【作者】 刘志强； 沈亚飞； 王文博； 徐金平；

【Author】 LIU Zhiqiang;SHEN Yafei;XU Jinping;State Key Laboratory of Millimeter Waves, Southeast University;

【机构】 东南大学毫米波国家重点实验室；

【摘要】 以宽带DDS信号作为锁相环的参考信号是实现宽频带、高频率分辨率微波扫频源的有效手段。为了直接产生高端频率能覆盖到1GHz的高性能参考信号,本文选用ADI公司的系统时钟频率高达3.5GHz的DDS芯片AD9914,设计了一种300MHz至1000MHz的宽带频率源。DDS电路的系统时钟由100MHz温补晶振激励低相位噪声的34倍高次倍频链路得到。通过配置芯片内部数字斜坡发生器,实现周期为20us到50ms可调的三角波调频信号。在所需工作频率范围内,实测得到单频点输出时相位噪声在偏离载频100kHz时为-147dBc/Hz~-138dBc/Hz,杂散抑制优于54dBc。更多还原

【Abstract】 Employing a broadband DDS source as the reference signal of phase-locked loop is an effective approach to develop wideband, high frequency resolution microwave sweep sources.In order to generate a high performance reference signal directly with frequency covering up to 1 GHz, ADI’s DDS IC AD9914 with a system clock frequency as high as 3.5 GHz is chosen in this paper to design the 300 MHz~1000 MHz wideband frequency source.The system clock of the DDS circuit is achieved by exciting a low phase noise 34-times multiplier chain with a 100 MHz TCXO.By configuring the IC’s internal digital ramp generator, a triangular frequency modulated signal with a tunable period of 20 us to 50 ms is achieved.In the required frequency band, the measured phase noise is between-147 dBc/Hz and-138 dB c/Hz at 100 k Hz offset, and the spurious suppression is better than 54 dBc for single frequency signals delivered by the frequency source.更多还原