基于DDS芯片正弦信号源设计(附程序,电路图,PCB图)(开题报告,中期报告,论文18000字)
摘 要
本文主要介绍了采用直接数字频率合成DDS芯片实现正弦信号输出，并完成调频，调幅功能。它采用美国模拟器件公司（AD公司）的芯片AD9851，并用AT89C51单片机对其控制，首先从DDS芯片的输出，经低通滤波得到正弦信号，然后对该信号进行调频，调幅。其中调频部分可以通过在软件中修改DDS芯片的频率控制字，相位控制字等来实现，而调幅部分需在DDS输出正弦信号之后外加一调幅器实现。调幅部分将DDS输出作为载波信号，RC振荡器提供1KHz振荡作为调幅信号，它利用了乘法器MC1496完成对正弦信号调制。该系统输出稳定度、精度极高，适用于当代的尖端的通信系统和精密的高精度仪器。
本文首先介绍了直接数字合成的原理，然后提出了系统总体设计方案，还有系统硬件电路和软件编写设计等，其中如采用的AD9851芯片和调幅模块电路设计作了详细介绍。
关键词：直接数字频率合成(DDS)；AD9851；调频；调幅
Abstract
This article mainly introduced uses the direct digital frequency to synthesize the DDS chip to realize the sine signal output, and completes the frequency modulation, the amplitude modulation function. It uses the American simulation component company (AD Corporation) chip AD9851, and with the AT89C51 monolithic integrated circuit to its control, first from the DDS chip output, obtains the sine signal after the low pass filter, then carries on the frequency modulation to this signal, the amplitude modulation. Frequency modulation partial may through revise the DDS chip in software the frequency control word, the phase control word and so on realizes, but the amplitude modulation are partial must after the DDS output sine signal sur- amplitude modulator realization. The amplitude modulation partially the DDS output took the intelligence signal, the RC oscillator provides the 1KHz vibration to take the amplititude-modulated signal, it used multiplier MC1496 to complete to the sine signal modulation. This system output stability, the precision are extremely high, is suitable for the contemporary acme communications system and the precise precision instrument.
This article first introduced the direct digital synthesis principle, then proposed the system system design plan, but also has the system hardware electric circuit and the software compilation design and so on, like uses the AD9851 chip and the amplitude modulation module circuit design has made the detailed introduction.
Key word: Direct digital frequency synthesis (DDS)； AD9851； frequency modulation；amplitude modulation
目 录
引言 1
1直接数字频率合成（DDS）原理及性能综述 1
1.1 DDS原理 1
1.2 DDS性能 6
2 课题总体方案设计及论证 7
2.1 设计任务及初步规划设计 7
2.2 方案提出及系统整体设计框图 7
2.2.1 系统各部分设计方案 7
2.2.2 系统整体设计框图 9
3 硬件电路设计 9
3.1 直接数字频率合成模块 9
3.1.1 AD9851内部结构 10
3.1.2 AD9851芯片引脚分布及功能介绍 10
3.2 单片机控制电路设计 14
3.3 调幅模块设计 16
3.3.1 MC1496内部结构 16
3.3.2 MC1496静态工作点的设置 17
3.3.3 MC1496在振幅调制中的应用 17
3.4 键盘与显示模块设计 20
4 软件设计 21
4.1 软件实现思想 21
4.2 软件流程图及程序 22
5 系统调试 30
5.1 硬件电路调试 31
5.1.1 调试与测试所用仪器 31
5.1.2 调试过程 31
5.1.3 调试经验总结 31
5.2 软件调试 31
5.3 总调试 31
6 结论 32
谢 辞 34
参考文献 35
附 录 36
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