新的高镜像抑制比DAB接收机射频前端架构的研究

Research on a new topology of RF front-end with a high image-rejection ratio for digital audio broadcasting receivers

提出一种新的适用于数字音频广播（DAB）的接收机射频前端架构，并对其镜像抑制比（IRR）性能做了研究。它采用双正交直接下变频一上变频的镜像抑制结构，其中第一级下变频采用双正交直接变频，第二级上变频到2．048MHz中频。直接下变频具有高集成度的优点，而双正交下变频结构对正交信号的幅度和相位失配不敏感，从而提高了镜像抑制能力。理论分析和系统仿真表明，这种新的接收机射频前端架构降低了镜像抑制对第一级高频正交信号相位和幅度失配的敏感程度，因此大大改善了镜像抑制性能。

A new architecture of radio frequency（RF） front-end with the high image-rejection ratio （IRR） performance for digital audio broadcasting （DAB） receivers is presented in this paper. It adopts the image-rejection topology of double quadrature direct downconversion-upconversion frequency. The receiver is firstly double-quadrature down- converted to zero-intermediate frequency（zero-IF） and then up-converted to 2. 048MHz IF finally. The zero-IF has the advantage of high integration, and the IRR of double quadrature topology is insensitive to the mismatch of quadrature signals. The theoretical analysis and system simulation show that the proposed architecture decreases the sensitivity of IRR versus the phase and gain mismatch of the high frequency part in the first stage. It improves the performance of image-rejection ratio greatly.