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A low-power and low-phase-noise 11.55-GHz quadrature voltage-controlled oscillator (QVCO) using intrinsic-tuned technique is demonstrated in a standard 0.18-μm complimentary metal oxide semi-conductor (CMOS) technology. Intrinsic-tuned technique means the intrinsic junction capacitances at the drain terminals of the cross-coupled transistors are regarded as varactors, so no extra low-Q accumulation-mode MOS varactors are needed. This in turn results in a reduction of power consumption, a minimisation of parasitic capacitance effect (i.e. an increase of the operation frequency) and an improvement of phase noise. The QVCO core draws 2.7μmA current from a 0.63μV power supply, that is, it only consumes 1.7μmW. The QVCO achieves a tuning range of 3.9μ (11.11μ11.55μGHz) and a low phase noise of μ114.7μdBc/Hz at 1μMHz offset from 11.55μGHz. The corresponding figure-of-merit is μ193.6μdBc/Hz, one of the best results ever reported for an X-band CMOS QVCO/VCO. The core circuit occupies a chip area of only 0.64μ0.58μmm2, that is, 0.37 mm2.