一种低噪声C类LC压控振荡器的设计

Design of low⁃noise Class⁃C LC voltage controlled oscillator

为了改善压控振荡器相位噪声,基于40 nm CMOS工艺,设计一种低噪声C类LC压控振荡器。交叉耦合NMOS对管通过电流镜偏置作为电路的电流源,并采用共模反馈偏置电路使交叉耦合PMOS对管工作在饱和区,保证LC压控振荡器实现C类振荡。通过差分可变电容的设计,压控振荡器的增益减小,压控振荡器的相位噪声得到改善。设计了4组开关电容进行调节,增大压控振荡器的调谐范围。仿真结果表明,处于1.2 V的电压下,压控振荡器振荡频率范围在4.14~5.7 GHz,频率调谐范围变化率达到31.2%,相位噪声为-112.8 dBc/Hz。

In order to improve the phase noise of voltage controlled oscillators,a low noise Class⁃C LC voltage controlled oscillator is designed based on a 40 nm CMOS process.The cross coupled NMOS pair is biased by a current mirror as the current source of the circuit,and a common mode feedback bias circuit is used to make the cross coupled PMOS pair operate in the saturation region,ensuring that the LC voltage controlled oscillator achieves Class⁃C oscillation.Through the design of differential variable capacitors,the gain of the voltage controlled oscillator is reduced,and the phase noise of the voltage controlled oscillator is improved.Four groups of switching capacitors are designed to increase the tuning range of the voltage controlled oscillator.The simulation results show that at voltage of 1.2 V,the oscillation frequency range of the voltage controlled oscillator is between 4.14 GHz and 5.7 GHz,the frequency tuning range variation rate can reach 31.2%,and the phase noise is-112.8 dBc/Hz.