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A fully integrated LC voltage controlled oscillator (VCO) with 1V low voltage supply, applied in the frequency synthesizer of 2.4GHz IEEE802.15.4/ZigBee Wireless Sensor Network (WSN), is designed and implemented based on TSMC 0.18μm RF/MS CMOS process with low power dissipation and excellent phase noise performance. The possible structures under 1V voltage supply are compared and this paper uses PMOS transistors as differential negative resistance and NMOS transistor as tail current source to limit current dissipation. The inductor's quality value is simulated and optimized. Phase noise optimization methods are utilized, include lowering the AM-FM noise conversion, decreasing the tail current source's noise contribution, and exploiting the 2nd harmonic filters. The layout area is 520μm×830μm. Under the condition of 1V supply voltage, tt corner process and 27°C, post-simulation indicates that the tuning range is 18% and phase noise of 118.8dBc/Hz is obtained at 1MHz offset with the carrier from 4.80-4.97GHz. And the current consumption of the core circuit is only 2mA.