US Patent 8665098 Non-contact motion detection apparatus

A non-contact motion detection apparatus includes at least one reception antenna, at least one transmission antenna, a voltage-controlled oscillator (VCO) and a phase lock loop (PLL). The at least one reception antenna receives a first wireless radio frequency (RF) signal. The at least one transmission antenna transmits a second wireless RF signal to an object which reflects the second wireless RF signal into the first wireless RF signal. The VCO outputs an oscillation signal to the at least one transmission antenna. The first wireless RF signal received by the at least one reception antenna is injected to the VCO. The PLL generates a control voltage to the VCO according to the oscillation signal from the VCO and a reference frequency. Controlled by the control voltage, which represents a motion information of the object, the oscillation signal of the VCO is locked to the reference frequency.