Abstract:A novel low phase noise Voltage Controlled Oscillator(VCO) based on a new tuned resonator is introduced. This resonator adopts cross coupling between the source and load port and can produce a transmission zero so that improve the Q-factor. This resonator realizes the voltage controlled filter by using weak coupling between the resonator and the varactor. Finally the novel resonator is utilized to design a narrow band VCO which is simulated in Advanced Design System(ADS). The simulation results show that the center frequency of this VCO is 6.15 GHz, the tuning band is almost 60 MHz, phase noise is better than -132 dBc/Hz at 1 MHz offset frequency in the whole band, the output power is 8.4 dBm, and the flatness of the output power is ±0.1 dBm.