Σ-Δ调制技术在小数分频器中的应用

Applications of Sigma-Delta Modulating Technology in Fractional-N Frequency Synthesizer

小数分频技术解决了锁相环频率合成器中鉴相频率和输出频率分辨率的矛盾。但一般的小数分频技术引入了严重的小数杂散问题。因为Δ-Σ调制技术对噪声具有整形的作用,把Σ-Δ调制技术应用在小数分频频率合成器中,与传统的PLL(锁相环)频率合成器相比具有明显的优越性,他可以提供很宽的频率范围、极高的频率分辨率、较低的单边带相位噪声以及良好的杂散性能。

Fractional- N technology resolve the contradiction between the pulse detection frequency and the output frequency resolution of the single PLL frequency synthesizer, but the severe phase noise is introduced. Because sigma -delta modulating technology has plastic function to noise,it has obvious advantage that frequency synthesizers utilizing ∑- A modulation fractional divider compare with conventional PLL frequency synthesizers. It has wideband frequency, fine frequency resolution,low single sideband phase noise and low spur.