学海网

毕业论文 基于51单片机的频率合成设计论文 共32页，14693字
摘 要
本系统以51单片机为控制核心，由正弦信号发生模块、功率放大模块、调幅（AM）、调频（FM）模块、数字键控（ASK，PSK）模块以及测试信号发生模块组成。采用数控的方法控制DDS芯片AD9850产生0Hz－30MHz正弦信号，经滤波、放大和功放模块放大至6v并具有一定的驱动能力。测试信号发生模块产生的1kHz正弦信号经过调幅（AM）模块、调频（FM）模块，对高频载波进行调幅或调频。二进制基带序列信号送入数字键控模块，产生二进制PSK或ASK信号，同时对ASK信号进行解调，恢复出原始数字序列。
另外，本系统从简单、调整方便、功能完备为出发点，基本实现了设计中的要求，波形输出较稳定，且精度较高。本设计还配备有LED显示屏、键盘，提供了友好的人机交互界面。
关键词：直接数字频率合成（DDS）AD9850锁相环VCO 调幅 调频 数字键控
ABSTRACT
This system is in the core of Micro-Processor , consist of sine signal generating module, Power amplifier, Amplitude Modulator, Frequency Modulator, ASK/PSK module and test signal generating module. The AD9850 controlled by Micro－Process in digital way to generate sine signal with the bandwidth 0Hz to 30MHz adjustable per 1Hz. After processing by LPF & power amplifier, the output signal has a peak value of move than 6V. The sine signal at 1 KHz was send to AM and FM module to modulate the high frequency carrier waveform. The binary sequential was send to the relative module to generate ASK and PSK signal. At last demodulate module demodulate the ASK signal and got the same binary sequential as set before.
In addition,the design of this system is basically satisfy the requirements of the symplification ,easy-modification and full-function..the output square wave is very stable and its precision is also very high. In order to provide a friendly user interface, the LED and remote infrared control keyboard was introduced in this system.
Key words：DDS ; AD9850; PLL; VOC; AM; FM; ASK; PSK