中文摘要：

针对传统导航接收机射频前端在实现多频点信号接收时复杂度高、灵活性差的问题，提出了一种基于直接射频采样的数字化射频前端设计方法．该方法针对整个导航频段信号主要集中在低频和高频2个频段的特点，将这2个频段视为2个整体的带通信号，通过多带通信号采样率选择算法选定射频直采的采样率；由于采样率较高，设计了一种滤波抽取网络来降低数据速率，它利用了射频直采专用A／D可输出半采样率数据的特性，最终实现了各频点导航信号的下变频和分离．该设计方法只需修改软件就可实现多频信号接收，使得系统灵活性大大增加．实验证明该方法是有效的．

英文摘要：

Traditional global navigation satellite system （GNSS） receiver front-ends is very complex and inflexible when receiving multi-system signals. To solve such a problem, a digitized radio frequency （RF） front-end design was proposed based on the direct RF sampling. Considering that GNSS signals primarily concentrate on low frequency band and high frequency band, like two integral band-pass signals, the sampling rate of such signals can＇t be low due to the wide band. In this paper, firstly, the sampling rate selection algorithm for multiple band-pass signals was discussed. Then the direct RF sampling rate for such two GNSS band-pass bands was determined. For the purpose of lowering the aforementioned high sampling rate, a decimation and filtering network was designed. Finally, based on the fact that analog to digital converter （A/D） specially designed for direct RF sampling is capable of outputting the data at half the sampling rate, the digital down-conversion of the signal of interest as well as its separation from the entire band was realized. Thus multi-frequency signal receiving can be achieved by software implementation of the design and the system flexibility will be greatly improved. Experiments have proved the effectiveness of the design.