A simple design for antennaintegrated planar oscillator with convenient controlling of operating frequency is presented. The oscillator circuit consists of a broadband negativeresistance active part and a passive load including a patch antenna. In the proposed design, patch antenna is resonator as well as radiating element. Hence, the antenna radiation frequency automatically becomes oscillation frequency. To verify the design method, two negative resistance circuits capable of supporting oscillation over full C-band and X-band are fabricated. The oscillation frequencies, output powers and phase noises at 100-KHz offset for different patch antennas are measured.