《DDS的VHDL语言实现及其高纯谱研究》-毕业论文.doc

《DDS的VHDL语言实现及其高纯谱研究》-毕业论文.doc

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PAGE PAGE 2 基于FPGA的DDS正弦波信号源设计 内容摘要:频率合成技术在现代电子技术中具有重要的地位。在通信、雷达和导航等设备中,它可以作为干扰信号发生器;在测试设备中,可作为标准信号源,因此频率合成器被人们称为许多电子系统的“心脏”。直接数字频率合成(DDS——Digital Direct Frequency Synthesis)技术是一种全新的频率合成方法,是频率合成技术的一次革命。本文主要分析了DDS的基本原理及其输出频谱特点,并采用VHDL语言在FPGA上实现。对于DDS的输出频谱,一个较大的缺点是:输出杂散较大。针对这一缺点本文使用了两个方法加以解决。首先是压缩ROM查找表,在相同ROM容量的情况下,压缩后相当于把512点查找表扩展为2048点,过采样的引入提高了DDS输出谱的纯度。其次,采用了相位随机抖动技术,引入了M序列作为DDS采样输出的相位随机抖动,这个方法把原来的均匀查表抽样变成为伪随机非均匀抽样,使得DDS输出谱的杂散分量白化,同样使输出频谱纯度得到提高。本文最后用频谱分析仪做了相关实验测试,在实验上验证了设计思想。 关键词:DDS FPGA VHDL M序列 频谱 The realization of DDS with VHDL and its high pure spectrum research Abstract;The frequency synthesis technology has the important status in the modern electronic technology. In equipment such as correspondence, radar and navigation, it may work as the unwanted signal generator; In the test facility, may work as the standard signal source, therefore the frequency synthesizer is called by the people as the heart of many electronic systems .DDS——Digital Direct Frequency Synthesis technology is one brand-new frequency synthetic method, is a frequency synthesis technology revolution. This paper analyzes the basic principle of DDS and its output frequency spectrum characteristic, and realizes it with VHDL language on FPGA. In regard to the output frequency spectrum of DDS, a shortcoming is: The output spurious is bigger. In view of this shortcoming this article uses two methods to solve. First compress the ROM search table, in the same capacity of ROM, it is equal to expand 512 searches tables to 2,048 after the compression, the introduction of over sampling enhance the spectrum purity of DDS output. Then utilize the phase random dither technology, use the M sequence as the phase random dither of the DDS sampling output .this method causes evenly look up table sampling turn to for pseudo-random non- even sampling, it make the output spurious component of DDS change to white noise, similarly enhance purity of the output frequency spectrum to This article finall

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