基于AD8349的简介及应用电路设计

字数:7680,页数:28

摘要

简要介绍专为RF正交调制器设计的AD8349的功能，内部结构，引脚排列及典型的应用电路。AD8349内部电路可分为5个单元：本地振荡器，基带电压—电流转换器，混频器，差动—单端放大器，及偏置回路。

AD8349可用作数字通信的直接射频调制器，如GSM，CDMA和WCDMA的基站，QPSK或QAM宽带无线存取发射机。它的高调制范围和调制精度也可使其在LMDS中作为一个采用合成调制方式的好的IF调制器使用。
关键字： 正交调制  电压—电流变频器  差动—单端放大器  D/A转换器

Abstract
It briefly introduced the AD8349 designed for RF quadrature modulator applications function, internal structure, pin array and typical apply circuit .The AD8349 can be divided into five sections : the local oscillator(OL) interface ,the baseband  voltage–to-current(V-to-I) converter ,the mixers , the differential-to-single-ended (D-to-S) amplifier , and the bias circuit.

  The AD8349 can be used as a direct-to-RF modulator in digital communication systems such as GSM , CDMA , and WCDMA base stations , and QPSK or QAM broadband wireless access transmitters .Its high dynamic range and high modulation local multipoint distribution systems (LMDS) using complex modulation formats.
     Key words :  Quadrature modulator  V-to-I converter  D-to-S amplifier  DAC

目 录

1. AD8349 芯片简介..................................................................4

2. AD8349 芯片封装与引脚功能........................................................5

3. AD8349内部结构与工作原理  .......................................................6

3．1  等效电路......................................................................6

3．2  典型性能特性..................................................................7

3．3电路描述.......................................................................13

  3. 3. 1 概观.....................................................................13

  3．3. 2 LO接口...................................................................13

3．3. 3 V-TO-I变压器...............................................................13

3．3. 4混频器......................................................................13

3．3. 5 D-TO-S放大器...............................................................13

3．3. 6 偏置回路...................................................................13

3．3. 7 输出使能端.................................................................14

3．4   基本连接 ...................................................................14

3．4. 1 基带I和Q输入...............................................................14

3．4. 2 单端基带驱动...............................................................14

3．4. 3 LO输入驱动电平.............................................................15

     3．4. 4 频率范围..............................................................16

3．4. 5 LO输入阻抗.................................................................16

3．4. 6 单端LO驱动.................................................................16

3．4. 7 RF输出.....................................................................17

3．4. 8 输出使能端 ................................................................17

3．4. 9 基带DAC接口................................................................17

3．4. 10 AD9777接口................................................................18

3．4. 11 偏置器和滤波器............................................................18

3．4. 12 减少边带漏泄 .............................................................19

3．4. 13 LO馈通的畸变..............................................................20

3．4. 14 改善三次谐波畸变..........................................................21

4.  AD8349应用电路设计.............................................................21

4．1  3GPP WCDMA 单传输应用........................................................21

4．2 WCDMA 数字传输应用............................................................21

4．3  GSM/EDGE的应用...............................................................25

4．4 总结信息......................................................................25

4．5 LO 发生器用于锁相环路.........................................................25

4．6 传输DAC 选择..................................................................26

4．7 特性描述设置..................................................................26

5. 总结............................................................................28

参考文献...........................................................................28