Design of push-push oscillators for reducing 1/f noise upconversion

In this paper the design of push-push oscillators with symmetrical waveforms is proposed for low phase noise. The presence of the large second harmonic components may degrade the waveform symmetry of the oscillation waveforms in two sub-oscillators, thus leading to the significant 1/f noise upconversion. Therefore, to minimize 1/f noise upconversion in push-push oscillators, the phases of Fourier coefficients of all harmonics need to be equal. The experimental results show that a 15 dB phase noise improvement at 100 kHz offset frequency can be obtained by satisfying the waveform symmetry condition.