Abstract: A radiation type oscillator including a radiation type oscillator substrate including a microwave transistor for generating negative resistance by short-duration operation and a resonant cavity structure; a high-frequency pulse signal of an oscillation frequency/frequency bandwidth determined by negative resistance produced by the short-duration operation of the microwave transistor and the resonant cavity structure is generated as a transmitted RF signal and simultaneously radiated into space. The radiation type oscillator performs oscillating operation when a received RF signal that is a reflected wave of the transmitted RF signal from an object of detection enters the radiation type oscillator, an IF signal is acquired from an IF signal output terminal owing to homodyne mixing by the radiation type oscillator itself, and this is analyzed and processed to detect the object of detection.