Research On VCO Of Low Phase Noise Rf Transceiver Chip

Due to the popularity of the Internet,the exploration of wireless communication systems has become more and more hot.In the research work of wireless communication systems,improving the performance of radio frequency transceivers is the focus of research.An RF transceiver system is mainly composed of LNA(Low noise amplifier),mixer,ADC/DAC(analog-to-digital/digital-to-analog converter),PA(power amplifier),frequency synthesizer,filter network and other functional modules.VCO is the core module in PLL frequency synthesizer.The tuning range of the VCO determines the output frequency band of the PLL system,and the phase noise and power consumption performance have a great contribution to the PLL and even the entire wireless transceiver system.Therefore,as a key part of the PLL system,it is necessary to deeply study the various performances of the VCO.However,how to realize a VCO circuit with wide tuning,low phase noise,and large oscillation amplitude is a market demand and a difficulty in VCO design.Therefore,it is very meaningful to discuss and research high-performance VCO.This thesis mainly designs an LC-type voltage-controlled oscillator based on the requirements of the RF transceiver system.In the design process,the two performance indicators of VCO are focused on:output frequency range and phase noise.At the same time,the power consumption and oscillation amplitude have been compromised in each design link.First of all,in order to achieve a wide tuning output,a four-position switch controlled capacitor combination structure is designed,and a combination of a fixed switched capacitor array and an improved variable capacitor array is adopted,which not only achieves a wide tuning output,but also reduces voltage control gain.Secondly,for power consumption and oscillation amplitude,a bias current array composed of multiple switch resistors is used.Compared with the current mirror structure used in most VCO designs,this structure can greatly increase the output amplitude while dynamically adjusting the current by controlling the switch,so that the power consumption is not wasted.Finally,the focus is on optimizing the phase noise performance,by reducing the voltage control gain,improving the tuning linearity,optimizing the Q value of the inductor,and using the noise reduction filter structure to make the VCO excellent in terms of phase noise.This time,the TSMC 0.18?m RF CMOS process is adopted,and the layout drawing and simulation verification work are carried out on the Cadence platform.The simulation results show that:The LC-VCO of this design starts to vibrate quickly,and it oscillates stably in about 10ns,and the amplitude reaches-0.9?3.5V;the output oscillation frequency is from3.88GHz to 5.15GHz,and the tuning range reaches 28.1%;under the 2.5V supply voltage,the working current is 4.6m A,the core power consumption is controlled at 11.5m W;the phase noise of the VCO at the center frequency is-129.3d Bc/Hz@1MHz;the layout area is560×804?m~2.All indicators have been completed,and the performance is excellent in terms of phase noise,tuning range,and oscillation amplitude.