基于直接数字频率合成的混合频率恒流源设计.pdfVIP

学兔兔 第31卷 第9期 仪 器 仪 表 学 报 Vo1．31 No．9 2010年9月 Chinese Journal of Scientific Instrument Sep．2010 基于直接数字频率合成的混合频率恒流源设计术 鞠 康，何 为，何传红，李 冰，罗海军 (重庆大学输配电装备及系统安全与新技术国家重点实验室 重庆 400044) 摘 要：对比已有的混合频率恒流源实现方式，提出一种灵活性好、稳定性高的实现结构。从系统组成角度分别介绍直接数字 频率合成、电压控制增益放大器、电压控制电流源三个模块及其实现方法。从仿真及实测结果看，设计的恒流源能够达到较高 的输出阻抗。通过实测电流的时域波形图及频谱图分析，恒流源能输出混合任意两种频率正弦波形的电流，且噪声水平较低。 该设计在三维多频电阻抗成像系统中得到良好的应用，可提高成像系统的测量速度及精度，并使电阻抗成像技术有效应用于阻 抗变换快的检测对象。 关键词：混合频率；恒流源；电阻抗成像 中图分类号：Q．334 文献标识码：A 国家标准学科分类代码：310．61 Design of mixing frequency constant·current source based on direct digital synthesizer ju Kang，He Wei，He Chuanhong，Li Bing，Luo Haijun (State Key Laboratory of Power Transmission EquipmentSystem Security and New Technology， Chongqing University，Chongqing 400044，China) Abstract：A mixing~equency constant—current source was designed with better flexibility and higher stability than existing devices．Three models，i．e．direct digital synthesizer，voltage control gain amplifier and voltage control cur— rent source，and their implementation are introduced from the point of view of system composition．Simulation and experiment results show that the designed system has high output impedance and can output sine wave current with any two mixed frequencies and low noise．The design finds good applications in three—dimension multifrequency dec- trieal impedance tomography system，and can improve the measurement speed and precision of the imaging system， which could be used to detect the objeets with fast changing impedance． Key words：mixing frequency；constant—current source；electrical impedance tomography