - A method for reducing the deployment and maintenance cost of a mobile telecommunication network comprising the step of deploying a substantial part of the sites of the network with the radiating systems according to claims 37 through 42.

45. - A dual-band dual-polarized radiating system for a cellular base station, said radiating system including at least three antenna arrays radially displaced from a central common mounting structure, wherein said three antenna arrays are symmetrically placed within three 120°

angular sectors around said central common mounting structure, wherein each of the said three arrays comprises at least two sub-arrays adapted to operate at a first and at a second frequency band respectively, wherein said first and a second frequency bands are selected within the 1700 MHz-2700 MHz frequency range, the ratio between the largest and the smaller of said frequency bands being smaller than 2, wherein each of the said at least three arrays includes a set of small radiating elements, wherein said elements are smaller than (λ

/2) or smaller than (λ

/3) of the longest operating wavelength (λ

).

46. - Radiating system according to claim 45 wherein the ratio between the largest and the smaller of said frequency bands is smaller than 1.6, 1.5, 1.4 or 1.3 wavelengths.

47. - Radiating system according to claim 45 wherein said at least two subarrays operating at two different frequency bands are colinearly aligned one on top of each other in a stacked arrangement such that the distance between the center to center of each sub array is larger than one operating wavelength.

48. - Radiating system according to any of the claims 45 to 47 wherein at least one of said sub-arrays operating at different frequencies includes a set of phase shifters for featuring variable electrical downtilt, wherein at least one phase shifter feeds two radiating elements together through a power splitter network.

49. - Antenna array according to any of the claims 45 to 48 wherein the phase-shifter comprises a first transmission line slideably mounted on a second transmission line.

50. - Antenna array according to any of the claims 45 to 49 wherein the phase-shifter comprises a first transmission line on a first substrate, and a second transmission line on a second substrate, being the said first substrate mounted onto the said second substrate so that there is a region in which at least a portion of the said first transmission line is in the projection of at least a portion of the said second transmission line, and wherein the said first substrate can slide along a direction contained in the plane defined by the said second substrate so that the extension of said region is varied.