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The invention relates to methods and devices for precise geolocation of low-power, broadband, amplitude-modulated rf and microwave signals having poor coherency. The invention provides a basis for dramatic improvements in RF receiver technology, offering much higher sensitivity, very strong rejectio

The invention relates to methods and devices for precise geolocation of low-power, broadband, amplitude-modulated rf and microwave signals having poor coherency. The invention provides a basis for dramatic improvements in RF receiver technology, offering much higher sensitivity, very strong rejection of unintended signals, and novel direction finding techniques. When mounted on an airborne surveillance platform, the invention can detect and geolocate weak, broadband, incoherent RF and/or microwave signals. Embodiments of the invention are implemented by dual channel receivers (heterodyne or tuned-RF) that use crystal detection and Fast Fourier Transform (FFT) analysis for geolocation. Geolocation is accomplished using a subsystem of phased arrays and an angle of arrival technique.

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1. A system for analyzing an amplitude-modulated signal, comprising:an antenna array that generates at least two antenna beams and an output signal for each of the at least two antenna beams;an RF subsystem that processes the outputs for each of the at least two antenna beams and produces at least t

1. A system for analyzing an amplitude-modulated signal, comprising:an antenna array that generates at least two antenna beams and an output signal for each of the at least two antenna beams;an RF subsystem that processes the outputs for each of the at least two antenna beams and produces at least two channel outputs; anda computational subsystem comprising a detector to detect amplitude modulations optionally superimposed on the amplitude-modulated signal, an analog-to-digital converter to generate digital output data, and a digital signal processing unit to analyze said digital output data to characterize a source of the amplitude-modulated signal. 2. The system of claim 1, wherein the antenna array comprises a 16-element phased antenna array. 3. The system of claim 2, wherein the 16-element phased antenna array is configured to generate two 8-element phased antenna arrays. 4. The system of claim 3, wherein the two 8-element phased antenna arrays operate to simultaneously provide the at least two channel outputs representing the at least two antenna beams having a squint angle. 5. The system of claim 4, where the squint angle ranges from about ±1° to about ±10°. 6. The system of claim 4, where the squint angle has a value of about ±2°. 7. The system of claim 4, where the squint angle has a value of about ±3.2. 8. The system of claim 4, wherein the at least two antenna beams have a beam width of about 1° to about 20°. 9. The system of claim 4, wherein the at least two antenna beams have a beam width of about 2° to about 10°. 10. The system of claim 4, wherein the at least two antenna beams have a beam width of about 5° to about 7°. 11. The system of claim 4, wherein the at least two antenna beams have a beam width of about 6.4°. 12. The system of claim 1, wherein the digital signal processing unit comprises software that analyzes said digital output data to determine a location of the source of the amplitude-modulated signal. 13. The system of claim 1, wherein the digital signal processing unit comprises software that analyzes said digital output data and tracks a relative location of the source of the amplitude-modulated signal. 14. The system of claim 1, wherein the digital signal processing unit comprises an FFT processor that analyzes said digital output data to determine a location of the source of the amplitude-modulated signal. 15. The system of claim 14, further comprising:a display capable of displaying an output from the FFT processor. 16. The system of claim 14, further comprising:a display that is capable of displaying a location of a source of an amplitude-modulated signal. 17. The system of claim 14, wherein the RF subsystem is designed to operate upon RF/microwave signal having a frequency of about 2.5 GHz. 18. A system for analyzing an RF/microwave signal, comprising:an antenna assembly that generates at least two antenna beams, each of said at least two antenna beams generating an output signal;a receiver for each of the at least two antenna beams to receive output signals from the antenna assembly;at least one crystal detector for each output signal, each crystal detector detecting amplitude modulations optionally present on the RF/microwave signal;an analog to digital converter to convert the detected amplitude modulations to digital data; anda digital signal processor that processes the digital data to determine directional information for a source of the RF/microwave signal. 19. The system of claim 18, wherein each receiver comprises:an amplifier with a gain G for amplifying the output signals from the antenna assembly; anda band pass filter wherein gain G is at least 65 dB. 20. The system of claim 18, wherein each receiver comprises:at least two amplifiers for amplifying the output signal from the antenna assembly; andat least one band pass filter wherein the at least two amplifiers and the at least one band pass filter are configured to operate with an overall gain G of at least 65 dB. 21. The system of claim 18, wherein the antenna assembly is configured to operate in at least two modes:search mode, wherein the antenna assembly generates at least eight beams to scan at least one of a horizontal direction and a vertical direction; andprecision mode, wherein the antenna assembly generates two antenna beams. 22. The system of claim 18, wherein the antenna assembly and the receiver are configured to operate on frequencies in the range of about 1 GHz to about 5 GHz, and wherein the at least one crystal detector is selected to detect frequencies in the range of 20 Hz to 10 KHz. 23. The system of claim 18, wherein the antenna assembly and the receiver are configured to operate on frequencies in the range of about 2.4 GHz to about 2.5 GHz, and wherein the at least one crystal detector is configured to detect frequencies in the range of about 50 Hz to 180 Hz. 24. The system of claim 18, further comprising:a switching unit that interacts between the antenna assembly and the receivers to rapidly switch the output signals between the receivers to minimize the effect of gain differences between receiver channels. 25. The system of claim 18, wherein the digital signal processor comprises FFT algorithms that analyze the digital data to determine location information of the source of the RF/microwave signal. 26. The system of claim 18, wherein the system contains at least two crystal detectors for each output signal, and wherein each receiver comprises:at least two amplifiers for amplifying the output signal from the antenna assembly; andat least one band pass filter wherein the at least two amplifiers and the at least one band pass filter are configured to operate with an overall gain G of at least 65 dB, and wherein each of the at least two crystal detectors is configured to detect amplitude modulations at each output stage from the at least two amplifiers. 27. A radio direction finder system for determining location information for a source of an RF/microwave signal, comprising:an antenna assembly that generates a first and a second antenna beam, the first and second antenna beams generating a first and second RF output digital signals, respectively;a first receiver for receiving the first RF output signal;a second receiver for receiving the second RF output signal;a first AM detector that extracts amplitude variations from the first RF output signal to generate a first detected signal;a second AM detector that extracts amplitude variations from the second RF output signal to generate a second detected signal; anda digital signal processor that determines directional information from the first and second detected signals. 28. The radio direction finder system of claim 27, wherein the antenna assembly comprises:a phased antenna array having an even number N elements, each of the N elements generating an element output signal, and N being a multiple of 2;two multiple-input RF combiners, each of which combines the element output signals from N/2 elements to create a combined RF output signal;two power splitters to divide each of the combined RF output signals into a first divided RF output signal and a second divided RF output signal;a first power combiner to combine each of the first divided RF output signals into a first RF output signal; anda second power combiner to combine each of the second divided RF output signals into a second RF output signal wherein the digital signal processor uses FFT algorithms to analyze the information provided from the first and second detected signals to determine location information. 29. The radio direction finder system of claim 27, wherein each of the first and second AM detectors comprise a diode detector. 30. The radio direction finder system of claim 27, wherein the system is configured to operate from a moving platform. 31. A system for analyzing an RF/microwave signal, comprising:an antenna assembly that generates at least two antenna beams, each of said at least two antenna beams generating an RF output signal;a receiver for each of the at least two antenna beams to receive the RF output signals from the antenna assembly;at least one crystal detector to detect amplitude modulations that may be present on the RF/microwave signal;an analog to digital converter to convert the detected amplitude modulations to digital data; anda digital signal processor that processes the digital data to determine information about a source of the RF/microwave signal. 32. The system of claim 31, wherein the antenna assembly comprises:a phased antenna array having an even number N elements, each of the N elements generating an element output signal;N 2 multiple-input RF combiners, each of which combines the element output signals from N 1 elements to create a combined RF output signal, N, N 1 , and N 2 being chosen such that N 1 is a factor of N and N 1 is an integer less than or equal to N/2, and N 2 is an integer equal to N/N1;at least two power splitters to divide each of the combined RF output signals into at least two divided RF output signals; andat least two power combiners to combine at least two divided RF output signals into RF output signals. 33. The system of claim 31, wherein the processor comprises software comprising FET algorithms to analyze the digital data to determine location information about a source of the RF/microwave signal. 34. The system of claim 31, wherein the processor comprises:software that utilizes digital signal processing to analyze the digital data to determine information about identity of the source of the RF/microwave signal. 35. The system of claim 31, wherein the processor comprises software comprising FFT algorithms to maximizes a signal-to-noise ratio of a detected signal. 36. The receiver of claim 31, further comprising at least one spectrum analyzer. 37. A method for characterizing a source of an RF signal having amplitude modulations, comprising:receiving an RF signal;filtering the RF signal;amplifying the filtered RF signal;detecting amplitude modulations from the filtered RF signal;converting the amplitude modulations into digital data; andprocessing the digital data utilizing digital signal processing to characterize a source of the RF signal to maximize a signal-to-noise ratio of a detected signal. 38. The method of claim 37, wherein the step of processing the digital data further comprises processing the digital data to determine directional information about the source of the RF signal. 39. The method of claim 37, wherein the step of processing the digital data further comprises processing the digital data to determine a classification for the source for the RF signal. 40. The method of claim 37, wherein the step of detecting amplitude modulations from the filtered signal is accomplished with a diode detector. 41. The method of claim 37, wherein the RF signal detected has a signal frequency in a microwave frequency band. 42. A method for analyzing a source of an RF signal having amplitude modulations, comprising:providing a first antenna beam from a phased antenna array, the first antenna beam having a first beam width;providing a second antenna beam from a second phased antenna array, the second antenna beam having a second beam width and being offset from the first antenna beam by a squint angle, said first antenna beam overlapping at least partially with said second antenna beam;searching for an RF signal by manipulating the first and second antenna beams; anddetecting amplitude modulations from the RF signal;converting the amplitude modulations with an analog to digital converter to generate digital data; andanalyzing the digital data to geolocate a source of the RF signal. 43. The method of claim 42, wherein the step of detecting amplitude modulations from the RF signal is accomplished with a diode detector. 44. A system for geolocating a source of an RF signal, comprising:i) a first detection system compri sing:an antenna assembly that generates at least two antenna beams, each of said at least two antenna beams generating an output signal;a receiver for each of the at least two antenna beams to receive the output signals from the antenna assembly;at least one crystal detector for each output signal, each crystal detector detecting amplitude modulations optionally present on the RF signal;an analog to digital converter to convert the detected amplitude modulations to digital data; anda digital signal processor that processes the digital data to determine a first angular location of the source of the RF signal relative to a second detection system; andii) the second detection system comprising:an antenna assembly that generates at least two antenna beams, each of said at least two antenna beams generating an output signal;a receiver for each of the at least two antenna beams to receive the output signals from the antenna assembly;at least one crystal detector for each output signal, each crystal detector detecting amplitude modulations optionally present on the RF signal;an analog to digital converter to convert the detected amplitude modulations to digital data; anda digital signal processor that processes the digital data to determine a second angular location of the source of the RF signal relative to the first detection system;whereby the first detection system is spaced apart from the second detection system such that the range of the source of the RF signal can be determined using the first angular location, the second angular location, the location of the first detection system, and the location of the second detection system. 45. The system for claim 44, wherein the RF signal being detected is a signal having a frequency in the microwave frequency band. 46. A method for geolocating a source of an RF signal having amplitude modulations, comprising:locating a first antenna assembly at a known location relative to a second antenna assembly;receiving the RF signal using the first antenna assembly and generating a first output signal;detecting amplitude modulations from the first output signal;converting the amplitude modulations into digital data; andprocessing the digital data to determine an angular location of the source of the RF signal relative to first antenna assembly;receiving the RF signal using the second antenna assembly and generating a second output signal;detecting amplitude modulations from the second output signal;converting the amplitude modulations into digital data; andprocessing the digital data to determine an angular location of the source of the RF signal relative to second antenna assembly; anddetermining the range and location of the source of the RF signal using the first angular location, the second angular location, and the relative locations of the first antenna assembly and the second antenna assembly. 47. The system for claim 46, wherein the RF signal being detected is a signal having a frequency in the microwave frequency band. 48. A system for analyzing an RF/microwave signal, comprising:an antenna assembly that generates at least one antenna beam that generates a left RF output signal;an antenna assembly that generates at least one antenna beam that generates a right RF output signal;a first RF splitter that splits the left RF output signal into a first component left RF signal and a second component left RF signal;a second RF splitter that splits the right RF output signal into a first component right RF signal and a second component right RF signal;a first RF phase shifter to shift a phase of the first component left RF signal;a second RF phase shifter to shift a phase of the second component right RF signal;a first RF combiner to combine the second component left RF signal with the phase-shifted second component right RF signal to create a second channel output;a second RF combiner to combine the first component right RF signal with the phase-shifted first component left RF signal to creat e a first channel output;a first receiver to receive the first channel output signal, said first receiver comprising:at least one crystal detector to detect amplitude modulations optionally present on the first channel output signal; andan analog to digital converter to convert the detected amplitude modulations to first channel digital data;a second receiver to receive the second channel output signal, said second receiver comprising:at least one crystal detector to detect amplitude modulations optionally present on the second channel output signal; andan analog to digital converter to convert the detected amplitude modulations to second channel digital data; anda digital signal processor that processes the first channel digital data and the second channel digital data to determine information about a source of the RF/microwave signal. 49. A The system of claim 48 analyzing the RF/microwave signal, wherein the digital signal processor comprising FFT algorithms to analyze the first channel digital data and the second channel digital data to determine location information about the source of the RF/microwave signal. 50. The system of claim 48 for analyzing the RF/microwave signal, wherein the first RF phase shifter and the second RF phase shifter shift their input signals by approximately equal and opposite phase angles. 51. The system of claim 50 for analyzing the RF/microwave signal, wherein one of the first RF phase shifter and the second RF phase shifter operates at +60 degrees and the other operates at −60 degrees. 52. The system of claim 50 for analyzing the RF/microwave signal, wherein one of the first RF phase shifter and the second RF phase shifter operates at +90 degrees and the other operates at −90 degrees. 53. The system of claim 48 for analyzing the RF/microwave signal, further comprising:a third RF phase shifter to shift the phase of the first component right RF signal before said first component right RF signal is combined by the second RF combiner; anda fourth RF phase shifter to shift the phase of the second component left RF signal before said second component left RF signal is combined by the first RF combiner.