Patent ID: 8576664

Claim:
A moving object detection system, comprising: an oscillator configured to generate a first reference signal having a first frequency; a transmitter configured to emit energy waves having the first frequency to a detection area in accordance with the first reference signal; a receiver configured, when receiving incoming energy waves from the detection area, to generate an electric signal corresponding to the incoming energy waves; a phase shifter configured to shift the phase of the first reference signal to produce a second reference signal; a first detection part configured to mix the electric signal generated through the receiver with the first reference signal generated through the oscillator to produce a first detection signal, the first detection signal becoming a first Doppler shift signal when at least one second frequency different from the first frequency is obtained from the electric signal, the first Doppler shift signal having a frequency of the difference between the first frequency and the at least one second frequency; a second detection part configured to mix the electric signal generated through the receiver with the second reference signal produced through the phase shifter to produce a second detection signal, the second detection signal becoming a second Doppler shift signal when the at least one second frequency is obtained from the electric signal, the second Doppler shift signal having a frequency of the difference between the first frequency and the at least one second frequency and being different in phase from the first Doppler shift signal; an existence detection part configured, based on the first and second detection signals, to calculate a rotation angle of each transition factor that is obtained from the first and second detection signals and rotates around the origin of a two-dimensional coordinate system, said existence detection part being configured so that the rotation angle becomes smaller than 90 degrees; an integrating part configured to integrate each rotation angle calculated with the existence detection part to obtain an integrated angle; and an existence judgment part configured to judge whether or not a moving object approaching or leaving the receiver exists in the detection area based on the integrated angle and a threshold angle.