Remote detection of electronic devices
View Patent ↗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.
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.