Radio-based direction-finding navigation system using small antenna

• US 8,305,265 B2
• Filed: 06/12/2009
• Issued: 11/06/2012
• Est. Priority Date: 05/29/2007
• Status: Active Grant

• Current Assignee: Toyon Research Corporation
• Original Assignee: Toyon Research Corporation
• Inventors: Ezal, Kenan O., Werner, Benjamin D.
• Primary Examiner(s): Tarcza, Thomas
• Assistant Examiner(s): GALT, CASSI J
• Application Number:
  US12/457,512
• Publication Number:
  US 20100007555A1
• Time in Patent Office: 1,243 Days
• Field of Search: 342/357.02, 342/357.11, 342/357.12, 342/357.36
• US Class Current: 342/357.36
• CPC Class Codes: G01C 21/005 with correlation of navigation data from several sources, e.g. map or contour matching G01C21/30 takes precedence
• CPC Class Codes: G01S 19/36 relating to the receiver frond end
• CPC Class Codes: G01S 19/45 by combining measurements of signals from the satellite radio beacon positioning system with a supplementary measurement
• CPC Class Codes: G01S 3/043 Receivers
• CPC Class Codes: G01S 3/32 derived from different combinations of signals from separate antennas, e.g. comparing sum with difference
• CPC Class Codes: G01S 3/48 the waves arriving at the antennas being continuous or intermittent and the phase difference of signals derived therefrom being measured
• CPC Class Codes: H01Q 1/28 Adaptation for use in or on aircraft, missiles, satellites, or balloons
• CPC Class Codes: H01Q 1/288 Satellite antennas
• CPC Class Codes: H01Q 1/38 formed by a conductive layer on an insulating support patch antennas H01Q9/0407; microstrip dipole antennas H01Q9/065; microstrip slot antennas H01Q13/106; transmission line microstrip antennas H01Q13/206; manufacturing reflecting surfaces using insulating material for supporting the reflecting surface H01Q15/142
• CPC Class Codes: H01Q 25/00 Antennas or antenna systems providing at least two radiating patterns arrangements for changing or varying the orientation or the shape of the directional pattern H01Q3/00
• CPC Class Codes: H01Q 9/27 Spiral antennas

Abstract

An exemplary radio-based navigation system uses a small multimode direction-finding antenna and a direction-finding receiver capable of determining platform position, velocity, attitude, and time while simultaneously providing protection against narrowband and broadband sources of interference. Global Navigation Satellite System (GNSS) signals such as those from the Global Positioning System (GPS) provide attitude measurements with a compact multimode direction-finding antenna (e.g., a small two-arm spiral with improved angle-of-arrival performance over the entire hemisphere enhanced through the use of a conductive vertical extension of the antenna ground plane about the antenna perimeter and/or conductive posts placed evenly around the antenna perimeter) which provides simultaneous protection against jammers. The multimode spiral may be treated as an array of rotationally-symmetric antenna elements. The GPS receiver architecture also may be modified for direction-finding and thereby attitude determination by increasing the requisite number of input signals from one to at least two while minimizing the required number of correlators and mixers.

Claims

1. A radio-based navigation system for receiving selected radio-frequency signals of a known origin and a known waveform, and for determining the system position, velocity, three-dimensional attitude and time, said system comprising:

a. a radio-frequency-to-digital front-end configured to accept a minimum of two feed signals from a direction-finding antenna having a maximum aperture dimension that is less than 0.7 wavelength at the lowest operating frequency and capable of supporting a minimum of two unchanging direction-finding modes that are substantially cylindrically symmetric about a single unchanging antenna boresight and to convert the feed signals to digital signals; and

b. a receiver module configured to process said digital signals wherein said receiver module is configured to;

(1) combine the digital signals to form a minimum of two direction-finding signals corresponding to said direction-finding modes;

(2) thereafter combine the digital signals or the direction-finding signals to create at least one navigation signal such that said selected radio-frequency signals are enhanced and the effects of interference signals, if any, are reduced;

(3) determine the system position, velocity, and time from said selected radio-frequency signals obtained from said at least one navigation signal; and

(4) determine two-dimensional angles of arrival of said selected radio-frequency signals and thereby the system three-dimensional attitude from the direction-finding signals via simultaneous mode comparison techniques.

2. The radio-based navigation system of claim 1 wherein the direction-finding antenna comprises a single-aperture.

3. The radio-based navigation system of claim 2 wherein the direction-finding antenna comprises a two-arm spiral antenna, wherein the largest dimension is less than six-tenths of a wavelength at the lowest frequency of its operational band.

4. The radio-based navigation system of claim 1 wherein the largest dimension of the direction-finding antenna is less than six-tenths of a wavelength at the lowest frequency of its operational band.

5. The radio-based navigation system of claim 1 wherein said selected radio-frequency signals are generated by at least one global navigation satellite system.

6. The radio-based navigation system of claim 4 wherein at least a subset of said selected radio-frequency signals comprises global positioning system signals.

7. The radio-based navigation system of claim 4 wherein:

a. said radio-frequency-to-digital front-end further includes a common clock and common phased-lock loops for synchronously down-converting each of said minimum of two feed signals to an intermediate frequency or baseband; and

b. said receiver module further generates a replica waveform for each one of said selected radio-frequency signals and produces a predetermined number of corresponding in-phase and quadrature-phase signals for the navigation signal and the direction-finding signals and wherein said receiver module;

(1) determines the system position, velocity, and time from the in-phase and quadrature-phase signals corresponding to each one of said selected radio-frequency signals obtained from the navigation signal and/or the direction-finding signals; and

(2) determines the two-dimensional angles of arrival of said selected radio-frequency signals and thereby the system three-dimensional attitude from the in-phase and/or quadrature-phase signals corresponding to the direction-finding signals via simultaneous mode comparison techniques.

8. The radio-based navigation system of claim 7 wherein the in-phase and quadrature-phase signals corresponding to the navigation signal and the direction-finding signals are produced via a shared carrier- and code-tracking loop for each one of said selected radio-frequency signals, thereby minimizing the processing power requirements and system complexity.

9. The radio-based navigation system of claim 5 wherein said receiver module further reduces the effects of said interference signals and/or enhances the direction-finding signals and thereby said selected radio-frequency signals.

10. The radio-based navigation system of claim 9 wherein said receiver module further reduces the effects of said interference signals and/or enhances said selected radio-frequency signals via space-time adaptive and/or space-frequency adaptive processing.

11. The radio-based navigation system of claim 6 wherein said radio-frequency-to-digital front-end further includes an analog mode- or beam-forming network.

12. The radio-based navigation system of claim 6 wherein the receiver module further includes a beam-forming network.

13. The radio-based navigation system of claim 1 wherein a feedback control loop in said receiver module further tracks amplitude and phase modulation due to rotation of the direction-finding antenna, whereby also determining the system spin rate, if any, and substantially removes said amplitude and phase modulation from the direction-finding signals and said at least one navigation signal, thereby effectively translating said selected radio-frequency signals into a non-rotating coordinate frame to determine the system position, velocity, attitude and time.

14. The radio-based navigation system of claim 5 wherein additional measurements from alternative sources are processed to further improve the system position, velocity, attitude and time.

15. The radio-based navigation system of claim 14 wherein the additional measurements are obtained from an inertial measurement unit.

16. The radio-based navigation system of claim 1 further comprising:

a. platform actuator and sensor measurement inputs;

b. a platform guidance and command system that generates platform commands using the system position, velocity, attitude and time estimates; and

c. a dynamic platform model that generates a platform state prediction based on the system position, velocity, attitude and time estimates, the platform commands, and the platform measurement inputs,

wherein the platform state prediction is fused with said at least one navigation signal and/or the direction-finding signals to further improve the system position, velocity, attitude and time estimates.

17. A method for determining a radio signal receiver'"'"'s position, velocity, three-dimensional attitude and time, said method comprising:

a. converting a minimum of two feed signals to digital signals wherein said feed signals are provided by a direction-finding antenna having a maximum aperture dimension that is less than 0.7 wavelength at the lowest operating frequency and capable of (1) supporting a minimum of two unchanging direction-finding modes that are substantially cylindrically symmetric about a single unchanging antenna boresight and (2) receiving selected radio-frequency signals of a known origin and waveform;

b. combining the digital signals to form a minimum of two direction-finding signals corresponding to said direction-finding modes;

c. combining the digital signals or the direction-finding signals to create at least one navigation signal such that said selected radio-frequency signals are enhanced and the effects of interference signals, if any, are reduced;

d. determining the receiver'"'"'s position, velocity, and time from said selected radio-frequency signals obtained from said at least one navigation signal; and

e. determining two-dimensional angles of arrival of said selected radio-frequency signals and thereby the receiver'"'"'s three-dimensional attitude from the direction-finding signals via simultaneous mode comparison techniques.

18. The method of claim 17 wherein the direction-finding antenna comprises a single-aperture.

19. The method of claim 18 wherein the direction-finding antenna comprises a two-arm spiral antenna, wherein the largest dimension is less than six-tenths of a wavelength at the lowest frequency of its operational band.

20. The method of claim 17 wherein the largest dimension of the direction-finding antenna is less than six-tenths of a wavelength at the lowest frequency of its operational band.

21. The method of claim 17 wherein said selected radio-frequency signals are generated by at least one global navigation satellite system.

22. The method of claim 20 wherein at least a subset of said selected radio-frequency signals comprises global positioning system signals.

23. The method of claim 20 further comprising:

a. down-converting each of said minimum of two feed signals synchronously to an intermediate frequency or baseband through the use of a common clock and common phased-lock loops;

b. generating a replica waveform for each one of said selected radio-frequency signals;

c. producing a predetermined number of in-phase and quadrature-phase signals corresponding to the replica waveforms for the navigation signal and the direction-finding signals;

d. determining the receiver'"'"'s position, velocity, and time from the in-phase and quadrature-phase signals corresponding to the navigation signal and/or the direction-finding signals; and

e. determining the two-dimensional angles of arrival of said selected radio-frequency signals and thereby the receiver'"'"'s three-dimensional attitude from the in-phase and/or quadrature-phase signals corresponding to each one of said selected radio-frequency signals obtained from the direction-finding signals via simultaneous mode comparison techniques.

24. The method of claim 23 further comprising producing the in-phase and quadrature-phase signals corresponding to the navigation signal and the direction-finding signals via a shared carrier- and code-tracking loop for each one of said selected radio-frequency signals, thereby minimizing the processing power requirements and system complexity.

25. The method of claim 21 further comprising further reducing the effects of said interference signals and/or enhancing the direction-finding signals and thereby said selected radio-frequency signals.

26. The method of claim 25 further comprising further reducing the effects of said interference signals and/or enhancing said selected radio-frequency signals via space-time adaptive and/or space-frequency adaptive processing.

27. The method of claim 22 further comprising filtering said minimum of two feed signals through an analog mode-forming network.

28. The method of claim 22 further comprising creating a beam-forming network prior to forming the direction-finding signals.

29. The method of claim 17 further comprising:

a. tracking amplitude and phase modulation due to rotation of the direction-finding antenna, whereby also determining the receiver spin rate, if any, and

b. substantially removing said amplitude and phase modulation from the direction-finding signals and said at least one navigation signal and thereby effectively translating said selected radio-frequency signals into a non-rotating coordinate frame to determine the system position, velocity, attitude and time.

30. The method of claim 17 wherein additional measurements from alternative sources are fused with said at least one navigation signal and/or the direction-finding signals to further improve the system position, velocity, attitude and time estimate.

31. The method of claim 30 wherein the additional measurements are obtained from an inertial measurement unit.

32. The method of claim 17 further comprising:

a. obtaining platform actuator and sensor measurement inputs;

b. generating platform commands using the receiver'"'"'s position, velocity, attitude and time estimates;

c. determining a platform state prediction based on a dynamic platform model, the system position, velocity, attitude and time estimates, the platform commands, and the platform measurement inputs; and

d. fusing the platform state prediction with said at least one navigation signal and/or the direction-finding signals to further improve the system position, velocity, attitude and time estimates.