高频课程设计-小信号发生器

《高频电路原理与分析》

课程报告

设计名称：高频小信号发生器

学院：计算机科学与技术学院

班级：通信07-2班

学号：8

姓名：

教师：玉娜

2010 年9 月16 日

目录

目录···············································································································I

一、选题意义·····························································································- 1 -

二、设计要求·····························································································- 1 -

三、总体方案设计······················································································- 2 -

3.1 高频小信号调谐放大器简述： ······························································- 2 -

3.2 高频小信号谐振放大器工作原理 ···························································- 3 -

四、各部分设计及原理分析 ········································································- 4 -

4.1 放大器的性能分析 ············································································- 4 -

4.2 谐振回路的性能分析 ··········································································- 6 -

五、调谐放大器的性能参数 ········································································- 6 -

六、参考电路及参数选择·········································································· - 10 -

七、实验结果与结论 ················································································ - 12 - 八．心得体会··························································································· - 12 - 九、参考文献··························································································· - 13 - 附：高频小信号放大器完整电路图···························································· - 14 -

一、选题意义

高频小信号放大器是通信设备中常用的功能电路，它所放大的信号频率在数百千赫至数百兆赫。高频小信号放大器的功能是放大各种无线设备中的高频小信号，从信号所含频谱来看，输入信号频谱与放大后输出信号的频谱是相同的，这里说的小信号是强调输入信号的电平较低，放大器工作在它的线性围。高频小信号放大器的分类：

1.按元器件分为：晶体管放大器、场效应管放大器、集成电路放大器;

2.按频带分为：窄带放大器、宽带放大器;

3.按电路形式分为：单级放大器、多级放大器;

4.按负载性质分为：谐振放大器、非谐振放大器;

其中高频小信号调谐放大器广泛应用于通信系统和其它无线电系统中，特别是在发射机的接收端，从天线上感应的信号是非常微弱的，这就需要用放大器将其放大。高频信号放大器理论非常简单，但实际制作却非常困难。其中最容易出现的问题是自激振荡，同时频率选择和各级间阻抗匹配也很难实现。本文以理论分析为依据，以实际制作为基础，用LC振荡电路为辅助，来消除高频放大器自激振荡和实现准确的频率选择；另加其它电路，实现放大器与前后级的阻抗匹配。

二、设计要求

主要技术指标：谐振频率

MHz

f7.

10

=，谐振电压放大倍数2

≥

V

A，通频带

宽为1MHz，矩形系数小于10。

1、对设计的电路方案各部分电路进行分析；

2、根据性能指标计算电路元件参数，选取合适的电路元件；

3、画出完整电路图；

三、总体方案设计

3.1 高频小信号调谐放大器简述：

高频小信号放大器的功用就是无失真的放大某一频率围的信号。按其频带宽度可以分为窄带和宽带放大器，而最常用的是窄带放大器，它是以各种选频电路作负载，兼具阻抗变换和选频滤波功能。对高频小信号放大器的基本要：（1）增益要高，即放大倍数要大。例如，用于个汇总发接收机中的中频放大器，其电压放大倍数可达45

1010，及电压增益为80~100dB，靠多级放大器才能实现。

（2）频率选择性要好，即选择所需信号和抑制无用信号的能力要强，通常用Q值来表示，其频率特性曲线如图-1所示,带宽BW=f2-f1= 2Δf0.7，品质因数Q=fo/2Δf0.7.

图3.1 频率特性曲线

（3）工作稳定可靠，这要求放大器的性能尽可能地不受温度、电源电压等外界因素变化的影响，部噪声要小，特别是不产生自激，加入负反馈可以改善放大