摘要
随着频率合成理论和高速大规模集成电路的发展,信号发生器作为一类重要的仪器,在通信、检测、导航等领域有着广泛的应用。就短波通信对抗、雷达对抗及通信系统而言,因为所需要的激励信号形式及其参数各不相同,激励器所产生的信号形式、参数及工作方式等都要根据系统要求实时地进行灵活调整。因此,激励器必须具备信号产生方法灵活、参数变化速度快、信号频谱纯度高,系统稳定可靠等特点。而激励器的信号形式和参数实时可变的特点正体现在实现信号产生器的技术上。本文因此重点研究了FPGA内嵌DDS技术实现信号发生器的方法。
本文首先论述了频率合成技术的发展,并将直接数字频率合成技术(DDS)与传统的频率合成技术进行了比较。然后深入研究了DDS的工作原理和基本结构,分析了理想情况和实际存在杂散情况下DDS的输出频谱,其中,详细分析了引起输出杂散的三个主要因素,并介绍了抑制DDS杂散的常用方法。
其次,本文对FPGA技术的发展以及技术特点进行了阐述,随后,对FPGA芯片内嵌DDS技术实现信号发生器进行了方案的设计。此处重点研究了包括流水线加法器,注入抖动技术,ROM压缩算法等优化系统结构的方法。结合了Matlab和FPGA的开发软件Quartus II对方案进行了实现,并分析了设计的结果。
再次,本文在已经搭建的FPGA内嵌DDS实现信号发生器的平台上,首先分别设计了通信领域的二进制幅移键控,二进制频移键控以及二进制差分相移键控信号,然后对雷达领域的线性调频信号进行了设计,并做了仿真研究和结果分析。
最后,在开发平台TDS5410-TDK的基础上,对54系列DSP做了软件开发,设计了信号采集,信号发生,FIR,IIR滤波器,以及FFT实验。并做测试和分析。
With the development of frequency synthesis theory and high speed LSI (Large Scale Integration), the signal generator, as an electronic equipment, has been widely applied in many fields such as communication, detection and navigation. Specially, in the field of shortwave communications antagonize and radar antagonize as well as communication system, as different type and parameters, powers need timely and flexibly change their work type to generate the needed signals. So, the powers must can change parameters quickly, safely, and have pure spectrum. Because the traits powers have above are rightly show by the technology of generators, so this paper will mainly research a new method, FPGA with Direct Digital Frequency Synthesizer (DDS) to realize generators.
Firstly, this paper addressed the development of frequency synthesis theory and made a compare between DDS and traditional methods. Then this paper made a deep research on both of the ideal and nonideal spectrum traits after introducing the principle and basic structure of DDS.
Secondly, based on the introduction of FPGA, this paper made a detail design of FPGA in-line of DDS, which strongly researched optimized methods such as pipelining adder, dithering measure, the ROM compression methods etc. After which, by the help of the software Matlab and FPGA’s developing software QuartusII, the author made a detail design of DDS system and analyzed the results.
Further , with the DDS platform built above, the author respectively designed the communication signal BASK, BFSK, and DPSK, as well as LFM signal, then analyzed the results.
Finally, the author made software development of 54X series DSP by the platform of TDS5410-TDK. During which, the author realized signal sampling, signal generating,FIR filter, IIR filter, and FFT technology. After that, the author also made some test and analysis.
引文
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