Abstract:

The frequency source is the core of modern radio communication systems,plays a decisive role for the normal operation of the entire system.The frequency source of the RF circuit is good or bad relationship with the overall system performance.Direct digital frequency synthesis (DDS) has an insignificant frequency tuning and phase resolution.Integration of analog and digital technology,DDS is the ideal way to produce high quality and high spectral purity wideband frequency.This paper describes the basic working principle of DDS,as well as the limitations of the DDS technology.Implements a programmable low phase noise frequency synthesizer based on FPGA+DDS,output signal range 170～228 MHz.The experimental results show that the frequency source has a high frequency resolution and low phase noise,meeting the design requirements of the communication system on the frequency source.

Key words: DDS;FPGA;AD9912;frequency synthesizer