Lighting device with microwave detection function

A lighting device includes a microwave sensor for adjusting its sensing range based on a range gate selected from multiple range gates. An active antenna module transmits first FMCW signal toward a target based on the selected range gate and for receiving second FMCW signal reflected from the target. The microwave sensor demodulates the first FMCW signal and the second FMCW signal to generate beat frequency signal. Then another demodulator demodulates the beat frequency signal to generate Doppler signal. The microwave sensor calculates a range between the microwave sensor and the target based on the beat frequency signal, calculates velocity of the target according to frequency of the Doppler signal, and determine whether to generate triggering signal according to the calculated velocity and the calculated range, when the object located within the range gate. The power module enables a lamp based on the triggering signal.