RFID reader system which is based on passive RFID tags typically takes the“zero-IF”receiving solution.This so-lution will cause carrier leakage between the sender and receiver of RF signal .This carrier leakage will cause two undesirable re-sults:one is that it’s easier for the front of receiver to become saturated which will reduce the communication distance of system;the other is that the“DC offset”phenomenon will be caused then the bit error rate of system will be increased .Therefore,two measures are proposed in this paper to solve this problem .Firstly,the carry cancellation technology is be applied in the RFID reader at 2.45GHz band,and the microstrip circuit is used in the design.By simulation and prototyping test,the results of leakage power of improved circulator are given .Secondly,a wideband and high-gain DC amplifier with DC feedback loop is proposed,it is used as the baseband signal amplifier without distortion and it can compensate the DC component brought by the mixer automatically .Thus, it will reduce the bit error rate of RFID readers when the electronic tags are readed .%基于无源电子标签的RFID读写器系统通常采用所谓“零中频”接收方案，采用该方案会造成射频信号发射端和接收端之间的载波泄漏，其结果是一方面接收机前端容易饱和因而减少了系统通信距离；另一方面会带来所谓的“直流偏移”问题从而增加了系统误码率．本文提出了两个措施来解决或改善这一问题．首先，将载波抵消技术应用到2.45 GHz频段的RFID读写器中，采用微带电路进行载波泄漏抵消电路的设计，通过ADS软件仿真、制作并测试样机，文中给出了改进后环行器泄漏功率的抵消结果．其次，提出一种带有直流反馈环路的宽带高增益直流放大器，用于放大基带信号并自动补偿混频器带来的直流分量，输出波形无明显失真，从而降低了读写器读取电子标签数据的误码率．
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