Differential navigation system for remote mobile users

[54] DIFFERENTIAL NAVIGATION SYSTEM FOR REMOTE MOBILE USERS

[75] Inventor: Harold L. Longaker, Houston, Tex.

[73] Assignee: Oceanonics, Inc., Houston, Tex.

[21] Appl. No.: 821,009

[22] Filed: Jan. 21,1986

[51] Int. Q.* G01S 5/02; H04B 7/185

[52] U.S. a 342/357; 342/356;

342/361; 342/457

[58] Field of Search 342/357, 356, 361, 362,

342/457

[56] References Cited

U.S. PATENT DOCUMENTS

3,544,995 12/1970 Bottenberg et al 342/357

4,077,005 2/1978 Bishop 342/357

4,276,553 6/1981 Schaefer 342/357

4,359,733 10/1982 O'Neill 343/100

4,445,118 4/1984 Taylor et al 342/357

4,455,651 6/1984 Baran 370/104

OTHER PUBLICATIONS

Ralph Eschenbach & Roger Helkey, "Performance/Cost Ratio Optimized for GPS Receiver Design", Microwave Systems News, Nov. 1984, pp. 43-46, 51-52. Robert P. Denaro, "NAVSTAR Global Positioning System Offers Unprecedented Navigational Accuracy", Microwave Systems News, Nov. 1984, pp. 54, 58-59, 62, 65, 67-68, 70, 75-78, 83. Bradford W. Parkinson, "GPS Accuracy and Reliability Improved with Pseudolites", Microwave Systems News, Nov. 1984, pp. 85-86, 91-94, 97. Rudolph M. Kalafus et al, Recommendations of Special Committee 104 Differential Navstar/GPS Service, Feb. 20, 1985.

K. M. Keen, "Method Permits Gain Estimation for

Very-Wide-Beam, Satellite-Terminal Antennas", Communications Technology, Oct. 1985, pp. 83-84, 87. "Filter Center", Aviation Week & Space Technology, Aug. 12, 1985, p. 69.

Philip J. Klass, "Arinc Proposes Satellite-Based Surveillance, Data Link System", Aviation Week & Space Technology, Aug. 26, 1985, pp. 14-15. Edwin B. Parker, "Micro Earth Stations as Personal Computer Accessories", Proceedings of the IEEE, vol. 72, No. 11, Nov. 1984, pp. 1526-1531. Edwin B. Parker, "Micro Earth Stations Make Business Satcom Affordable", Microwave Systems News, Nov. 1982.

Wideband Antennas and Control Systems, Catalog 1984/1985, pp. 52-55, 68, 69.

Primary Examiner—Theodore M. Blum
Assistant Examiner—David Cain
Attorney, Agent, or Firm—Vaden, Eickenroht,
Thompson & Boulware

[57] ABSTRACT

A differential navigation system applicable to mobile users and covering a wide range geographic area, including remote regions. A reference receiver of known location tracks a navigation information service, computes differential data with respect to that information and communicates the data to a transmitting unit. The transmitting unit transmits differential data via a commercial geosynchronous earth satellite relay to a mobile user located no more than 500 miles from the reference receiver, but possibly located in a remote region. The mobile user receives the relayed signal with a nondirectional, circularly polarized, non-stabilized antenna. Reception at a sufficient data rate with sufficient reliability is made possible by formatting the differential data using spread spectrum techniques.

11 Claims, 4 Drawing Sheets