This paper designs a LC-VCO in the frequency synthesizer based on 1V low voltage with TSMC 0.18μm RF-CMOS process. Negative resistor pair and source of tail current are provided. Switched capacitor array,second harmonic filter and large capacitor filter,and switched currents source are used to improve performance. Test results show that core power is 2.7-4.1mW, output frequency range is 4.66-6.78GHz with 37% tuning range, and phase noise is -94 to -108dBc/Hz@1MHz and -104 to -124dBc/Hz@3.5MHz.
