Method and apparatus for remote detection of radio-frequency devices

• US 8,131,239 B1
• Filed: 08/21/2007
• Issued: 03/06/2012
• Est. Priority Date: 08/21/2006
• Status: Active Grant

• Current Assignee: Vadum Inc.
• Original Assignee: Vadum Inc.
• Inventors: Buff, Peter Marcus III, Walker, Aaron Lael
• Primary Examiner(s): Nguyen, Duc M
• Application Number:
  US11/842,264
• Publication Number:
  US 20120071105A1
• Time in Patent Office: 1,659 Days
• Field of Search: 455/67.11, 455/67.13, 455/90.1, 455/227, 455/337, 455/456.4, 455/565, 342/193, 342/22, 342/44, 340/572.2, 340/10.42
• US Class Current: 455/227
• CPC Class Codes: G01S 13/04 Systems determining presence of a target based on relative movement of target G01S13/56
• CPC Class Codes: G01S 7/021 Auxiliary means for detecting or identifying radar signals or the like, e.g. radar jamming signals
• CPC Class Codes: G01S 7/412 based on a comparison between measured values and known or stored values

Abstract

Methods and apparatus for detecting the presence of electronic communications devices, such as cellular phones, are disclosed. In an exemplary method, a complex radio frequency stimulus is transmitted into a target area, and nonlinear reflection signals received from the target area are processed to obtain a response measurement. The response measurement is compared to a pre-determined filter response profile to detect the presence of a radio device having a corresponding filter response characteristic. In some embodiments, the pre-determined filter response profile comprises a pre-determined band-edge profile, so that comparing the response measurement to a pre-determined filter response profile comprises comparing the response measurement to the pre-determined band-edge profile to detect the presence of a radio device having a corresponding band-edge characteristic.

Claims

1. A method for detecting the presence of a radio device, comprising:

transmitting a complex radio frequency stimulus into a target area by transmitting a first component at a first frequency and sweeping a second component between a second and third frequency, wherein the first, second, and third frequencies are selected so that third-order intermodulation products of the first and second components traverse a band-edge of a predicted device response;

processing nonlinear reflection signals received from the target area to obtain a response measurement, wherein the processed nonlinear reflection signals correspond to the third-order intermodulation products and wherein the response measurement comprises a first amplitude value corresponding to at least one frequency below a band-edge of a predicted device response and a second amplitude value corresponding to at least one frequency above said band-edge; and

comparing the response measurement to a pre-determined filter response profile to detect the presence of a radio device having a corresponding filter response characteristic by comparing the difference between the first amplitude value and the second amplitude value to a pre-determined threshold.

2. The method of claim 1, wherein the pre-determined filter response profile comprises a pre-determined band-edge profile, wherein comparing the response measurement to a pre-determined filter response profile comprises comparing the response measurement to the pre-determined band-edge profile to detect the presence of a radio device having a corresponding band-edge characteristic.

3. The method of claim 1, wherein processing nonlinear reflection signals comprises filtering the nonlinear reflection signals to reject the transmitted complex radio frequency stimulus.

4. The method of claim 1, wherein the response measurement comprises a plurality of amplitude values corresponding to a plurality of frequencies, and wherein comparing the response measurement to a pre-determined filter response profile comprises comparing the amplitude values to one or more masks characterizing the pre-determined filter response profile.

5. The method of claim 1, wherein transmitting a complex radio frequency stimulus comprises transmitting a first component from a first transmitter and transmitting a second component from a second transmitter chain.

6. A method for detecting the presence of a radio device, comprising:

transmitting a complex radio frequency stimulus into a target area;

processing nonlinear reflection signals received from the target area to obtain a response measurement; and

comparing the response measurement to a pre-determined filter response profile to detect the presence of a radio device having a corresponding filter response characteristic;

wherein transmitting a complex radio frequency stimulus comprises transmitting a first component at a first frequency and transmitting a modulated second component at a second frequency, the modulated second component having a modulation bandwidth, wherein the first frequency, the second frequency, and the modulation bandwidth are selected so that a third-order intermodulation product produced by the first and second components has a bandwidth that substantially overlaps a band-edge of a predicted device response; and

wherein the processed nonlinear reflection signals correspond to the third-order intermodulation product of the first and second component.

7. The method of claim 6, wherein the first and second components comprise quadrature and in-phase components, respectively, of the complex radio frequency stimulus.

8. An apparatus for detecting the presence of a radio device, comprising:

a transmitter section configured to transmit a complex radio frequency stimulus into a target area, the complex radio frequency stimulus comprising a first component at a first frequency and a second component swept between a second and third frequency, wherein the first, second and third frequencies are selected so that third-order intermodulation products of the first and second components traverse a band-edge of a predicted device response;

a receiver section configured to receive nonlinear reflection signals from the target area wherein the nonlinear reflection signals correspond to the third-order intermodulation products; and

a signal processing section configured to process the received signals to obtain a response measurement and to compare the response measurement to a pre-determined filter response profile to detect the presence of a radio device having a corresponding filter response characteristic, wherein the signal processing section is configured to obtain a response measurement comprising a first amplitude value corresponding to at least one frequency below a band-edge of a predicted device response and a second amplitude value corresponding to at least one frequency above said band-edge, and wherein the signal processing section is further configured to compare the difference between the first amplitude value and the second amplitude value to a pre-determined threshold to detect the presence of the radio device.

9. The apparatus of claim 8, wherein the receiver section comprises a filter configured to reject the transmitted complex radio frequency stimulus while passing the nonlinear reflection signals.

10. The apparatus of claim 8, wherein the signal processing section is configured to obtain a response measurement comprising a plurality of amplitude values corresponding to a plurality of frequencies, and wherein the signal process section is further configured to compare the amplitude values to one or more masks characterizing the pre-determined band-edge profile.

11. The apparatus of claim 10, wherein the first and second components comprise in-phase and quadrature components, respectively, of the complex radio frequency stimulus.

12. The apparatus of claim 8, wherein the transmitter section comprises a first transmitter chain configured to transmit a first component of the complex radio frequency stimulus and a second transmitter chain configured to transmit a second component of the complex radio frequency stimulus.

13. An apparatus for detecting the presence of a radio device, comprising:

a transmitter section configured to transmit a complex radio frequency stimulus into a target area;

a receiver section configured to receive nonlinear reflection signals from the target area; and

a signal processing section configured to process the received signals to obtain a response measurement and to compare the response measurement to a pre-determined filter response profile to detect the presence of a radio device having a corresponding filter response characteristic;

wherein the transmitter section is configured to transmit a complex radio frequency stimulus by transmitting a first component at a first frequency and transmitting a modulated second component at a second frequency, the modulated second component having a modulation bandwidth, wherein the first frequency, the second frequency, and the modulation bandwidth are selected so that a third-order intermodulation product produced by the first and second components has a bandwidth that substantially overlaps a band-edge of a predicted device response; and

wherein the nonlinear reflection signals correspond to the third-order intermodulation product of the first and second component.