∑-Δ调制器MASH模型的结构寄生研究  

The Structure Spuriousness of MASH Model in ∑-Δ Modulation

作　　者：刘祖深[1,2] 

机构地区：[1]中国电子科技集团公司第四十一研究所,蚌埠233010 [2]电子信息测试技术安徽省重点实验室,蚌埠233010

出　　处：《微波学报》2017年第6期1-6,共6页Journal of Microwaves

基　　金：国家科技重大专项(2017ZX03001021)

摘　　要：∑-Δ调制小数分频频率合成器利用噪声成型技术,将量化噪声的频谱搬移到频率高端,借助锁相环路的低通特性对这种高频噪声进行抑制,不但实现了锁相环输出频率的精细步进,而且解决了小数分频存在的尾数调制问题。然而,作为有限状态机,特定输入情形下会形成特有的杂散谱,即∑-Δ调制器的结构寄生。介绍了∑-Δ调制器MASH模型的结构寄生,详细推导了1阶、2阶和3阶MASH模型的输出序列长度关系式,揭示了序列长度与输入数值和累加器初始值密切关系,获得了避免极短序列长度的有效方法,有效消除了结构寄生,为高性能∑-Δ调制小数分频频率合成器的设计提供了理论依据。分析方法也适合其它新型调制器结构寄生的分析,具有重要意义。∑-Δ modulation fractional division frequency synthesizer moves the spectrum of quantization noise to the high frequency using noise shaping technology and suppresses the high frequency noise using the low-pass characteristic of phase-locked loop. This technology has not only realized the fine stepping of phase-locked loop output frequency, but also solved the mantissa modulation problems of the fractional division. However, all ∑-Δ modulators are finite state machines. In some specific input case, a unique hybrid spread spectrum, also known as ∑-Δ modulator structure spuriousness, will be created. This paper introduces structure spuriousness of MASH model in ∑-Δ modulation, deduces the output sequence length relations of 1st order, 2nd order and 3st order MASH model in detail. It reveals that the sequence length is closely re- lated to the input value and the initial value of accumulators. An effective method is achieved to avoid short sequence length, which effectively eliminate structure spuriousness. The study provides a theoretical basis for the design of high performance ∑-Δ modulation fractional N frequency synthesizer. The analytical method adopted is also suitable for the analysis of the spu- riousness analysis of other new modulator structures, and is of great significance.

关 键 词：小数分频 ∑-Δ调制器 结构寄生 序列长度 多级噪声成型(MASH) 

分 类 号：TN761[电子电信—电路与系统]