网络分析仪频率合成技术的研究

【作者】 刘虹；

【导师】 鲍景富；

【作者基本信息】 电子科技大学 ， 电路与系统， 2007， 硕士

【摘要】 随着通信技术的发展，射频测量仪器的需求量越来越大，而目前射频测量仪器的现状不容乐观。西方国家的相关产品占领了国内市场的大部分份额，不仅价格昂贵，而且还对一些高端仪器实施禁运，这些严重阻碍了民族工业的发展。在生产线上，需要大量的仪器进行调试工作，在很多场合并不需要太高的精度，如果全部使用国外高端仪器，那是不经济、不合理、也不现实的做法。在这种状况下，迫切需要低成本、指标适中的射频测量仪器。本课题即是为研制网络分析仪中低成本、小体积、细步进锁相扫频源而开展的。课题的难点是实现低成本、宽频段、细步进的扫频源。目前实现细步进可以采用小数分频和DDS技术，但是小数分频技术比较复杂，杂散大，实现体积也比较大。由于大规模集成电路的发展，已经出现了单片集成的DDS芯片，可以实现细步进，并且跳频时间极快，满足设计要求。但是DDS的输出频率上限较低，而且在宽带输出时杂散比较严重。本文根据网络分析仪对扫频源的要求，在理论分析的基础上将DDS和PLL相结合，研制出一种细步进、低成本、宽频带的扫频源，输出300kHz～1300MHz的步进为1Hz的扫频信号。系统分为两大部分，一部分实现固定点频2340MHz的产生，另一部分利用DDS+PLL的技术，实现2340.3MHz～3640MHz的步进为1Hz的锁相扫频信号，两路信号混频后产生所需要的300KHz～1300MHz的扫频信号。实验结果表明，系统的频率分辨率达到1Hz；DDS输出通过锁相环直接倍频，简化了系统的设计，降低了系统成本，并且也满足了所要求的指标。系统整体相位噪声优于-82dBc／H@10kHz，谐波杂散优于-31dBc。更多还原

【Abstract】 With the development of communication technology, more and more RF measurement instruments are needed. But the status of RF instrument is not good. Western country’s products occupy most of the market. These instruments are expensive, what’s worse, many of the high precision instruments are prohibited selling to china. National’s industry is blocked seriously. On product line, quantity of measurement instruments are needed, in many situations, there’s no need for high precision instruments. Using high precision RF instrument is neither economical nor reasonable. So, low cost, good performance RF measurement instruments are needed. This project aim to research low cost, small size and fine resolution phase lock sweep source, which will be used in network analyzer.The difficulty of this project are realizing low cost, wide frequency band and fine resolution sweep frequency synthesizer. In order to realize fine resolution, fractional-N PLL or DDS technology can be used. But the former technology is more complex, bigger size and worse spur. Due to the development of LSI, we could use single chip DDS to get fine resolution and fast frequency hopping time. But DDS technology’s shortcomings include low output frequency and serious spur when output wide band signal.According to the demand of the network analyzer, this paper analyzed DDS and PLL technique, and then combined them together, developed a type of fine resolution, low cost, wide band sweep source, which output 300KHz~1300MHz sweep signal with 1Hz frequency resolution. System include two main parts: one generates 2340MHz const frequency and the other make use of DDS+PLL technology realizing 2340.3MHZ～3640MHz phase lock signal with 1Hz resolution. Two signal are mixed to generate 300 kHz～1300MHz frequency sweep signal.Experiment has testified that, system’s resolution achieved 1Hz. DDS output signal is multiplied directly, which make the system less complex, and cost lower. System’s entire phase noise is better than -82dBc/Hz@10kHz, humorous spur is better than -31dBc.更多还原