WO2001035494A1 - Faisceaux terrestres générés à partir d'un véhicule spatial - Google Patents
Faisceaux terrestres générés à partir d'un véhicule spatial Download PDFInfo
- Publication number
- WO2001035494A1 WO2001035494A1 PCT/US2000/027998 US0027998W WO0135494A1 WO 2001035494 A1 WO2001035494 A1 WO 2001035494A1 US 0027998 W US0027998 W US 0027998W WO 0135494 A1 WO0135494 A1 WO 0135494A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- earth
- energy beams
- space vehicle
- beams
- beam forming
- Prior art date
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Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q3/00—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system
- H01Q3/26—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture
- H01Q3/2605—Array of radiating elements provided with a feedback control over the element weights, e.g. adaptive arrays
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q1/00—Details of, or arrangements associated with, antennas
- H01Q1/27—Adaptation for use in or on movable bodies
- H01Q1/28—Adaptation for use in or on aircraft, missiles, satellites, or balloons
- H01Q1/288—Satellite antennas
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q25/00—Antennas or antenna systems providing at least two radiating patterns
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/14—Relay systems
- H04B7/15—Active relay systems
- H04B7/204—Multiple access
- H04B7/2041—Spot beam multiple access
Definitions
- the invention relates to space vehicles and, more particularly, to techniques for generating multiple energy beams from a space vehicle.
- the space vehicle In a communications system where earth-based subscriber units communicate with an orbiting space vehicle, the space vehicle must generate energy beams in order to service areas occupied by the earth-based subscriber units in order to convey information.
- the energy beams typically generated by the space vehicle move relative to the earth- based subscriber units at a velocity which is commensurate with the velocity of the space vehicle.
- an individual earth-based subscriber unit may be illuminated by a particular energy beam for a limited period of time before the energy beam moves beyond the area occupied by the subscriber.
- the space vehicle must assign the subscriber unit to an adjacent beam so that communications with the space vehicle can continue. This process of subscriber beam-to-beam hand over may be repeated throughout the entire field of view of the space vehicle as the space vehicle moves overhead.
- a more favorable approach to facilitating communications between earth- based subscriber units and an orbiting space vehicle is to make use of energy beams which are fixed relative to an area occupied by the earth-based subscriber unit. This allows the energy beam generated from the space vehicle to move relative to the space vehicle while remaining stationary in relation to a constant area fixed to the surface of the earth. This technique is preferred since it reduces the need to hand over a particular subscriber unit from one communications beam to another as the space vehicle moves in its orbit. This reduction in the need for beam-to-beam hand over reduces the frequency management and administration tasks which the space vehicle must execute in order to maintain contact with the earth-based subscriber.
- the multi-beam antenna of a space vehicle it is highly desirable for the multi-beam antenna of a space vehicle to generate communications beams over the field of view of the space vehicle, and to keep these beams fixed to areas on the earth's surface as the space vehicle moves relative to the earth's surface. It is further desirable for the technique to be implemented in a simple and inexpensive manner. This enables the space vehicle to provide services to earth-based subscribers while reducing the need for beam-to- beam hand over as the space vehicle moves relative to the subscriber. This, in turn, can reduce the cost to subscribers for these types of services.
- FIG. 1 shows a space vehicle providing communication services to an earth- based subscriber unit in accordance with a preferred embodiment of the invention
- FIG. 2 is a block diagram of an apparatus for generating multiple earth-fixed beams by a space vehicle in accordance with a preferred embodiment of the invention
- FIG. 3 shows relative beam pattern areas at nadir and at edge of coverage generated by an orbiting space vehicle in accordance with a preferred embodiment of the invention
- FIG. 4 shows an exemplary coverage pattern of beams in real space generated from the apparatus of FIG. 2 in accordance with a preferred embodiment of the present invention
- FIG. 5 shows a subset of the beam coverage pattern of FIG. 4 when the subset is used to illuminate a surface of the earth in accordance with a preferred embodiment of the invention
- FIG. 6 shows the effect on beam overlap which results from over sampling in a multiple beam former in accordance with a preferred embodiment of the present invention
- FIG. 7 is a diagram showing the geometrical quantities used in the derivation of angular beam rate for a phased array antenna which provides multiple earth-fixed beams in accordance with a preferred embodiment of the invention
- FIG. 8 is a diagram which shows the geometrical quantities used in the derivation of beam grid velocity relative to the earth for a phased array antenna which provides multiple earth-fixed beams in accordance with a preferred embodiment of the invention
- FIG. 9 is a graph showing the relationship of beam velocity (as a fraction of space vehicle velocity) as a function beam pointing angle using a space vehicle mounted phased array antenna which provides multiple earth-fixed beams in accordance with a preferred embodiment of the invention.
- FIG. 10 is a graph showing the relationship of beam position error as a function the of beam pointing angle using a phased array antenna which provides multiple earth-fixed beams in accordance with a preferred embodiment of the invention.
- FIG. 11 is a flow chart of a method for multiple earth-fixed beam generation from a space vehicle in accordance with a preferred embodiment of the invention.
- FIG. 1 shows a space vehicle providing communication services to an earth- based subscriber unit in accordance with a preferred embodiment of the invention.
- satellite 10 is representative of any type of space vehicle which moves relative to surface of the earth 60.
- satellite 10 can represent a space vehicle or airborne vehicle which provides navigation information, broadcast or multicast audio or video, or any other type of information.
- Satellite 10 can also represent a space vehicle which receives information from various locations on surface of the earth 60.
- satellite 10 radiates multiple energy beams, such as communications beam 20, which provides communication services to earth-based subscriber unit 30.
- Satellite 10 preferably illuminates surface of the earth 60 with numerous other communications beams, such as communications beam 25 of FIG. 1.
- satellite 10 is a low earth orbit satellite which moves relative to surface of the earth 60 and earth-based subscriber unit 30.
- a set of multiple communications beams, such as communications beams 20 and 25 is steered in the opposite direction so that areas illuminated by each communications beam remain constant and fixed to a corresponding area on the surface of the earth.
- FIG. 2 is a block diagram of an apparatus for generating multiple earth-fixed beams by a space vehicle in accordance with a preferred embodiment of the invention.
- phased array antenna 120 provides the physical means by which energy beams, such as communications beams 20 and 25 of FIG. 1 , are generated.
- the radiating elements which comprise phased array antenna 120 can be any type of elements which are capable of launching an electromagnetic wave in response to an electrical current present on a surface of the radiating element. Suitable examples include dipoles, helices, and patch antennas.
- Phased array antenna 120 can also make use of radiating elements such as waveguide slots and horns which launch an electromagnetic wave as a function of a potential generated across an aperture. It is contemplated that the number and arrangement of the radiating elements which comprise phased array antenna 120 are designed in accordance with the particular, power, gain, and directivity requirements of the communication system represented by satellite 10 of FIG. 1.
- each of phased shifters 140 is coupled to a corresponding one of the "N" radiating elements which comprise of phased array antenna 120.
- Phase shifters 140 can be of any conventional type, such as those that employ ferroelectric devices, field effect transistors, PIN diodes, or micro- electromechanical switches. However, it is preferable that phase shifters 140 be capable of modifying phase by at least a substantial portion of a 2 ⁇ radian range under the control of controller 130. Desirably, this broad range of control over the phase of phase shifters 140 allows beam scanning over the entire field of view of phased array antenna 120.
- Phase shifters 140 are coupled to outputs of controller 130 and to multiple beam forming network 1 10.
- multiple beam forming network 1 10 incorporates a number of outputs equal to the number of elements of phased array antenna 120. It is contemplated that multiple beam forming network 1 10 will accept a number of inputs commensurate with the number of beams which are generated by multiple beam forming network 1 10, typically within the range of 50 to 500 beams, although a greater or lesser number of beams (and inputs) can be used according to the requirements of the particular application.
- Multiple beam forming network 110 can be any type of conventional multiple beam forming network.
- multiple beam forming network 1 10 can make use of a Butler matrix.
- Other suitable multiple beam forming network architectures include Nolan and Blass matrices.
- it is desirable that multiple beam forming network 1 10 is an orthogonal network, since an orthogonal network can exhibit a lesser amount of loss through the beam forming network in comparison with other beam forming techniques, orthogonality is not mandatory in order to practice the invention. Any multiple beam forming network capable of providing either receive or transmit beams can be exploited in multiple beam forming network 1 10.
- Switch matrix/power combiner 100 coupled to multiple beam forming network 110, generates "M" number of beam outputs for use by multiple beam forming network 110.
- switch matrix/power combiner 100 incorporates beam switches 105, and power combiners 107.
- Beam switches 105 and power combiners 107 are representative of any conventional design, provided that each is capable of functioning to combine and separate the beams formed by multiple beam forming network 1 10.
- power combiners 107 are illustrated as three-way combiners, this is not intended to be limiting in any way, as the use of different types of combiners, such as two-way, four-way, and five-way power combiners can be used as well, according to the number of beams generated by multiple beam forming network 110 and the desired complexity of switch matrix/power combiner 100.
- Controller 130 supplies steering commands to each of phase shifters 140 in the form of a uniform phase shift amount. These steering commands function to steer the beams created by phased array antenna 120. As each beam is steered across the field of view of phased array antenna 120, controller 130 can inactivate any beams that are scanned beyond an edge of coverage. This ensures that space vehicle transmit beams illuminate only locations on surface of the earth 60, and do not transmit into free space. Controller 130 also maps subscriber units to each of the "M" beams generated by multiple beam forming network 110 and manages the beam combination and separation functions.
- FIG. 3 shows relative beam pattern areas at nadir and at edge of coverage generated by an orbiting space vehicle in accordance with a preferred embodiment of the invention.
- satellite 10 moves relative to surface of the earth 60. Satellite 10 generates numerous energy beams, however, only three such beams are shown (communications beams 210, 220, and 230, for example).
- each of the aforementioned communications beams occupies a substantially constant angular area, denoted as angle ⁇ .
- communications beams 210 and 230 encompass a larger area on surface of the earth 60 than communications beam 220, even though each of communications beams 210, 220, and 230 subtends a substantially constant angular area.
- the number of earth-based subscribers which can be serviced by each of communications beams 210 and 230 is greater than the number of subscribers which can be serviced by communications 220.
- the area encompassed by the beam becomes smaller, reaching a minimum area at the nadir of satellite 10.
- the beam pattern area begins to increase in size until reaching the area encompassed by communications beam 230.
- FIG. 4 shows an exemplary coverage pattern of beams in real space generated from the apparatus of FIG. 2 in accordance with a preferred embodiment of the present invention.
- the beam coverage pattern of FIG. 4 illustrates a smaller number of the 256 beams available from a 16x16 element phased array antenna, such as phased array antenna 120 of FIG. 2.
- Both the horizontal and vertical axes of FIG. 4 represent beam pointing angles (in radians) and are linear in sine space.
- Sine space has been chosen in FIG. 4 since it allows the -4 dB beam contours within the field of view to be illustrated without significant distortion.
- the inner circular area indicates an exemplary 40 degree grazing angle contour for a space vehicle located at an altitude of 1400 Km above the surface of the earth.
- FIG. 5 shows a subset of the beam coverage pattern of FIG. 4 when the subset is used to illuminate a surface of the earth in accordance with a preferred embodiment of the invention.
- the horizontal and vertical axes of FIG. 5 represent range from a nadir point for a space vehicle located at an altitude of 1400 Km above the surface of the earth.
- those beams at nadir near the center of the figure
- those at edge of coverage near the edges of the figure
- the beams nearest the corners of FIG. 4 include the largest area of any of the 96 beams subset of FIG. 4,
- FIG. 6 shows the effect on beam overlap which results from over sampling in a multiple beam former (FIG. 3, 110) in accordance with a preferred embodiment of the present invention.
- the horizontal and vertical axes of FIG. 6 represent range from a nadir point for a space vehicle located at an altitude of 1400 Km above the surface of the earth.
- coverage between beams generated by a phased array antenna is improved by way of over sampling an exemplary Butler matrix in the vertical axis.
- a rank 18 Butler matrix has been used with 2 inputs being loaded per column. This reduces the spacing between beams, and increases beam overlap to a power level of -3dB.
- over sampling tends to increase the loss in multiple beam forming network 1 10, the additional loss can be traded against the advantages of increased beam overlap.
- FIG. 7 is a diagram showing the geometrical quantities used in the derivation of angular beam rate for a phased array antenna which provides multiple earth-fixed beams in accordance with a preferred embodiment of the invention.
- satellite 10 moves with a velocity vector denoted by 'V and orbits above surface of the earth 60 at an altitude "/r".
- 'V velocity vector denoted by 'V
- /r altitude
- the rate of change in the phase of each of phase shifters 140 of FIG. 2 in order to maintain the beams at constant areas fixed to the surface of the earth.
- d ⁇ o/dt -(d ⁇ n /dt)/(nkd(cos ⁇ 0 )).
- d ⁇ dt is chosen to produce the proper beam rate, d ⁇ o/dt, at the nadir of the space vehicle.
- the beam rate at edge of coverage is a factor of 1/(cos(49.7°), or approximately 1.5 times the rate at nadir, for an altitude "If equal to 1200 kilometers, and edge of coverage defined by elevation equal 25 degrees (or ⁇ 0 ⁇ 50 degrees).
- d ⁇ o/dt is the angular rate of the beam relative to the antenna (which is fixed to the space vehicle), while d ⁇ /dt is the total angular rate of the beam relative to the earth.
- the phase shifter settings (which can be used by phase shifters 140 of FIG. 2 to generate earth-fixed beams) cause an increase in beam angular velocity towards the edges of coverage in front of and behind the space vehicle. This increase is useful in synchronizing the beam to the ground.
- FIG. 8 is a diagram which shows the geometrical quantities used in the derivation of beam grid velocity relative to the earth for a phased array antenna which provides multiple earth-fixed beams in accordance with a preferred embodiment of the invention.
- V ⁇ , el
- v h vsin( ⁇ 9 + el)- (d ⁇ /dt) s ' (el)
- FIG. 9 is a graph showing the relationship of beam velocity (as a fraction of space vehicle velocity) as a function beam pointing angle using a space vehicle mounted phased array antenna which provides multiple earth-fixed beams in accordance with a preferred embodiment of the invention. From FIG. 9, it can be seen that the beam velocity as a fraction of the space vehicle velocity (— ) is zero
- V V at the nadir of the space vehicle, as predicted by the equation for — .
- V for beam pointing values which approach .9 radians, — remains a relatively small quantity, indicating little motion of the beam across the surface of the earth. Only for values which approach 1.00 radian does — becomes significant, indicating
- FIG. 10 is a graph showing the relationship of position error, P(Km), as a function the of beam pointing angle using a phased array antenna which provides multiple earth-fixed beams in accordance with a preferred embodiment of the invention.
- FIG. 10 results from the integration of the expression for — derived in
- V relation to FIG. 8. This yields the position of the beam relative to a point on the earth that the beam is intended to cover, as a function of ⁇ .
- c 1 is the total angular velocity of the beam, which has been set to:
- FIG. 11 is a flow chart of a method for multiple earth-fixed beam generation from a space vehicle in accordance with a preferred embodiment of the invention.
- the apparatus of FIG. 2 is suitable for performing the method of FIG. 1 1.
- the method begins with step 310, where weighting coefficients for elements of a phased array antenna are determined. These weighting coefficients include a relative amplitude and phase and are desirably applied to each element of the phased array antenna in order generate multiple earth-fixed beams. Also in step 310, a determination is made as to which of the multiple beams will be used to transmit communications information from the space vehicle to one or more earth-based subscriber units, and which beams will be used to receive communications information from earth-based subscriber units.
- step 320 the phase component of the weighting coefficients are shifted by a proportionality constant which is approximately in the range of
- n represents a particular element of said phased array
- k represents a wave number
- d represents a spacing between elements of the phased array antenna
- v represents a velocity of the space vehicle
- r represents a radius of the earth
- h represents an altitude of the orbiting space vehicle
- t represents time, thereby illuminating a substantially constant area fixed to a surface of the earth as the space vehicle moves relative to the earth.
- step 330 a determination is made as to whether a particular beam is pointing beyond an edge of coverage. If the decision of step 330 indicates that a beam is pointing beyond an edge of coverage, step 340 is executed in which the beam is inactivated. This beam inactivation ensures that any transmitted energy is incident on a surface of the earth, where earth-based subscribers can be expected to be located, and that energy not broadcast to an unoccupied region of free space. If the decision of step 330 indicates that the beam is not being pointed beyond an edge of coverage, step 360 is executed in which the space vehicle activates the particular receive or transmit beam. Following step 360, step 370 is executed in which the beam is combined with a second beam as the beam is being pointed from an edge of coverage to a nadir. Also in step 370, the space vehicle performs any subscriber beam-to-beam hand over which is required in order to continue communications between the space vehicle and the earth-based subscribers.
- step 380 the space vehicle performs any required separation of beams as the combined beam is scanned from nadir to an edge of coverage.
- Step 380 also includes any assigning of earth-based subscriber units to appropriate communications beams as the beams are separated.
- step 390 the space vehicle determines if a beam is pointing beyond and edge of coverage. If the decision of step 390 indicates that a communications beam is not pointing beyond and edge of coverage, step 400 is executed in which the beam continues its scan. If, however, the decision of step 390 indicates that the beam is pointing beyond and edge of coverage, step 410 is executed in which the particular beam is inactivated.
- Steps 330 through 410 are repeated for each beam generated by the multiple beam forming network.
- several beams generated by the multiple beam forming network are being processed by various steps within the sequence of steps 330 to 410.
- steps 370 may be undergoing processing by step 370, in which individual beams are being combined with others as the beams are scanned from an edge of coverage to nadir.
- other beams may be undergoing processing by step 380, in which beams are being separated as they are scanned from nadir to an edge of coverage.
- a method and system for multiple earth-fixed beam generation from an orbiting space vehicle provides the capability for a space vehicle to generate multiple earth-fixed beams and reduce beam-to-beam hand over as the space vehicle moves relative to an earth-based subscriber.
- the method and system can be operated in conjunction with a variety of multiple beam forming networks, such as those that employ Butler, Nolan, and Blass matrices. Additionally, proper control over the phase shifters results in beam position and velocity errors which are negligible over large ranges of beam pointing angles.
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Abstract
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AU11948/01A AU1194801A (en) | 1999-11-05 | 2000-10-10 | Earth-fixed beams from a space vehicle |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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US43460199A | 1999-11-05 | 1999-11-05 | |
US09/434,601 | 1999-11-05 |
Publications (1)
Publication Number | Publication Date |
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WO2001035494A1 true WO2001035494A1 (fr) | 2001-05-17 |
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Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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PCT/US2000/027998 WO2001035494A1 (fr) | 1999-11-05 | 2000-10-10 | Faisceaux terrestres générés à partir d'un véhicule spatial |
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AU (1) | AU1194801A (fr) |
WO (1) | WO2001035494A1 (fr) |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN1316836C (zh) * | 2005-05-11 | 2007-05-16 | 西安海天天线科技股份有限公司 | 基于波束切换式智能天线的移动通信基站及波束切换方法 |
CN101375522B (zh) * | 2004-10-28 | 2011-08-31 | 美商内数位科技公司 | 形成、操控、选择方位角和仰角中的波束路径 |
CN111641425A (zh) * | 2020-05-18 | 2020-09-08 | 南京华成微波技术有限公司 | 一种低成本多波束射频前端的实现方式 |
Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
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US5408237A (en) * | 1991-11-08 | 1995-04-18 | Teledesic Corporation | Earth-fixed cell beam management for satellite communication system |
US5612701A (en) * | 1995-09-18 | 1997-03-18 | Motorola, Inc. | Adaptive beam pointing method and apparatus for a communication system |
US5621415A (en) * | 1994-11-15 | 1997-04-15 | Teledesic Corporation | Linear cell satellite system |
US5736959A (en) * | 1991-10-28 | 1998-04-07 | Teledesic Corporation | Earth-fixed cell beam management for satellite communication system using dielectic lens-focused scanning beam antennas |
EP0837523A2 (fr) * | 1996-10-18 | 1998-04-22 | Kabushiki Kaisha Toshiba | Antenne adaptative |
WO1999035766A1 (fr) * | 1998-01-05 | 1999-07-15 | Motorola Inc. | Gestion de faisceaux dans un systeme de telecommunications par satellite |
-
2000
- 2000-10-10 WO PCT/US2000/027998 patent/WO2001035494A1/fr active Application Filing
- 2000-10-10 AU AU11948/01A patent/AU1194801A/en not_active Abandoned
Patent Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5736959A (en) * | 1991-10-28 | 1998-04-07 | Teledesic Corporation | Earth-fixed cell beam management for satellite communication system using dielectic lens-focused scanning beam antennas |
US5408237A (en) * | 1991-11-08 | 1995-04-18 | Teledesic Corporation | Earth-fixed cell beam management for satellite communication system |
US5621415A (en) * | 1994-11-15 | 1997-04-15 | Teledesic Corporation | Linear cell satellite system |
US5612701A (en) * | 1995-09-18 | 1997-03-18 | Motorola, Inc. | Adaptive beam pointing method and apparatus for a communication system |
EP0837523A2 (fr) * | 1996-10-18 | 1998-04-22 | Kabushiki Kaisha Toshiba | Antenne adaptative |
WO1999035766A1 (fr) * | 1998-01-05 | 1999-07-15 | Motorola Inc. | Gestion de faisceaux dans un systeme de telecommunications par satellite |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN101375522B (zh) * | 2004-10-28 | 2011-08-31 | 美商内数位科技公司 | 形成、操控、选择方位角和仰角中的波束路径 |
CN1316836C (zh) * | 2005-05-11 | 2007-05-16 | 西安海天天线科技股份有限公司 | 基于波束切换式智能天线的移动通信基站及波束切换方法 |
CN111641425A (zh) * | 2020-05-18 | 2020-09-08 | 南京华成微波技术有限公司 | 一种低成本多波束射频前端的实现方式 |
CN111641425B (zh) * | 2020-05-18 | 2022-06-07 | 南京华成微波技术有限公司 | 一种低成本多波束射频前端的实现方式 |
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Publication number | Publication date |
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