阐述了时钟频率高达3.2 GHz的新型直接数字频率合成器的设计方案,由该方案设计的直接数字频率合成器最高输出频率可达1 500 MHz,并且可以产生线性调频、脉冲步进、调频步进等多种调制信号.通过对该直接数字频率合成器与DDS芯片AD9858进行相位噪声以及杂散进行对比分析,时钟为3.2 GHz的直接数字频率合成器不仅输出带宽得以扩展,其相位噪声在所测试点比AD9858要优10 dB,窄带杂散也较AD9858有很大提高.

In this paper,design of a new direct digital frequency synthesizer is proposed,which clock frequency is up to 3.2 GHz. The design can generate single signal,chirp signal,stepped-frequency signal and stepped-frequency chirp signal to 1 500 MHz. The design details are shown in this paper. Some conclusions are drawn after comparing the new DDS with AD9858: the phase noise and spurious spectrum of the new DDS are better than those of AD9858.

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