一种反馈DAC优化技术

An Optimal Technique for Feedback DAC

介绍了一种采用模拟电流自校正与数字加权平均(DWA)双重优化方法的电流舵DAC,在此基础上,根据文献设计了用于无线通讯的Sigma-Delta调制器,该调制器采用单环三阶结构,量化器采用4位9级量化器。在64MHz时钟频率,3.3V电源电压驱动下,Spectr仿真显示,采用该优化电流舵DAC的调制器达到79.6dB的信噪比和2MHz的信号带宽。与传统的单纯采用DWA和模拟校正技术的调制器进行比较,此调制器的信噪比比采用DWA技术提高68dB,比采用模拟校正技术提高16.3dB,同时比文献中的调制器提高7.6dB。从而说明,采用DWA和模拟校正混合优化技术改善反馈DAC的性能可进一步提高系统性能。

The theory of continuous time sigma-delta modulator is discussed.The continuous time sigma-delta modulator for wireless communication is presented.Analyzing the factor of affect performance of modulator,the technique of mixing DWA and analog error cancellation was adopted in feedback DAC in modulator.With the clock frequency of 64MHz,simulated under 3.3V supply voltage driven,the modulator achieves 76.6dB SNR and 2MHz bandwidth（16 over-sampling ratio）.The result show that this modulator＇s SNR improved 6.8dB than DWA and 16.3dB than analog error cancellation compared with the traditional DWA and analog error cancellation implemented in circuit,and it also improved 7.6dB SNR compared with the conference.So the technique of mixing DWA and analog error cancellation in feedback DAC can improved the performance of modulator more.