Handheld device with two antennas, and method of enhancing the isolation between the antennas

• US 20090262028A1
• Filed: 07/18/2006
• Published: 10/22/2009
• Est. Priority Date: 07/21/2005
• Status: Active Grant

• Current Assignee: Fractus SA
• Original Assignee: Fractus SA
• Inventors: Soler, Jordi, Anguera, Jaume, Mumbru, Josep, Puente, Carles
• Granted Patent: US 8,115,686 B2
• Time in Patent Office: Days
• US Class Current: 343/702
• CPC Class Codes: H01Q 1/243 with built-in antennas
• 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 1/52 Means for reducing coupling between antennas; Means for reducing coupling between an antenna and another structure absorbing means H01Q17/00
• CPC Class Codes: H01Q 1/521 reducing the coupling between adjacent antennas
• CPC Class Codes: H01Q 13/10 Resonant slot antennas
• CPC Class Codes: H01Q 13/106 Microstrip slot antennas patch antenna elements H01Q9/0407
• CPC Class Codes: H01Q 21/28 Combinations of substantially independent non-interacting antenna units or systems multiple beam H01Q25/00
• CPC Class Codes: H01Q 5/371 Branching current paths

Abstract

The invention relates to a handheld device comprising a first antenna (401, 701, 901, 931, 961, 1101, 1151, 1301, 1501) arranged to operate in at least a first frequency band, and a second antenna (402, 702, 902, 1102, 1302, 1502, 2210) arranged to operate in at least a second frequency band, wherein said second frequency band is different from said first frequency band. According to the invention, the second antenna comprises a slot antenna comprising at least one slot in at least one conductive layer. The invention also relates to enhancement of the isolation between first and second antennas in a handheld device.

Claims

1. A handheld device comprising:

at least one printed circuit board (400, 900, 1100, 1300, 1350, 1500, 2300),

a first antenna (401, 701, 901, 931, 961, 1101, 1151, 1301, 1501) arranged to operate in at least a first frequency band,

a second antenna (402, 702, 902, 1102, 1302, 1502, 2210) arranged to operate in at least a second frequency band,

wherein the said second frequency band is different from said first frequency band;

and wherein the said second antenna comprises a slot antenna comprising at least one slot in at least one conductive layer.

2. Handheld device according to claim 1, wherein said conductive layer is a conductive layer of said printed circuit board, so that said slot antenna (402, 702, 902, 1102, 1302, 1502) comprises at least one slot in said conductive layer of said printed circuit board.

3. Handheld device according to claim 1, wherein said at least one slot (2213) is embodied in a conductive layer (2211) of a surface mount technology component (2210) mounted on said printed circuit board (2300).

4. Handheld device according to claim 3, wherein said surface mount technology component comprises at least one contact terminal (2215) accessible from outside the component and arranged to electrically connect said conductive layer (2211) to a conductive layer of the printed circuit board (2300).

5. Handheld device according to any of claims 3-4, wherein the printed circuit board (2300) comprises a conductive layer forming at least part of a ground-plane of said hand-held device, said conductive layer (2211) of said surface mount technology component being arranged over said printed circuit board, whereby, within a first area defined by the orthogonal projection of the conductive layer (2211) of said surface mount component on said printed circuit board (2300), there is a second area of the printed circuit board in which there is no ground-plane, the projection of the slot (2213) on the printed circuit board being within said second area.

6. Handheld device according to claim 5, wherein said second area corresponds to at least 50% of said first area.

7. Handheld device according to claim 6, wherein said second area corresponds to at least 80% of said first area.

8. Handheld device according to any of the preceding claims, wherein said slot has a closed end (407, 2217) and an open end (2216), said open end being arranged in correspondence with a perimeter of said conductive layer, whereby said slot is not completely surrounded by conductive material in the plane or planes of said conductive layer.

9. Handheld device according to any of the preceding claims, wherein said second antenna comprises at least one feed point (408, 2214), said feed point being situated closer to said closed end than to said open end.

10. Handheld device according to any of claims 1-7, wherein said slot has two closed ends, whereby said slot is completely surrounded by conductive material in the plane or planes of said conductive layer.

11. Handheld device according to any of the preceding claims, wherein said second antenna comprises at least one feed point (408, 2214), said feed point being situated at a distance from a closed end of said slot less than, or equal to, a value selected from the group comprising 0.2%, 0.4%, 0,8%, 1.2%, 1.6%, 2.5%, 3.3%, 4% and 8% of a free-space operating wavelength of the second antenna.

12. Handheld device according to any of the preceding claims, wherein said slot antenna has a size so that it can be inscribed in a rectangle having a width (405) of less than 1/50 of a free-space operating wavelength of the slot antenna.

13. Handheld device according to any of the preceding claims, wherein said slot antenna has a size so that it can be inscribed in a rectangle having a length (404) of less than ¼

of a free-space operating wavelength of the slot antenna.

14. Handheld device according to any of the preceding claims, wherein said slot has an unfolded length corresponding to approximately (2N−

1)*A/4, where A is an operating wavelength of the second antenna and N is an integer, N>

1.

15. Handheld device according to any of claims 1-13, wherein said slot has an unfolded length corresponding to approximately (2N)*A/4, where A is an operating wavelength of the antenna and N is an integer, N>

1.

16. Handheld device according to any of the preceding claims, wherein said printed circuit board comprises a ground-plane having a generally rectangular configuration comprising two shorter sides and two longer sides, wherein said slot antenna comprises at least one slot extending in a direction substantially parallel to one of said longer sides.

17. Handheld device according to claim 16, wherein said first antenna is arranged extending in a direction substantially parallel to one of said shorter sides.

18. Handheld device according to claim 16 or 17, wherein said second antenna is arranged substantially at a center portion of one of said longer sides.

19. Handheld device according to any of claims 16-18, wherein said first antenna is arranged substantially adjacent to one of said shorter sides.

20. Handheld device according to any of claims 16-19, wherein said second antenna has a longitudinal extension substantially parallel to one of said longer sides.

21. Handheld device according to any of the preceding claims, said handheld device further comprising at least one slot (1304) in a ground-plane of said printed circuit board, said slot being arranged for providing enhanced isolation between a feeding point of said first antenna and a feeding point of said second antenna, by providing a high impedance path in said ground-plane between said feeding points, at at least one frequency band corresponding to an operating band of one of said first and second antennas.

22. Handheld device according to claim 21, wherein said slot (1304) in the ground-plane has en open end in correspondence with a perimeter of said ground-plane.

23. Hand-held device according to any of claims 21-22, wherein said slot in the ground-plane has a length of approximately (2N−

1)*A/4, wherein A is a wavelength corresponding to a frequency within said operating band, and N is an integer, N>

1.

24. Hand-held device according to any of claims 21-23, wherein said at least one slot in said ground-plane comprises a plurality of said slots, said slots having different lengths for providing enhanced isolation between said feeding points at a plurality of frequency bands.

25. Handheld device according to any of the preceding claims, further comprising at least one conductive strip (1354) arranged on a ground-plane of the printed circuit board, said conductive strip being connected to the ground-plane at at least one point.

26. Handheld device according to claim 25, said conductive strip being connected to the ground-plane by one end of said conductive strip.

27. Handheld device according to any of claims 25 and 26, said conductive strip being arranged so as to provide a high impedance path in said ground-plane between a feeding point of said first antenna and a feeding point of said second antenna, at at least one frequency band corresponding to an operating band of one of said antennas.

28. Hand-held device according to any of claims 25-27, wherein said conductive strip has a length, from its connection to the ground-plane, of approximately (2N−

1)*A/4, wherein A is a wavelength corresponding to a frequency within said operating band, and N is an integer, N>

1.

29. Handheld device according to any of claims 25-28, comprising a plurality of said strips, said strips having different lengths.

30. Handheld device according to any of the preceding claims, wherein a conductive strip (1504) is arranged between said first antenna and said second antenna so as to provide an electromagnetic shielding between said antennas at at least one frequency band corresponding to an operating band of one of said antennas.

31. Handheld device according to claim 30, wherein said conductive strip has a length of N*A/2, wherein A is a wavelength corresponding to a frequency within said operating band, and N is an integer, N>

1.

32. Handheld device according to any of the preceding claims, wherein said first antenna comprises a slot having a length selected so as not to substantially radiate at a frequency within an operating band of the second antenna.

33. Handheld device according to any of the preceding claims, wherein said first antenna comprises a radiating arm, the length of which is chosen so that said radiating arm does not radiate within an operating band of the second antenna.

34. Handheld device according to any of the preceding claims, wherein said first antenna and said second antenna are arranged on a printed circuit board of the hand-held device, said first antenna being substantially arranged at one end of said printed circuit board and said second antenna being substantially arranged at a second end of said printed circuit board, opposite to said first end.

35. Handheld device according to any of the preceding claims, wherein at least one of said first and said second antenna comprises at least one portion of conductive material shaped as a space-filling curve.

36. Handheld device according to any of the preceding claims, wherein at least one of said first and said second antenna comprises at least one portion of conductive material shaped as a box-counting curve, having a box-counting dimension larger than 1.1.

37. Handheld device according to claim 36, said box-counting curve having a box-counting dimension larger than 1.5.

38. Handheld device according to any of the preceding claims, wherein at least one of said first and said second antenna comprises at least one portion of conductive material shaped as a grid-dimension curve, having a grid dimension larger than 1.1.

39. Handheld device according to claim 38, said grid dimension curve having a grid dimension larger than 1.5.

40. Handheld device according to any of claims 35-39, wherein said portion comprises at least one part of a slot of the second antenna.

41. Handheld device according to any of claims 35-40, wherein said portion comprises at least one part of the first antenna.

42. Handheld device according to any of the preceding claims, wherein said first antenna is an antenna selected from the group comprising a monopole antenna, an inverted-F antenna, a patch antenna and a planar inverted-F antenna.

43. Handheld device according to any of the preceding claims, wherein said first antenna is not a slot antenna.

44. Handheld device according to any of the preceding claims, said hand-held device comprising at least two ground-planes, one of said ground-planes being slidably connected to the other ground-plane so that the position of one of said ground-planes with regard to the other ground-plane can be modified by sliding one of said ground-planes with respect to the other one of said ground-planes, whereby said first antenna and said second antenna are placed in correspondence with one of said ground-planes (400, 900, 1100, 1300, 1500).

45. Handheld device according to any of the claims 1-43, said hand-held device comprising at least two ground-planes, one of said ground-planes being pivotally connected to the other ground-plane so that the position of one of said ground-planes with regard to the other ground-plane can be modified by pivoting one of said ground-planes with respect to the other one of said ground-planes, whereby said first antenna and said second antenna are placed in correspondence with one of said ground-planes (400, 900, 1100, 1300, 1500).

46. Handheld device according to any of the preceding claims, said handheld device being a mobile telephone.

47. Handheld device according to any of the preceding claims, wherein the first antenna is arranged to operate in at least one frequency band used for mobile communication services, selected from the group comprising GSM, UMTS, WCDMA and or CDMA.

48. Handheld device according to any of the preceding claims, wherein said first antenna is arranged for operating in accordance with at least one mobile communication standard allocated within at least one frequency band, each such frequency band being fully contained within one of the following regions of the electromagnetic spectrum:

the 810 MHz-960 MHz region,

the 1710 MHz-1990 MHz region,

and the 1900 MHz-2170 MHz region.

49. Handheld device according to any of the preceding claims, wherein said second antenna is arranged to operate in at least one frequency band used for a wireless service in accordance with Bluetooth™

, IEEE802.11a, IEEE802.11b, IEEE802.11g, WLAN, WiFi, UWB, ZigBee, GPS, Galileo, SDARs, XDARS, WiMAX, DAB, FM, DVB-H, or DMB.

50. Handheld device according to any of the preceding claims, wherein said second antenna is arranged for operating in at least one frequency band fully contained within one of the following regions of the electromagnetic spectrum:

the 902 MHz-928 MHz region,

the 2400 MHz-2500 MHz region,

the 5650 MHz-5925 MHz.

51. Handheld device according to any of the preceding claims, wherein the first antenna is arranged to substantially behave as an electric current source and wherein said second antenna is arranged to substantially behave as a magnetic current source, said first and second antennas being oriented so that during operation of the antennas, electric currents excited on at least a portion of said conductive layer by said first antenna are substantially parallel to equivalent magnetic currents excited on at least a portion of said second antenna.

52. Handheld device according to any of claims 1-50, wherein the first antenna is arranged to substantially behaves as a magnetic current source and wherein said second antenna is arranged to substantially behave as a magnetic current source, said first and second antennas being oriented so that during operation of the antennas, magnetic currents excited on at least a portion of said first antenna are substantially orthogonal to magnetic currents excited on at least a portion of said second antenna.

72. Method according to any of claims 54-71, said handheld device being a handheld device according to any of claims 1-53.

73. Use of said slot antenna in a handset according to any of claims 1-53, for providing a wireless connectivity function.

74. Use of said slot antenna in a handset according to any of claims 1-53, for providing an antenna set in which said first antenna radiates with a first polarization and said second antenna radiates with a second polarization substantially orthogonal to said first polarization.

53. A handheld device comprising:

a first antenna operating in at least a first frequency band,

a second antenna operating in at least a second frequency band,

a printed circuit board including a ground plane,

wherein the said second frequency band is different from the said first frequency band;

wherein the said first antenna is selected from the group consisting essentially of monopole antenna, IFA, patch antenna, and PIFA;

wherein the said second antenna comprises a slot antenna, wherein the said slot antenna is included in the ground plane of the said printed circuit board,

wherein the longest straight segment of the slot is substantially parallel to the longest edge of the said printed circuit board, wherein one open end of the slot is in contact with one edge of the said printed circuit board;

wherein the width of the rectangular area in which the said slot antenna is inscribed, divided by a free-space operating wavelength of the said slot antenna is smaller than, or equal to, at least one of the following fractions;

1/10, 1/30, 1/50, 1/60, 1/70, or 1/80;

wherein the length of the rectangular area in which the said slot antenna is inscribed, divided by a free-space operating wavelength of the said slot antenna is smaller than, or equal to, at least one of the following fractions;

½

, ⅓

, or ¼

;

wherein the said handheld device is a mobile handset, operating in at least one of the following mobile communication and wireless connectivity services;

GSM (GSM850, GSM900, GSM1800, American GSM or PCS1900, GSM450), UMTS, WCDMA, CDMA, Bluetooth™

, IEEE802.11ba, IEEE802.11b, IEEE802.11g, WLAN, WiFi, UWB, ZigBee, GPS, Galileo, SDARs, XDARS, WiMAX, DAB, FM, DMB.

54. Method of improving isolation between a first antenna and a second antenna in a handheld device, characterized in that it comprises modifying a radiating portion of at least one of said antennas so as to prevent said radiating portion from substantially radiating within an operating band of another one of said antenna.

55. Method according to claim 54, involving the step of modifying the length of a slot (903, 933) by shortening a radiating arm (904, 934) adjacent to said slot.

56. Method according to claim 54, involving the step of modifying the length of a slot (903, 963) by modifying the shape of a radiating arm (904, 964) adjacent to said slot.

57. Method according to claim 54, involving the step of modifying the length of a slot by shaping the slot (1003) as a meander-like curve.

58. Method according to claim 54, involving the step of modifying the length of a slot by adding a conductive strip (1154) inside the aperture of the slot.

59. Method of improving isolation between a first antenna and a second antenna of a handheld device, by establishing at least one slot (1304) in a ground-plane of said handheld device, so as to provide for enhanced isolation between a feeding point of said first antenna and a feeding point of said second antenna, by providing a high impedance path in said ground-plane between said feeding points, at at least one frequency band corresponding to an operating band of one of said first and second antennas.

60. Method according to claim 59, wherein said slot (1304) in the ground-plane is arranged so as to have en open end in correspondence with a perimeter of said ground-plane.

61. Method according to any of claims 59-60, wherein said slot in the ground-plane is arranged so as to have a length of approximately (2N−

1)*A/4, wherein A is a wavelength corresponding to a frequency within said operating band, and N is an integer, N>

1.

62. Method according to any of claims 59-61, wherein said establishing said at least one slot in said ground-plane comprises the step of establishing a plurality of said slots, said slots having different lengths for providing enhanced isolation between said feeding points at a plurality of frequency bands.

63. Method of improving isolation between a first antenna and a second antenna of a handheld device, comprising the step of providing at least one conductive strip (1354) arranged on a ground-plane of said hand-held device, and connecting said conductive strip being to the ground-plane at at least one point.

64. Method according to claim 63, wherein said conductive strip is connected to the ground-plane by one end of said conductive strip.

65. Method according to any of claims 63-64, wherein said conductive strip is arranged so as to provide a high impedance path in said ground-plane between a feeding point of said first antenna and a feeding point of said second antenna, at at least one frequency band corresponding to an operating band of one of said antennas.

66. Method device according to any of claims 63-65, wherein said conductive strip has an effective length, from its connection to the ground-plane, of approximately (2N−

1)*A/4, wherein A is a wavelength corresponding to a frequency within said operating band, and N is an integer, N>

1.

67. Method according to any of claims 63-66, comprising connecting a plurality of said strips to said ground-plane, said strips having different lengths, so as to provide for enhanced isolation at a plurality of frequency bands.

68. Method of improving isolation between a first antenna and a second antenna of a handheld device, comprising the step of arranging a conductive strip (1504) between said first antenna and said second antenna so as to provide an electromagnetic shielding between said antennas at at least one frequency band corresponding to an operating band of one of said antennas.

69. Method according to claim 68, wherein said conductive strip has a length of N*λ

/2, wherein A is a wavelength corresponding to a frequency within said operating band, and N is an integer, N>

1.

70. Method of improving isolation between a first antenna and a second antenna of a handheld device, said second antenna being a slot antenna, comprising the step of arranging said slot antenna so that it extends in a longitudinal direction substantially parallel to a longer side of a substantially rectangular ground-plane of said handheld device.

71. Method of improving isolation between a first antenna and a second antenna of a handheld device, said second antenna being a slot antenna, comprising the step of arranging said first antenna to radiate with a first polarization and said second antenna to radiate with a second polarization substantially orthogonal to said first polarization.