|Publication number||USRE41027 E1|
|Application number||US 11/123,254|
|Publication date||Dec 1, 2009|
|Filing date||May 6, 2005|
|Priority date||Oct 10, 2000|
|Also published as||US6560440|
|Publication number||11123254, 123254, US RE41027 E1, US RE41027E1, US-E1-RE41027, USRE41027 E1, USRE41027E1|
|Inventors||Edward K. Orcutt, Randy L. Turcotte|
|Original Assignee||Orcutt Edward K, Turcotte Randy L|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (24), Non-Patent Citations (1), Classifications (9), Legal Events (4)|
|External Links: USPTO, USPTO Assignment, Espacenet|
The present invention relates to satellite communications systems, which include communication between two moving satellites, between one moving satellite and a ground-based station (moving or stationary), between a spaced-based vehicle and an airborne (but not space-based) vehicle, or any combination of the above.
In a satellite communications system, one satellite vehicle (SV1) transmits and receives data from another satellite vehicle (SV2). Even though one or both vehicles may be moving, if the relative distance between the two vehicles is constant, the carrier frequency on which data is transmitted from one vehicle to another is the same carrier frequency received by the receiving vehicle. In the more typical case, the relative motion between the two vehicles in communication is not constant, and Doppler effects come into play. As long as the relative motion between the transmitter and receiver is within the design constraints of those devices, classical techniques, such as those described in Spiker, James J., Digital Communications by Satellite, Prentice-Hall, Ch. 12, 1995, may be employed to compensate for the carrier frequency shift due to the relative motion between the two vehicles. For example, a frequency-locked loop or a phase-locked loop technique may be employed to track Doppler frequency shifts and maintain communication between the two vehicles. However, these classical tracking techniques often involve broadening the bandwidth of the frequency tracking device and/or the bandwidth of the receiver's noise limiting front-end filter, which tends to reduce the signal-to-noise ratio of the received signal. When the relative motion between the transmitter and the receiver is unacceptably high, the signal-to-noise ratio can become unacceptably low, rendering known compensation techniques insufficient.
A technique is thus needed which allows satellite vehicles to communicate with one another when the relative motion and the change in relative motion between two vehicles is high, while maintaining an acceptable signal-to-noise ratio of the received signal.
The subject invention will hereinafter be described in conjunction with the appended drawing FIGURE, wherein the referenced numerals in the drawing FIGURE correspond to the associated descriptions provided below, and the drawing FIGURE is a schematic block diagram of a preferred embodiment of a frequency compensation system in accordance with the present invention.
In a preferred embodiment of the present invention, a first satellite vehicle (SV1) desires to transmit data to a second satellite vehicle (SV2), wherein the second satellite vehicle (SV2) may be a member of a constellation of satellites having known communication protocols. The first satellite vehicle SV1, which in this example is not a member of the constellation, may conveniently communicate with the second satellite vehicle SV2 as long as satellite SV1 comports with the protocols of the constellation to which satellite SV2 belongs. When the relative motion between SV1 and SV2 is sufficiently low, classical compensation techniques may be employed to account for the Dopplar shift in the transmitted frequency as a result of the relative motion between the two vehicles. Typically, the receiving satellite (in this example, SV2) would monitor a frequency range within which the received signal is expected to fall. However, when the Doppler effects render the use of conventional tracking techniques inadequate, the following compensation system may be employed.
Referring now to the drawing FIGURE, a compensation system 100 which, in a preferred embodiment, resides only on SV1, suitably comprises an SV1 motion predictor 102, an SV2 motion predictor 104, and a processor 116 for computing a predictive algorithm. More particularly, SV1 motion predictor 102 suitably comprises a static or dynamic flight plan associated with satellite vehicle SV1, which may include information relating to speed, trajectory, acceleration, and other position and motion information; SV2 motion predictor 104 suitably includes similar functionality for second satellite vehicle SV2. An output 126 of the SV1 motion predictor 102, and an output 124 of the SV2 motion predictor 104, are suitably supplied to processor 116, whereupon processor 116 outputs a predicted transmission carrier frequency signal 120, and a predicted receiver carrier frequency 122 based upon the predicted relative motion between the two vehicles. In the context of the illustrated embodiment, predicted transmission carrier frequency signal 120 represents the extent to which the transmitter on SV1 should compensate its frequency based on the predicted relative motion between the two vehicles; similarly, predicted receiver carrier signal 122 represents the extent to which the receiver on SV1 should compensate for the predicted relative motion between the two vehicles by adjusting to the frequency at which the received signal is expected to arrive at the receiver.
If the information regarding the motion of the two satellite vehicles (contained in respective predictors 102 and 104), as well as the algorithm contained within processor 116 were perfect, vehicles moving relative to one another could always communicate with a very high signal-to-noise ratio. In reality, however, the predictive models of satellite vehicle motion, as well as the algorithms used to calculate frequency compensation, are imperfect and, over time, degradation in frequency compensation will result. Thus, the foregoing compensation model may be enhanced, if desired, by applying, where practicable, real-time updates to the compensation model including ephemeris data of one or both space vehicles.
With continued reference to the drawing FIGURE, a measured SV1 ephemeris data block 114 supplies real-time updates to SV1 motion predictor 102; similarly, a measured SV2 ephemeris data block 118 is configured to supply real-time updates to SV2 motion predictor 104. More particularly, an output 128 of block 114, which comprises real-time information relating to the actual position and/or motion of satellite vehicle SV1, is supplied to a summing node 110. Output 126 of SV1 motion predictor 102 is suitably delayed through a delay element 106 and supplied to node 110, whereupon summing node 110 computes the difference between the predicted motion of first satellite vehicle SV1 and the measured motion of first satellite vehicle SV1. The difference between these two values, represented by a signal 134, is then supplied to SV1 motion predictor 102. Feedback signal 134 drives the error between the measured motion of SV1 (represented by output signal 128) and the predicted motion of SV1 (represented by output signal 126) to a minimum.
In a similar fashion, an output 130 of block 118, which comprises real-time information relating to the actual position and/or motion of satellite vehicle SV2, is supplied to a summing node 112. Output 124 of SV2 motion predictor 104 is suitably delayed through a delay element 108 and supplied to node 112, whereupon summing node 112 computes the difference between the predicted motion of second satellite vehicle SV2 and the measured motion of second satellite vehicle SV2, the difference between these values, represented by a signal 132, is then supplied to SV2 motion predictor 104. Feedback signal 132 drives the error between the measured motion of SV2 (represented by output signal 130) and the predicted motion of SV2 (represented by output signal 124) to a minimum.
By employing real-time position and/or motion data of one or both of the vehicles involved in a communication session to the compensation model as illustrated in the drawing FIGURE, the frequency compensation model can be significantly improved, thereby allowing computation of frequency compensation information, even in the presence of high relative motion dynamics between the two vehicles.
Although the present invention has been described with reference to the drawing FIGURE, those skilled in the art will appreciate that the scope of the invention is not limited to the specific forms shown in the FIGURE. Various modifications, substitutions, and enhancements may be made to the descriptions set forth herein, without departing from the spirit and scope of the invention which is set forth in the appended claim.
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US4074201||Jul 26, 1976||Feb 14, 1978||Gte Sylvania Incorporated||Signal analyzer with noise estimation and signal to noise readout|
|US5222252||Aug 13, 1991||Jun 22, 1993||Robert Bosch Gmbh||Stereo radio receiver multipath disturbance detection circuit|
|US5289194||Jun 25, 1992||Feb 22, 1994||The United States Of America As Represented By The Secretary Of The Navy||Combiner for two dimensional adaptive interference suppression system|
|US5343496||Sep 24, 1993||Aug 30, 1994||Bell Communications Research, Inc.||Interference suppression in CDMA systems|
|US5432521 *||Jan 14, 1994||Jul 11, 1995||Motorola, Inc.||Satellite receiver system having doppler frequency shift tracking|
|US5471657||Dec 4, 1992||Nov 28, 1995||Hughes Aircraft Company||Frequency tuning for satellite ground stations|
|US5493710||Aug 3, 1992||Feb 20, 1996||Hitachi, Ltd.||Communication system having oscillation frequency calibrating function|
|US5524281||Mar 7, 1995||Jun 4, 1996||Wiltron Company||Apparatus and method for measuring the phase and magnitude of microwave signals|
|US5596570||May 22, 1996||Jan 21, 1997||Qualcomm Incorporated||System and method for simulating interference received by subscriber units in a spread spectrum communication network|
|US5694421||Dec 20, 1995||Dec 2, 1997||Samsung Electronics Co., Ltd.||Frequency-selective interference signal detecting apparatus and method thereof|
|US5697056||May 8, 1995||Dec 9, 1997||Motorola, Inc.||Communication system in which radio subscriber units mitigate interference|
|US5703595 *||Aug 2, 1996||Dec 30, 1997||Motorola, Inc.||Method and apparatus for erratic doppler frequency shift compensation|
|US5754537||Mar 8, 1996||May 19, 1998||Telefonaktiebolaget L M Ericsson (Publ)||Method and system for transmitting background noise data|
|US5758271||Nov 25, 1997||May 26, 1998||Motorola, Inc.||Apparatus and method for optimizing the quality of a received signal in a radio receiver|
|US5778310||Nov 30, 1995||Jul 7, 1998||Northern Telecom Limited||Co-channel interference reduction|
|US5874913 *||Aug 29, 1996||Feb 23, 1999||Motorola, Inc.||Method and apparatus to compensate for Doppler frequency shifts in a satellite communication system|
|US5881367||Dec 11, 1995||Mar 9, 1999||Alcatel Espace||Method of regulating the power of a signal transmitted by a first station to a second station in a satellite telecommunication network|
|US5926767||Dec 26, 1996||Jul 20, 1999||Motorola, Inc.||Method and system reestablishing a temporarily interrupted dynamic communication link under intermittent fade conditions|
|US5983080||Jun 3, 1997||Nov 9, 1999||At & T Corp||Apparatus and method for generating voice signals at a wireless communications station|
|US5987320||Jul 17, 1997||Nov 16, 1999||Llc, L.C.C.||Quality measurement method and apparatus for wireless communicaion networks|
|US5999797||Nov 3, 1997||Dec 7, 1999||Motorola, Inc.||Method and apparatus for providing private global networks in a satellite communication system|
|US6023615||Nov 29, 1995||Feb 8, 2000||Motorola, Inc.||Method for controlling a diversity receiver apparatus in a radio subscriber unit|
|US6034952||Apr 14, 1997||Mar 7, 2000||Ntt Mobile Communications Networks, Inc.||Method and instrument for measuring receiving SIR and transmission power controller|
|US6356740 *||Jun 30, 1995||Mar 12, 2002||Hughes Electronics Corporation||Method and system of frequency stabilization in a mobile satellite communication system|
|1||E-mail regarding search, from email@example.com to Michael Messinger, sent Mar. 27, 2006, 10:42 AM, 5 pages.|
|U.S. Classification||455/13.1, 455/67.13, 455/501|
|International Classification||H04B7/185, H04B17/00, H04L27/00|
|Cooperative Classification||H04L2027/0065, H04B7/18513|
|Jun 19, 2009||AS||Assignment|
Owner name: GENERAL DYNAMICS DECISION SYSTEMS, INC., ARIZONA
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:MOTOROLA, INC.;REEL/FRAME:022849/0420
Effective date: 20010928
Owner name: MOTOROLA, INC., ILLINOIS
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:ORCUTT, EDWARD K;TURCOTTE, RANDY L;REEL/FRAME:022849/0387
Effective date: 20001010
Owner name: LEWIS SALES LLC, NEVADA
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:GENERAL DYNAMICS DECISION SYSTEMS, INC.;REEL/FRAME:022849/0444
Effective date: 20041118
|Oct 25, 2010||FPAY||Fee payment|
Year of fee payment: 8
|Oct 28, 2014||FPAY||Fee payment|
Year of fee payment: 12
|Dec 17, 2015||AS||Assignment|
Owner name: ZARBANA DIGITAL FUND LLC, DELAWARE
Free format text: MERGER;ASSIGNOR:LEWIS SALES LLC;REEL/FRAME:037317/0171
Effective date: 20150811