A low-sensitivity switched-capacitance VCO

A low sensitivity switched capacitance VCO is described along with its use in a fully-integrated, student-designed Bluetooth transmitter. Using a switched capacitor method to tune the VCO reduces the required sensitivity and tuning range of the VCO and reduces the lock time of the PLL. An open loop architecture is used for the transmitter and the low sensitivity VCO reduces frequency drift usually associated with this architecture. MOSCAPs are used for the digital tuning and design considerations for max to min capacitance ratio are discussed. Simulation results using Agilent EESof are shown