The Study Of CMOS Two Point Modulation Voltage Controlled Oscillator

With the rapid development of wireless communication technology,a variety of wireless communication terminals and radio frequency receiver are explosive growth.AIS Man Overboard is a new kind of positioning equipment based on automatic identification technology of the ship and applied to personal emergency search and rescue at sea.VCO is the buoy signal transmission unit of the carrier frequency circuit in AIS MOB and AIS.Voltage controlled oscillator(VCO)is the carrier frequency generating circuit of the signal transmission unit of AIS MOB and AIS relay buoys.It has high requirements on performance indexes such as frequency deviation,stability and phase noise.Its performance has attracted more and more attention.The development of CMOS chip technology provides a reliable guarantee for the manufacture of integrated voltage-controlled oscillator.The voltage-controlled oscillator chip used in AIS terminal can change the voltage-controlled oscillator circuit in AIS device from discrete device to integrated circuit.It makes the stability and reliability of AIS equipment improved greatly,the production process to be simplified.It has a wide range of market prospects.In this paper,the circuit structure of CMOS VCO is analyzed in detail.It chooses inductance capacitance voltage controlled oscillator circuit structure.And It selects the inversion type PMOS and the inversion NMOS two kinds of variable condenser structure to realize to control voltage and adjust the electric capacity.This structure has a good frequency adjustment effect.In this paper,it detailed analysis of LC VCO circuit cross-coupled transistor structure,and the circuit design of the mirror current source circuit,bandgap reference circuit.When we design the modulation carrier circuit in the AIS terminal,a phase locked loop(PLL)two-point modulation method is adopted,namely,the modulation signal is inputted to the local oscillator end and the VCO terminal,respectively.This design ensures that the system has good high frequency response and low frequency response.It needs to input two control voltages in the VCO end,controls its output frequency.In this paper,an AIS two-point modulation-based integrated voltage-controlled oscillator chip is designed based on the CSMC 0.35 ?m standard CMOS process using Empyrean EDA tool.By testing,It meets the oscillation range is 306 MHz-342 MHz,the center frequency is 324 MHz,and the control voltage is 0-3.3V.The effect of phase noise on the output signal of the VCO is observed through the “eye diagram”.The simulation results show that the eye trace is clear and clear,the line is slender and the up and down span space of “eyes” is large.VCO output oscillation waveform has good noise performance.Finally,through the layout design and post-simulation test,it shows that the designed chip structure is correct,layout and wiring is reasonable,the chip can achieve the circuit design requirements.