Multitone Harmonic Radar and Method of Use

• US 20150253415A1
• Filed: 04/25/2013
• Published: 09/10/2015
• Est. Priority Date: 04/25/2013
• Status: Active Grant

• Current Assignee: United States Of America As Represented By The Secretary Of The Army (Government of the United States of America)
• Original Assignee: US Army Research Laboratory (Government of the United States of America)
• Inventors: Martone, Anthony F., Mazzaro, Gregory James
• Granted Patent: US 9,395,434 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01S 13/04 Systems determining presence of a target based on relative movement of target G01S13/56
• CPC Class Codes: G01S 13/887 for detection of concealed objects, e.g. contraband or weapons
• CPC Class Codes: G01S 7/02 of systems according to group G01S13/00
• CPC Class Codes: G01S 7/354 Extracting wanted echo-signals Doppler systems G01S13/50
• CPC Class Codes: G01S 7/414 Discriminating targets with respect to background clutter

Abstract

A multitone nonlinear radar system (and a method of operating such a system) comprising a transmitter that transmits a signal comprising at least two predetermined frequency components; a receiver operating to receive return signals comprising harmonics of at least two predetermined frequencies, combinations of the at least two predetermined frequency components, and combinations of the harmonics of the at least two predetermined frequency components that are within a predetermined selected frequency range that has been predetermined to enable detection and/or classification of an electronic device; at least one antenna operating to transmit and receive electromagnetic radiation operatively connected to the transmitter and receiver; the receiver comprising at least one high pass filter for attenuating linear reflections at the two predetermined frequencies, and an analyzer;

whereby electronic devices may be detected and identified by analyzing return signals within a predetermined frequency range.

Claims

1. A multitone nonlinear radar system comprising:

a transmitter that transmits a signal comprising at least two predetermined frequency components;

a receiver operating to receive return signals comprising harmonics of at least two predetermined frequencies, combinations of the at least two predetermined frequency components, and combinations of the harmonics of the at least two predetermined frequency components that are within a predetermined selected frequency range that has been predetermined to enable detection and/or classification of an electronic device;

at least one antenna operating to transmit and receive electromagnetic radiation operatively connected to the transmitter and receiver;

the receiver comprising at least one high pass filter for attenuating linear reflections at the two predetermined frequencies, and an analyzer;

whereby electronic devices may be detected and identified by analyzing return signals within a predetermined frequency range.

2. The system of claim 1 wherein the at least two predetermined frequency components may be represented by frequencies f₁ and f₂, and the combination and harmonics of f₁ and f₂ comprise combinations that may be represented by Af₁ and Bf₂, where A and B are positive and negative integer values selected so that the combination is within the predetermined selected frequency range.

3. The system of claim 1 wherein by receiving combinations of the at least two predetermined frequency components, and combinations of the harmonics of the at least two predetermined frequency components that within the predetermined selected frequency range the detection of an electronic device may be determined, and wherein the system comprises a variable amplifier for amplifying the signal to be transmitted operatively connected to the transmitter that varies the amplitude of the at least two frequency components, and wherein the analyzer analyses the amplitudes of received signals such that by varying the amplitude of the at least two frequency components at a predetermined rate and detecting the rate of change in amplitude of the frequency components of the received signals, a detected electronics device may be classified as one of a cellphone or radio.

4. The system of claim 3 wherein the system operates to detect whether or not the electronics device is capable of transmitting RF signals.

5. The system of claim 1 wherein the range of the detected electronics device from the transmitter is determined the difference between the time of transmission of the transmitted signal and the time of arrival of the return signals, and wherein the direction to the detected electronic device is determined by the direction of the at least one antenna which maximizes the return signals for the at least two predetermined frequencies and a fixed transmit power.

6. The system of claim 1 wherein the transmitter comprises a first filter that is tuned to provide transmission of signals having frequencies within a predetermined range and wherein a continuous wave is generated to enable more power on the targeted area for maximum detection. and wherein the phase of the signal is measured by the analyzer.

7. The system of claim 1 wherein the herein the predetermined selected frequency range is selected to maximize the response from a target based upon the operating frequency of the target.

8. The system of claim 1 adapted to be used in conjunction with one of the operation of hospital medical equipment in order to avoid interference between unknown electronics devices and the medical equipment and the operation of a plane in order to avoid interference between the operation of detected electronics devices by the passengers and the operation of the plane'"'"'s electronic equipment.

9. The system of claim 1 wherein the system comprises a variable signal generator and an amplifier operatively connected to the transmitter that vary the amplitude and power of the at least two predetermined frequency components, and wherein the electronic devices to be detected comprise cellphones, and based upon the combinations of the at least two predetermined frequency components, and combinations of the harmonics of the at least two predetermined frequency components, the analyzer analyses the amplitude and power of received signals, whereby by varying the power of the at least two frequency components and detecting the rate of change in amplitude of the frequency components of the return signals, a detected electronics device may be classified as a cellphone or radio.

10. The system of claim 9 wherein the at least one antenna is a single antenna, and wherein the signals transmitted by the transmitter mix with the signals emitted by a target device to enable the generation and reception of mixing products centered on harmonics of the at least two predetermined frequencies.

11. The system of claim 1 wherein the transmitter further comprises a waveform generator used as a source of the transmitted signal, a step generator which adjusts the transmit signal power in at least approximately one decibel increments, a low pass filter that attenuates system generated harmonics before amplification, and an amplifier for amplifying the signal to be transmitted.

12. The system of claim 11 wherein the step generator operates to vary the power of the transmitted signal, and wherein the analyzer operates to detect how the harmonics change with varying transmitted power and wherein amplitudes that are received at different transmit powers effects the signature of the electronic device that enable classification as to the type of electronic device and whether or not the electronic device is designed to transmit and receive information.

13. The system of claim 1 wherein the at least one high pass filter comprises an adjustable high pass filter and wherein the receiver further comprises an amplifier operatively connected to the at least one adjustable high pass filter for passage of the harmonics within the predetermined selected frequency range and a plurality of band pass filters operatively connected to the amplifier, each of the plurality of band pass filters being limited to reception of a selected harmonic or selected combination of the at least two frequency components or harmonics.

14. The system of claim 13 wherein the receiver further comprises a plurality of detectors, each of the plurality of detectors being operatively connected to a different one of the plurality of band pass filters and wherein the detectors operate to detect signals within the predetermined selected frequency range of the receiver to output a voltage dependent on the RF power received and wherein how a target responds to differently powered transmitted signals is correlated with the voltage of the detector to determine information concerning the target and wherein the analyzer comprises a classifier which classifies the detected harmonics as originating from different types of electronic devices, the classifier being operatively connected to the plurality of detectors.

15. The system of claim 1 wherein the analyzer comprises an algorithm which looks for patterns in the information and makes a decision as to the target type based on the patterns, the patterns comprising the transmit signal frequencies, the power of the transmit signal, the differences between the transmitted signal and the received return signals, the rate of variation of the transmit signal power and the rate of variation of the received signal power relative to the rate of variation of the transmit signal.

16. The system of claim 1 wherein the transmitter comprises at least two sine wave generators, each sine wave generator operating to transmit at a signal at a different predetermined frequency, a combiner for combining the signals at the least two predetermined frequencies operatively connected to the at least two sine wave generators, and a low pass filter operatively connected to the combiner.

17. The system of claim 1 wherein the analyzer determines the type of electronic device detected using detection methodology based upon one of match filter, Bayesian decision theory, Generalized Likelihood Ratio Test, and constant false alarm rate processing to determine whether a nonlinearity is present.

18. The system of claim 1 wherein the analyzer classifies the type of electronic device detected using a classification method based upon one of Bayesian discriminate functions, nearest neighbor classifiers, support vector machines, neural networks, tree-based algorithms, and unsupervised learning algorithms for determining the type of RF device.

19. The system of claim 1 wherein the receiver is tunable to receive and process odd-order or even-order information, depending upon the harmonic to which the receiver is tuned.

20. A method of detecting electronic devices comprising:

providing a transmitter that transmits a signal comprising at least two predetermined frequency components;

providing a receiver operating to receive return signals comprising harmonics of at least two predetermined frequencies, combinations of the at least two predetermined frequency components, and combinations of the harmonics of the at least two predetermined frequency components that are within a predetermined selected frequency range that has been predetermined to enable detection and/or classification of an electronic device;

at least one antenna operating to transmit and receive electromagnetic radiation operatively connected to the transmitter and receiver;

the receiver comprising at least one high pass filter for attenuating linear reflections at the two predetermined frequencies, and an analyzer;

whereby electronic devices may be detected and identified by analyzing return signals within a predetermined frequency range.