GPS/BD射频接收机中镜像抑制混频器设计

摘要

针对GPS/BD射频接收机中镜像干扰信号难消除的问题,采用TSMC 0.18 μm COMS工艺,设计了一款高镜像抑制比(IRR)、高转换增益、单边带噪声系数(NF)和线性度指标良好的镜像抑制混频器.基于传统Hartely镜像抑制结构,混频器中采用了共射频输入端正交混频结构和无源多相滤波器(Poly Phase Filter,PPH),有效地抑制了所需频带内镜像信号的干扰.另外在PPH后级设计了加和电路,对前级PPH引起的电路损耗进行增益补偿.利用Candence软件中的Spectre对电路进行仿真表明,针对GPS L1和北斗B1两个不同频段,镜像抑制混频器输出中频频率均为4 MHz,IRR均为47.8 dB,转换增益均为24 dB,输入1 dB压缩点(P1dB)均为-23.4 dBm,单边带NF均为14.9 dB.%In this paper,a high IRR,high conversion gain,good linearity and good single-side band NF image rejection mixer is proposed in TSMC 0.18 μm COMS process.It can be used to solve the problem that image interference signal is difficult to eliminate.Based on the traditional Hartely image suppression structure,the quadrature mixer for common RF input and PPH are used,effectively restrain the image signal in the desired frequency band.Besides,the summing circuit is used after PPH to compensate the gain loss.The circuit is simulated by the Spectre in Candence which indicates that IF output signals are both 4 MHz for B1 and L1 bands.The IRR are both 47.8 dB.The conversion gain are both 24 dB.The input P1dB are both-23.4 dBm.The singleside band NF are both 14.9 dB.