基于六端口混频器的研究

Research based on six-port mixer

在航天测控系统中通常对射频信号采用多级变频的方式来得到中频信号,传统的变频方式结构复杂,射频端口与本振端口具有隔离度小等缺点。针对航天系统中传统变频器的这些缺陷,设计了一个由功分器和耦合器组成无源六端口结、平方率检波器以及差分放大器组成的六端口混频器结构,其工作中心频率为2.25GHz。首先对六端口混频器结构和变频原理进行了分析,采用ADS软件分别对六端口结和六端口混频器进行了仿真。仿真表明六端口结具有很好的隔离度和相位传输特性,六端口混频器具有变频损耗小,动态范围大以及所需本振功率低等特点。同时六端口混频器结构简单,因此用六端口混频器替代传统的混频器结构有一定的优势。

In the system of TTC,the RF signal into IF signalby the multi-stage frequency conversion,the traditional frequency conversion structure is complex,the isolation between RF port and LO port is small.For these defects of the traditional mixer,this paper designs a six-port mixer structure consisting of a passive six-port junction,a square-law detector,and a differential amplifier,its work center frequency is 2.25 GHz.Firstly,the structure and frequency conversion principle of six-port mixer are analyzed,the six-port junction and six-port mixer were simulated by ADS software.The simulation shows that the six-port junction has good isolation and phase transmission characteristics,six-port mixer with low conversion loss,large dynamic range and low required local oscillator power.So the use of six-port mixer to replace the traditional mixer structure has some advantages with a simple structure.