基于开关电容的差分无源N通道滤波器

Differential Passive N-path Filter Based on Switched Capacitors

针对传统N通道滤波器不能抑制谐波、谐波混叠且具有一定插入损耗的问题,本文设计一款基于开关电容的差分无源N通道滤波器。该滤波器使用不同容值的电容加权多相信号来消除奇次谐波,利用不同时钟信号叠加的原理抑制谐波混叠,同时,采用电容堆叠技术提供一定的增益减小插入损耗。滤波器采用TSMC 40 nm CMOS工艺,Cadence Spectre RF软件仿真结果表明:该滤波器的中心频率fs可调范围为0.3~1.5 GHz,当fs=500 MHz时,对3次和5次谐波均有48 dB以上的抑制效果,对最强谐波混叠抑制达到60 dB以上,且没有插入损耗,噪声系数(NF)为2.5~2.8 dB,线性度(IIP3)在15 dBm以上。

A differential passive N-path filter based on switching capacitors is designed to address the issue that traditional N-path filters are unable to suppress harmonics and harmonic aliasing,and have certain insertion losses.This filter eliminates odd harmonics by using capacitance weighted multiphase signals with different capacitance values,suppresses harmonic aliasing by combining different clock signals,and uses capacitance stacking technology to provide certain gain and reduce insertion loss.The filter adopts TSMC 40 nm CMOS process,and the simulation results show that the center frequency fs of the filter can be adjusted from 0.3-1.5 GHz,and the rejection effect of fs=500 MHz is more than 48 dB for the 3rd and 5th harmonics,and the suppression of the most powerful harmonic folding reaches more than 60 dB,and there is no insertion loss,the noise figure(NF)is 2.5-2.8 dB,and the linearity(IIP3)is above 15 dBm.