New planar high Q active resonator and its application to low phase noise oscillators

This paper presents a technique to design a high Q active resonator using an amplifier which is located at the loop of the resonator. By adjusting the phase of the loop, the equivalent negative resistance is generated at the one coupling port of the resonator, which leads to high Q property without the negative resistance circuit. The bandstop resonator using this technique shows a high Q factor of 548.62 from measurement at 10GHz resonant frequency. To demonstrate the validity of the proposed active resonator, an oscillator incorporated with this active resonator was designed, fabricated and measured. The phase noise performance of the active resonator oscillator is -112.6 dBc/Hz at 100KHz offset, which is reduced by 11.3-14.4dB compared to the passive resonator oscillator.