In this paper, a novel technique is proposed to improve the phase-noise of an LC-VCO. The LC-VCO includes two series LC second harmonic filters which consist of a spiral inductor and two varactors. The resonant frequency of the series LC filter is tunable with the control voltage, and the resonator largely prevents the noise modulation in the LC-VCO, improving the phase-noise of the LC-VCO with wide frequency range. The LC-VCO is fabricated using 0.13 ?m CMOS technology, and fully evaluated on wafer. The measured phase-noise of - 112dBc/Hz at 1MHz offset from the 15 GHz carrier is obtained.