Comparison of low power, wide tuning range 5 GHz quadrature phase LC CMOS VCO with different devices for resonant circuit
Foo, Jo Yi (2005) Comparison of low power, wide tuning range 5 GHz quadrature phase LC CMOS VCO with different devices for resonant circuit. Masters thesis, Iowa State University.
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Three low power 5 GHz LC cross-couple quadrature VCO with different resonant circuits were designed and fabricated in a standard 0.18µm single-poly, six metal layer mixed-signal CMOS process. Combination pairs of an active inductor, spiral inductor, junction varactor and MOScap are used to make the resonant circuit of the quadrature VCO in order to have the best possible performance circuit. Active inductor used in the design is a simple common-source amplifier structure with a PMOS feedback while the passive inductor used is a spiral inductor design using two of the highest level of metal in the process. Junction varactors used in the resonant circuit made use of the capacitance of NWELL and P-implant. All three VCO’s have the same topology structure, which is the LC cross-coupled structure. This architecture is used in the design because of the simplicity while the cross-coupled featured will minimize the phase noise of the oscillator. Output drivers and pre-drivers are design to drive the VCO to a 50 ohm load. Phase noise, power dissipation, output power, spectrum accuracy and quadrature phase error are looked for and tested both in the simulation and on chip. Results of all three different types of resonant circuit VCO’s are compared and discuss. All the circuits were fabricated through the MOSIS Educational Program.
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