The Design Of Hign-Frequency Dualband CMOS LC Quadrature VCO

Voltage-controlled oscillator (VCO), which outputs frequency controlled by varying voltage is a key component in frequency generator. Increasing pressure for low power, small volume, low cost, and reduced bill of matetrials in such radio applications as mobile communications has driven academia and industry to resurrect the Direct Conversion Receiver(DCR). The design of VCO integrated circuit using standard CMOS technics with hign frequency, wide tuning rage, low phase noise and low power had been the goal of the IC design industry.In this paper, the principle of LC cross-coupled VCO had been particularly analysed, the model of VCO's phase noise had been lucubrated, and the optimized design strategy of CMOS capacitance and inductance had been comprehensively expatiated. based on these analysis, a new CMOS Quadrature VCO(QVCO) with hign frequency, dualband, wide tuning rage, low phase noise and low power had been disigned.The design of the new quadrature VCO is obtained through a cross-coupled double LC oscillator, using the coupling coefficient to control oscillation frequency. Because of the frequency control no longer depended on MOS varactors, the tuning range of oscillation frequency had great increased. The circuit was designed by TSMC18rf CMOS process, and simulated by Cadence Spectre. The results indicated that when VDD is equal to 1.8V, the frequency ranged from 1.78GHz to 4.03GHz, and tuning range was about 77%. The phase noise is -120dB/Hz at 1MHz offset for the oscillation frequency of 2GHz, and -104dB/Hz at 1MHz offset for the oscillation frequency of 4GHz. The layout of QVCO was designed by Virtuoso Layout Editor which provided by Cadence company.