使用背靠背MOS变容管的低噪声全数控LC振荡器

Low noise fully digitally controlled LC oscillator with back-to-back in series MOS varactors

为了解决全数控电感电容振荡器(fully digitallycontrolled inductor-capacitor oscillator,DCO)大信号工作时所引起的数控变容管的非线性问题,在对该种非线性进行分析的基础上,提出一种背靠背串联数控金属氧化物半导体(metal oxide semiconductor,MOS)变容管。该结构通过将两支MOS变容管反方向串联,有效改善了非线性,从而降低了DCO的相位噪声。在中芯国际0.18μm互补MOS工艺下设计了采用背靠背串联数控MOS变容管的DCO。仿真结果表明:当该DCO振荡在3.4 GHz的中心频率时,在1.2 MHz频偏处的相位噪声为-129.4 dBc/Hz,与使用普通数控MOS变容管的DCO相比,其相位噪声最多可改善8.1 dB。

The nonlinearity of metal oxide semiconductor （MOS） varactors caused by large output signals of the fully digitally controlled inductor-capacitor oscillator （DCO） can influence the DCO performance. A back-to-back in series digitally controlled MOS varactors was developed to avoid the nonlinear effect in the varactors. The DCO was designed in a semiconductor manufacturing international corporation （SMIC） 0. 18 μm complementary metal oxide semiconductor （CMOS） process with a central running frequency of 3.4 GHz. Simulation results show that the phase noise is below - 129.4 dBc/Hz at 1.2 MHz frequency offset when running at 3. 4 GHz. With the back-to-back structure, the DCO phase noise can be reduced by up to 8.1 dB.