Developing Of Frequency Synthesizer With Better Spurious And Phase Noise Characteristics

The frequency synthesizer has been widely used in electronic devices,different frequency synthesizer application indicators have different needs.When the frequency synthesizer oscillator of the radio receiver as often need thereof has a good spurious phase noise performance.The contents of this article to have good phase noise and spurious performance of the frequency synthesizer Development。This article discusses the basic theory of the existing frequency synthesizer includes a phase locked loop frequency synthesizer and spectral characteristics of the basic principles,the basic principle and spectral characteristics of DDS frequency synthesizer,modular synthesizer basic principles and characteristics.Select the frequency synthesis scheme of DDS excitation phase-locked loop according to the design requirements.Hardware implementation and hardware system is completed。Test results the performance of the function of the frequency synthesizer shown to meet the design specifications of the requirements。First,the features of single phase-locked loop,single DDS,The combination of phase-locked loop and DDS are compared.Compare the advantages and disadvantages.Select a phase-locked loop frequency source for the DDS offers this program as a hardware implementation of the system,given the system program diagram.Then,circuit of frequency synthesizer was designed.The system uses AD9954 DDS chip;The ADF4002 is selected as PLL chip;The AD8353 is selected as amplifier chip;MSP430F149 is selected as MCU chip.Frequency synthesizer hardware production and system software program have been completed。Finally,frequency synthesizer performance was tested.Final technical indicators of frequency Synthesizer are as follows:Frequency step 1Hz,external reference frequency 9.8304MHz,phase noise<-110dBc/Hz@10kHz,stray<-70dBc,output power 4.5dBm±1.5dB,supply voltage +5 V,current 200mA+10%。...