Method and apparatus for multipath mitigation using antenna array

• US 6,882,312 B1
• Filed: 03/23/2004
• Issued: 04/19/2005
• Est. Priority Date: 03/23/2004
• Status: Active Grant

• Current Assignee: Topcon GPS, LLC
• Original Assignee: Topcon GPS, LLC
• Inventors: Veitsel, Andrew V., Vorobiev, Michael Yu., Pushkarev, Sergey N., Zhdanov, Alexey V., Zhodzishsky, Mark I., Veitsel, Victor A.
• Primary Examiner(s): Phan, Dao
• Application Number:
  US10/806,781
• Time in Patent Office: 392 Days
• Field of Search: 342/357.06, 342/357.12, 342/372, 342/374, 342/442, 701/207, 701/213, 455/269, 455/276.1, 455/277.1, 455/277.2
• US Class Current: 342/374
• CPC Class Codes: H01Q 3/30 varying the relative phase between the radiating elements of an array H01Q3/2605, H01Q3/2658, H01Q3/2682, H01Q3/44 take precedence

Abstract

Disclosed is a method and apparatus for multipath mitigation using an antenna array. An antenna array made up of a plurality of antennas is used to receive satellite signals from satellites. Various configurations of antenna arrays is disclosed, including a linear vertical antenna array and a horizontal antenna array in which the antenna elements are located in a horizontal plane. A switch sequentially connects each of the antenna outputs to a single processing path to generate a common additive signal. The common additive signal is provided to satellite channel processors, each of which processes the signals from an associated satellite. A phase shift correction signal associated with each of the antennas is generated and synchronously applied to a carrier phase reference signal. A blocking signal may be applied to the satellite channel processors in order to block the processing of signals from an unwanted satellite.

Claims

1. A method comprising the steps of:

receiving a plurality of satellite signals at a plurality of antennas;

sequentially and cyclically switching an output of each of said plurality of antennas to a single signal processing path to generate a common additive signal;

providing said common additive signal to each of a plurality of satellite channel processors; and

processing signals from each of said plurality of satellites in a respective one of said plurality of satellite channel processors.

2. The method of claim 1 wherein said step of processing signals from each of said plurality of satellites in a respective one of said plurality of said satellite channel processors further comprises, in each of said satellite channel processors, the step of:

tracking a carrier phase of a satellite signal using a reference signal.

3. The method of claim 2 further comprising the step of:

generating a plurality of phase shift correction signals, each of said phase shift correction signals associated with one of said antennas; and

wherein said step of processing signals from each of said plurality of satellites in a respective one of said plurality of satellite channel processors further comprises, in each of said satellite channel processors, the step of synchronously applying the phase shift correction signal associated with a particular antenna to the reference signal during processing of the component of the satellite signal associated with said particular antenna.

4. The method of claim 3 wherein said antennas are implemented as a horizontal antenna array and wherein said phase shift correction signals φ

_ik for an i-th antenna and a k-th satellite are calculated according to;

φ

_ik=(2π

L_i/λ

)(cosθ

_kθ

_icos(α

_k−

α

_i)+sinθ

_ksinθ

_i)

where

λ

is the wavelength of carrier oscillation;

Li is the distance between the i-th antenna and an antenna center;

θ

i is the elevation angle of a line that connects the antenna center to the i-th antenna;

θ

k is the elevation angle of the k-th satellite;

α

i is the azimuth of a line that connects the antenna center to the i-th element; and

α

k is the azimuth of the k-th satellite.

5. The method of claim 3 wherein said antennas are implemented as a vertical antenna array with an antenna center on the vertical axis and wherein said phase shift correction signals φ

_ik for an i-th antenna and a k-th satellite are calculated according to;

φ

_ik=(2L_i/λ

)sinθ

_k

where

λ

is the wavelength of carrier oscillation;

L_i is the distance between the i-th antenna and an antenna center; and

θ

_k is the elevation angle of the k-th satellite.

6. The method of claim 1 wherein said step of processing signals from each of said plurality of satellites in a respective one of said plurality of satellite channel processors further comprises, in each of said satellite channel processors, the step of:

tracking a pseudo-random code of a satellite signal using a delay locked loop circuit.

7. The method of claim 1 wherein said step of processing signals from each of said plurality of satellites in a respective one of said plurality of satellite channel processors further comprises, in each of said satellite channel processors, the steps of:

tracking a carrier phase of a satellite signal using a phase locked loop circuit; and

tracking a pseudo-random code of a satellite signal using a delay locked loop circuit.

8. The method of claim 1 further comprising the step of applying a blocking signal to said plurality of satellite channel processors to block the processing of signals from an unwanted satellite.

9. The method of claim 8 wherein said plurality of antennas are arranged as a vertical antenna array and wherein said unwanted satellite is located above a threshold elevation angle relative to said antenna array.

10. An apparatus comprising:

a plurality of antennas;

a switch connected to said plurality of antennas for sequentially and cyclically switching an output of each of said plurality of antennas to a single signal processing path and thereby producing a common additive signal on said single signal processing path; and

a plurality of satellite channel processors each having an input connected to said signal path for receiving said common additive signal and each for processing signals from a respective one of said satellites.

11. The apparatus of claim 10 wherein each of said plurality of satellite channel processors comprises:

a phase locked loop circuit for tracking a carrier phase of a satellite signal using a reference signal.

12. The apparatus of claim 11 further comprising a phase shift correction module for generating a plurality of phase shift correction signals, each of said phase shift correction signals associated with one of said antennas.

13. The apparatus of claim 12 wherein each of said plurality of satellite channel processors further comprises a phase shifter for receiving said phase shift correction signals and for applying said phase shift correction signals to said reference signal.

14. The apparatus of claim 12 wherein said antennas are implemented as a horizontal antenna array and wherein said phase shift correction signals φ

_ik for an i-th antenna and a k-th satellite are calculated according to;

φ

_ik=(2π

L_i/λ

)(cosθ

_kθ

_icos(α

_k−

α

_i)+sinθ

_ksinθ

_i)

where

λ

is the wavelength of carrier oscillation;

L_i is the distance between the i-th antenna and an antenna center;

θ

_i is the elevation angle of a line that connects the antenna center to the i-th antenna;

θ

_k is the elevation angle of the k-th satellite;

θ

_i is the azimuth of a line that connects the antenna center to the i-th element; and

θ

_k is the azimuth of the k-th satellite.

15. The apparatus of claim 12 wherein said antennas are implemented as a vertical antenna array with an antenna center on the vertical axis and wherein said phase shift correction signals φ

_ik for an i-th antenna and a k-th satellite are calculated according to;

φ

_ik(2π

L_iλ

)sinθ

_k

where

λ

is the wavelength of carrier oscillation;

L_i is the distance between the i-th antenna and an antenna center; and

θ

_k is the elevation angle of the k-th satellite.

16. The apparatus of claim 10 further comprising a blocking module for generating a blocking signal and providing said blocking signal to said plurality of satellite channel processors to block the processing of signals from an unwanted satellite.

17. The apparatus of claim 16 wherein said plurality of antennas are arranged as a vertical antenna array and wherein said unwanted satellite is located above a threshold elevation angle relative to said antenna array.

18. An apparatus comprising:

a plurality of antennas for receiving a plurality of satellite signals;

means for sequentially and cyclically switching an output of each of said plurality of antennas to a single signal processing path to generate a common additive signal;

means for providing said common additive signal to each of a plurality of satellite channel processors; and

a plurality of satellite channel processors, each for processing signals from a respective one of said plurality of satellites.

19. The apparatus of claim 18 wherein each of said satellite channel processors further comprises:

means for tracking a carrier phase of a satellite signal using a reference signal.

20. The apparatus of claim 19 further comprising:

means for generating a plurality of phase shift correction signals, each of said phase shift correction signals associated with one of said antennas; and

wherein each of said satellite channel processors further comprises means for synchronously applying the phase shift correction signal associated with a particular antenna to the reference signal during processing of the component of the satellite signal associated with said particular antenna.

21. The apparatus of claim 20 wherein said antennas are implemented as a horizontal antenna array and wherein said means for generating a plurality of phase shift correction signals φ

_ik for an i-th antenna and a k-th satellite calculates said phase shift correction signals according to;

φ

_ik=(2π

L_i/λ

)(cosθ

_kθ

_icos(α

_k−

α

_i)+sinθ

_ksinθ

_i)

where

λ

is the wavelength of carrier oscillation;

L_i is the distance between the i-th antenna and an antenna center;

θ

_i is the elevation angle of a line that connects the antenna center to the i-th antenna;

θ

_k is the elevation angle of the k-th satellite;

α

_i is the azimuth of a line that connects the antenna center to the i-th element; and

α

_k is the azimuth of the k-th satellite.

22. The apparatus of claim 20 wherein said antennas are implemented as a vertical antenna array with an antenna center on the vertical axis and wherein said means for generating a plurality of phase shift correction signals φ

_ik for an i-th antenna and a k-th satellite calculates said phase shift correction signals according to;

φ

_ik=(2π

L_i/λ

)sinθ

_k

where

λ

is the wavelength of carrier oscillation;

L_i is the distance between the i-th antenna and an antenna center; and

θ

_k is the elevation angle of the k-th satellite.

23. The apparatus of claim 18 wherein each of said satellite channel processors further comprises:

means for tracking a pseudo-random code of a satellite signal using a delay locked loop circuit.

24. The apparatus of claim 18 wherein each of said satellite channel processors further comprises:

means for tracking a carrier phase of a satellite signal using a phase locked loop circuit; and

means for tracking a pseudo-random code of a satellite signal using a delay locked loop circuit.

25. The apparatus of claim 18 further comprising:

means for of applying a blocking signal to said plurality of satellite channel processors to block the processing of signals from an unwanted satellite.

26. The apparatus of claim 25 wherein said plurality of antennas are arranged as a vertical antenna array and wherein said unwanted satellite is located above a threshold elevation angle relative to said antenna array.