A 5.6-GHz 1-V balanced LC-tank Colpitts voltage controlled oscillator is designed and implemented with a TSMC 0.18-µm CMOS process. This proposed Colpitts VCO circuit adopts two single-ended complementary LC-tank VCOs coupled by two pairs of varactors. The proposed VCO operates at low power consumption because it has the same dc current path as the np-MOSFETs. The Measured results of the proposed VCO achieve tuning range of 670MHz from 5.23 to 5.9GHz while the controlled voltage is tuned from 0 to 1-V, phase noise of -118.8dBc/Hz at 1MHz offset frequency from the carrier of 5.6GHz and output power of -10.97dBm at the supply voltage of 1V. The power consumption of the core circuit is 1.79mW and the chip area including pads is 0.451 (0.55×0.82) mm².