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镜像抑制混频器是通讯和其它电子系统中不可缺少的部件之一.一般达到镜像抑制的方法有两种,在混频器信号输入端设置带通滤波器(或带阻滤波器);另一种是在混频器设计中利用相位关系来区分中频输出是真正射频或镜频干扰信号,使有用中频信号输入到接收机,而镜像信号产生的干扰信号消耗或反射在匹配负载上.前者设计较简单,仅适用于高中频系统;但对工作频带较宽、频率捷变和低中频接收机系统就不适用.因此就只能采用后者,亦即移相型双平衡电路结构.
Image rejection mixer is one of the indispensable components in communication and other electronic systems.Generally, there are two ways to achieve image rejection: setting a bandpass filter (or band-stop filter) at the input of mixer signal; One is to use the phase relationship in the mixer design to distinguish the IF output is a real RF or image interference signal so that the useful IF signal input to the receiver and the interference signal generated by the image signal is consumed or reflected in the matching load.The former The design is simple, only applies to high frequency system; but for wide operating frequency band, frequency agility and low IF receiver system is not applicable, so can only use the latter, that is, phase-shift type double balanced circuit structure.