Abstract: A method and apparatus for detecting an object. A first collimated beam having a first frequency and a second collimated beam having a second frequency is transmitted. At least one of the first frequency and the second frequency is changed through a range of frequencies and a power level for at least one of the first collimated beam and the second collimated beam is changed through a range of power levels. A range of fundamental difference frequency signals for each power level in the range of power levels are monitored for, in response to transmitting the first collimated beam and the second collimated beam using the range of frequencies and the range of power levels. The range of fundamental difference frequency signals is generated by the object having non-linear electrical characteristics in response to receiving the first collimated beam and the second collimated beam.

Abstract: A method and apparatus for detecting objects. A first plurality of electromagnetic signals having a first frequency and a second plurality of electromagnetic signals having a second frequency are transmitted. At least one of the first frequency and the second frequency is changed through a range of frequencies. A delayed difference frequency signal substantially equal to a difference between the first frequency and the second frequency is monitored for. The delayed difference frequency signal is generated by an object having non-linear electrical characteristics in response to the object receiving the first plurality of electromagnetic signals and the second plurality of electromagnetic signals. A range measurement is generated for the object by comparing the delayed difference frequency signal and an undelayed difference frequency signal. The undelayed difference frequency signal is substantially equal to the difference between the first frequency and the second frequency.

Abstract: A method and apparatus for transmitting beams of electromagnetic energy. A plurality of beams having a first number of frequencies and a number of beams having a second number of frequencies are transmitted. The plurality of beams and the number of beams overlap each other at an area with a pattern of intensities in the area. Difference frequency signals having a number of difference frequencies equal to a difference between the first number of frequencies and the second number of frequencies are monitored. The difference frequency signals are generated by an object having non-linear electrical characteristics in response to receiving the plurality of beams and the number of beams.

Abstract: A method and apparatus for detecting objects. A first plurality of electromagnetic signals having a first frequency and a second plurality of electromagnetic signals having a second frequency are transmitted. At least one of the first frequency and the second frequency is changed through a range of frequencies. A delayed difference frequency signal substantially equal to a difference between the first frequency and the second frequency is monitored for. The delayed difference frequency signal is generated by an object having non-linear electrical characteristics in response to the object receiving the first plurality of electromagnetic signals and the second plurality of electromagnetic signals. A range measurement is generated for the object by comparing the delayed difference frequency signal and an undelayed difference frequency signal. The undelayed difference frequency signal is substantially equal to the difference between the first frequency and the second frequency.

Abstract: A method and apparatus for transmitting beams of electromagnetic energy. A plurality of beams having a first number of frequencies and a number of beams having a second number of frequencies are transmitted. The plurality of beams and the number of beams overlap each other at an area with a pattern of intensities in the area. Difference frequency signals having a number of difference frequencies equal to a difference between the first number of frequencies and the second number of frequencies are monitored. The difference frequency signals are generated by an object having non-linear electrical characteristics in response to receiving the plurality of beams and the number of beams.