射频MOS管的非线性特性分析与线性度提高技术

Nonlinear analysis and linearity enhancement techniques of RF MOS

基于射频（RF） MOS管的等效电路及非线性等效模型,采用Agilent公司ADS软件中的Symbolically Defined Device（SDD）,对RF MOS管的非线性特性进行了综合分析.在此基础上,针对栅源电容（Cgs）、跨导（gm）、输出导纳（gds）和漏极结电容（Cjd）四个主要非线性源,提出了多栅晶体管补偿、PMOS管补偿、NMOS管补偿、共栅管栅电容补偿、深N阱和二次谐波短路等线性度提高技术.将这些线性度提高技术应用在射频功率放大器（PA）上,该PA采用TSMC 0.18 μm RF CMOS工艺设计,仿真结果表明：采用线性度提高技术后,该功率放大器的线性度提高了4-10 dB.

Based on the equivalent circuit and nonlinear equivalent model of RF MOSFET（radio frequency metal-oxide-silicon field-effect transistors）, a comprehensive analysis of its nonlinear behavior by Symbolically Defined Device （SDD） in Agilent＇s ADS software was presented. Furthermore, to decrease the nonlinearity which mainly came from gate-source capacitance （Cgn）, trans-eonductance（gm）, output conductance（gds） and drain junction capacitance（Cjd）, different techniques such as the differential multiple gate transistor （DMGTR）,PMOS compensation, NMOS compensation, capacitance compensation of common-gate MOSFET, deep N-Well and second harmonic resonance technique were proposed. Finally, various linearization techniques were respectively applied in a CMOS power amplifier（PA） based on TSMC 0.18μm RF CMOS process. Simulation results show that the third-order inter-modulation distortion（IMD3） of PA improves by 4-10 dB after using the linearity enhancement techniques.