Low Phase-Noise Planar Oscillators Based on Low-Noise Active Resonators

A very low phase-noise planar X -band oscillator employing an active resonator has been demonstrated. The high frequency selectivity of the active filter, used as the resonator, is the key factor in phase-noise reduction. A design procedure to achieve the resonator´s optimum performance for low phase-noise applications is presented. In particular, the effect of the excess noise introduced by the active filter is addressed and its impact on the oscillator´s phase noise is minimized. The oscillator, operating at 8 GHz, shows a measured phase noise of -150 dBc/Hz at 1-MHz frequency offset with 10-dBm output power. To the best of our knowledge, this oscillator demonstrates the lowest phase noise among published X -band planar oscillators to date.