Mitigation of radio frequency interference (RFI) in global positioning system (GPS) signals

Patent metadata

Field	Value
Publication number	US-9632183-B2
Application number	US-201314088154-A
Country	US
Kind code	B2
Filing date	Nov 22, 2013
Priority date	Nov 22, 2013
Publication date	Apr 25, 2017
Grant date	Apr 25, 2017

Abstract

A technology is provided for reducing pulsed radio frequency interference. The GPS signal may be received at a GPS device. The GPS device may include a GPS receiver. The GPS signal may include a plurality of sign and magnitude bits. Pulsed RFI may be detected in the GPS signal based on samples of the magnitude bits in the GPS signal. The pulsed RFI received at the GPS receiver may be reduced by communicating a blank signal when the samples of the magnitude bits indicate the pulsed RFI.

First claim

What is claimed is:

1. A method for reducing pulsed radio frequency interference (RFI), the method comprising:
receiving a GPS signal at a GPS device, wherein the GPS signal includes a plurality of sign and magnitude bits and the GPS device includes a GPS receiver;
detecting pulsed RFI in the GPS signal based on samples of the magnitude bits in the GPS signal;
reducing the pulsed RFI received at the GPS receiver by communicating a blank signal when the samples of the magnitude bits indicate the pulsed RFI;
detecting the pulsed RFI in the GPS signal based on GPS signal samples; and
reducing the pulsed RFI received at the GPS receiver by communicating the blank signal to the GPS receiver for a predefined period of time in accordance with a timer.

2. The method of claim 1 , further comprising communicating GPS signals that do not contain pulsed RFI to the GPS receiver, the GPS signals including one or more intervals of blank signals.

3. The method of claim 1 , further comprising communicating GPS signals that do not contain pulsed RFI to a selective availability anti-spoofing module (SAASM) included in the GPS device.

4. The method of claim 1 , further comprising detecting pulsed RFI in the GPS signal by detecting at least 100 consecutive magnitude bits out of 128 samples indicate that the GPS signal contains the pulsed RFI.

5. The method of claim 1 , further comprising lowering an automatic gain control (AGC) of the GPS device to increase the signal gain when 1280 consecutive samples of the magnitude bits do not indicate pulsed RFI.

6. The method of claim 1 , further comprising
communicating the blank signal to the GPS receiver for up to 100 microseconds.

7. The method of claim 6 , further comprising:
detecting that the GPS signal samples do not indicate the pulsed RFI when the blank signal is being communicated to the GPS receiver in accordance with the timer; and
communicating the blank signal to the GPS receiver for an additional 160 samples for reducing the pulsed RFI received at the GPS receiver.

8. The method of claim 1 , further comprising detecting that the samples of the GPS signal do not include the pulsed RFI by detecting that less than 100 consecutive magnitude bits out of 128 samples indicate a presence of pulsed RFI in the GPS signal.

9. The method of claim 1 , further comprising:
determining that GPS signal samples indicate continuous RFI upon expiry of the timer; and
adjusting an automatic gain control (AGC) of the GPS device to compensate for the continuous RFI.

10. The method of claim 9 , wherein adjusting the AGC includes providing a fixed ratio of 16% of the samples of the magnitude bits indicating pulsed RFI to the AGC.

11. The method of claim 1 , further comprising receiving the GPS signal at a First In-First Out (FIFO) delay buffer included in the GPS device.

12. A global positioning system (GPS) device, the GPS device comprising:
a FIFO delay buffer configured to receive a GPS signal with pulsed radio frequency interference (RFI);
a state machine configured to detect pulsed RFI in the GPS signal and communicate a blank signal instead of the GPS signal for a predefined time period; and
a positioning module configured to receive the blank signal and a GPS signal without pulsed RFI and determine a geographical location of the GPS device using the GPS signal without pulsed RFI,
wherein the state machine is configured to reduce the amount of pulsed RFI received at the positioning module by sending the blank signal to the positioning module upon detection of the pulsed RFI in the GPS signal.

13. The GPS device of claim 12 , wherein the state machine is further configured to detect the pulsed RFI in the GPS signal by detecting 100 consecutive GPS signal samples out of 128 samples that indicate a presence of pulsed RFI in the GPS signal.

14. The GPS device of claim 12 , wherein the state machine is configured to reduce the amount of pulsed RFI received at the positioning module by sending a blank signal, to the positioning module, for the predefined time period.

15. The GPS device of claim 12 , wherein the state machine sends the blank signal to the positioning module for up to 100 microseconds.

16. The GPS device of claim 12 , wherein the state machine is configured to:
determine that the GPS signal samples do not indicate pulsed RFI in the GPS signal; and
reduce the amount of pulsed RFI received at the GPS receiver by communicating a blank signal to the GPS receiver for an additional 160 samples.

17. The GPS device of claim 12 , wherein the FIFO delay buffer and the state machine are included in a field programmable gate array (FPGA) circuit, the FPGA circuit being described by a plurality of Very High Speed Integrated Circuits (VHSIC) Hardware Description Language (VHDL) instructions.

18. A system for reducing pulsed radio frequency interference (RFI), the system comprising:
a receiving module configured to receive a GPS signal at a GPS device, the GPS device including a GPS receiver and the GPS signal including a plurality of sign and magnitude bits;
a pulsed RFI detection module configured to detect pulsed RFI in the GPS signal based on samples of the magnitude bits in the GPS signal; and
a pulsed RFI reduction module configured to reduce the pulsed RFI received at the GPS receiver by communicating a blank signal along with the GPS signal to the GPS receiver for a predefined time period,
wherein the pulsed RFI reduction module multiplexes the blank signal with the GPS signal when the pulsed RFI is detected in the GPS signal, and reduces the pulsed RFI received at the GPS receiver by communicating the blank signal to the GPS receiver for an additional predefined number of samples after predefined time period.

19. The system of claim 18 , wherein the pulsed RFI detection module is further configured to communicate the blank signal for the predefined time period when the samples of the magnitude bits indicate the pulsed RFI.

20. The system of claim 18 , wherein the pulsed RFI detection module is further configured to detect at least 100 consecutive magnitude bits out of 128 samples indicating that the GPS signal includes the pulsed RFI.

21. The system of claim 18 , wherein the pulsed RFI reduction module
multiplexes the blank signal with the GPS signal for up to 100 microseconds; and
communicates the blank signal, to the GPS receiver, for an additional 160 samples after the 100 microseconds.

Assignees

• Raytheon Co

Inventors

• Zehnpfennig David M
• Goldmann Kenneth
• Cherchian Omid
• Gonzales Brian R

Classifications

• G01S19/21 Primary

  Interference related issues {; Issues related to cross-correlation, spoofing or other methods of denial of service} · CPC title

• G01S19/215

  issues related to spoofing · CPC title