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本文从矢量合成的观点出发,分析了镜像抑制混频器的镜像抑制度及器件的频带宽度。笔者由信号中频和镜像中频在中频正交桥输出端的矢量合成图推出了镜像抑制度的计算公式,并利用所得的公式对混频器的镜像抑制度和工作频带作了定量的分析,得出如下结论:1.要提高混频器的镜像抑制度就必须提高射频3dB正交混合接头、两路混频器之间、中频正交桥三者的幅度和相位精度。2.要展宽混频器的工作频带,就要减小射频3dB正交混合接头、两路混频器之间,中频正交桥三者的幅度不平衡。但在给定的镜像抑制度下,混频器的工作频带有一个理论极限值。
In this paper, from the viewpoint of vector synthesis, we analyze the image rejection of the image rejection mixer and the bandwidth of the device. The author deduces the formula of the image suppression degree from the vector composite diagram of the signal intermediate frequency and the image intermediate frequency at the output end of the intermediate frequency quadrature bridge and makes a quantitative analysis of the image rejection degree and working frequency band of the mixer by using the obtained formula. The following conclusions: 1. To improve the image rejection of the mixer, it is necessary to improve the amplitude and phase accuracy of the radio frequency 3dB quadrature hybrid connector, the two-way mixer and the intermediate frequency quadrature bridge. 2. To broaden the mixer’s operating band, it is necessary to reduce the radio frequency 3dB quadrature hybrid connector, mixer between the two, intermediate frequency of the three cross-bridge unbalanced. However, for a given degree of image rejection, the mixer’s operating band has a theoretical limit.