A 5 . 5 GHz Voltage Control Oscillator ( VCO ) with a Differential Tunable Active and Passive Inductor

By using a differential tunable active and passive inductor for LC tank, respectively a wide tuning rang and high phase noise performance CMOS voltage control oscillator (VCO) is introduced and compared. In the proposed circuits' structure, the coarse frequency tuning is provided by the tunable active inductor, while the fine tuning is controlled by varactor. Using a 0.18μm CMOS process, complete pattern VCOs are designed in ADS. The output frequency in both structures is 5.5GHz. The design based on active inductor generates unacceptable phase noise in compare with on passive inductor. The measured phase noise in 1-MHz offset is -81 and -106.4dBc in VCO with active and passive inductor respectively. The non existence of passive components in the first structure causes VCO to have the smaller chip area than the circuit with passive inductors.

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