论文部分内容阅读
Σ-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Σ-Δ调制器的结构寄生。介绍了Σ-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Σ-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。
Sigma-Delta Modulation Fractional-Frequency Synthesizer utilizes noise shaping technology to shift the spectrum of quantization noise to the high end of the frequency and suppress this high-frequency noise with the low-pass characteristics of the phase-locked loop. This not only enables the output of the phase-locked loop The frequency of fine step, but also to solve the fractional fractional mantissa modulation problems exist. However, as a finite state machine, a specific spurious spectrum is formed in a specific input situation, that is, a structure parasitism of a sigma-delta modulator. The structural parasitics of the MASH model of Σ-Δ modulator is introduced. The relationship between the length of the output sequence of the first, second and third order MASH models is deduced in detail. The relationship between the sequence length and the input value and the initial value of the accumulator is revealed. The effective method to avoid the extremely short sequence length effectively eliminates the structural parasitics and provides a theoretical basis for the design of high-performance Σ-Δ modulation fractional-N frequency synthesizer. Analytical methods are also suitable for the analysis of parasitic structures of other new modulators, which is of great significance.