Phase-Noise Reduction of $X$-Band Push–Push Oscillator With Second-Harmonic Self-Injection Techniques

A low phase-noise X-band push-push oscillator using proposed feedback topology is presented in this paper. The oscillator core was implemented in a 0.18-mum CMOS process. By using a power splitter and a delay path in the feedback loop connecting the output and current source of the oscillator, a part of the oscillator output power injects to the oscillator itself. With the proper phase delay in the feedback loop and high transconductance of the current source, a low phase-noise oscillator is achieved. The amplitude stability and phase stability are analyzed, the phenomena of the phase-noise reductions are derived, and the device-size selections of the oscillator are investigated. The time-variant function, impulse sensitivity function, is also adopted to analyze the phase-noise reductions of the second-harmonic self-injected push-push oscillator. These theories are verified by the experiments. This self-injected push-push oscillator achieves low phase noise of -120.1 dBc/Hz at 1-MHz offset from the 9.6-GHz carrier. The power consumption is 13.8 mW from a 1.0-V supply voltage. The figure-of-merit of the oscillator is -188.3 dBc/Hz. It is also the first attempt to analyze the second-harmonic self-injected push-push oscillator