基于DDS的雷达信号源设计

发布时间：2018-04-17 05:16

本文选题：直接数字频率合成 + 现场可编程门阵列　；参考：《西安电子科技大学》2014年硕士论文

【摘要】：作为雷达系统的重要组成部分,雷达信号源在现代雷达系统中扮演着越来越重要的角色。雷达信号源的质量对雷达系统整体性能的提高起着决定性的作用。相较于传统的频率合成方法,直接数字频率合成(DDS)技术作为一种全新的频率合成技术以其频率分辨率高、频率捷变速度快、相对带宽较宽、频率稳定度高和频率变化相位连续等优点,在雷达系统领域的应用越来越广泛。第一章首先介绍了直接频率合成技术(DS)、间接频率合成技术(IS)和直接数字频率合成技术,然后讨论了这三种频率合成方法的优缺点,最后分析了直接数字频率合成技术在国际和国内的发展和应用情况。第二章首先重点用数学方法阐述了DDS技术的实现原理,并且介绍了DDS技术的各个组成部分:相位累加器、正弦查询表、数模转换器和低通滤波器。接下来重点分析了DDS技术在理想情况和非理想情况下的频谱特点以及杂散的形成原因。最后根据相位截断误差和幅度量化误差产生的原因和特点提出了几种抑制DDS系统杂散的方法。第三章首先根据DDS技术的原理和结构特点,设计了可以产生4路正弦信号或线性调频信号的雷达信号源系统方案,开发了以FPGA+DAC为主要核心的板卡。接着讨论了雷达信号源板卡的各个主要模块:FPGA模块、D/A模块、USB控制模块、DDS控制模块、低通滤波器模块以及时钟和电源模块的设计,并且介绍了各个模块芯片的选型和硬件电路连接情况。第四章对系统方案中主要模块的功能进行了逻辑实现。首先介绍了在配置芯片的内置寄存器时常用的SPI协议,并且利用此协议实现了时钟芯片的配置。接下来实现了利用USB芯片完成上位机与FPGA通信的目的。然后利用DDS芯片产生了一路频率、相位、幅度可调的正弦信号。接下来在FPGA中实现了DDS技术的主要功能模块:相位累加器和正弦查询表,产生了雷达信号源中比较常见的正弦信号和线性调频信号。最后针对改善DDS技术的杂散问题提出了增大正弦查询表寻址位数和压缩波形存储量的方法,降低了相位截断误差,提高了输出频谱的质量,并且对DDS实现流程进行了改良与优化。第五章总结了本文的主要工作和有待改进之处。
[Abstract]:As an important part of radar system, radar signal source plays a more and more important role in modern radar system.The quality of radar signal source plays a decisive role in improving the overall performance of radar system.Compared with the traditional frequency synthesis method, direct digital frequency synthesis (DDS) technology is a new kind of frequency synthesis technology, because of its high frequency resolution, fast frequency agility and wide relative bandwidth.Because of its high frequency stability and continuous phase variation, it has been widely used in radar systems.The first chapter introduces the direct frequency synthesis technology, the indirect frequency synthesis technology and the direct digital frequency synthesis technology, and then discusses the advantages and disadvantages of these three kinds of frequency synthesis methods.Finally, the development and application of direct digital frequency synthesis technology in international and domestic are analyzed.In the second chapter, the realization principle of DDS technology is introduced by mathematical method, and the components of DDS technology are introduced, such as phase accumulator, sine look-up table, digital-to-analog converter and low-pass filter.Then, the spectrum characteristics of DDS in ideal and non-ideal cases and the cause of stray are analyzed.Finally, according to the causes and characteristics of phase truncation error and amplitude quantization error, several methods to suppress stray in DDS system are proposed.In the third chapter, according to the principle and structure characteristics of DDS technology, we design a radar signal source system that can generate four channels of sinusoidal signal or linear frequency modulation signal, and develop a board with FPGA DAC as the main core.Then the design of DDS control module, low pass filter module, clock and power supply module are discussed, which are the main modules of radar signal source card:: FPGA module / D / A module, USB control module / DDS control module, low pass filter module, clock and power supply module.The selection of each module chip and the connection of hardware circuit are also introduced.In the fourth chapter, the function of the main modules in the system is implemented logically.This paper first introduces the SPI protocol which is commonly used to configure the built-in register of the chip, and realizes the configuration of the clock chip by using this protocol.The purpose of communication between host computer and FPGA is realized by using USB chip.Then the DDS chip is used to generate a sinusoidal signal with adjustable frequency, phase and amplitude.Then the main function modules of DDS technology are implemented in FPGA: phase accumulator and sinusoidal look-up table, which produce sinusoidal signal and linear frequency modulation signal which are common in radar signal source.Finally, aiming at improving the spurious problem of DDS technology, a method is proposed to increase the number of addressing bits and compress waveform storage of sine look-up table, which reduces the error of phase truncation and improves the quality of output spectrum.And the DDS implementation process has been improved and optimized.The fifth chapter summarizes the main work of this paper and the need for improvement.
【学位授予单位】：西安电子科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN957.51

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