Remote detection of electronic devices

• US 8,275,334 B1
• Filed: 04/09/2009
• Issued: 09/25/2012
• Est. Priority Date: 04/09/2008
• Status: Active Grant

• Current Assignee: TRIAD National Security, LLC
• Original Assignee: Los Alamos National Security LLC (Government of the United States of America)
• Inventors: Judd, Stephen L., Fortgang, Clifford M., Guenther, David C.
• Primary Examiner(s): HANNON, CHRISTIAN A
• Application Number:
  US12/421,623
• Publication Number:
  US 20120236905A1
• Time in Patent Office: 1,265 Days
• Field of Search: 455 411- 412, 4551151-1154, 455/140, 4551611-1612, 455/165.1, 4552261-2264, 455227-228, 324 7641- 7643
• US Class Current: 455/227
• CPC Class Codes: G01S 13/18 wherein range gates are used
• CPC Class Codes: G01S 13/284 using coded pulses
• CPC Class Codes: G01S 13/887 for detection of concealed objects, e.g. contraband or weapons
• CPC Class Codes: H04B 1/707 using direct sequence modulation

Abstract

An apparatus and method for detecting solid-state electronic devices are described. Non-linear junction detection techniques are combined with spread-spectrum encoding and cross correlation to increase the range and sensitivity of the non-linear junction detection and to permit the determination of the distances of the detected electronics. Nonlinear elements are detected by transmitting a signal at a chosen frequency and detecting higher harmonic signals that are returned from responding devices.

Claims

1. An apparatus for remotely locating solid-state electronics, comprising in combination:

an RF generator for generating a chosen frequency RF signal;

a signal splitter for dividing the RF signal into a transmitted portion and a reference portion;

a modulator for encoding a chosen code onto the transmitted portion of the RF signal;

a controller for generating the chosen code, and for directing the code to said modulator;

a power amplifier for amplifying the encoded RF signal;

an antenna for transmitting the amplified, encoded RF signal;

an antenna for receiving a similarly encoded second harmonic frequency of the encoded RF signal;

a demodulator for receiving the second harmonic frequency and the chosen code delayed by a selected time interval from said controller, and for removing the modulation from the second harmonic frequency;

a frequency doubler for doubling the frequency of the reference portion of the RF signal;

a mixer for comparing the doubled frequency of the reference portion of the RF signal with the demodulated second harmonic frequency, and for generating a DC signal if the doubled frequency of the reference portion of the RF signal is correlated with the demodulated second harmonic frequency; and

a computer for receiving the DC signal, for directing said controller and for calculating distance between located solid-state electronics and said transmitting antenna.

2. The apparatus of claim 1, wherein said modulator and said demodulator comprise quadrature phase modulators.

3. The apparatus of claim 2, wherein the chosen code is imparted to the transmitted portion of the RF signal by binary phase shift keying spread-spectrum modulation.

4. The apparatus of claim 3, wherein the code is chosen from M-sequences, Gold codes, Kasami sequences, and q-ary codes.

5. The apparatus of claim 3, wherein the binary phase shift keying spread-spectrum modulation has a modulation frequency of less than about 100 MHz.

6. The apparatus of claim 1, wherein said chosen code is imparted to the transmitted portion of the RF signal by frequency shift keying spread-spectrum modulation.

7. The apparatus of claim 1 wherein said controller comprises a field programmable gate array.

8. The apparatus of claim 1, wherein said transmitting antenna is a directional antenna.

9. The apparatus of claim 1, wherein said receiving antenna is a directional antenna.

10. The apparatus of claim 1, wherein said transmitting antenna and said receiving antenna are disposed on a movable vehicle.

11. The apparatus of claim 1, wherein said transmitting antenna and said receiving antenna are disposed on an elevated platform.

12. The apparatus of claim 1, wherein said chosen frequency is between about 870 MHz and about 920 MHz.

13. The apparatus of claim 1, further comprising at least one RF filter for reducing interference of harmonics of the chosen frequency generated in said apparatus.

14. The apparatus of claim 1, wherein the DC signal is averaged over a selected number of cycles of said apparatus.

15. The apparatus of claim 1, further comprising a low-noise amplifier for amplifying the encoded second harmonic frequency of the encoded RF signal received by said receiving antenna.

16. A method for remotely locating solid-state electronics, comprising the steps of:

generating a chosen frequency RF signal;

dividing the RF signal into a transmitted portion and a reference portion;

encoding a chosen code onto the transmitted portion of the RF signal;

amplifying the encoded RF signal;

transmitting the amplified, encoded RF signal;

receiving a similarly encoded second harmonic frequency of the encoded RF signal;

removing the encoding from the second harmonic frequency;

doubling the frequency of the reference portion of the RF signal;

comparing the doubled frequency of the reference portion of the RF signal with the second harmonic frequency for which the encoding has been removed;

generating a DC signal if the doubled frequency of the reference portion of the RF signal is correlated with the second harmonic frequency for which the encoding has been removed; and

calculating a distance between located solid-state electronics and the location of said step of transmitting the amplified, encoded RF signal.

17. The method of claim 16, wherein the code in said step of encoding the chosen code is imparted to the transmitted portion of the RF signal by binary phase shift keying spread-spectrum modulation.

18. The method of claim 17, wherein the code is chosen from M-sequences, Gold codes, Kasami sequences, and q-ary codes.

19. The method of claim 17, wherein the binary phase shift keying spread-spectrum modulation has a modulation frequency of less than about 100 MHz.

20. The method of claim 16, wherein the code in said step of encoding the chosen code is imparted to the transmitted portion of the RF signal by frequency shift keying spread-spectrum modulation.

21. The method of claim 16, wherein said step of transmitting the amplified, encoded RF signal is performed using a directional transmitting antenna.

22. The method of claim 16, wherein said step of receiving an encoded first harmonic frequency of the encoded RF signal is performed using a directional receiving antenna.

23. The method of claim 21, further comprising the step of disposing the directional transmitting antenna on a movable vehicle.

24. The method of claim 22, further comprising the step of disposing the directional receiving antenna on a movable vehicle.

25. The method of claim 21, further comprising the step of disposing the directional transmitting antenna on an elevated platform.

26. The method of claim 22, further comprising the step of disposing the directional receiving antenna on an elevated platform.

27. The method of claim 16, wherein the chosen frequency is between about 870 MHz and about 920 MHz.

28. The method of claim 16, further comprising the step of filtering for reducing interference of generated harmonics of the chosen frequency.

29. The method of claim 16, further comprising the step of averaging the DC signal over a selected number of cycles of said method.

30. The method of claim 16, further comprising the step amplifying the similarly encoded second harmonic frequency of the encoded RF signal.