Method and apparatus for reducing electromagnetic interference and jamming in GPS equipment operating in rolling environments

• US 20040164900A1
• Filed: 03/03/2004
• Published: 08/26/2004
• Est. Priority Date: 12/04/2001
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Electro-Radiation Incorporated
• Inventors: Van Alstine, David J., Rosen, Murray W., Casabona, Mario M.
• Granted Patent: US 6,861,983 B2
• Time in Patent Office: Days
• US Class Current: 342/420
• 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 19/36 relating to the receiver frond end
• CPC Class Codes: H04K 3/228 Elimination in the received signal of jamming or of data corrupted by jamming interference suppression in receivers H04B1/10
• CPC Class Codes: H04K 3/90 related to allowing or preventing navigation or positioning, e.g. GPS

Abstract

A method and apparatus for reducing electromagnetic interference (EMI) and jamming in Global Positioning System (GPS) receivers operating on rolling or spinning platforms and/or environments is provided. An antenna system having a pair of diametrically-mounted elements provides interferometric cancellation for spatial and polarization nulling of interference signals. The antenna system, operating in conjunction with multiplexing and anti-jamming electronics, provides interference suppression for a GPS receiver connected thereto. Interference cancellation is provided in jamming and non-jamming environments by selectively employing spatial or polarization nulling of the interference signal.

Claims

1. A method for reducing interference and jamming in a receiver operating on a moving platform comprising:

receiving a radio signal with an antenna system mounted on the platform;

sensing interference or jamming in the radio signal;

determining platform roll;

implementing a polarization nulling technique to cancel interference or jamming where there is no roll or slow roll; and

implementing a spatial nulling technique to cancel interference or jamming where roll exceeds slow roll.

2. The method of claim 1, further comprising synchronizing the nulling technique with a source of interference without using external references.

3. The method of claim 1, further comprising switching from spatial nulling to polarization nulling when platform roll changes from a fast roll to a slow roll.

4. The method of claim 1, further comprising switching from polarization nulling to spatial nulling when platform roll changes from a slow roll to a fast roll.

5. The method of claim 1, further comprising wrap calibrating the polarization nulling technique to produce an optimal polarization null pattern.

6. The method of claim 1, further comprising wrap calibrating the spatial nulling technique to produce an optimal spatial null pattern.

7. An apparatus for reducing interference in a receiver operating on a rolling platform comprising:

a pair of diametrically-mounted antennas mounted on the rolling platform;

means for determining interference levels of radio signals received by the antennas;

means for determining roll rates of the rolling platform;

a modulator for generating a spatial null pattern and a polarization null pattern; and

means for selecting between the spatial null pattern and the polarization null pattern based upon the roll rates.

8. The apparatus of claim 7, further comprising means for combining the pair of antennas to produce a receive signal when no interference or jamming is present.

9. The apparatus of claim 7, further comprising a multiplexer connected to the antennas.

10. The apparatus of claim 9, wherein the multiplexer switches the antennas between spatial and polarization nulling modes.

11. The apparatus of claim 7, wherein the modulator modulates phases and amplitudes of radio signals received by the antennas to generate the spatial null pattern and the polarization null pattern.

12. The apparatus of claim 7, further comprising a controller for controlling the modulator.

13. The apparatus of claim 12, wherein the controller controls the modulator in response to sensed interference levels.

14. A method for reducing interference in a receiver operating on a moving platform comprising:

detecting interference or jamming in a radio signal received by the receiver;

creating a spatial null pattern if platform roll exceeds slow roll;

calibrating and maintaining the spatial null pattern with a downhill gradient process if interference levels exceed predetermined thresholds and platform roll exceeds slow roll;

creating a polarization null pattern if the platform has no roll or slow roll; and

calibrating and maintaining the polarization null pattern with a downhill gradient process if interference is present and the platform has no roll or slow roll.

15. The method of claim 14, wherein the steps of calibrating and maintaining the spatial and polarization null patterns comprises:

monitoring relative phases and amplitudes of the radio signal using a tracking loop;

determining the best null in response to the monitored phases and amplitudes; and

creating the best null by adjusting the phases and amplitudes of the radio signal.

16. The method of claim 14, further comprising removing the null patterns when interference is not present.