Masked Dithering of MASH Digital Delta-Sigma Modulators with Constant Inputs Using Linear Feedback Shift Registers
Masked Dithering of MASH Digital Delta-Sigma Modulators with Constant Inputs Using Linear Feedback Shift Registers
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DOI：
10.1109/tcsi.2016.2565060
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发表时间：
2016-07
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影响因子：
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通讯作者：
Hongjia Mo;Michael Peter Kennedy
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文献类型：
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作者：
Hongjia Mo;Michael Peter Kennedy
数字δ - σ调制器（dddms）是有限状态机；当它们通过少量状态在时间上重复循环时，它们的光谱具有强周期性音调（所谓的杂散）的特征。当输入是常数或周期时，这种情况特别容易发生。基于线性反馈移位寄存器（LFSRs）的抖动发生器被广泛用于分解ddsm中的周期性循环，以消除底层周期性行为产生的杂散。不幸的是，lfsr产生的伪随机抖动信号本身是周期性的，因此可能效果有限。本文对基于lfsr的伪随机抖动的DDSMs进行了严格的数学分析，并提出了一种有效实现掩膜抖动的设计方法。
Digital delta-sigma modulators (DDSMs) are finite state machines; their spectra are characterized by strong periodic tones (so-called spurs) when they cycle repeatedly in time through a small number of states. This is particularly likely to happen when the input is constant or periodic. Dither generators based on linear feedback shift registers (LFSRs) are widely used to break up periodic cycles in DDSMs in order to eliminate spurs produced by underlying periodic behavior. Unfortunately, pseudorandom dither signals produced by LFSRs are themselves periodic and therefore may have limited effectiveness. This paper presents a rigorous mathematical analysis of DDSMs with LFSR-based pseudorandom dither, and a design methodology to achieve effectively masked dithering.