【作者】 周峰；

【导师】 高攸纲；

【作者基本信息】 北京邮电大学 ， 电磁场与微波技术， 2008， 硕士

【摘要】 DDS(直接数字合成)信号和基于DDS的调频信号被广泛用于电子通信设备和电磁兼容测试领域。学位论文第一、二章介绍了DDS技术的特点、典型应用、关键器件,说明了DDS技术的原理,重点分析了DDS信号发生模块中的各个组成部分。本章第3章和第4章是本学位论文的核心,系统阐述了论文作者在DDS单频率信号和DDS调频(DDFM信号)频谱研究方面的创新成果。第3章中,分析了“较高频DDS输出”时数模转换器(DAC)的非理想特性,特别是转换(slew time)和闪变(glitch)阶段,建立了波形模型,求得相应的Fourier变换,从而得到新的频谱解析式。试验采用ADI公司的DDS芯片AD9851,测量了信号幅频特性,证明了较以往解析式,新解析式和实测更接近。第4章中,首次推导得到了余弦调制DDFM信号的频谱解析式,解析式和文献测量结果吻合良好。DDFM与标准FM信号相比,含有谐波分量,基于解析式对此进行了更深入的研究,由于一次谐波是信号失真的重要原因,所以采用数值计算结果函数拟合方法得到了DDFM信号一次谐波失真(FHD)新的近似公式,新公式比文献公式有更好的适用性和精确度。。由于总谐波功率较之一次谐波功率更容易被测量,本章也给出了DDFM总谐波失真THP的仿真结果。不仅如此,该部分首次指出,基于DDS的直接数字调频(DDFM)信号基波内存在失真。基于频谱计算,本章定义了新的失真指标:总基波失真TFD,并且求得了TFD的近似公式,TFD在DDFM信号谐波被抑制的信号发生结构中尤其有意义,我们的研究发现,FHD与常用的一次谐波失真指标TFD的dB值成近似为二分之一比例关系另一方面,本章仿真研究了ADC与DDS幅度量化效应对DDFM信号频诺杂散的影响,得出了量化杂散影响因素的准定量关系。第5章是结论和展望,全面总结了学位论文的结论,并且探讨了下一步的研究的两个方向:抑制谐波的滤波器设计研究和调制域抽样理论的深入发展。在本研究过程中,共发表学术论文(含录用)5篇,参见附录论文列表,若干成果受到了专家的肯定和好评。更多还原

【Abstract】 DDS signal is widely used in electronic and wireless device, especially in the field of EMC test and measurement .the chapter 1 and 2 of dissertation introduce the features, typical application, key incorporated chip about DDS technology, then introduce the basic principles of DDS, especially the main elements of DDS signal generation structure.Chapter 3 and 4 is the core of dissertation; expound the innovation research result about the frequency spectrum of DDS and FM signal based on DDS.In chapter 3, non-ideal characteristics of DAC when "higher frequency DDS signal" is on is analyzed, especially the performance in DAC’s Slew stage and Glitch stage, then a waveform model is constructed and it’s Fourier transform is got, at last a novel analytical expression of "higher frequency DDS signal" is obtained. The experiment based on DDS IC AD9851 produced by ADI Inc, and amplitude spectrum of DDS signal is measured, demonstrating that compare with former expression, the novel expression fit measurement better.In chapter 4, this dissertation got analytical expression of spectrum of cosine modulation DDFM signal firstly. Analytical expression fit measurement by former literature well. DDFM signal contains extra harmonics comparing with standard FM signal; harmonics, especially first harmonic is the main factor of distortion of DDFM signal. Based on analytical expression, by the method of function fitting, got new approximate expression of first harmonic distortion (FHD). Compare with former expression, new expression is more precise and more applicable. As total harmonic power THP can be measured more easily than first harmonic power, dissertation THP and its deciding factors, and calculation result is showed. Based on frequency spectrum calculation, a novel measurement of distortion is defined: total fundamental distortion TFD, TFD is useful especially in the DDFM signal generator with harmonics be filtered. This paper point out that TFD is a about half of former measurement: first harmonic distortion FHD.On the other hand, effects of ADC and the DDS amplitude quantization on the power levels of the spurious spectrum are studied by computer simulation; quasi-quantitative relationship between spurs level and its deciding factors is obtained.Chapter 5 is about conclusion and prospect. We give a comprehensive summary of dissertation, and discussed the next phase of the study in two directions: the harmonic suppression filter design and modulation domain sampling theory which should be deeply developed.During the course of the study, were published 5 academic papers (including recruitment), see the Appendix List of papers. Some of innovation achievement is well received by the relevant experts.更多还原