Antenna Assembly and a Method for Satellite Tracking

• US 20070290936A1
• Filed: 10/19/2005
• Published: 12/20/2007
• Est. Priority Date: 11/04/2004
• Status: Active Grant

• Current Assignee: Spacecom Holding ApS
• Original Assignee: Spacecom Holding ApS
• Inventors: Nielsen, Peter
• Granted Patent: US 7,492,323 B2
• Time in Patent Office: Days
• US Class Current: 343/758
• CPC Class Codes: H01Q 1/125 Means for positioning
• CPC Class Codes: H01Q 1/18 Means for stabilising antennas on an unstable platform
• CPC Class Codes: H01Q 21/28 Combinations of substantially independent non-interacting antenna units or systems multiple beam H01Q25/00
• CPC Class Codes: H01Q 3/08 for varying two co-ordinates of the orientation

Abstract

The present invention relates to a method for satellite tracking by use of an antenna assembly having a master antenna for receiving and transmitting first satellite signals to and from a first satellite called master antenna satellite in a first frequency band, and a slave antenna for receiving second satellite signals from a second satellite called slave antenna satellite in a second satellite band, where the master and slave antennas have physical bore-sight axes which can be arranged at different directions in relation to each other. The method of the invention includes a master antenna search routine and a slave antenna search routine. The master antenna search routine comprises the steps of changing or switching a direction of reception of the master antenna, monitoring, during the changing or switching of direction of reception of the master antenna, one or more signals carrying information representing variations in receiving signal strength of one or more signals transmitted from the master antenna satellite, and mechanically moving the master antenna in response to the results of the monitoring of the signal strength information signal(s) corresponding to the signal(s) from the master antenna satellite, thereby obtaining a direction of the physical bore-sight axis of the master antenna resulting in reduced pointing errors of the master antenna in relation to the master antenna satellite. The slave antenna search routine comprises the steps of arranging the direction of the physical bore-sight axis of the slave antenna at a first slave direction, where the first slave direction is at least partly based on the obtained direction of the physical bore-sight axis of the master antenna. It is preferred that following the arrangement of the physical bore-sight axis of the slave antenna at the first slave direction, the slave antenna search routine further comprises changing or switching a direction of reception of the slave antenna, monitoring, during the changing or switching of direction of reception of the slave antenna, one or more signals carrying information representing variations in receiving signal strength of one or more signals transmitted from the slave antenna satellite, and mechanically moving the slave antenna in response to the results of the monitoring of the signal strength information signal(s) corresponding to the signal(s) from the slave antenna satellite, thereby changing the direction of a physical bore-sight axis of the slave antenna so as to reduce pointing errors of the slave antenna in relation to the slave antenna satellite.

Claims

1-42. -42. (canceled)

43. An antenna assembly for satellite tracking, said antenna assembly comprising:

a master antenna for receiving and transmitting first satellite signals to and from a master antenna satellite in a first frequency band,

a slave antenna for receiving second satellite signals from a slave antenna satellite in a second satellite band, said master and slave antennas being mounted on the same stabilizing platform,

a master drive assembly for mechanically changing the direction of a physical bore-sight axis of the master antenna, and

a slave drive assembly for mechanically changing the direction of a physical bore-sight axis of the slave antenna,

wherein said master and slave assemblies are adapted for arranging the physical bore-sight axes of the master antenna and the slave antenna at different directions in relation to each other in response to one or more master-slave control signals,

wherein the antenna assembly further comprises control means for providing one or more master-slave control signals to the slave drive assembly to thereby control the arrangement of the direction of the physical bore-sight axis of the slave antenna in relation to the physical bore-sight axis of the master antenna so that the angular distance in azimuth between said physical bore-sight axes is set at a given azimuth value, ALPHA(AZ), and

wherein the control means for providing the one or more master-slave controls signals to the slave drive assembly is further adapted for providing control signals to thereby control the arrangement of the direction of the physical bore-sight axis of the slave antenna so that the angular distance in elevation between the physical bore-sight axis of the slave antenna and the horizontal plane is set at a given elevation value, ALPHA(ELS).

44. An antenna assembly according to claim 43, wherein the master antenna is mounted on the slave antenna with the slave antenna being mounted to the stabilizing platform.

45. An antenna assembly according to claim 43, wherein the slave antenna is further adapted for transmitting second satellite signals to the slave antenna satellite in the second satellite band.

46. An antenna assembly according to claim 43, wherein the master antenna is movably secured to the master drive assembly, and the slave antenna is movably secured to the slave drive assembly.

47. An antenna assembly according to claim 43, wherein the master drive assembly is rigidly fixed in relation to the slave antenna.

48. An antenna assembly according to claim 43, further comprising master antenna switching means for changing or switching a direction of reception of the master antenna.

49. An antenna assembly according to claim 48, wherein the master antenna switching means is adapted for performing a mechanically changing or switching of the direction of the physical bore-sight axis of the master antenna followed by an electrically changing or switching of the direction of reception of the master antenna.

50. An antenna assembly according to claim 49, wherein the master antenna is an array antenna.

51. An antenna assembly according to claim 50, wherein the master antenna switching means is adapted for performing the electrically changing or switching of the direction of reception of the master antenna by use of beam switching or beam squint technology.

52. An antenna assembly according to claim 48, further comprising monitor means for monitoring, during the changing or switching of direction of reception of the master antenna, one or more signals carrying information representing variations in receiving signal strength of one or more signals transmitted from the master antenna satellite.

53. An antenna assembly according to claim 52, further comprising control means for providing one or more master control signals to the master drive assembly and/or the slave drive assembly to thereby control the movement of the master antenna in response to the results of the monitoring of the signal strength information signal(s) corresponding to the signal(s) from the master antenna satellite, thereby changing the direction of the physical bore-sight axis of the master antenna so as to reduce pointing errors of the master antenna in relation to the master antenna satellite.

54. An antenna assembly according to claim 43, further comprising slave antenna switching means for changing or switching a direction of reception of the slave antenna.

55. An antenna assembly according to claim 54, wherein the slave antenna switching means is adapted for performing a mechanically changing or switching of the direction of the physical bore-sight axis of the slave antenna,

56. An antenna assembly according to claim 55, wherein the slave antenna switching means is adapted for performing the mechanically changing or switching of the direction of the physical bore-sight axis of the slave antenna as a so-called step track switching.

57. An antenna assembly according to claim 54, further comprising monitor means for monitoring, during the changing or switching of direction of reception of the slave antenna, one or more signals carrying information representing variations in receiving signal strength of one or more signals transmitted from the slave antenna satellite.

58. An antenna assembly according to claim 57, further comprising control means for providing one or more slave control signals to the slave drive assembly and/or the master drive assembly to thereby control the movement of the slave antenna in response to the results of the monitoring of the signal strength information signal(s) corresponding to the signal(s) from the slave antenna satellite, thereby changing the direction of the physical bore-sight axis of the slave antenna so as to reduce pointing errors of the slave antenna in relation to the slave antenna satellite.

59. An antenna assembly according to claim 47, further comprising one or more control systems being adapted for providing control signals to the master and slave drive assemblies in order to lock the physical bore-sight axes of the master antenna and the slave antenna in the same vertical plane, whereby when mechanically moving the master antenna to change the direction in azimuth of the physical bore-sight axis of the master antenna, the direction of the physical bore-sight axis of the slave antenna is mechanically changed to the same degree in azimuth.

60. An antenna assembly according to claim 43, wherein the slave drive assembly is adapted for rotating or turning the physical bore-sight axis of the slave antenna in the azimuth direction by use of a slave azimuth axis, and for rotating or turning the physical bore-sight axis of the slave antenna in the elevation direction by use of a first slave elevation axis.

61. An antenna assembly according to claim 60, wherein the slave drive assembly is further adapted to maintain the first slave elevation axis in a substantial horizontal position by rotating the first slave elevation axis by use of a second slave elevation axis arranged perpendicular to the first slave elevation axis, said second slave elevation axis being a slave cross elevation axis.

62. An antenna assembly according to claim 43, wherein the master drive assembly is adapted for rotating or turning the physical bore-sight axis of the master antenna in the azimuth direction by use of a master azimuth axis, and for rotating or turning the physical bore-sight axis of the master antennae in the elevation direction by use of a first master elevation axis.

63. An antenna assembly according to claim 62, wherein the master drive assembly is further adapted to maintain the master azimuth axis in a substantial vertical position by rotating the master azimuth axis by use of a second master elevation axis arranged perpendicular to the first master elevation axis, said second master elevation axis being a master counter elevation axis.

64. An antenna assembly according to claim 63, further comprising a censor system adapted to provide control signals to the slave drive assembly in order to control rotating about the second slave elevation axis to thereby maintain the first slave elevation axis in a substantially horizontal position during a movement of the antenna assembly.

65. An antenna assembly according to claim 64, wherein the censor system is further adapted to provide one or more control signals to the master drive assembly in order to control rotating about the second master elevation axis to thereby maintain the first master azimuth axis in a substantial vertical position during a movement of the antenna assembly.

66. An antenna assembly according to claim 43, wherein the slave antenna comprises a main reflector for reflecting said slave antenna satellite signals and a feed unit for receiving the reflected slave antenna satellite signals.

67. An antenna assembly according to claim 66, wherein the slave antenna is of the Cassegrain type having a sub-reflector arranged substantially inside the focus of the main reflector, and having the feed unit arranged substantially at the surface of the main reflector.

68. An antenna assembly according to claim 67, wherein the master drive assembly is arranged at least partly at a blind spot of the slave antenna in front of the sub-reflector.

69. An antenna assembly according to claim 43, wherein the second satellite signals in the second frequency band are transmitted in the X or K band.

70. An antenna assembly according to claim 43, wherein the first satellite signals in the first frequency band are transmitted in the L or S band.

71. A method for satellite tracking by use of an antenna assembly having a master antenna for receiving and transmitting first satellite signals to and from a master antenna satellite in a first frequency band, and a slave antenna for receiving second satellite signals from a slave antenna satellite in a second frequency band, said master and slave antennas being mounted on the same stabilizing platform and having physical bore-sight axes which can be arranged at different directions in relation to each other, said method including:

a) a master antenna search routine comprising the steps of;

changing or switching a direction of reception of the master antenna,

monitoring, during the changing or switching of direction of reception of the master antenna, one or more signals carrying information representing variations in receiving signal strength of one or more signals transmitted from the master antenna satellite, and

mechanically moving the master antenna in response to the results of the monitoring of the signal strength information signal(s) corresponding to the signal(s) from the master antenna satellite, thereby obtaining a direction of the physical bore-sight axis of the master antenna resulting in reduced pointing errors of the master antenna in relation to the master antenna satellite; and

b) a slave antenna search routine comprising the steps of;

arranging the direction of the physical bore-sight axis of the slave antenna at a first slave direction,

wherein the arrangement of the direction of the physical bore-sight axis of the slave antenna at the first slave direction comprises arranging the angular distance in azimuth between the physical bore-sight axes of the master antenna and the slave antenna at a given azimuth value, and

wherein the arrangement of the direction of the physical bore-sight axis of the slave antenna at the first slave direction further comprises arranging the angular distance in elevation between the physical bore-sight axis of the slave antenna and the horizontal plane at a given elevation value, ALPHA(ELS),

said given azimuth value and said given elevation value being determined from the obtained direction of the physical bore-sight axis of the master antenna, the orbital position of the master antenna satellite, the orbital position of the slave antenna satellite, and the geographical position of the antenna assembly.

72. A method according to claim 71, wherein the master antenna is mounted on the slave antenna with the slave antenna being mounted to the stabilizing platform.

73. A method according to claim 71, wherein after the arrangement of the physical bore-sight axis of the slave antenna at the first slave direction, the slave antenna search routine further comprises:

changing or switching a direction of reception of the stave antenna,

monitoring, during the changing or switching of direction of reception of the slave antenna, one or more signals carrying information representing variations in receiving signal strength of one or more signals transmitted from the slave antenna satellite, and

mechanically moving the slave antenna in response to the results of the monitoring of the signal strength information signal(s) corresponding to the signal(s) from the slave antenna satellite, thereby changing the direction of a physical bore-sight axis of the slave antenna so as to reduce pointing errors of the slave antenna in relation to the slave antenna satellite.

74. A method according to claim 71, said method further including an initial setting routine being performed before the master antenna search routine, said initial setting routine comprising:

locking the physical bore-sight axes of the master antenna and the slave antenna in the same vertical plane, whereby when mechanically moving the master antenna to change the direction in azimuth of the physical bore-sight axis of the master antenna, the direction of the physical bore-sight axis of the slave antenna is mechanically changed to the same degree in azimuth, said locking being maintained during the master search routine.

75. A method according to claim 74, wherein the initial setting routine comprises arranging and maintaining the physical bore-sight axis of the slave antenna at a substantially horizontal position.

76. A method according to claim 75, wherein the initial setting routine further comprises arranging and maintaining the physical bore-sight axis of the master antenna at a substantially horizontal position.

77. A method according to claim 71, wherein the changing or switching of the direction of reception of the master antenna in the master antenna search routine comprises a mechanically changing or switching of the direction of the physical bore-sight axis of the master antenna followed by an electrically changing or switching of the direction of reception of the master antenna.

78. A method according to claim 77, wherein the electrically changing or switching of the direction of reception of the master antenna is initiated when one or more signals transmitted from the master antenna satellite are received by a given signal strength.

79. A method according to claim 77, wherein the master antenna is an array antenna and the electrically changing or switching of the direction of reception of the master antenna is performed using beam switching or beam squint technology.

80. A method according to claim 73, wherein the changing or switching of the direction of reception of the slave antenna in the slave antenna search routine comprises a mechanically changing or switching of the direction of the physical bore-sight axis of the slave antenna.

81. A method according to claim 80, wherein the mechanically changing or switching of the direction of the physical bore-sight axis of the slave antenna is performed as a so-called step track switching.

82. A method according to claim 71, wherein the slave antenna comprises a main reflector for reflecting said slave antenna satellite signals and a feed unit for receiving the reflected slave antenna satellite signals.

83. A method according to claim 82, wherein said slave antenna is of the Cassegrain type having a sub-reflector arranged substantially inside the focus of the main reflector, and having the feed unit arranged substantially at the surface of the main reflector.

84. A method according to claim 83, wherein the master antenna is movably secured to a master drive assembly being arranged at least partly at a blind spot of the slave antenna in front of the sub-reflector.

85. A method according to claim 71, wherein the second satellite signals in the second frequency band are transmitted in the X or K band.

86. A method according to claim 71, wherein the first satellite signals in the first frequency band are transmitted in the L or S band.