Advanced instrument landing system

• US 4,866,450 A
• Filed: 10/14/1988
• Issued: 09/12/1989
• Est. Priority Date: 05/15/1986
• Status: Expired due to Fees

• Current Assignee: Sundstrand Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: Sundstrand Data Control, Inc.
• Inventors: Chisholm, John P.
• Primary Examiner(s): Tarcza, Thomas H.
• Assistant Examiner(s): Issing, Gregory C.
• Application Number:
  US07/258,060
• Time in Patent Office: 333 Days
• Field of Search: 342/352, 342/356, 342/357, 342/393, 342/410-412, 342/414, 342/30, 342/31, 342/33, 342/34, 342/35, 364/428, 364/429
• US Class Current: 342/410
• CPC Class Codes: G01S 1/10 using amplitude comparison of signals transmitted sequentially from antennas or antenna systems having differently-oriented overlapping directivity characteristics, e.g. equi-signal A-N type
• CPC Class Codes: G01S 11/08 using synchronised clocks
• CPC Class Codes: G01S 19/15 Aircraft landing systems

Abstract

A system for landing an aircraft is described, using a ground installation and an airborne installation which are synchronized together using GPS system time. Specifically, the ground installation includes a ground transmitter which radiates the sequence of signals which provide precision guidance information to the aircraft, an aircraft installation which includes a radio receiver and a processor to receive and process the transmitted guidance signals and to provide indications to aid the pilot in landing the aircraft, a GPS receiver in the air and on the ground for producing signals representative of GPS system time, and a channel selector in the aircraft for actuating the processor to synchronize its operation with the ground installation transmitter. Range information is provided by measuring the time interval between the transmission of a reference at the ground and its receipt in the air.

Claims

1. A system for guiding a vehicle along a path utilizing a plurality of satellites each of which transmits signals representing the position of the satellite and precise time in a common time reference, comprising:

a guidance station including;

means for receiving said position and precision timing signals to provide a precision, guidance station clock signal in said common time reference;

means responsive to said precision, guidance station clock signal for transmitting, within a time period associated with said guidance station, guidance signals with respect to said guidance path to direct a vehicle along said path;

said vehicle including;

means for receiving said position and precision timing signals to provide a precision, vehicle clock signal in said common time reference, said precision, vehicle clock signal being in synchronization with said precision, guidance station clock signal;

means for receiving said guidance signals; and

means coupled to said guidance signal receiving means and responsive to said vehicle clock signal for processing guidance signals received only in said time period associated with said guidance station to guide said vehicle along said path.

2. A system for guiding a vehicle along a path as recited in claim 1 wherein said transmitting means transmits a pair of overlapping precision guidance signal beams symmetrically disposed about said path.

3. A system for guiding a vehicle along a path as recited in claim 2 wherein said transmitting means transmits said signal beams in a predetermined sequence.

4. A system for guiding a vehicle along a path as recited in claim 1 including a plurality of guidance stations wherein the transmitting means associated with each of said guidance stations transmits said guidance signals at the same frequency.

5. A system for guiding a vehicle along a path as recited in claim 4 wherein each of said transmitting means has an operating range and each guidance station within the operating range of one or more other guidance stations has an associated time period that is nonoverlapping with the time periods associated with the other of said guidance stations.

6. A system for guiding a vehicle along a path as recited in claim 1 wherein said transmitting means has an operating range and said time period is sufficiently long to allow a guidance signal transmitted within said time period to be received within said time period by a vehicle within said operating range.

7. A system for guiding a vehicle along a path as recited in claim 1 including a range gate for tracking received guidance signals;

means for storing guidance signals falling within said range gate;

means for averaging said storage guidance signals; and

means for determining whether a stored guidance signal falls within limits associated with said average, wherein only guidance signals falling within said limits are used to guide said vehicle along said path.

8. A system for guiding a vehicle along a path as recited in claim 1 wherein said guidance station has a fixed position relative to the surface of the earth and said vehicle means for receiving said position and precision timing signals includes means for determining said vehicle'"'"'s geographic position relative to the surface of the earth and further including means for storing said fixed position of said guidance station;

and means responsive to said vehicle'"'"'s position and to said guidance station'"'"'s position for determining the range between said vehicle and said guidance station.

9. A system for guiding a vehicle along a path as recited in claim 1 wherein said guidance station is located at a known position and includes:

means for determining the position of said guidance station in response to the signals received from said satellite;

means for measuring the difference between said determined position and said known position; and

means for providing a correction signal based on said difference, said correction signal being transmitted by said transmitting means.

10. A system for guiding a vehicle along a path utilizing a plurality of satellites each of which transmits signals representing the position of the satellite and precise time in a common time reference comprising:

first means for receiving said position and precision timing signals to provide a first clock signal in said common time reference;

means responsive to said first clock signal for transmitting within a time period associated with said transmitting means guidance signals with respect to said guidance path to direct a vehicle along a path and a reference signal, said reference signal being transmitted at a precise time with respect to said first clock signal and within said time period;

second means disposed in said vehicle for receiving said position and precision timing signals to provide a second clock signal in said common time reference, said second clock signal being in synchronization with said first clock signal;

means disposed in said vehicle for receiving said guidance and reference signals; and

means coupled to said guidance and reference signal receiving means and to said second means for processing guidance signals received only in said time period associated with said guidance station to guide said vehicle along said path, said processing means including;

means for determining the time of receipt of said reference signal in said common time reference; and

one way range determining means for determining the range of said vehicle from said transmitting means based upon the difference between said precise time at which said reference signal is transmitted and said time of receipt of said reference signal.

11. A system for guiding a vehicle along a path as recited in claim 10 wherein said transmitting means includes an omni-directional antenna for radiating said reference signal.

12. A system for guiding a vehicle along a path as recited in claim 10 wherein said reference signal is encoded to identify said guidance station.

13. A system for guiding a vehicle along a path as recited in claim 33 wherein said guidance station has a fixed position relative to the surface of the earth and said vehicle means for receiving said position and precision timing signals includes means for determining said vehicle'"'"'s geographic position relative to the surface of the earth and further including means for storing said fixed position of said guidance station;

and means responsive to said vehicle'"'"'s position and to said guidance station'"'"'s position for determining the range between said vehicle and said guidance station.

14. A system for guiding a vehicle along a path as recited in claim 13 including means for comparing said range determinations to check the accuracy thereof.

15. A system for guiding a vehicle utilizing a plurality of satellites each of which transmits signals representing the position of the satellite and precise time in a common time reference, comprising:

first means for receiving said position and precision timing signals to provide a first clock signal in said common time reference;

means responsive to said first clock signal for transmitting a range signal at a precise time with respect to said first clock signal and within a time period associated with said transmitting means;

second means disposed in said vehicle for receiving said position and precision timing signals to provide a second clock signal in said common time reference, said second clock signal being in synchronization with said first clock signal;

means disposed in said vehicle for receiving said range signal; and

one way range means coupled to said range signal receiving means and to said second means for processing a range signal received within said time period to determine range from the difference between said precise time of transmission and the time of receipt of said range signal.

16. A system for guiding a vehicle as recited in claim 15 wherein said transmitting means further transmits a pair of overlapping precision guidance signal beams symmetrically disposed about a path within said time period and said processing means includes means for processing guidance signal beams received by said receiving means to guide said vehicle along said path.

17. A system for guiding a vehicle as recited in claim 16 wherein said transmitting means transmits said signal beams in a predetermined sequence.

18. A system for guiding a vehicle as recited in claim 15 wherein said first means and transmitting means are located at a ground station.

19. A system for guiding a vehicle as recited in claim 18 including a plurality of ground stations wherein the transmitting means associated with each of said ground stations transmits said guidance signals at the same frequency.

20. A system for guiding a vehicle along a path as recited in claim 19 wherein each of said transmitting means has an operating range and each ground station within the operating range of one or more other ground stations has an associated time period that is nonoverlapping with the time periods associated with the other of said guidance stations.

21. A system for guiding a vehicle as recited in claim 15 wherein said transmitting means has an operating range and said time period is sufficiently long to allow a range signal transmitted within said time period to be received within said time period by a vehicle within said operating range.

22. A system for guiding a vehicle as recited in claim 15 wherein said transmitting means includes an omni-directional antenna for radiating said range signal.

23. A system for guiding a vehicle as recited in claim 15 wherein said range signal is encoded to identify said guidance station.

24. A system for guiding a vehicle as recited in claim 15 wherein said guidance station having a fixed position relative to the surface of the earth and said vehicle means for receiving said position and precision timing signals includes means for determining said vehicle'"'"'s geographic position relative to the surface of the earth and further including means for storing said fixed position of said guidance station;

and means responsive to said vehicle'"'"'s position and to said guidance station'"'"'s position for determining the range between said vehicle and said guidance station.

25. A system for guiding a vehicle as recited in claim 24 including means for comparing said range determinations to check the accuracy thereof.