Design And Implementation Of Direct Digital Frequency Synthesis With High Hopping Wideband And Low Noise

Stable frequency source is a very important portion in wireless hopping communication. The output of frequency synthesizer affects communication quality of the hopping communication system. My design is to design a direct digital frequency source with high hopping wideband and low noise based on engineering requirement. Direct digital frequency synthesis (DDS) and the phase-lock loop (PLL) are used to design the frequency synthesizer because DDS can provide stable frequency and high frequency precision and PLL can provide low phase noise, good spurious emission attenuation and high frequency used for division. Primary working and achievements are list:1. In this article, the scheme to achieve the system bandwidth(357MHz) in VHF has been made based on the analysis of some key parameters such as frequency switch time, frequency stablity, frequency precision and phase noise. The VCO is designed as a single module whose frequency band is compartmentalized into three segments. New frequency band according with new engineering requirements can be implemented only by changing control software and VCO module. The design is easy to design and to debug. And its design period can be reduced. At the same time, the design is very economical in project design.2. In this article, the effects in the system of phase distinguisher and amplifier in PLL are analyzed. Some special components are selected to design loop filter.Anti-jamming is used in circuit design to assure the system parameters'implementation. The design has been used well in production for one year. The anticipant aims are implemented in the design which accord with the engineering requirements.