The analytic model for noise of direct digital frequency synthesizer

An analytic model based on device physics and circuit theory for noise characteristics is presented. In the model, the delay time introduced by the switching process and its influence on the current output of the digital analogue converter (DAC) were discussed. The simulation revealed that the main noise of the direct digital frequency synthesizer (DDS) is caused by the switching operation style of the DAC´s weight tree and current source, and the noise characteristic is sorely determined by the device performance and IC technology. The noise characteristics and spectral line structure revealed in the simulation results are in good agreement with the practical test result reported in others publication