射频模拟前端对数字中频接收机动态范围影响的研究

射频模拟前端(RFAF)是实现大动态宽带数字中频接收机(DIFR)的技术瓶颈之一,其在很大程度上制约着DIFR的带宽、动态范围等关键性能指标.本文研究实现宽带大动态DIFR的约束条件.基于ADC的性能指标,分析了RFAF的噪声系数、带宽以及中频欠采样的"处理增益"与DIFR灵敏度之间的关系,以及RFAF的增益和噪声系数与DIFR的动态范围之间的关系.推导并仿真了RFAF的增益和ADC的信噪比与DIFR的瞬时动态范围,以及数字自动增益控制(DAGC)的步长和调节范围与DIFR的扩展动态范围之间的关系.讨论了RFAF的最优化设计问题,给出了设计实例.

The Research on the Effect of the RF Analog Front End to the Large Dynamic Range and Broadband Digital Intermediate Frequency Receivers

RF Analog Front-end(RFAF) is one technique-bottleneck to realize the large dynamic range and broadband Digital Intermediate Frequency Receivers(DIFR),and could restrict the bandwidth,dynamic range and some other key parameters of the DIFR.It has been researched that the constraint condition for the broadband and large dynamic range of the DIFR.Based on the ADC parameters,the correlation expression for the following characters is given:the noise figure,bandwidth,"processing gain" of the under-sampling,and the sensitivity of the DIFR.The relational expression for the gain and noise figure of the RFAF and the dynamic range of the DIFR is also performed.It is reduced and simulated that the relationship between the gain of the RFAF,the signal-to-noise ratio of the ADC and the instantaneous dynamic range,and the step and adjust-range of the RF-DAGC and the extended dynamic range of DIFR.It is discussed the optimization design of RFAF,and provided a practical design example.