The article analyses the improvement of sigma delta to S/N, introduces the application of sigma delta in A/D into N digit fractional divider, simply describes the improvement of sigma delta to the output phase vibration of N fractional divider, raises the conception of repeatedly cycled utilization of a sigma delta accumulator replacting multiple accumulators.

A new micro accelerometer is designed based on Σ-Δ modulation technique and the system model is established.

The paper analyzes the fractional-N PLL frequency synthesizer and applies the Σ-Δ modulation technology to it.

The article firstly gives a brief account of the frequency synthesizer technology,and then conducted the research and the design to the score frequency synthesizer making the use of Sigma-Delta technology.