Patent Number: 
Section: claims

1. A method, comprising:concurrently modulating an X-ray signal with a first radio frequency signal and with a second radio frequency signal to generate a modulated X-ray signal;transmitting the modulated X-ray signal into a field of view containing a sample;receiving backscatter of the modulated X-ray signal reflected from the sample; andprocessing the backscatter to identify the sample from a pattern of detected harmonics of the first radio frequency signal and the second radio frequency signal. 2. The method of claim 1, wherein the backscatter is generated by diffraction of the modulated X-ray signal by the sample. 3. The method of claim 1, wherein the detected harmonics include spurious harmonic products of the first radio frequency signal and the second radio frequency signal. 4. The method of claim 1, wherein processing the backscatter to identify the sample includes comparing a detected harmonic pattern against a plurality of a priori known harmonic pattern signatures. 5. An X-ray RADAR apparatus, comprising:means for concurrently modulating an X-ray signal with a first radio frequency signal and with a second radio frequency signal to generate a modulated X-ray signal;means for transmitting the modulated X-ray signal into a field of view containing a sample;means for receiving backscatter of the modulated X-ray signal reflected from the sample; andmeans for processing the backscatter to identify the sample from a pattern of detected harmonics of the first radio frequency signal and the second radio frequency signal. 6. The X-ray RADAR apparatus of claim 5, wherein the detected harmonics include spurious harmonic products of the first radio frequency signal and the second radio frequency signal. 7. The X-ray RADAR apparatus of claim 5, wherein processing the backscatter to identify the sample includes comparing a detected harmonic pattern against a plurality of a priori known harmonic pattern signatures. 8. The X-ray RADAR apparatus of claim 5, further comprising means for collimating the modulated X-ray signal before the transmitting. 9. A computer-implemented method, comprising:receiving data representative of backscatter of a radio frequency modulated X-ray signal reflected from a sample, the radio frequency modulated X-ray signal being concurrently radio frequency modulated with a first radio frequency signal and with a second radio frequency signal; andprocessing the data to identify the sample from a pattern of detected harmonics of the first radio frequency signal and the second radio frequency signal. 10. The computer-implemented method of claim 9, wherein the data is generated by diffraction of the radio frequency modulated X-ray signal by the sample. 11. The computer-implemented method of claim 9, wherein the detected harmonics include spurious harmonic products of the first radio frequency signal and the second radio frequency signal. 12. The computer-implemented method of claim 9, wherein processing the data to identify the sample includes comparing a detected harmonic pattern against a plurality of a priori known harmonic pattern signatures. 13. A program storage medium encoded with instructions that, when executed by a processor, perform a software implemented method, the software implemented method comprising:receiving data representative of backscatter of a radio frequency modulated X-ray signal reflected from a sample, the radio frequency modulated X-ray signal being radio frequency modulated concurrently with a first radio frequency signal and with a second radio frequency signal; andprocessing the data to identity the sample from a pattern of detected harmonics of the first radio frequency signal and the second radio frequency signal. 14. The program storage medium of claim 13, wherein the data is generated by diffraction of the radio frequency modulated X-ray signal by the sample. 15. The program storage medium of claim 13, wherein the detected harmonics include spurious harmonic products of the first radio frequency signal and the second radio frequency signal. 16. The program storage medium of claim 13, wherein processing the data to identify the sample includes comparing a detected harmonic pattern against a plurality of a priori known harmonic pattern signatures. 17. A computing apparatus, comprising:a processor;a bus system;a storage communicating with the processor over the bus system; andan application residing on the storage that, when invoked by the processor, performs a software implemented method, comprising:receiving data representative of backscatter of a radio frequency modulated X-ray signal reflected from a sample, the radio frequency modulated X-ray signal being radio frequency modulated concurrently with a first radio frequency signal and with a second radio frequency signal; andprocessing the data to identify the sample from a pattern of detected harmonics of the first radio frequency signal and the second radio frequency signal. 18. The computing apparatus of claim 17, wherein processing the data to identify a sample includes comparing the detected harmonic pattern against a plurality of a priori known harmonic pattern signatures. 19. An X-ray RADAR apparatus, comprising:a transmitter capable of:concurrently modulating an X-ray signal with a first radio frequency signal and with a second radio frequency signal to generate a modulated X-ray signal; andtransmitting the modulated X-ray signal into a field of view;a receiver capable of receiving backscatter of the modulated X-ray signal reflected from a sample within the field of view; anda processing unit capable of processing the backscatter to identify the sample from a pattern of detected harmonics of the first radio frequency signal and the second radio frequency signal. 20. The X-ray RADAR apparatus of claim 19, wherein the processing unit comprises:a processor;a bus system;a storage communicating with the processor over the bus system; andan application residing on the storage that, when invoked by the processor, performs a software implemented method, comprising:processing the backscatter to identify the sample from the pattern of the detected harmonics of the first radio frequency signal and the second radio frequency signal.