Method and apparatus for GPS signal receiving that employs a frequency-division-multiplexed phased array communication mechanism

• US 6,784,831 B1
• Filed: 05/05/2003
• Issued: 08/31/2004
• Est. Priority Date: 05/05/2003
• Status: Expired due to Fees

• Current Assignee: TIA Mobile Incorporated
• Original Assignee: TIA Mobile Incorporated
• Inventors: Yang, Chau-Chin, Wang, James June-Ming, Lin, Wen Yen
• Primary Examiner(s): Blum, Theodore M.
• Application Number:
  US10/429,492
• Time in Patent Office: 484 Days
• Field of Search: 342/357.12, 342/357.06, 342/372, 701/213
• US Class Current: 342/357.63
• CPC Class Codes: G01S 19/21 Interference related issues ; Issues related to cross-correlation, spoofing or other methods of denial of service
• CPC Class Codes: G01S 19/22 Multipath-related issues
• CPC Class Codes: G01S 19/36 relating to the receiver frond end
• CPC Class Codes: H01Q 21/065 Patch antenna array

Abstract

An improved GPS signal receiver (and corresponding method of operation) includes a plurality of antenna elements each receiving a plurality of GPS signals (e.g., GPS LI signals or GPS L2 signals). A plurality of mixers (which correspond to the array of antenna elements) and a combining node convert the GPS signals received at the antenna elements in a frequency-division-multiplexed (FDM) manner over FDM frequency bands logically assigned to the antenna elements to produce a composite signal representing such GPS signals. An analog-to-digital converter converts an analog signal derived from the composite signal (which may be an intermediate frequency signal or a baseband signal) into a digital word stream. Demultiplexing logic extracts GPS signal components in the digital word stream. The GPS signal components correspond to the FDM frequency bands logically assigned to the antenna elements. Beam forming logic, operably coupled to the demultiplexing logic, applies variable phase delay and variable gain to each GPS component in accordance with a set of weight values supplied thereto. Preferably, the beam forming logic is controlled to perform adaptive beam steering/nulling operations that provide for interference cancellation, multipath rejection and improved signal reception.

Claims

1. A global positioning system (GPS) signal receiver comprising:

a) a plurality of antenna elements each receiving a plurality of GPS signals, each GPS signal comprising a baseband signal modulated onto a carrier signal within a predetermined first frequency band;

b) a plurality of mixers corresponding to said array of antenna elements, said mixers converting said GPS signals received at said antenna elements in a frequency-division-multiplexed manner to produce GPS signals within a set of second frequency bands that correspond to said antenna elements, wherein successive bands in said set of second frequency bands are separated from each other;

c) a combiner node that combines output of each mixer to produce a composite signal;

d) an analog-to-digital converter that converts an analog signal derived from said composite signal into a digital word stream;

e) demultiplexing logic that extracts components of said digital word stream, said components corresponding to said set of second frequency bands and said antenna elements; and

f) beam forming logic, operably coupled to said demultiplexing logic, that applies variable phase delay and variable gain to each component in accordance with a set of weight values supplied thereto.

2. A GPS signal receiver according to claim 1, further comprising:

g) beam forming control logic that analyzes said components extracted by said demultiplexing logic to identify a given set of weight values that nulls at least one interfering signal, and dynamically supplies said given set of weight values to said beam forming logic to null said at least one interfering signal.

3. A GPS signal receiver according to claim 2, wherein:

said beam forming control logic identifies a direction of arrival for each one of said interfering signals and generates said given set of weight values such that antennae nulls are provided for directions corresponding to said direction of arrival for said interfering signals.

4. A GPS-signal receiver according to claim 3, wherein:

said beam forming control logic generates said given set of weight values by

i) calculating a set of eigenvectors of a covariance matrix derived from said components;

ii) defining a spatial spectrum based upon said set of eigenvectors;

iii) locating peaks in said spatial spectrum; and

iv) calculating said given set of weight values based upon location of said peaks in said spatial spectrum, to thereby provide nulls in the direction of unwanted GPS signals and gain in the direction of direct line of sight GPS signals.

5. A GPS signal receiver according to claim 1, wherein:

each mixer comprises a series of stages including an amplifier stage, bandpass filter stage and frequency shifting mixer stage.

6. A GPS signal receiver according to claim 1, wherein:

said analog signal derived from said composite signal comprises one of an intermediate frequency signal and a baseband signal.

7. A GPS signal receiver according to claim 6, wherein:

said intermediate frequency signal is produced by downconversion circuitry including a first bandpass filter stage, a downconverting mixer stage, a second bandpass filter stage, and an amplifier stage.

8. A GPS signal receiver according to claim 1, wherein:

said demultiplexing logic includes a downconverting mixer logic block and low pass filter logic block corresponding to each mixer and antenna element.

9. A GPS signal receiver according to claim 1, wherein:

said beam forming logic comprises a complex digital multiplier that multiplies data output by said demultiplexing logic and a vector component supplied thereto.

10. A GPS signal receiver according to claim 1, wherein:

said plurality of antenna elements comprises a plurality of patch antenna elements spatially arranged in a hexagonal pattern.

11. A GPS signal receiver according to claim 8, wherein:

centers of said patch antenna elements are spaced apart by a ½

wavelength of said GPS signals.

12. A GPS signal receiver according to claim 1, wherein:

said plurality of mixers generates signals within successive bands in said second set of frequency bands, each successive band pair having center frequencies separated by 12.5 MHz.

13. A GPS signal receiver according to claim 1, further comprising:

summation logic that sums output of said beam forming logic;

digital-to-analog conversion circuitry that converts output of said summation logic into an analog signal; and

modulation circuitry that modulates said analog signal onto a carrier signal within said first predetermined frequency band for output to a GPS receiver.

14. A GPS signal receiver according to claim 13, wherein:

said modulation circuitry comprises a series of stages including a SAW filter stage, upconverting mixer stage, and bandpass filter stage.

15. A GPS signal receiver according to claim 1, further comprising:

a multi-channel GPS correlator circuitry and microprocessor, operably coupled to output of said beam forming logic, wherein said multi-channel GPS correlator correlates the digital signals output by said multiplier logic with an internally generated replica of satellite codes to be received to form accumulated data, wherein said accumulated data is transferred to said microprocessor for extraction of the navigation messages contained therein and analysis of said navigation messages from a plurality of GPS satellites to calculate position coordinates and time for output therefrom.

16. A GPS signal receiver according to claim 2, wherein:

said beam forming control logic identifies an estimated pointing direction of a GPS satellite with respect to said GPS signal receiver and adjusts said given set of weight values in accordance with said estimated pointing direction.

17. A GPS signal receiver according to claim 16, wherein:

said beam forming control logic is adapted to perform a scanning mode that scans over a range of antenna pointing directions to identify a pointing direction with maximum signal strength.

18. A GPS signal receiver according to claim 16, wherein:

said beam forming control logic is adapted to perform a tracking mode that dithers over a range of antenna pointing directions to identify a pointing direction with maximum signal strength.

19. A method for receiving a plurality of global position satellite (GPS) signals, each GPS signal comprising a baseband signal modulated onto a carrier signal within a predetermined first frequency band, the method comprising the steps of:

a) providing a plurality of antenna elements that receive said plurality of GPS signals;

b) converting GPS signals received at said antenna elements in a frequency-division-multiplexed manner to produce GPS signals within a set of second frequency bands that correspond to said antenna elements, wherein successive bands in said set of second frequency bands are separated from each other;

c) combining said GPS signals within said second set of frequency bands to produce a composite signal;

d) converting an analog signal derived from said composite signal into a digital word stream;

e) extracting GPS signal components of said digital word stream, said GPS signal components corresponding to said set of second frequency bands and said antenna elements; and

f) applying variable phase delay and variable gain to each GPS signal component in accordance with a set of weight values supplied thereto.

20. A method for receiving a plurality of GPS signals according to claim 19, further comprising the step of:

g) analyzing said GPS signal components to identify a given set of weight values that nulls at least one interfering signal, and dynamically updating said set of weight values to correspond to said given set in order to null said at least one interfering signal.

21. A method for receiving a plurality of GPS signals according to claim 20, wherein:

step g) identifies a direction of arrival for each one of said interfering signals and generates said given set of weight values such that antennae nulls are provided for directions corresponding to said direction of arrival for said interfering signals.

22. A method for receiving a plurality of GPS signals according to claim 21, wherein:

step g) generates said given set of weight values by

i) calculating a set of eigenvectors of a covariance matrix derived from said components,

ii) defining a spatial spectrum based upon said set of eigenvectors,

iii) locating peaks in said spatial spectrum, and

iv) calculating said given set of weight values based upon location of said peaks in said spatial spectrum, to thereby provide nulls in the direction of unwanted GPS signals and gain in the direction of direct line of sight GPS signals.

23. A method for receiving a plurality of GPS signals according to claim 19, wherein:

step b) utilizes an array of bandpass filter stages and frequency shifting mixers that are adapted to convert GPS signals received at said antenna elements in a frequency-division-multiplexed manner.

24. A method for receiving a plurality of GPS signals according to claim 19, wherein:

said analog signal derived from said composite signal comprises one of an intermediate frequency signal and a baseband signal.

25. A method for receiving a plurality of GPS signals according to claim 24, wherein:

said intermediate frequency signal is produced by downconversion of said composite signal.

26. A method for receiving a plurality of GPS signals according to claim 19, wherein:

step e) utilizes a downconverting mixer logic block and low pass filter logic block corresponding to said second set of frequency bands to produce said GPS signal components.

27. A method for receiving a plurality of GPS signals according to claim 19, wherein:

step f) utilizes an array of complex digital multipliers that multiplies said GPS signal components that multiplies data output by a weight vector supplied thereto.

28. A method for receiving a plurality of GPS signals according to claim 19, wherein:

said plurality of antenna elements comprises a plurality of patch antenna elements spatially arranged in a hexagonal pattern.

29. A method for receiving a plurality of GPS signals according to claim 28, wherein:

said patch antenna-elements are spaced apart by a ½

wavelength of said GPS signals.

30. A method for receiving a plurality of GPS signals according to claim 19, wherein:

step b) generates signals within successive bands in said second set of frequency bands, each successive band pair having center frequencies separated by 12.5 MHz.

31. A method for receiving a plurality of GPS signals according to claim 19, further comprising the steps of:

summing said GPS signal components to generate a combined signal in digital form;

converting said combined signal into analog form; and

modulating said combined signal onto a carrier signal within said first predetermined frequency band for output to a GPS receiver.

32. A method for receiving a plurality of GPS signals according to claim 19, further comprising the steps of:

outputting said GPS signal components to a multi-channel GPS correlator circuitry and microprocessor.

33. A method for receiving a plurality of GPS signals according to claim 20, further comprising the step of:

identifying an estimated pointing direction of a GPS satellite with respect to said GPS signal receiver and adjusting said given set of weight values in accordance with said estimated pointing direction.

34. A method for receiving a plurality of GPS signals according to claim 33, further comprising the step of:

performing scanning mode operations that scan over a range of antenna pointing directions to identify a pointing direction with maximum signal strength.

35. A method for receiving a plurality of GPS signals according to claim 33, further comprising the step of:

performing tracking mode operations that dither over a range of antenna pointing directions to identify a pointing direction with maximum signal strength.