基于FPGA的DDS函数信号发生器

IDDS便携式信号源设计摘要函数信号发生器在教学、通信、测量等领域是非常重要的工具，制作高性能信号发生器的关键在于频率合成技术。目前，常用的频率合成技术有直接频率合成、锁相频率合成和直接数字频率合成（DDS）等。其中全数字化的DDS技术是一种新的频率合成方法，由于其具有频率分辨率高、频率切换速度快、相位噪声低和频率稳定度高等优点，DDS技术成为现代频率合成技术中的佼佼者。现场可编程门阵列（FPGA）设计灵活、速度快，在数字专用集成电路的设计中得到了广泛应用。在本设计中利用FPGA实现了一个DDS系统，该DDS系统的硬件结构是以FPGA为核心实现的，使用的是Xilinx公司的Spartan6系列FPGA。为建立友好的人机交互界面，实现DDS信号信息的实时显示（包括信号类型和信号频率、幅度参数），在本设计中采用了CPU与FPGA构成联合系统的方案。其中，CPU选用的是Cortex-M4系列ARM单片机。本设计最终实现了基于FPGA的DDS便携式信号源的设计，并且实现了对DDS信号源的控制及参数的实时显示，实现了预期设定的目标。关键字：DDS信号源；FPGA；ARMCortex-M4IIPortableSignalSourceDesignBasedonDDSABSTRACTFunctiongeneratorisaveryindispensabletoolincommunications,measu-rement,teachingandotherfields,andthekeytomakeahighperformancesignalgeneratoristhetechnologyoffrequencysynthesis.Atpresent,thetechnologyoffrequencysynthesisconsistsofdirectsynthesis,phase-lockedsynthesisandDirectDigitalfrequencySynthesis(DDS),etc.ThefullydigitalDDStechnologyhassuchadvantagesashighfrequencyresolution,fastfrequencyswitchingspeed,lowphasenoiseandhighstability,anditoutshinesotherfrequencysynthesismethods.FieldProgrammableGateArray(FPGA),becauseofitsflexibledesigningandhighspeed,hasbeenusedmorewidelyindigitalASIC.ThisdesignmainlydiscusseshowtorealizeaDDSsystemwithFPGA.ThehardwareofthedesignisSpartan6seriesFPGAmadebyXilinxInc.Inordertobuildafriendlyman-machineinterfacetomakesuretheinformationsuchasthetype,frequencyandamplitudeofthesignaldisplayinthescreenattherealtime,wechoosethedesignbasedonbothCPUandFPGA.ThehardwareoftheCPUisARMCortex-M4seriessinglechipmicrocomputer.ThisdesignrealizestheportablesignalsourcebasedonDDSintheFPGAboard,anditrealizesthereal-timedisplayandthecontroloftheparametersofIIIthesignalsource.Finally,itachievesthedesiredobjectives.Keywords：DDSsignalsource；FPGA；ARMCortex-M4IV目录1绪论.............................................................................................................-1-1.1引言....................................................................................................-1-1.2国内外现状及发展史........................................................................-2-1.2.1频率合成技术及其发展.........................................................-2-1.2.2可编程逻辑器件及其发展.....................................................-5-1.2.3基于FPGA实现DDS技术的意义.......................................-7-1.3DDS设计重点与主要工作...............................................................-8-2DDS技术原理及FPGA简介...................................................................-10-2.1DDS技术原理.................................................................................-10-2.1.1DDS技术概述.......................................................................-10-2.1.2DDS技术基本原理...............................................................-11-2.1.3DDS的特性分析及优化.......................................................-14-2.2FPGA简介.......................................................................................-19-2.2.1FPGA的基本结构.................................................................-20-2.2.2FPGA的基本特点.................................................................-21-2.2.3FPGA的开发流程.................................................................-22-2.2.4FPGA的开发平台.................................................................-24-3基于FPGA实现DDS技术的方案与实现.............................................-27-3.1系统设计方案..................................................................................-27-3.1.1系统总体方案........................................................................-27-3.1.2系统方案论证........................................................................-28-V3.2系统硬件设计..................................................................................-29-3.2.1DDS信号源模块...................................................................-29-3.2.2通讯接口模块设计................................................................-34-3.2.3D/A数模转换电路设计........................................................-35-3.2.4显示电路设计........................................................................-37-3.3系统软件设计..................................................................................-38-3.3.1基于IAR的嵌入式开发环境...............................................-38-3.3.2通讯接口设计........................................................................-40-3.3.3液晶屏显示驱动设计............................................................-40-3.3.4ADC电压检测设计...............................................................-42-4系统测试...................................................................................................-44-4.1DDS模块测试.................................................................................-44-4.2FPGA与CPU通讯接口测试.........................................................-48-4.3CPU总控平台测试.........................................................................-50-4.4系统测试..........................................................................................-51-5总结与展望...............................................................................................-54-5.1全文工作总结.........................................................