基于CMOS 的AD9831芯片数字频率合成器的电路设计

字数:9445,页数:25

摘   要
AD9831为RF/通信系统设计的新型集成芯片。它把脉冲控制器（NCO）、正弦查询表、频率和相位调制器、（DAC）等电路集成在一块芯片上。
AD9831适合于调制应用。它可以用来完成简单的调制。如FSK ,另外如GMSK和QPSK等更复杂的调制电路也以利用AD9831来实现。AD9831 也可以作为信号发生器使用。芯片有很低的电流消耗，因此，它还可以作为本机振荡器使用。另外，这部分工作时只需要3.3V±10%电源电压。AD9831有四个相位寄存器，使能这一部分则能够完成PSK调制。
工作时，芯片需要一个基准时钟、一个低精度电阻和八个去耦电容，以提供数位产生的正弦波，频率可达12.5MHZ。除了可以产生这个RF信号外，芯片还有实现较复杂的调制功能。在数字领域，利用DSP可以简单而精确地实现这些复杂的调制方案。

关键字：脉冲控制器  正弦查询表  频率和相位调制器   数模转换
Abstract
This DDS device is a numerically controlled oscillator employing a phase accumulator, a sine look-up table and a 10-bit D/A converter integrated on a single CMOS chip. Modulation capabilities are provided for phase modulation and frequency modulation.
The AD9831 contains functions which make it suitable for modulation applications. The part can be used to perform simple modulation such as FSK. More complex modulation schemes such as GMSK and QPSK can also be implemented using the AD9831. The AD9831 is also suitable for signal generator applications. With its low current consumption, the part is suitable for applications in which it can be used as a local oscillator. In addition, the part is fully specified for operation with a +3.3 V± 10%。 The AD9831 has four phase registers; this enables the part to perform PSK.
When it works ,Chip need for one reference clock, one short precision resistance and eight decouple capacitance，withal endue digitally bring sine wave forth with to. frequency approve reach 12.5mhz。Except to could bring these RF signal besides，Chip in addition realize compare complicated modulate function forth. At Digit  region，DSP is used for realizing these modulation scheme simply  and accurately.

Key word:     Push controller   Sine look-up table   D/A converter  
Modulator for frequency and phase     

目   录

1.  AD9831芯片简介...................................................................3
1.1  总体描述 .......................................................................3
1.2  芯片特点 .......................................................................4
1.3  应用领域........................................................................4
2.  AD9831芯片封装与引脚功能.........................................................5
3. AD9831工作原理与内部结构 .........................................................8
3．1  电路原理.......................................................................8
3．2  AD9831典型工作特性.............................................................9
3．3  内部结构......................................................................12
3．4   DSP和微处理器接口 ...........................................................13
4．AD9831应用电路设计 ..............................................................14
4. 1 AD9831应用信息 ................................................................15
4. 2  接地和布局 ...................................................................15
4. 3  AD9831的评估板 ...............................................................16
4. 4  使用AD9831评估板 .............................................................16
4. 5  样机制作区域..................................................................18
4. 6   XO和外部时钟 ................................................................18
4. 7   供电电源.....................................................................18
4. 8  AD8931的技术要求 .............................................................18
4．9  专业名词 .....................................................................21
4．10  其它技术要求.................................................................22
5. 总结 ............................................................................23
参考文献 ...........................................................................24