摘要
为了研究宽带低杂散的L波段捷变频频率源，采用DDS技术从数学方法上对DDS输出信号模型表达式进行展开和近似，在精度允许范围内将DDS输出信号近似为小信号锯齿波调制正弦波的结果，深入分析了锯齿波的频谱和频率控制字之间的关系．根据信号调制理论分析了DDS输出信号杂散分布及杂散频率和频率控制字之间的关系，DDS杂散谱线数量也与频率控制字相关，得出了相应的规律．结合实际工程和DDS杂散分布规律，设计了L波段（1．225～1．425GHz）的捷变频频率源，在频率误差允许范围内选择合适的DDS输出频率范围和频率控制字，提高了系统宽带杂散抑制，DDS输出信号经滤波器之后杂散电平优于-83dBc，经8倍频和滤波后杂散电平优于-70dBc．
Direct digital synthesis （DDS） technology was adopted to implement a wideband low spurious free dynamic range （SFDR） L band fast hopping frequency synthesizer. The signal model was approximated, using a mathematical method. The DDS output signal was modeled as a kind of sine signal modulated by a small toothed signal. The relationship between the spectrum of the toothed signal and word frequency was investigated. Based on modulation theory, the relationships between the spurious spectrum position, spurious frequency, and word frequency were analyzed. Rules governing the relationships were proposed. The L band （1. 225- 1. 425 GHz） fast hopping synthesizer was designed and developed by considering practical issues in applying these rules. The wideband SFDR of the synthesizer was improved at the cost of increasing frequency error within the limit. The tested wideband SFDR level of the filtered DDS output signal is better than -83 dBc. The SFDR level of the L band fast hopping frequency synthesizer is better than -70 dBc.
出处
《哈尔滨工程大学学报》
EI
CAS
CSCD
北大核心
2008年第12期1324-1329,共6页
Journal of Harbin Engineering University
基金
总装备部预研基金资助项目(623010101)
