基于FPGA的正弦信号发生器研究与设计

基于FPGA的正弦信号发生器研究与设计(任务书,开题报告,论文19000字)
摘要
在电子电路、雷达通信等领域的研究和应用中，信号发生器，可以输入一些需要的信号，也可以为系统提供时钟源，也称之为信号源或者振荡器。我们主要对信号发生器的频率分辨率、频率变换速度、输出杂散性等性能指标进行研究。至今国内外已研制出包括任意波形信号发生器、合成信号源等频率源。随着时代变迁，科学技术日新月异的发展，信号发生器也在更新换代去配合不断精细高级的电路，以前实现信号发生前的方法有着频带狭窄、分辨率低等问题，难以满足新时代的应用与需求。直接数字频率合成技术的使用可以改善这些问题。
频率合成技术在信息技术领域广泛应用。DDFS、PLLFS和DDFS是目前最常用的三种频率合成技术。直接数字频率合成器基于数字取样技术，由Phase accumulator、波形存储器ROM、DAC模块和低通滤波器构成，是基于数字电子技术进行设计的频率合成器。DDS有着输出频率精度高、频率能快速转换、频率切换时相位连续、存储波形可以选择灵活输出等优点。全数字化的构造能让集成水平进一步增加，极大改进了过往频率合成方案带来的设计繁杂、外形笨重、资金高昂等缺点。
FPGA技术全称为现场可编程门阵列。FPGA是硬件编程技术，解决了硬件逻辑可以任意编程而不需要改动硬件的问题。利用FPGA技术设计的产品从外观来说重量比较轻，成品体积小。此外，利用FPGA技术可以带来运行速度快、保密程度高、功耗低的优点，可以增加电子产品竞争力。FPGA技术能在很大程度上减少设计周期，降低设计花销，设计风险维持在比较低的水平，性价高。本次基于FPGA的正弦信号发生器设计采用Direct digital synthesis实现。波形在设计过程中，以数字化离散点呈现，再借助DAC和滤波器模块转换为所需的模拟信号进行显示。
本文阐述了信号发生器的起源与之后发展，对目前信号源的设计与实现进行分析。阐述了直接数字频率合成技术的工作原理，据此画出电路结构框图。借助Quartus II硬件仿真软件，按照设计框图和流程图对本系统进行设计。通过FPGA硬件语言verilog编写代码，画出原理图电路，借助这两种形式建立模块并设计顶层原理图文件进行仿真。最终实现直接数字频率合成技术，产生稳幅正弦波。学习理解AM、FM、ASK、PSK调制原理，通过仿真验证实现。此外利用protel和Keil uVision4 软件进行程序编写，设计人机交互部分，实现单片机与LCD液晶显示屏和键盘的电路连接与频率输入控制。
关键词：现场可编程门阵列；直接数字频率合成；正弦信号发生器；Quartus II

Abstract
In the studies and application of electronic circuits, radar network and other fields, signal generator can input some needed signals and also provide clock source for the system, which is also called signal source or oscillator.We mainly study the performance indexes of signal generator, such as frequency accuracy, frequency conversion speed and output spuriousness.Up to now, frequency sources including arbitrary waveform signal generator and synthetic signal source have been developed at home and abroad.With the change of times and the rapid development of science and technology, the signal generator is also upgrading to match the fine and advanced circuits. The previous methods to achieve the signal before the occurrence have the problems of narrow frequency band and low resolution, which are difficult to meet the application and demand of the new era.This application based on DDS system can solve these problems.
Frequency synthesis technology is widely appliedin many kinds of technologic fields.Direct analog frequency synthesis, phase locked loop frequency synthesis and direct digital frequency synthesis are the three most commonly used frequency synthesis techniques.DDFS is based on digital electronic technology, which is composed of phase accumulator, waveform memory, D/A and suitable filter.Direct digital frequency synthesizer has the advantages of high output frequency accuracy, fast frequency switching speed. When switching frequencies, phase change continuous. And it’s flexible while selecting the desired waveform signal.The fully digital structure can greatly improve the degree of integration, greatly improving the past frequency synthesis technology circuit complex, large size, high cost shortcomings.
FPGA is a hardware programming technology, which solves the problem that hardware logic can be programmed arbitrarily without changing the hardware.Products designed with FPGA technology are lighter in weight and smaller in size.In addition, the use of FPGA technology can bring the advantages of fast operation, high degree of confidentiality, low power consumption,,give products greet competitiveness, can reduce the design time,  minimize the design loss and risk.The design of sinusoidal signal generator based on FPGA is realized by direct digital synthesis technology.In the design process, the waveform is digitized and discretized, and then converted into the required analog signal for display by means of DAC and filter modules.
This paper describes the origin and development of the signal generator, and analyzes the design and implementation of the current signal source.Learn and understand how the DDS signal generator works, according to the DDS working principle drawn the circuit structure block diagram. On the Quartus II development platform, the system was designed using a hierarchical design approach. Through the FPGA hardware programming language verilog and schematic input two forms, build the module and design the top schematic file for simulation. Finally, DDS technology is achieved, which produces a stable sine wave and realizes four types of modulated signals such as AM, FM, ASK, and PSK. In addition, we connect the circuits in protel software and write the related program by Keil uVision4 software. The human-computer interaction part is designed to realize the circuit connection and frequency input control of the single-chip computer and LCD liquid crystal display and keyboard.
Keywords:FPGA;DDS; Sinusoidal Signal Generator;Quartus II

研究内容与安排
本文基于FPGA对正弦发生器进行研究与设计，并实现正弦信号、AM、FM、ASK与PSK调制信号的选择输出，具体各章内容安排如下：
第一章为绪论部分，阐述了研究目的与意义，国内外研究现状分析，介绍了本次设计研究的信号发生器的发展情况，论述了FPGA的优势，选择第三代频率合成技术，对DDS系统的特点和优势进行学习。
第二章介绍了DDS的基本原理与结构组成，阐述了正弦波形的产生过程。
第三章进行系统设计，按照设计要求对FPGA实现正弦波形的过程进行参数设计，设计单片机与FPGA、LCD、按键的电路连接与软件编写。
第四章介绍Quartus II和Modelsim的软件开发流程，并以此设计DDS、AM、FM、ASK、FSK控制模块，设计顶层原理图进行波形选择输出，并对其进行仿真验证。
第五章阐述了该系统的不足与日后研究方向，对全文进行总结与展望。

目录
第1章绪论    1
1.1研究目的与意义    1
1.2国内外研究现状    1
1.3研究内容与安排    3
第二章 DDS结构与原理    4
2.1 DDS的原理    4
2.2 DDS的结构    4
2.3 本章小结    6
第三章系统方案设计介绍    7
3.1 FPGA设计与参数设置    7
3.2 DAC及滤波模块设计    8
3.3 单片机设计    9
3.3.1单片机与FPGA通信设计    9
3.3.2 LCD液晶与键盘设计    9
3.3.3单片机软件设计及仿真    10
3.4 本章小结    12
第四章基于FPGA的设计与实现    13
4.1 软件简介    13
4.1.1 Quartus II软件简介及开发流程    13
4.1.2 ModelSim 软件简介    13
4.2 DDS子模块设计    14
4.2.1相位累加器模块    14
4.2.2波形存储器ROM模块    15
4.2.3 DDS正弦信号原理图及仿真    18
4.3 幅度调制（AM）控制模块    21
4.4 频率调制（FM）控制模块    23
4.5 振幅键控（ASK）调制模块    25
4.6 相移键控（PSK）调制模块    27
4.7 DDS系统顶层设计    29
4.8本章小结    33
第五章总结与展望    34
5.1 总结    34
5.2 展望    35
参考文献    36
致谢    37