毕业设计（论文）中英文资料
题目
函数信号发生器
专 业 名 称
电子信息工程
班 级 学 号
118501106
学 生 姓 名
蔡伟攀
指 导 教 师
邓洪峰
填 表 日 期
201
5 年
3 月
27 日
外文资料译文
任意波形信号发生器的设计
陈晓和陈健翔
南京工业大学电子与信息工程学院，信息科学与技术,210044中国，南京
摘要
信号发生器在电子测量仪器、电子电路、自动控制、雷达和其他电子系统的沟通中起着非常重要的作用,。直接数字合成(DDS)技术可以很容易地控制信号的频率波形的直接合成。本文设计了一个振幅和频率调制信号发生器，采用AD9850频率合成器和AT89S52单片机(SCM)为核心。详细的设计原理和思路进行了讨论。DDS芯片AD9850的用于生成波形。外部输入的频率数据可以通过简单的并行或串行通讯接口与单片机转化为芯片的频率相位控制字。幅度调制是由AD7520芯片实现。该系统不仅结构简单，易于实现，而且也方便，价格便宜。它具有理论和实用价值。
1.绪论
信号发生器可以作为信号源,它提供了一个已知的测试信号的电路。它可以用来测量感兴趣的参数。在各种实验测试应用程序和处理中,信号源作为激励源可以模拟各种测试信号,提供实际需要的电路[1]。
信号发生器在通信技术中，电子测量仪器、电子电路、自动控制、雷达和其他电子系统中发挥非常重要的作用。随着数字技术的飞速发展，出现了高精度数字-模拟转换器，通过使用多频技术，这是DDS技术产生一个标准的参考频率的数字控制方法[2].任意波形信号发生器能够满足复杂的字段，用户定义信号和计算机技术的结合，并使其更加精确和稳定。随着电子技术的发展现状，该信号发生器具有很大的应用。
2.系统
我们设计了一个信号发生器,可以产生任意波形。我们可以控制振幅和频率的大小,提供多种信号测试电路。
利用AT89S52微控制器，AD9850(DDS)和数模转换技术，完整的硬件和软件设计。通过键盘输入模块，我们可以调整波形的振幅和频率。波形生产的过程是通过微控制器来实现的。所以理论上我们可以编写一个程序来生成任意所需的波形。单片机产生数字信号。为了获得所需的波形，我们应该有一个单一的芯片变化的数字信号转化为模拟信号。
DDS芯片的AD9850是用来产生波形的。外部输入的频率数据可以通过简单的并行或串行通讯接口与单片机转化为芯片的频率相位控制字。幅度调制是由AD7520芯片实现的。该系统的设计如图1所示。
该系统使用单片机控制DDS芯片AD9850产生仪器所需的测试的信号。单片机控制多路复用器。方波或正弦波DA转换器AD7520的参考电压信号。 AD7520的输出信号，经调节和放大之后，是一个15V的峰值频率的信号。经互补推挽放大电路后，我们终于得到必要的频率信号。当负荷变化时，为了确保信号的稳定性和频率峰值，放大器电路中的放大器的输出要加上适当的负反馈频率。 3.硬件
该电路的设计主要是两个方面，包括硬件和软件设计。硬件部分是信号生成电路，MCU（单片机）控制电路，振幅控制电路和显示电路。软件主要由主程序和中断服务程序构成。
AT89S52是由美国ATMEL公司生产的，它是一个低电压，高性能CMOS 8位微控制器芯片具有重复包含8K字节可擦除只读闪存（Flash）程序存储器和256字节的随机存取数据存储器。AT89S52可以操作到0 Hz静态逻辑，支持两种软件可选的省电模式[3]。
在本设计中，单片机是最重要的核心组成部分。其工作时间为12MHz。内置闪存（flash）存储的工作程序。通过键盘输入，该电路可以知道需要产生的波形，振幅和频率。我们还可以调整任何波形的振幅和频率。
图1.系统方案
在这个系统中，我们使用了一个独立式键盘。该设计采用一个矩阵键盘，使用软件扫描按钮访问必要的关键信息和用软件编程实现。这样可以节省硬件资源，简化电路设计。通过矩阵键盘，我们可以很容易地设置各种微控制器。 在这个设计中，P0端口连接液晶显示器，AD9850和AD7520 IC芯片是用于数据传输的链接。因为原来的I/O端口是不够的，我们需要在其他外设借口扩展微控制芯片。在这个电路中，我们使用8255芯片，这是一个可编程并行I/O接口芯片。
高度集成的频率合成器AD9850是一个典型的采用DDS技术的产品。AD9850采用先进的CMOS工艺。它的电源在3.3V时只有155mw。在扩展工业温度范围为-40〜+80摄氏度，28引脚小外形封装表面贴装形式。
AD9850 DDS系统包括可编程和高速比较器，全数字编程来实现频率合成的控制。AD9850可以产生一个模拟正弦波输出且是可编程控制的频率和相位，连接到该精确时钟和写入的频率。该正弦波的频率信号，可直接用作源或内部的高速比较器转换为方波输出.在125MHz的时钟，32位频率控制字AD9850可以输出0.0291Hz的输出频率分辨率[4]。
在这个电路设计中，从D0-D7是控制信号输入到寄存器中。在W_CLK（P3.0）的上升沿的第一个字节加载和指针移动到下一个输入寄存器。连续5上升沿，它停止工作。然后当上升沿FQ_UD（P3.1），数据被加载到频率/相位寄存器。在这个时候DDS的输出频率和相位更新。然后，指针重置电路等待下一个频率/相位控制字的输入。
显示模块。考虑到实际情况，我们采用点阵LED实现显示。LCD1602显示输出波形的平率、振幅以及特定类型。 LCD1602和8255芯片PA口相连。三个端子RS，RW，E分别连接在微控制器P2.7-P2.5。该软件可以控制波形的显示和波形频率的类型。
RS是一个选择寄存器是选择数据寄存器高，低，指令寄存器。RW为读写信号线，高为读取、低为写入操作。当RS和RW为低，液晶可以写入指令或者显示地址。当RS低和RW是高时，LCD可被读取。当RS为低和高-RW时，液晶可以被写入数据。 E引脚是能源方面。当E引脚从高电平变为低电平，在LCD上执行命令。
AD9805输出恒定的波幅度。我们使用一个D / A转换器AD7520实现幅度的调整。 AD7520芯片的内部电阻网络是由一个可编程可变增益放大器。AD7520集成了10个模拟开关的电阻网络是可编程的。内部电阻器网络与AD7520可编程放大器被用作电路的增益[5]。
倍率可以在1到1024之间调整，只要改变BIT1-BIT10相应的逻辑状态变化可以控制放大倍数。当BIT1-BIT10是3FFH，放大倍率为1倍，这为0dB。当是98H，放大率是10倍，这为20dB。为了实现可编程增益，我们连接的74LS373 PC端口和单片机的P2口与AD7520引脚BIT1-BIT10。通过程序，微控制器控制I/ O口输出状态来完成可编程增益[5]。 该系统需要一个5V直流电源提供给所有电路。直流电源一般由电源变压器，整流器，滤波器电路和电压调节器组成的。
电力变压器的作用是将220V交流电压功率转换为整流滤波电路所需的交流电压。整流器的作用是将交流电压转换成直流电压的单脉冲。滤波电路是滤除整流后的输出电压纹波。整流电路的输出之后，波形仍含有大量的AC分量而会影响负载电路的正常运行。我们需要通过滤波电容器的纹波过滤。滤波电路是用电容滤波电路。
固定输出电压调节部分选用三端集成稳压器。采用三端稳压器可以很容易地集成固定输出电源集成形式。
4.软件
软件采用C语言编程并且不同功能模块的程序是通过模块化的程序设计思想实现的。这种结构化方法使程序层次清晰，便于使用、维护和调试。该软件设计完成的信号发生器的所有功能管理，由初始化模块、功能模块两部分组成。初始化模块是为各种硬件寄存器，数据寄存器，和显示装置的初始化。
初始化模块设计是由四个部分组成，微处理器的初始化，AD9850芯片的初始化，AD7520芯片的初始化和LCD1602的初始化。
功能模块是一个显示模块、键盘输入模块和信号调节模块和振幅组件。键盘模块主要是用于设置的频率、相位和振幅。
主系统的软件编程方法使用结构方法。该功能模块由主程序分离和子程序产生的波形。延迟可以插入改变频率。
首先，我们进行了微控制器，AD9850，AD7520和液晶显示器的初始化。然后我们通过键盘选择波形。频率调节是通过AD9850芯片完成，波形振幅调制可以通过AD7520芯片来实现
整个过程实现了以下功能：插上电源，液晶显示器，然后循环。如果一个键被检测到，它被暗示电路开始传输数字。程序继续检测键盘和不同的密钥的控制具有不同的功能。
只要信号生成模块通过键盘控制输出的几个基本波形，AD9850芯片可以通过线性组合产生不同的波形具有不同的频率。振幅是相对稳定的。
5.结论
所设计的信号发生器主要由单片机AT89S52，DDS芯片AD9850，AD7520芯片，显示电路和滤波电路。单片机控制整个电路，由AD9850芯片产生信号的频率。信号通过滤波器电路滤波。在单片机AT98S52的控制下，AD7520芯片调制信号的振幅。我们可以通过显示电路观察信号的频率和幅度。通过使用AD9850的芯片，使得具有相当高的稳定性和产生的波非线性失真系数相对较小。该系统不仅结构简单，易于实现，而且也方便，价格便宜。它具有理论和实用价值。
致谢
这项工作是由中国国家自然科学基金（10904073号）资助。
参考文献
[1] 万雍伦，司强，卢有新，王学刚，超宽带雷达信号产生技术的双通道。信号处理，87卷，第12期，2007年，页3101-3107。
[2] 沃尔特·凯斯特。直接数字频率合成（DDS）。数据转换手册，2005年，页677-691。 [3] 孙华，新ATMEL公司的AT89S52单片机及其应用，2004年-北京：清华大学出版社。 [4] CMOS125MHz的完整的DDS 合成器AD9850。
[5] 杰夫·沃克杰拉德Ledwich。宽带考虑多级转换器 IEEE 电力电子产品，1999年,14（1）：110221105
外文资料原文
Design of An arbitrary waveform signal generator
Xiao Chen and Jian xiang Chen School of Electronic and Information Engineering, Nanjing University of Information Science and Technology, Nanjing 210044, China Abstract
Signal generator plays a very important role in communication, electronic measuring instruments, electronic circuits, automatic control, radar and other electronic systems.Direct Digital Synthesis (DDS) technology can easily control the frequency of the signal for direct synthesis of waveforms.This paper designed a signal generator with the amplitude and frequency modulation by using AD9850 as frequency synthesizer and AT89S52 single chip microcomputer (SCM) as the core.Detailed design principle and idea are discued.AD9850 of the DDS chip is used to generate the waveform.The frequency data of external input can be transformed to frequency phase control words of chip by simple parallel or serial communication interface with the single chip microcomputer.Amplitude modulation is realized by the AD7520 chip.The system is not only simple in structure, easy to implement, but also convenient and cheap.It has a theoretical and practical value.
1.Introduction
Signal generator can be used as a signal source, which provides a known test signal to the circuit.It can be used to measure parameters of interest.In a variety of experimental test applications and proceing, the signal source as the excitation source can simulate a variety of test signals, providing the practical needs to the circuit [1].
Signal generator play a very important role in communications, electronic measuring instruments, electronic circuits, automatic control, radar and other electronic systems.With the rapid development of digital technology, there has been high-precision digital-analog converter,digital control method by using a standard reference frequency generated by multiple frequency technology, which is the DDS technology [2].Arbitrary waveform signal generator can meet the complex fields, user-defined signal, and the combination of computer technology and make it more accurate and stable.With the current development of electronic technology, the signal generator has a great application.
2.System
We designed a signal generator, which can produce several arbitrary waveforms.We can control the size of amplitude and frequency, providing a variety of signals to the test circuit.
Using AT89S52 micro controller, AD9850 (DDS) and digital-analog conversion technology, we complete hardware and software design.Through the keyboard input module, we can adjust the amplitude and frequency of the waveform.Waveform generation proce is achieved by the micro controller.So theoretically we can write a program to generate any desired waveform.SCM generates digital signal.In order to obtain the desired waveform, we should have a single chip changing digital signals into analog signals.
AD9850 of the DDS chip is used to generate the waveform.The frequency data of external input can be transformed to frequency phase control words of chip by simple parallel or serial communication interface with the single chip microcomputer.Amplitude modulation is realized by the AD7520 chip.The system design is shown in Fig.1.
The system uses SCM to control DDS chip AD9850 which produce the required signal for test instrument.SCM controls the multiplexer.The square wave or sine is DA converter AD7520\'s voltage reference signal.AD7520\'s output signal, after conditioning and amplification, is a 15V peak frequency signal.After complementary push-pull amplifier circuit, we finally get the neceary frequency signals.To ensure the signal stability peak and frequency when the load changes, the amplifier circuit in the amplifier outputs are added with the appropriate negative feedback.
3.Hardware
The circuit design is mainly two aspects including hardware and software design.The hardware part is the signal generation circuit, MCU control circuit, amplitude control circuit and display circuit.Software is mainly composed of main program and interrupt routines.
The core controller is AT89S52.ATMEL AT89S52 produced by the U.S.is a low-voltage, high performance CMOS 8 bit micro controller chip with repeated contains 8k byte erasable read-only Flash program memory and 256 bytes of random acce data memory.AT89S52 can operate down to 0Hz static logic to support two kinds of software-selectable power-saving mode [3].
In this design, SCM is the most important core component.Its work time is 12MHz.The internal flash stores the working procedures.Through the keyboard input, the circuit can know what is required to generate the waveform, the amplitude and frequency.We can also adjust any waveform of amplitude and frequency.
Fig.1.The system scheme
In this system, we use an independent-type keyboard.The design uses a matrix keyboard, using the software scan button acce to key information as neceary and achieving with software programming.This can save hardware resources, simplifying circuit design.By the matrix keyboard we can easily set on a variety of micro controllers.
In this design, P0 port is connected with the LCD display, AD9850 and the AD7520 IC chip is for data transmiion.Because the original I/O ports are not enough, we need micro controller chip on the expansion of other peripheral interfaces.In this circuit, we use the 8255 chip, which is a programmable parallel I/O interface chip.
The highly integrated frequency synthesizer AD9850 is a typical use of DDS technology products.AD9850 uses advanced CMOS proce.Its power supply is only 155mw at 3.3V.The extended industrial temperature range is from -40 to +80 centigrade degree with 28-pin Shrink Small Outline surface mount form.
AD9850 DDS system includes programmable and high-speed comparators, all-digital programming to achieve the control of frequency synthesis.AD9850 can produce a frequency and phase is programmable control of the analog sine wave output when connected to the precision clock and the frequency of write.The sine wave frequency signal can be directly used as the source or the internal conversion of high-speed comparator for the square wave output.In the 125MHz clock, the 32-bit frequency control word can AD9850 output frequency resolution of 0.0291Hz [4].
In this circuit design, the control signal input from the D0-D7 into the register.In rising edge of W_CLK (P3.0) the first byte is loaded and the pointer moves to the next input register.A continuous 5 rising edge, it stops working.Then when the rising edge FQ_UD (P3.1), the data is loaded into the frequency/phase register.At this time the DDS output frequency and phase updates.Then the pointer reset and the circuit waits for the next frequency/phase control word input.
Display Module.Considering the actual situation, we adopt dot matrix LED to realize the display.LCD1602 can display the output waveform frequency, amplitude, and the specific type.LCD1602 and the PA port of 8255 chip are connected.Three terminals RS, RW, E connected the P2.7-P2.5 of micro controller respectively.The software can control the type of waveform display and waveform frequency.
RS is a register choice is to select the data register high, low, the instruction register.RW is the read write signal line, height is read, and write operation is low.When the RS and RW are low, the LCD can be written instruction or display the addre.When RS is low and RW is high, the LCD can be read.When RS is low and high-RW, the LCD can be written data.E pin is the energy side.When the E pin is from high to low, the LCD execute commands.
AD9805 outputs constant wave amplitude.We use a D/A converter AD7520 to achieve amplitude adjustment.
The internal resistor network of AD7520 chip is composed of a programmable variable gain amplifier.AD7520 integrates the resistance network of 10 analog switches which are programmable.Internal resistor network with the AD7520 programmable amplifier are used as gain of the circuit [5].
Magnification can be adjusted between 1 to 1024, as long as the change BIT1-BIT10 the corresponding bit changes logic state can control the magnification.When BIT1-BIT10 is 3FFH, the magnification is 1 time, which is 0dB.When 98H, the magnification is10 times, which is 20dB.To realize Programmable gain, we connect PC port of 74LS373 and P2 port of SCM with AD7520 pin BIT1-BIT10.Through program, the micro controller control I/O port output state to complete the programmable gain [5]. The system requires a 5V DC power supply to all circuits.DC power supply is generally composed of power transformer, rectifier, filter circuit and the voltage regulator circuit.
The role of power transformer is to transform 220V AC voltage power into AC voltage required by rectifier filter circuit.The role of rectifier is to transform AC voltage into DC voltage single pulse.Filter circuit is to filter out the rectified output voltage ripple.After the rectification circuit output, the waveform still contains a large AC component which will affect the normal operation of the load circuit.We need to filter through the filter capacitor ripple.Filter circuit is with capacitor filter circuit.Fixed output voltage regulator part selects three-terminal integrated voltage regulator.The use of three terminal regulator can be easily integrated form of fixed output power supply.
4.Software
The software design adopts C programming language and programs different functional modules by the modularization program design idea.This structured approach enables program-level clarity, ease of use, maintenance, and debugging.The software design completes management of all the features of the signal generator, the initialization module, and the function modules of two parts.Initialization module is for the various hardware registers, data registers, and display device initialization.
Initialization module design is composed of four parts-the microproceor initialization, AD9850 chip initialization, AD7520 chip initialization and LCD1602 initialization. Function module is a display module, keyboard input module and signal conditioning modules and amplitude components.The keyboard module is mainly used to set the frequency, phase and amplitude.
The main system software programming method uses the structural method.The function modules separate from the main program and subprograms generated waveforms.Delay can be inserted to change the frequency.
Firstly, we perform the initialization of the micro controller, AD9850, AD7520 and LCD displays.Then we choose waveform by keyboard.The frequency adjustment is done through the AD9850 chip and the waveform amplitude modulation can be accomplished through the AD7520 chip.
The entire proce to achieve the following functions: plug in the power, the liquid crystal display, and then loop.If a key is detected, it is implied that data transmiion circuit begins.The program continues to detect the keyboard and the control of different keys have different functions.As long as the signal generation module outputs a few basic waveforms through the keyboard control, AD9850 chip can produce different waveforms with different frequencies through the linear combination.The amplitudes are relatively stable.
5.Conclusion
The designed signal generator is mainly composed of AT89S52 single chip microcomputer, AD9850 DDS chip, AD7520 chip, display circuit and filter circuit.The single chip microcomputer controls the whole circuit, the signal frequency generated by the AD9850 chip.The signal is filtered through the filter circuit.The AD7520 chip adjusts the signal amplitude under the control of the AT89S52 single chip microcomputer.We can observe frequency and amplitude of the signal through display circuit.By using the AD9850 chip, it is relatively high stability and the wave generated by the nonlinear distortion factor is relatively small.The system is not only simple in structure, easy to implement, but also convenient and cheap.It has a theoretical and practical value.
Acknowledgements
This work is supported by National Natural Science Foundation of China (No.10904073).
References
[1] Yong lun Wan, Qiang Si, You xin Lu, Xue gang Wang.Ultra-wideband radar signals generated technology with two-channel.
Signal Proceing, Volume 87, Iue 12, 2007, Pages 3101-3107.
[2] Walt Kester.Direct Digital Synthesis (DDS).Data Conversion Handbook, 2005, Pages 677-691. [3] Y.SUN, The new ATMEL\'s AT89S52 and its applications, 2004 - Beijing: Tsinghua University Pre.
[4] CMOS 125MHz complete DDS synthesizerAD9850.
[5] Geoff Walker , Gerard Ledwich.Bandwidth Considerations for Multilevel Converters.IEEE Transactions on Power Electronics, 1999, 14 (1): 110221105
