基于usb20的虚拟数字存储示波器硬件系统设计.doc

基于USB20的虚拟数字存储示波器硬件系统设计

 摘  要
在计算机科学技术和测试技术持续发展的基础上，根据实际需求，产生了一种新型的测量仪器——虚拟仪器，本文设计的基于USB2.0的虚拟示波器正是虚拟仪器的一种，具有功能强、速度高、测量准确、实时性好、结构轻巧、人机界面友好及操作简单等优点，满足测量发展的需要，应用前景非常广阔。
本文紧紧围绕虚拟示波器的硬件结构设计这一课题展开，主要研究以下内容：
1．模拟通道电路设计。依据信号的流向，给出了耦合方式选择电路、无源衰减网络、阻抗变换电路、可程控固定倍率衰减、信号放大电路以及触发源选择电路和触发脉冲产生电路等信号调理通道和触发通道中几个主要硬件部分的设计方案。
2．数据采集系统设计。采用ADC+FPGA+DSP的系统构架，以多片低速ADC器件并行完成1GSPS实时采样率的技术指标，对采集数据运用并行分相存储技术缓存，由DSP处理器对采样数据进行实时处理，大大减少通讯接口压力。
3．USB接口模块设计及电源设计。选用USB2.0接口芯片设计接口电路用于连接仪器硬件和个人电脑，保障数据传输的速度和稳定性。电源模块的设计是为系统正常稳定工作提供一个合理的电源系统，其本身的质量直接影响着系统性能。
4．电磁兼容设计。从布局布线、电源及接地等方面分析了高速PCB布板中电磁兼容的设计，最大程度地降低干扰等对性能的影响。
5．最后，给出实验结果并结合调试工作，列举了调试过程中遇到的突出问题，并对解决过程给予描述，目的是提供一种分析问题、解决问题的思路和方法。

关键词：虚拟示波器，数据采集，交替采样，USB2.0，电源
 
Abstract
Based on the sustainable development of computer science and testing technology, virtual instruments, a new type of measuring instruments, emerge to meet the actual demands. The virtual oscilloscope, which is designed on the basis of USB2.0, is one kind of virtual instruments. Being characteristic of powerful functions, high speed, accurate measurement, real time, light structure, friendly man-machine interface and simple operation, it meets the needs of measurement development with a wide range of applications.
This paper mainly focuses on hardware structure design of the virtual oscilloscope. The research has been carried out in the following aspects:
1. Circuit design of the analog channel. According to signal flow, the paper presents a design proposal for several major hardware parts in signal conditioning channel and trigger channel, including circuit selection by coupling modes, passive attenuation network, impedance converting circuit, programmable fixed rate attenuation, signal amplifier and trigger source selection circuit and the trigger pulse generation circuits.
2. Data Acquisition System. With the adoption of the frame structure of ADC + FPGA + DSP, Parallel sampling module completes 1GSPS data acquisition system with multi-chip low-speed ADC devices, then the data processing is completed by the DSP processor, and it can significantly reduce the communication interface pressure.
3. USB interface module design and power design. USB2.0 interface chip is selected to design the interface circuit for connecting instrument hardware and personal computers and ensuring data transmission speed and stability. Power module is designed to provide a reasonable power system so as to guarantee the normal and stable operation of the whole system. Its own quality directly affects the system performance.
4. EMC Design. From the layout, power supply and ground, the paper analyzes the design of electromagnetic compatibility in high-speed PCB layout in order to minimize the interference on the performance.
5. Finally, Experimental results are presented and in combination with the debugging, the paper cites some serious problems and describes the resolving process with an aim to provide an idea and a method for analyzing and solving the problems.

Keywords: Virtual oscilloscope, data acquisition, alternative sampling, USB2.0, power supply

 
目  录
第一章 引言 1
1.1 虚拟仪器概述 1
1.2 虚拟仪器发展状况 2
1.3 选题背景及选题意义 3
1.4 课题目标及论文主要研究内容 3
第二章 虚拟数字存储示波器硬件系统总体方案 5
2.1 总体设计方案 5
2.2 系统结构 6
2.2.1 模拟通道 6
2.2.2 数据采集 7
2.2.3 数据处理及存储 7
2.2.4 通用串行总线 7
2.2.5 电源模块 8
第三章 硬件系统设计 9
3.1 模拟通道电路设计 9
3.2 数据采集及处理系统设计 16
3.2.1 关键器件的选型 16
3.2.2 并行采集电路 20
3.2.3高速采样时钟 25
3.2.4 数据并行存储 28
3.3 FPGA及外围电路 36
3.4 DSP处理电路设计 38
3.4.1 存储器扩展电路 38
3.4.2  JTAG接口电路 40
3.5 USB2.0硬件设计 41
3.5.1 USB总线特性 41
3.5.2 USB接口芯片 42
3.5.3 USB接口电路的实现 44
3.6 电源模块设计 46
3.6.1 DC-DC电压转换 46
3.6.2 LDO低压差线性稳压 50
3.7电磁兼容设计 52
3.7.1布局布线电磁兼容设计 52
3.7.2电源电磁兼容设计 54
3.7.3接地电磁兼容设计 55
第四章 系统调试与验证 57
4.1 电源模块的调试 57
4.2 FPGA的调试 59
4.3 DSP及ADC的调试 61
4.4 通道部分的调试 62
4.5 测试验证效果 63
第五章 结束语 67
致 谢 68
参考文献 69
附 录 71