GPS receiver and method for detecting a jammer signal using fast fourier transform

• US 20050285781A1
• Filed: 04/21/2005
• Published: 12/29/2005
• Est. Priority Date: 06/29/2004
• Status: Abandoned Application

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Park, Chan-Woo, Choi, Sun
• Application Number:
  US11/110,803
• Publication Number:
  US 20050285781A1
• Time in Patent Office: Days
• US Class Current: 342/357.48
• 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 19/254 relating to Doppler shift of satellite signals
• CPC Class Codes: G01S 19/29 carrier including Doppler, related G01S19/246 takes precedence
• CPC Class Codes: H04K 3/22 including jamming detection and monitoring
• CPC Class Codes: H04K 3/90 related to allowing or preventing navigation or positioning, e.g. GPS

Abstract

A global positioning system (GPS) receiver and method are provided for detecting a jammer signal using fast Fourier transform (FFT). A correlator correlates GPS signals received from GPS satellites with codes based on a plurality of carrier frequency signals having predetermined frequency offsets therebetween, and computes n correlated samples associated with each of the GPS satellites. A memory stores the n correlated samples associated with each of the GPS satellites and n FFT bins corresponding thereto. A FFT processor transforms the n correlated samples read from the memory using n-point FFT to obtain the n FFT bins, and transfers the n FFT bins to the memory. A peak detector detects largest peaks exceeding a lowered detection threshold from the FFT bins associated with each of the GPS satellites. A jammer detection unit makes a determination as to whether a peak relatively far away from other peaks is present among the largest peaks, and detects a signal of a peak far away from other peaks.

Claims

1. A method for detecting a jammer signal using fast Fourier transform (FFT) in a global positioning system (GPS) receiver, comprising:

correlating GPS signals received from GPS satellites with codes based on a plurality of carrier frequency signals having predetermined frequency offsets therebetween, and computing n correlated samples associated with each of the GPS satellites;

transforming the n correlated samples associated with each of the GPS satellites using n-point FFT to output n FFT bins;

detecting largest peaks exceeding a lowered detection threshold from the FFT bins associated with each of the GPS satellites; and

making a determination as to whether a peak relatively far away from other peaks is present among the largest peaks, and detecting, as a jammer signal, a signal of a peak far away from other peaks.

2. The method according to claim 1, wherein the lowered detection threshold is 3 dB less than a detection threshold in which false alarm probability of a jammer signal is less than 0.1%.

3. The method according to claim 1, wherein detecting the jammer signal comprises:

computing Doppler biases indicative of differences between frequencies of the peaks and a predicted Doppler center;

computing Delta biases indicative of differences between a common Doppler bias for the GPS satellites and the computed Doppler biases; and

detecting, as the jammer signal, a signal of a peak with a delta bias exceeding a predetermined limit among the delta biases.

4. The method according to claim 3, wherein the common Doppler bias is computed as an average of Doppler biases associated with a predetermined number of maximum peaks among the peaks.

5. The method according to claim 3, wherein the Doppler center is predicted by Doppler information provided from an assisted GPS (AGPS) server that receives the GPS signals from the GPS satellites.

6. A global positioning system (GPS) receiver for detecting a jammer signal using fast Fourier transform (FFT), comprising:

a correlator for correlating GPS signals received from GPS satellites with codes based on a plurality of carrier frequency signals having predetermined frequency offsets therebetween, and computing n correlated samples associated with each of the GPS satellites;

a memory for storing the n correlated samples associated with each of the GPS satellites and n FFT bins corresponding thereto;

a FFT processor for transforming the n correlated samples read from the memory using n-point FFT to obtain the n FFT bins, and transferring the n FFT bins to the memory;

a peak detector for detecting largest peaks exceeding a lowered detection threshold from the FFT bins associated with each of the GPS satellites; and

a jammer detection unit for making a determination as to whether a peak relatively far away from other peaks is present among the largest peaks, and detecting, as a jammer signal, a signal of a peak far away from other peaks.

7. The GPS receiver according to claim 6, wherein the lowered detection threshold is 3 dB less than a detection threshold in which false alarm probability of a jammer signal is less than 0.1%.

8. The GPS receiver according to claim 6, wherein the jammer detection unit comprises:

a bias measurer for computing Doppler biases indicative of differences between frequencies of the peaks and a predicted Doppler center;

a delta bias measurer for computing Delta biases indicative of differences between a common Doppler bias for the GPS satellites and the computed Doppler biases; and

a jammer detector for detecting, as the jammer signal, a signal of a peak with a delta bias exceeding a predetermined limit among the delta biases.

9. The GPS receiver according to claim 8, wherein the common Doppler bias is computed as an average of Doppler biases associated with a predetermined number of maximum peaks among the peaks.

10. The GPS receiver according to claim 8, wherein the Doppler center is predicted by Doppler information provided from an assisted GPS (AGPS) server that receives the GPS signals from the GPS satellites.