CAJ | 학술논문

相对于传统的超外差式接收机，低中频接收机由于不需要镜像抑制滤波器、中频滤波器等片外大体积昂贵器件，因而系统设计可以更加灵活，体积更小，成本更低，集成度更高。低中频接收机采用I/Q下变频进行镜像分离，但模拟前端I/Q不平衡导致的镜像抑制不足问题却是其一大缺点。本文提出了一种利用测试信号数字估计和补偿I/Q不平衡的方法来提高镜像抑制能力。仿真结果表明，在幅度不平衡不大于10%和相位不平衡不大于10°时，经补偿后的镜像抑制比能够达到50 dB以上。
상대우전통적초외차식접수궤，저중빈접수궤유우불수요경상억제려파기、중빈려파기등편외대체적앙귀기건，인이계통설계가이경가령활，체적경소，성본경저，집성도경고。저중빈접수궤채용I/Q하변빈진행경상분리，단모의전단I/Q불평형도치적경상억제불족문제각시기일대결점。본문제출료일충이용측시신호수자고계화보상I/Q불평형적방법래제고경상억제능력。방진결과표명，재폭도불평형불대우10%화상위불평형불대우10°시，경보상후적경상억제비능구체도50 dB이상。
Compared with the traditional super-heterodyne receiver, the low-IF receiver is much more flexible in system design, smaller in size,lower in cost and more highly integrated since it does not need for some large size ex-pensive components which are difficult to be integrated on the chip such as image rejection filter and IF filter,and so on. The low –IF receiver adopts I/Q down-conversion to separate image, however, insufficient image rejec-tion caused by I/Q imbalance of the analog front-end becomes one of disadvantages. In order to enhance the abili-ty of image rejection, a technique based on test signal to realize the digital I/Q imbalance estimation and compensa-tion is presented. Simulation results show the image rejection ratio after compensation can be over 50dB under con-dition that amplitude imbalance is not more than 10% and phase imbalance is not more than 10 ° .