L波段数字微波发射机射频前端研究

【作者】 龚宏伟；

【导师】 张玉兴；

【作者基本信息】 电子科技大学 ， 电路与系统， 2007， 硕士

【摘要】 发射机是发射电磁信号的设备，是决定电子系统性能的重要设备，在我们的生活中扮演着重要的角色。随着现代军事、国防及无线通信事业的发展，移动通信、雷达、制导武器和电子对抗等电子系统对发射机提出了越来越高的要求。现代通信体制对发射机的要求侧重于高纯频谱及线性度。本课题正是进行的数字微波发射机射频前端的研究与实现。在本数字微波发射机中，数字信号经过信源编码、信道编码及QPSK调制变成中频信号，调制的中频信号经过两次上混频成为L波段的射频信号，接着进行放大、滤波。本发射机采用间接变频发射方案，以便能够比较方便地滤除和频(或差频)以及不可避免的本振信号馈通。一部分信号通过定向耦合器分接出去，耦合信号经过放大、检波产生可变增益放大器的控制信号，通过自动电平控制电路维持适当的发送输出电平。驱动放大器放大信号到一个可以接受的输入量级以驱动功率放大器，放大后的射频信号被传送到天线分离滤波器进行滤波，最后通过天线发射出去。本文首先介绍了发射机系统的结构并进行了指标分析，然后介绍了发射机系统设计和本振频率源设计方法。接下来详细叙述了本课题所采用的方案，各模块功能的实现以及实际设计中遇到的困难，最后给出了系统的最终测试结果。更多还原

【Abstract】 Transmitter is the equipment which transmits electromagnetic signal. It determines the performance of the electronic equipments, plays the most important role in our lives. Along with the development of modern military, national defence and wireless communication, many electronic systems such as mobile communication, radars and guided weapons set increasingly higher requirements on the performance of transmitters. Modern communication system lays particular emphasis on high pure spectrum and linearity of transmitters.This project is exactly based on the research and realization of the digital microwave transmitter which can transmit digital signals. The digital signal is converted to intermediate frequency(IF) signal after source coding, channel coding and QPSK modulation. Then the IF signals is changed to radio frequency(RF) signal by way of being mixed twice with the local oscillation(LO) signal. A part of the RF signal which comes from the directional coupler is amplified and demodulated to direct current(DC) signal to control the gain of the variable gain amplifier(VGA). So the system may produce stable signal to transmit. The driving amplifier enlarges signal to reach an adaptive level in order to drive the power amplifier. The enlarged signal is delivered to a filter and transmitted through an antenna.In this paper, the structure of the wireless transmitter is introduced at first. Subsequently, the system design and frequency synthesizer design of the transmitter are introduced. Then the scheme of this transmitter, the realization of each functional module, and some questions which must be paid attention to in the system design are presented. Finally, the testing results are given in the paper.更多还原