Sign detection in multi-dimensional signal measurements

Patent metadata

Field	Value
Publication number	US-2016148448-A1
Application number	US-201414560713-A
Country	US
Kind code	A1
Filing date	Dec 4, 2014
Priority date	Nov 25, 2014
Publication date	May 26, 2016
Grant date	—

Abstract

Systems, methods, circuits and computer-readable mediums are disclosed for sign detection in multi-dimensional signal measurements. In some implementations, orthogonally oriented antennas are configured to generate signals in response to a magnetic field, where the signals correspond to components of magnetic field vectors in space. A circuit is coupled to the antennas and configured to: determine polarities of the signals based on phase measurements between the signals; reduce a possible number of magnetic field vector interpretations based on the determined polarities of the signals; reduce a possible number of angles or angle differences between the magnetic field vectors based on the reduced possible number of magnetic field vector interpretations; compare the reduced possible number of angles or angle differences to predetermined angle or angle differences; and detect a relay attack based on results of the comparing.

First claim

What is claimed is:

1 . A system comprising:
orthogonally oriented antennas configured to generate signals in response to a magnetic field, where the signals correspond to components of magnetic field vectors in space; a circuit coupled to the antennas and configured to:
determine polarities of the signals based on phase measurements between the signals;
reduce a possible number of magnetic field vector interpretations based on the determined polarities of the signals;
reduce a possible number of angles or angle differences between the magnetic field vectors based on the reduced possible number of magnetic field vector interpretations;
compare the reduced possible number of angles or angle differences to predetermined angle or angle differences; and
detect a relay attack based on results of the comparing.

2 . The system of claim 1 , where comparing the polarities of the signals includes comparing the signals with threshold values.

3 . The system of claim 2 , where the threshold values are a percentage of maximum values of the signals.

4 . The system of claim 1 , where the circuit comprises:
one or more signal amplifiers coupled to the antennas and configured to amplify the signals; one or more analog-to-digital converters (ADCs) coupled to the signal amplifiers and configured to convert the amplified signals to digital values; and one or more signal processors coupled to the one or more ADCs and configured for determining the polarities of the signals based on the digital values.

5 . The system of claim 3 , where the circuit comprises:
one or more signal amplifiers coupled to the antennas and configured to amplify the signals; comparators having inputs coupled to outputs of the signal amplifiers and the threshold voltages, the comparators configured for indicating when the signals exceed the threshold values; and logic configured to compare comparator outputs to determine the polarities of the signals.

6 . The system of claim 1 , where one or more ratios between the components of one or more magnetic field vectors are determined based on the reduced possible number of magnetic field vector interpretations; and the one or more actions related to the system are performed based on comparison of the ratios with expected ratios.

7 . The system of claim 6 , where the ratios are determined for same vector component for two different magnetic field vectors.

8 . The system of claim 6 , where the ratios are determined for different vector components for two different magnetic field vectors.

9 . The system of claim 1 , where the antennas and circuit are included in a key or key fob of a passive entry, passive start (PEPS) system of a vehicle.

10 . The system of claim 1 , where the possible number of magnetic field vector interpretations is reduced from eight to two.

11 . A method comprising:
generating, by orthogonally oriented antennas of a system, signals in response to a magnetic field, where the signals correspond to components of magnetic field vectors in space; determining, by a circuit of the system, polarities of the signals based on phase measurements between the signals; reducing, by the circuit, a possible number of magnetic field vector interpretations based on the determined polarities of the signals; reducing, by the circuit, a possible number of angles or angle differences between the magnetic field vectors based on the reduced possible number of magnetic vector interpretations; comparing, by the circuit, the reduced possible number of angles or angle differences to predetermined angles or angle differences; and detecting, by the circuit, a relay attack based on results of the comparing.

12 . The method of claim 11 , where comparing the polarities of the signals includes comparing the signals with threshold values.

13 . The method of claim 12 , where the threshold values are a percentage of maximum values of the signals.

14 . The method of claim 11 , further comprising:
amplifying the signals by one or more signal amplifiers coupled to the antennas; converting the amplified signals to digital values by one or more analog-to-digital converters (ADCs) coupled to the signal amplifiers; and determining, by one or more signal processors coupled to the one or more ADCs, the polarities of the signals based on the digital values.

15 . The method of claim 12 , further comprising:
amplifying the signals by one or more signal amplifiers coupled to the antennas; comparing the signals with threshold voltages, by comparators having inputs coupled to outputs of the signal amplifiers and the threshold voltages, to indicate when the signals exceed the threshold values; and comparing, by logic, comparator outputs to determine polarities of the signals.

16 . The method of claim 11 , further comprising:
determining one or more ratios between the components of one or more magnetic field vectors based on the reduced possible number of magnetic field vector interpretations; and performing one or more actions related to the system based on comparison of the ratios with expected ratios.

17 . The method of claim 16 , where the ratios are determined for same vector component for two different magnetic field vectors.

18 . The method of claim 16 , where the ratios are determined for different vector components for two different magnetic field vectors.

19 . A non-transitory, computer-readable storage medium having instructions stored thereon, which, when executed by one or more processors, causes the one or more processors to perform operations comprising:
generating, by orthogonally oriented antennas of a system, signals in response to a magnetic field, where the signals correspond to components of magnetic field vectors in space; determining polarities of the signals based on phase measurements between the signals; reducing a possible number of magnetic field vector interpretations based on the determined polarities of the signals; reducing a possible number of angles or angle differences between the magnetic field vectors based on the reduced possible number of magnetic vector interpretations; comparing the reduced possible number of angles or angle differences to predetermined angles or angle differences; and detecting a relay attack based on results of the comparing.

20 . The non-transitory, computer-readable storage medium of claim 19 , where comparing the signs or polarities of the signals includes comparing the signals with threshold values.

21 . The non-transitory, computer-readable storage medium of claim 20 , where the threshold values are a percentage of maximum values of the signals.

22 . The non-transitory, computer-readable storage medium of claim 19 , where one or more ratios between the components of one or more magnetic field vectors are determined based on the reduced possible number of magnetic field vector interpretations; and the one or more actions related to the system are performed based on comparison of the ratios with expected ratios.

23 . The non-transitory, computer-readable storage medium of claim 22 , where the ratios are determined for a same vector component for two different magnetic field vectors.

24 . The non-transitory, computer-readable storage medium of claim 22 , where the ratios are determined for different vector components for two different magnetic field vectors.

Assignees

• Atmel Corp

Inventors

• Blatz Werner

Classifications

• G07C9/28 Primary

  the pass enabling tracking or indicating presence · CPC title

• G07C2009/00555

  comprising means to detect or avoid relay attacks · CPC title

• G06K7/10257

  arrangements for protecting the interrogation against piracy attacks (computer security in general G06F21/00; jamming of communication, countermeasures H04K3/00; secret communication H04K1/00) · CPC title

• H04B7/00

  Radio transmission systems, i.e. using radiation field (H04B10/00, H04B15/00 take precedence) · CPC title

• G07C9/20

  involving the use of a pass · CPC title